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#1
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AFCI and UPS?
Hi all,
got a weird issue. In an upstairs bedroom, I have a computer that is running off a UPS. After investigating the wiring in the house, I have found a significant number of grounds "bootlegged." Little by little I am picking away at them, but until spring, the upstairs will remain as is because it's darn cold in the attic at the moment. So here's the deal. I have determined that there is one properly grounded outlet in the room where the computer is, because that outlet is fed directly from the breaker panel, and that homerun is in BX not the cloth covered Romex that the rest of the concealed wiring is. So as a stopgap until I get around to fixing everything correctly I wanted to make sure that the computer's UPS was plugged into that particular outlet for proper surge protection. I bought a heavy extension cord, unplugged the UPS from the outlet that it was plugged into, plugged the extension cord into the correct outlet. Then I plugged the UPS into the extension cord, and the lights went out. Reset the breaker, figuring that I just made an arc, if I plugged it in faster it would be OK. Same effect. Reset the breaker, plugged the UPS back into the outlet that it was using before, and everything is fine. This is a less than year old APC unit. Is there some fundamental incompatibility between this UPS and the AFCI? I'm wondering if the UPS tests for the presence of an earth ground (there is a "building wiring fault" light on it) and if so does that cause enough current to trip the AFCI? (I wouldn't have found this before, because the outlet into which it's currently plugged is not grounded but has the ground bootlegged to the neutral.) I've heard that some AFCIs are also GFCIs is why I'm asking. The AFCI is a Siemens Q115AF breaker in the breaker panel. I'll replace the receptacle in the morning (once it's light out) and see if that solves the problem, but I'm not sure what kind of fault could be in a receptacle that would cause a breaker, AFCI or not, to trip only when a load is connected to it but not when a plug is inserted. Does this mean also that I run the risk of having the AFCI trip if the surge protection of the UPS kicks in? Should I just give up the idea of having everything "to code" and ditch the AFCI and/or investigate the possibility of running a dedicated circuit to that bedroom to feed an outlet solely for the computer, not protected by the AFCI? any thoughts greatly appreciated... nate -- replace "fly" with "com" to reply. http://home.comcast.net/~njnagel |
#2
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AFCI and UPS?
AFCIs are rather new. Any installation that new should not have faked
grounds. Did you mean GFCIs? |
#3
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AFCI and UPS?
Charles Schuler wrote:
AFCIs are rather new. Any installation that new should not have faked grounds. Did you mean GFCIs? No, I put the AFCI in myself after purchasing the house. However, a lot of the wiring is late-40's vintage. That was a good enough reason in my mind to think that an AFCI would be if anything more important here than in new construction. nate -- replace "fly" with "com" to reply. http://home.comcast.net/~njnagel |
#4
Posted to alt.home.repair
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AFCI and UPS?
"Nate Nagel" wrote in message ... Hi all, got a weird issue. In an upstairs bedroom, I have a computer that is running off a UPS. After investigating the wiring in the house, I have found a significant number of grounds "bootlegged." Little by little I am picking away at them, but until spring, the upstairs will remain as is because it's darn cold in the attic at the moment. So here's the deal. I have determined that there is one properly grounded outlet in the room where the computer is, because that outlet is fed directly from the breaker panel, and that homerun is in BX not the cloth covered Romex that the rest of the concealed wiring is. So as a stopgap until I get around to fixing everything correctly I wanted to make sure that the computer's UPS was plugged into that particular outlet for proper surge protection. I bought a heavy extension cord, unplugged the UPS from the outlet that it was plugged into, plugged the extension cord into the correct outlet. Then I plugged the UPS into the extension cord, and the lights went out. Reset the breaker, figuring that I just made an arc, if I plugged it in faster it would be OK. Same effect. Reset the breaker, plugged the UPS back into the outlet that it was using before, and everything is fine. This is a less than year old APC unit. Is there some fundamental incompatibility between this UPS and the AFCI? I'm wondering if the UPS tests for the presence of an earth ground (there is a "building wiring fault" light on it) and if so does that cause enough current to trip the AFCI? (I wouldn't have found this before, because the outlet into which it's currently plugged is not grounded but has the ground bootlegged to the neutral.) I've heard that some AFCIs are also GFCIs is why I'm asking. The AFCI is a Siemens Q115AF breaker in the breaker panel. I'll replace the receptacle in the morning (once it's light out) and see if that solves the problem, but I'm not sure what kind of fault could be in a receptacle that would cause a breaker, AFCI or not, to trip only when a load is connected to it but not when a plug is inserted. Does this mean also that I run the risk of having the AFCI trip if the surge protection of the UPS kicks in? Should I just give up the idea of having everything "to code" and ditch the AFCI and/or investigate the possibility of running a dedicated circuit to that bedroom to feed an outlet solely for the computer, not protected by the AFCI? any thoughts greatly appreciated... nate Is that circuit part of a three wire cable (Black, red, white) used for two circuits or is it just a two wire bx with the armor as the grounding conductor? |
#5
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AFCI and UPS?
On Feb 17, 6:42 pm, Nate Nagel wrote:
No, I put the AFCI in myself after purchasing the house. However, a lot of the wiring is late-40's vintage. That was a good enough reason in my mind to think that an AFCI would be if anything more important here than in new construction. First, break the problem into parts; then diagnose those parts. For example, do you have other GFCIs in the bathroom or kitchen? If so, then good. Run that computer extension cord to that GFCI; see computer or extension cord causes the other GFCI to trip. Have you run anything significant on that tripping AGFI circuit? For example, if the AFGI circuit is somehow wired so that its neutral (white) wire is started with another circuit, then AGFI trip will occur. For example, an iron on that newly AGFIed circuit would be a good test. If any newly modified safety ground has somehow shorted to a neutral wire, then that also will trip the AGFI. But long before taking anything apart, first verify which suspect (computer and extension cord, or AGFI circuit) causes GFCI trip. Second, that plug-in protector is too far from earth AND is hoping to earth via a wire bundled with other wires. Just two in a long list of reasons why a power strip protector does not even claim (in numerical specifications) protection from surges that would cause damage. The length of that earthing wire (a short distance to earth and a significantly long distance between computer and surge protector) has long been necessary for effective protection. That also means the 1940s mains box must be upgraded so that earthing both meets and exceeds post 1990 National Electrical Code requirements. |
#6
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AFCI and UPS?
John Grabowski wrote:
"Nate Nagel" wrote in message ... Hi all, got a weird issue. In an upstairs bedroom, I have a computer that is running off a UPS. After investigating the wiring in the house, I have found a significant number of grounds "bootlegged." Little by little I am picking away at them, but until spring, the upstairs will remain as is because it's darn cold in the attic at the moment. So here's the deal. I have determined that there is one properly grounded outlet in the room where the computer is, because that outlet is fed directly from the breaker panel, and that homerun is in BX not the cloth covered Romex that the rest of the concealed wiring is. So as a stopgap until I get around to fixing everything correctly I wanted to make sure that the computer's UPS was plugged into that particular outlet for proper surge protection. I bought a heavy extension cord, unplugged the UPS from the outlet that it was plugged into, plugged the extension cord into the correct outlet. Then I plugged the UPS into the extension cord, and the lights went out. Reset the breaker, figuring that I just made an arc, if I plugged it in faster it would be OK. Same effect. Reset the breaker, plugged the UPS back into the outlet that it was using before, and everything is fine. This is a less than year old APC unit. Is there some fundamental incompatibility between this UPS and the AFCI? I'm wondering if the UPS tests for the presence of an earth ground (there is a "building wiring fault" light on it) and if so does that cause enough current to trip the AFCI? (I wouldn't have found this before, because the outlet into which it's currently plugged is not grounded but has the ground bootlegged to the neutral.) I've heard that some AFCIs are also GFCIs is why I'm asking. The AFCI is a Siemens Q115AF breaker in the breaker panel. I'll replace the receptacle in the morning (once it's light out) and see if that solves the problem, but I'm not sure what kind of fault could be in a receptacle that would cause a breaker, AFCI or not, to trip only when a load is connected to it but not when a plug is inserted. Does this mean also that I run the risk of having the AFCI trip if the surge protection of the UPS kicks in? Should I just give up the idea of having everything "to code" and ditch the AFCI and/or investigate the possibility of running a dedicated circuit to that bedroom to feed an outlet solely for the computer, not protected by the AFCI? any thoughts greatly appreciated... nate Is that circuit part of a three wire cable (Black, red, white) used for two circuits or is it just a two wire bx with the armor as the grounding conductor? It's two conductor BX with the armor grounded. nate -- replace "fly" with "com" to reply. http://home.comcast.net/~njnagel |
#7
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AFCI and UPS?
"Nate Nagel" wrote in message ... John Grabowski wrote: "Nate Nagel" wrote in message ... Hi all, got a weird issue. In an upstairs bedroom, I have a computer that is running off a UPS. After investigating the wiring in the house, I have found a significant number of grounds "bootlegged." Little by little I am picking away at them, but until spring, the upstairs will remain as is because it's darn cold in the attic at the moment. So here's the deal. I have determined that there is one properly grounded outlet in the room where the computer is, because that outlet is fed directly from the breaker panel, and that homerun is in BX not the cloth covered Romex that the rest of the concealed wiring is. So as a stopgap until I get around to fixing everything correctly I wanted to make sure that the computer's UPS was plugged into that particular outlet for proper surge protection. I bought a heavy extension cord, unplugged the UPS from the outlet that it was plugged into, plugged the extension cord into the correct outlet. Then I plugged the UPS into the extension cord, and the lights went out. Reset the breaker, figuring that I just made an arc, if I plugged it in faster it would be OK. Same effect. Reset the breaker, plugged the UPS back into the outlet that it was using before, and everything is fine. This is a less than year old APC unit. Is there some fundamental incompatibility between this UPS and the AFCI? I'm wondering if the UPS tests for the presence of an earth ground (there is a "building wiring fault" light on it) and if so does that cause enough current to trip the AFCI? (I wouldn't have found this before, because the outlet into which it's currently plugged is not grounded but has the ground bootlegged to the neutral.) I've heard that some AFCIs are also GFCIs is why I'm asking. The AFCI is a Siemens Q115AF breaker in the breaker panel. I'll replace the receptacle in the morning (once it's light out) and see if that solves the problem, but I'm not sure what kind of fault could be in a receptacle that would cause a breaker, AFCI or not, to trip only when a load is connected to it but not when a plug is inserted. Does this mean also that I run the risk of having the AFCI trip if the surge protection of the UPS kicks in? Should I just give up the idea of having everything "to code" and ditch the AFCI and/or investigate the possibility of running a dedicated circuit to that bedroom to feed an outlet solely for the computer, not protected by the AFCI? any thoughts greatly appreciated... nate Is that circuit part of a three wire cable (Black, red, white) used for two circuits or is it just a two wire bx with the armor as the grounding conductor? It's two conductor BX with the armor grounded. AFCI circuit breakers are not required here in New Jersey, so I don't have much experience diagnosing problems with them. My thoughts are that your AFCI does not like the BX armor ground, there is something else going on with the BX cable, or it does not like your UPS. Have you tried plugging in another three prong appliance into the outlet? |
#8
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AFCI and UPS?
John Grabowski wrote:
"Nate Nagel" wrote in message ... John Grabowski wrote: "Nate Nagel" wrote in message ... Hi all, got a weird issue. In an upstairs bedroom, I have a computer that is running off a UPS. After investigating the wiring in the house, I have found a significant number of grounds "bootlegged." Little by little I am picking away at them, but until spring, the upstairs will remain as is because it's darn cold in the attic at the moment. So here's the deal. I have determined that there is one properly grounded outlet in the room where the computer is, because that outlet is fed directly from the breaker panel, and that homerun is in BX not the cloth covered Romex that the rest of the concealed wiring is. So as a stopgap until I get around to fixing everything correctly I wanted to make sure that the computer's UPS was plugged into that particular outlet for proper surge protection. I bought a heavy extension cord, unplugged the UPS from the outlet that it was plugged into, plugged the extension cord into the correct outlet. Then I plugged the UPS into the extension cord, and the lights went out. Reset the breaker, figuring that I just made an arc, if I plugged it in faster it would be OK. Same effect. Reset the breaker, plugged the UPS back into the outlet that it was using before, and everything is fine. This is a less than year old APC unit. Is there some fundamental incompatibility between this UPS and the AFCI? I'm wondering if the UPS tests for the presence of an earth ground (there is a "building wiring fault" light on it) and if so does that cause enough current to trip the AFCI? (I wouldn't have found this before, because the outlet into which it's currently plugged is not grounded but has the ground bootlegged to the neutral.) I've heard that some AFCIs are also GFCIs is why I'm asking. The AFCI is a Siemens Q115AF breaker in the breaker panel. I'll replace the receptacle in the morning (once it's light out) and see if that solves the problem, but I'm not sure what kind of fault could be in a receptacle that would cause a breaker, AFCI or not, to trip only when a load is connected to it but not when a plug is inserted. Does this mean also that I run the risk of having the AFCI trip if the surge protection of the UPS kicks in? Should I just give up the idea of having everything "to code" and ditch the AFCI and/or investigate the possibility of running a dedicated circuit to that bedroom to feed an outlet solely for the computer, not protected by the AFCI? any thoughts greatly appreciated... nate Is that circuit part of a three wire cable (Black, red, white) used for two circuits or is it just a two wire bx with the armor as the grounding conductor? It's two conductor BX with the armor grounded. AFCI circuit breakers are not required here in New Jersey, so I don't have much experience diagnosing problems with them. My thoughts are that your AFCI does not like the BX armor ground, there is something else going on with the BX cable, or it does not like your UPS. Have you tried plugging in another three prong appliance into the outlet? No, that outlet has been unused since we've moved in. It is however the first one in the circuit so the only possibilities I can see are that the AFCI is actually a GFCI as well (anyone know?) and there's enough current flowing through the real ground due to the UPS's fault sensing circuit, OR that there is a physical problem with that receptacle, which I'll be attempting to rule out shortly, now that the sun is up. (I've been on a program of replacing all the receptacles as soon as wiring "issues" are cleared, because a lot of the old receptacles were loose as well.) nate -- replace "fly" with "com" to reply. http://home.comcast.net/~njnagel |
#9
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AFCI and UPS?
AFCI's do have GFCI functionality, but they trip at 60 ma instead of the 5
ma of a GFCI "Nate Nagel" wrote in message ... John Grabowski wrote: "Nate Nagel" wrote in message ... John Grabowski wrote: "Nate Nagel" wrote in message ... Hi all, got a weird issue. In an upstairs bedroom, I have a computer that is running off a UPS. After investigating the wiring in the house, I have found a significant number of grounds "bootlegged." Little by little I am picking away at them, but until spring, the upstairs will remain as is because it's darn cold in the attic at the moment. So here's the deal. I have determined that there is one properly grounded outlet in the room where the computer is, because that outlet is fed directly from the breaker panel, and that homerun is in BX not the cloth covered Romex that the rest of the concealed wiring is. So as a stopgap until I get around to fixing everything correctly I wanted to make sure that the computer's UPS was plugged into that particular outlet for proper surge protection. I bought a heavy extension cord, unplugged the UPS from the outlet that it was plugged into, plugged the extension cord into the correct outlet. Then I plugged the UPS into the extension cord, and the lights went out. Reset the breaker, figuring that I just made an arc, if I plugged it in faster it would be OK. Same effect. Reset the breaker, plugged the UPS back into the outlet that it was using before, and everything is fine. This is a less than year old APC unit. Is there some fundamental incompatibility between this UPS and the AFCI? I'm wondering if the UPS tests for the presence of an earth ground (there is a "building wiring fault" light on it) and if so does that cause enough current to trip the AFCI? (I wouldn't have found this before, because the outlet into which it's currently plugged is not grounded but has the ground bootlegged to the neutral.) I've heard that some AFCIs are also GFCIs is why I'm asking. The AFCI is a Siemens Q115AF breaker in the breaker panel. I'll replace the receptacle in the morning (once it's light out) and see if that solves the problem, but I'm not sure what kind of fault could be in a receptacle that would cause a breaker, AFCI or not, to trip only when a load is connected to it but not when a plug is inserted. Does this mean also that I run the risk of having the AFCI trip if the surge protection of the UPS kicks in? Should I just give up the idea of having everything "to code" and ditch the AFCI and/or investigate the possibility of running a dedicated circuit to that bedroom to feed an outlet solely for the computer, not protected by the AFCI? any thoughts greatly appreciated... nate Is that circuit part of a three wire cable (Black, red, white) used for two circuits or is it just a two wire bx with the armor as the grounding conductor? It's two conductor BX with the armor grounded. AFCI circuit breakers are not required here in New Jersey, so I don't have much experience diagnosing problems with them. My thoughts are that your AFCI does not like the BX armor ground, there is something else going on with the BX cable, or it does not like your UPS. Have you tried plugging in another three prong appliance into the outlet? No, that outlet has been unused since we've moved in. It is however the first one in the circuit so the only possibilities I can see are that the AFCI is actually a GFCI as well (anyone know?) and there's enough current flowing through the real ground due to the UPS's fault sensing circuit, OR that there is a physical problem with that receptacle, which I'll be attempting to rule out shortly, now that the sun is up. (I've been on a program of replacing all the receptacles as soon as wiring "issues" are cleared, because a lot of the old receptacles were loose as well.) nate -- replace "fly" with "com" to reply. http://home.comcast.net/~njnagel |
#10
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AFCI and UPS?
Nate Nagel wrote:
John Grabowski wrote: "Nate Nagel" wrote in message ... John Grabowski wrote: "Nate Nagel" wrote in message ... Hi all, got a weird issue. In an upstairs bedroom, I have a computer that is running off a UPS. After investigating the wiring in the house, I have found a significant number of grounds "bootlegged." Little by little I am picking away at them, but until spring, the upstairs will remain as is because it's darn cold in the attic at the moment. So here's the deal. I have determined that there is one properly grounded outlet in the room where the computer is, because that outlet is fed directly from the breaker panel, and that homerun is in BX not the cloth covered Romex that the rest of the concealed wiring is. So as a stopgap until I get around to fixing everything correctly I wanted to make sure that the computer's UPS was plugged into that particular outlet for proper surge protection. I bought a heavy extension cord, unplugged the UPS from the outlet that it was plugged into, plugged the extension cord into the correct outlet. Then I plugged the UPS into the extension cord, and the lights went out. Reset the breaker, figuring that I just made an arc, if I plugged it in faster it would be OK. Same effect. Reset the breaker, plugged the UPS back into the outlet that it was using before, and everything is fine. This is a less than year old APC unit. Is there some fundamental incompatibility between this UPS and the AFCI? I'm wondering if the UPS tests for the presence of an earth ground (there is a "building wiring fault" light on it) and if so does that cause enough current to trip the AFCI? (I wouldn't have found this before, because the outlet into which it's currently plugged is not grounded but has the ground bootlegged to the neutral.) I've heard that some AFCIs are also GFCIs is why I'm asking. The AFCI is a Siemens Q115AF breaker in the breaker panel. I'll replace the receptacle in the morning (once it's light out) and see if that solves the problem, but I'm not sure what kind of fault could be in a receptacle that would cause a breaker, AFCI or not, to trip only when a load is connected to it but not when a plug is inserted. Does this mean also that I run the risk of having the AFCI trip if the surge protection of the UPS kicks in? Should I just give up the idea of having everything "to code" and ditch the AFCI and/or investigate the possibility of running a dedicated circuit to that bedroom to feed an outlet solely for the computer, not protected by the AFCI? any thoughts greatly appreciated... nate Is that circuit part of a three wire cable (Black, red, white) used for two circuits or is it just a two wire bx with the armor as the grounding conductor? It's two conductor BX with the armor grounded. AFCI circuit breakers are not required here in New Jersey, so I don't have much experience diagnosing problems with them. My thoughts are that your AFCI does not like the BX armor ground, there is something else going on with the BX cable, or it does not like your UPS. Have you tried plugging in another three prong appliance into the outlet? No, that outlet has been unused since we've moved in. It is however the first one in the circuit so the only possibilities I can see are that the AFCI is actually a GFCI as well (anyone know?) and there's enough current flowing through the real ground due to the UPS's fault sensing circuit, OR that there is a physical problem with that receptacle, which I'll be attempting to rule out shortly, now that the sun is up. (I've been on a program of replacing all the receptacles as soon as wiring "issues" are cleared, because a lot of the old receptacles were loose as well.) nate Update: I replaced the receptacle. when I turned the breaker back on it tripped immediately. I popped the cover on the panel and ohmed everything out, seemed OK although the resistance hot to ground was lower than I thought (~1 meg; nothing plugged in) although granted my meter is very old and possibly inaccurate. Everything seemed OK so I tried pulling the wires *leaving* the receptacle I'd just replaced. Then reset the breaker. Fine. Plugged in UPS. Fine. Reattached wires and replaced breaker with regular 15A breaker. Fine. Tried another AFCI breaker (I just so happened to have one laying around because I wanted to split the upstairs into two circuits eventually.) Tripped immediately. Removed the wires leaving the receptacle again, new AFCI did not trip. So what I apparently have is something is causing the AFCI to electronically trip but not because of overcurrent. It's got to be a wiring fault because I have everything unplugged. and all I know is that it is somewhere upstairs - one circuit serves the whole second floor, except for one outlet in the hallway (apparently intended for an air conditioner.) I'm not sure why it tripped only when I plugged the UPS in before, coincidence, or just reached some kind of threshold? who knows? F'ing great. Of course it's about 10 degrees outside, and I assume most of this wiring is in the attic. I'm a little too paranoid to just leave the regular 15A breaker in... or are the Siemens AFCI breakers known to be problematic? nate -- replace "fly" with "com" to reply. http://home.comcast.net/~njnagel |
#11
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AFCI and UPS?
Nate Nagel wrote:
Nate Nagel wrote: John Grabowski wrote: "Nate Nagel" wrote in message ... John Grabowski wrote: "Nate Nagel" wrote in message ... Hi all, got a weird issue. In an upstairs bedroom, I have a computer that is running off a UPS. After investigating the wiring in the house, I have found a significant number of grounds "bootlegged." Little by little I am picking away at them, but until spring, the upstairs will remain as is because it's darn cold in the attic at the moment. So here's the deal. I have determined that there is one properly grounded outlet in the room where the computer is, because that outlet is fed directly from the breaker panel, and that homerun is in BX not the cloth covered Romex that the rest of the concealed wiring is. So as a stopgap until I get around to fixing everything correctly I wanted to make sure that the computer's UPS was plugged into that particular outlet for proper surge protection. I bought a heavy extension cord, unplugged the UPS from the outlet that it was plugged into, plugged the extension cord into the correct outlet. Then I plugged the UPS into the extension cord, and the lights went out. Reset the breaker, figuring that I just made an arc, if I plugged it in faster it would be OK. Same effect. Reset the breaker, plugged the UPS back into the outlet that it was using before, and everything is fine. This is a less than year old APC unit. Is there some fundamental incompatibility between this UPS and the AFCI? I'm wondering if the UPS tests for the presence of an earth ground (there is a "building wiring fault" light on it) and if so does that cause enough current to trip the AFCI? (I wouldn't have found this before, because the outlet into which it's currently plugged is not grounded but has the ground bootlegged to the neutral.) I've heard that some AFCIs are also GFCIs is why I'm asking. The AFCI is a Siemens Q115AF breaker in the breaker panel. I'll replace the receptacle in the morning (once it's light out) and see if that solves the problem, but I'm not sure what kind of fault could be in a receptacle that would cause a breaker, AFCI or not, to trip only when a load is connected to it but not when a plug is inserted. Does this mean also that I run the risk of having the AFCI trip if the surge protection of the UPS kicks in? Should I just give up the idea of having everything "to code" and ditch the AFCI and/or investigate the possibility of running a dedicated circuit to that bedroom to feed an outlet solely for the computer, not protected by the AFCI? any thoughts greatly appreciated... nate Is that circuit part of a three wire cable (Black, red, white) used for two circuits or is it just a two wire bx with the armor as the grounding conductor? It's two conductor BX with the armor grounded. AFCI circuit breakers are not required here in New Jersey, so I don't have much experience diagnosing problems with them. My thoughts are that your AFCI does not like the BX armor ground, there is something else going on with the BX cable, or it does not like your UPS. Have you tried plugging in another three prong appliance into the outlet? No, that outlet has been unused since we've moved in. It is however the first one in the circuit so the only possibilities I can see are that the AFCI is actually a GFCI as well (anyone know?) and there's enough current flowing through the real ground due to the UPS's fault sensing circuit, OR that there is a physical problem with that receptacle, which I'll be attempting to rule out shortly, now that the sun is up. (I've been on a program of replacing all the receptacles as soon as wiring "issues" are cleared, because a lot of the old receptacles were loose as well.) nate Update: I replaced the receptacle. when I turned the breaker back on it tripped immediately. I popped the cover on the panel and ohmed everything out, seemed OK although the resistance hot to ground was lower than I thought (~1 meg; nothing plugged in) although granted my meter is very old and possibly inaccurate. Everything seemed OK so I tried pulling the wires *leaving* the receptacle I'd just replaced. Then reset the breaker. Fine. Plugged in UPS. Fine. Reattached wires and replaced breaker with regular 15A breaker. Fine. Tried another AFCI breaker (I just so happened to have one laying around because I wanted to split the upstairs into two circuits eventually.) Tripped immediately. Removed the wires leaving the receptacle again, new AFCI did not trip. So what I apparently have is something is causing the AFCI to electronically trip but not because of overcurrent. It's got to be a wiring fault because I have everything unplugged. and all I know is that it is somewhere upstairs - one circuit serves the whole second floor, except for one outlet in the hallway (apparently intended for an air conditioner.) I'm not sure why it tripped only when I plugged the UPS in before, coincidence, or just reached some kind of threshold? who knows? F'ing great. Of course it's about 10 degrees outside, and I assume most of this wiring is in the attic. I'm a little too paranoid to just leave the regular 15A breaker in... or are the Siemens AFCI breakers known to be problematic? nate Heh... all right, I feel dumb now. When I started to replace the receptacle, I plugged the UPS and the associated extension cord into a receptacle in the hallway which was on a different circuit. I just went upstairs to start pulling receptacles out of the wall to inspect the wiring/try to track down the presumed ground fault. Despite the fact that I thought I'd unplugged every appliance upstairs, what did I see at the first receptacle I came to, but a printer plugged in to a wall receptacle. It, of course, was connected (by a USB cable) to the computer that was connected to the UPS. I feel obligated to point out at this point that I did *not* connect it this way, and in fact, the reason that I feel particularly stupid is I was just explaining yesterday why it was important to connect all peripherals of a computer to either the same power strip or the same UPS so there's no issues with floating grounds etc. and voltage imbalances that end up going through USB or other ports. (was actually on my list of things to rectify.) I dug out another extension cord (the reason the printer was plugged into a different receptacle is that it is on the other side of the room from the computer desk) and plugged the printer into the back of the UPS on one of the "surge only" receptacles. All appears to be good now. I'm still not sure why the breaker tripped when I simply tried to move the UPS' power feed from one receptacle to another, unless the fact that the UPS now had a proper ground while the printer still had a bootlegged ground was enough to cause a problem. I ASSume that this little exercise does indeed confirm that the Siemens AFCI is also a GFCI... nate -- replace "fly" with "com" to reply. http://home.comcast.net/~njnagel |
#12
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AFCI and UPS?
On Feb 18, 10:56 am, Nate Nagel wrote:
Heh... all right, I feel dumb now. When I started to replace the receptacle, I plugged the UPS and the associated extension cord into a receptacle in the hallway which was on a different circuit. ... Despite the fact that I thought I'd unplugged every appliance upstairs, ....a printer plugged in to a wall receptacle. It, of course, was connected (by a USB cable) to the computer that was connected to the UPS. ... I was just explaining yesterday why it was important to connect all peripherals of a computer to either the same power strip or the same UPS so there's no issues with floating grounds etc. and voltage imbalances that end up going through USB or other ports. ... I dug out another extension cord ... and plugged the printer into the back of the UPS on one of the "surge only" receptacles. All appears to be good now. I'm still not sure why the breaker tripped when I simply tried to move the UPS' power feed from one receptacle to another, unless the fact that the UPS now had a proper ground while the printer still had a bootlegged ground was enough to cause a problem. I ASSume that this little exercise does indeed confirm that the Siemens AFCI is also a GFCI... Yes the AFCI is a GFCI (plus). What the USB printer is plugged into should make no difference. Implied is that something is leaking via the printer. Printer on another circuit is not desireable only because backup protection is missing. But if working properly, powering from both circuits should not have contributed to AGFI tripping. Meanwhile, temporarily disconnect neutral wire and safety ground wire of the AGFI circuit in mains box. Infinite ohms should exist between those two wires. Also infinite ohms should exist between that disconnected neutral and mains box. All tests best performed with AC electric off so that leakage and other problems do not distort that ohm meter reading nor harm meter. Disconnected safety ground might or might not conduct to mains box - that is acceptable. But disconnected neutral must not measure conductivity to disconnected safety ground nor to mains box (test obviously done with appliances unplugged). One final test. Ohm meter test (use extension cord to measure this) should measure conductivity from receptacle safety ground prong to disconnected safety ground wire in mains box. If this conductivity does not exist, then that test explains everything seen previously and suggests problem still exists. Testing appliances (computer and printer) on another GFCI circuit, and tested with computer and printer split between GFCI and non-GFCI circuits should still be performed as posted earlier. Information from that test is necessary - and would provide more useful information for many reasons including because GFCI trips at only 5 ma. AGFIs have been required for years now in New Jersey on bedroom circuits. |
#13
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AFCI and UPS?
w_tom wrote:
On Feb 18, 10:56 am, Nate Nagel wrote: Heh... all right, I feel dumb now. When I started to replace the receptacle, I plugged the UPS and the associated extension cord into a receptacle in the hallway which was on a different circuit. ... Despite the fact that I thought I'd unplugged every appliance upstairs, ....a printer plugged in to a wall receptacle. It, of course, was connected (by a USB cable) to the computer that was connected to the UPS. ... I was just explaining yesterday why it was important to connect all peripherals of a computer to either the same power strip or the same UPS so there's no issues with floating grounds etc. and voltage imbalances that end up going through USB or other ports. ... I dug out another extension cord ... and plugged the printer into the back of the UPS on one of the "surge only" receptacles. All appears to be good now. I'm still not sure why the breaker tripped when I simply tried to move the UPS' power feed from one receptacle to another, unless the fact that the UPS now had a proper ground while the printer still had a bootlegged ground was enough to cause a problem. I ASSume that this little exercise does indeed confirm that the Siemens AFCI is also a GFCI... Yes the AFCI is a GFCI (plus). What the USB printer is plugged into should make no difference. Implied is that something is leaking via the printer. Printer on another circuit is not desireable only because backup protection is missing. But if working properly, powering from both circuits should not have contributed to AGFI tripping. all I can say is that it apparently did, because moving the power source to the UPS solved the problem. I printed a test page after hooking everything back up, so there appears to be no damage (thank you AFCI) Meanwhile, temporarily disconnect neutral wire and safety ground wire of the AGFI circuit in mains box. Infinite ohms should exist between those two wires. Also infinite ohms should exist between that disconnected neutral and mains box. All tests best performed with AC electric off so that leakage and other problems do not distort that ohm meter reading nor harm meter. Disconnected safety ground might or might not conduct to mains box - that is acceptable. But disconnected neutral must not measure conductivity to disconnected safety ground nor to mains box (test obviously done with appliances unplugged). One final test. Ohm meter test (use extension cord to measure this) should measure conductivity from receptacle safety ground prong to disconnected safety ground wire in mains box. If this conductivity does not exist, then that test explains everything seen previously and suggests problem still exists. I can't disconnect the "safety ground" because it grounds to the breaker box through the cable clamp... there's no separate ground conductor in the BX. (the wiring is cloth covered as well, and appears to be tinned, to give you an idea of the age of the stuff I'm dealing with.) I will test hot and neutral just to satisfy my curiosity however now that I have located *all* the appliances that were plugged in and can disconnect them all... When I get around to rewiring the second floor, I may see if I can drop a new homerun to the box, but I'm guessing that the BX has at least one hidden staple somewhere along the way. It'd be nice if I could do that though, because then I'd just pull some 12/2WG Romex and switch to a 20A breaker (assuming that everything else on that circuit is accessable from the attic.) Testing appliances (computer and printer) on another GFCI circuit, and tested with computer and printer split between GFCI and non-GFCI circuits should still be performed as posted earlier. Information from that test is necessary - and would provide more useful information for many reasons including because GFCI trips at only 5 ma. I could try that... I'd have to actually wire in a GFCI receptacle upstairs though, would be easier than moving all the equipment to the basement or kitchen (I actually do have a couple laying around though for future use in garage etc. so it's not a huge deal.) AGFIs have been required for years now in New Jersey on bedroom circuits. They've probably been required here for years as well, I don't think this house has had any electrical upgrades in the last 20 years however (previous owners were not really DIY types, and were here 18 years - while the owner before that was apparently a contractor, so I'm guessing he is responsible for a lot of the work) and I'm guessing that the work wasn't inspected then, ref: bootlegged grounds mentioned above. nate -- replace "fly" with "com" to reply. http://home.comcast.net/~njnagel |
#14
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AFCI and UPS?
"Nate Nagel" wrote in message ... Charles Schuler wrote: AFCIs are rather new. Any installation that new should not have faked grounds. Did you mean GFCIs? No, I put the AFCI in myself after purchasing the house. Unless the authorities "know" about what you are doing, I suggest you replace the AFCI with either a normal breaker or jus a GFCI breaker. The AFCI is quickly developing a reputation among the "pros" as something that will cause the homeowner to make a lot of trips between the bedroom and the basement. If the NEC really, really considered arc faults to be a special danger in bedrooms, it should have considered making arc detection set off an alarm rather than cutting off the power. This scheme (AFCI for bedroom circuits) is the equivalent of having a smoke detector turn off the lights rather than just make a loud noise. |
#15
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AFCI and UPS?
On Sun, 18 Feb 2007 22:41:04 -0500, "John Gilmer"
wrote: "Nate Nagel" wrote in message ... Charles Schuler wrote: AFCIs are rather new. Any installation that new should not have faked grounds. Did you mean GFCIs? No, I put the AFCI in myself after purchasing the house. Unless the authorities "know" about what you are doing, I suggest you replace the AFCI with either a normal breaker or jus a GFCI breaker. The AFCI is quickly developing a reputation among the "pros" as something that will cause the homeowner to make a lot of trips between the bedroom and the basement. If the NEC really, really considered arc faults to be a special danger in bedrooms, it should have considered making arc detection set off an alarm rather than cutting off the power. This scheme (AFCI for bedroom circuits) is the equivalent of having a smoke detector turn off the lights rather than just make a loud noise. you're supposed to light a candle :-) -- Mark Lloyd http://notstupid.laughingsquid.com "Unlike biological evolution. 'intelligent design' is not a genuine scientific theory and, therefore, has no place in the curriculum of our nation's public school classes." -- Ted Kennedy |
#16
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AFCI and UPS?
w_tom wrote:
Second, that plug-in protector is too far from earth AND is hoping to earth via a wire bundled with other wires. Just two in a long list of reasons why a power strip protector does not even claim (in numerical specifications) protection from surges that would cause damage. The length of that earthing wire (a short distance to earth and a significantly long distance between computer and surge protector) has long been necessary for effective protection. Complete bullcrap. Manufacturer specs for protection are readily available for plug-in suppressors. Both the IEEE guide on surges and surge protection at: http://www.mikeholt.com/files/PDF/Li...ion_May051.pdf and the NIST guide at: http://www.nist.gov/public_affairs/p.../surgesfnl.pdf say that plug-in suppressors are effective. Plug-in suppressors, as explained in the IEEE guide, work primarily by clamping the voltage on all wires (power and signal) to the common ground at the suppressor. They do not work primarily by earthing. -- bud-- |
#17
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AFCI and UPS?
This scheme (AFCI for bedroom circuits) is the equivalent of having a smoke detector turn off the lights rather than just make a loud noise. you're supposed to light a candle :-) I was a little too hard on the NEC. The AFCI will cut off a circuit well before a loose connection gets hot enough to actually be a safety problem. It does happen. I found a loose wire when I realized that a plug for a lamp was WARM. Years ago the fire department responded to a small fire from a "hot" outlet. I hope that withing a few years the AFCI manufacturers/NEC will sort things out. In the past the NEC as paid attention to the problems of false tripping. For the time being, I would suggest that folks don't volunteer to get them installed. -- Mark Lloyd http://notstupid.laughingsquid.com "Unlike biological evolution. 'intelligent design' is not a genuine scientific theory and, therefore, has no place in the curriculum of our nation's public school classes." -- Ted Kennedy |
#18
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AFCI and UPS?
John Gilmer wrote:
This scheme (AFCI for bedroom circuits) is the equivalent of having a smoke detector turn off the lights rather than just make a loud noise. you're supposed to light a candle :-) I was a little too hard on the NEC. The AFCI will cut off a circuit well before a loose connection gets hot enough to actually be a safety problem. The AFCIs out there now detect parallel arcs - line to neutral or ground (a fault). They don't detect a loose connection - a series arc. Series arc protection is required starting Jan 2008. Far as I know these devices are not yet on the market. Parallel arcs can draw high current and I have read AFCIs detect pulses around 60A. Series arcs are limited by the load (will usually be lower than the breaker amp rating) and should be much harder to detect and separate from "normal" arcs. It does happen. I found a loose wire when I realized that a plug for a lamp was WARM. Years ago the fire department responded to a small fire from a "hot" outlet. I hope that withing a few years the AFCI manufacturers/NEC will sort things out. In the past the NEC as paid attention to the problems of false tripping. For the time being, I would suggest that folks don't volunteer to get them installed. Starting in the 2008 code AFCIs will be required on all 15 & 20A 120V residential branch circuits. Coincidentally these will be the new AFCIs that include series arc detection that aren't yet on the market - large numbers of devices with inadequate field experience will be installed. In this instance perhaps you aren't hard enough on the NEC. It will be interesting if all the panel manufacturers even have the new AFCIs by 2008. At least the AFCIs out there now have a track record. Advice about not volunteering sounds much better for the new AFCIs. -- bud-- |
#19
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AFCI and UPS?
Starting in the 2008 code AFCIs will be required on all 15 & 20A 120V residential branch circuits. Coincidentally these will be the new AFCIs that include series arc detection that aren't yet on the market - large numbers of devices with inadequate field experience will be installed. In this instance perhaps you aren't hard enough on the NEC. It will be interesting if all the panel manufacturers even have the new AFCIs by 2008. At least the AFCIs out there now have a track record. Advice about not volunteering sounds much better for the new AFCIs. I guess I don't understand WTF is going on. A "series" fault is, exactly, what? My hope is that the gadgets detect a loose connection that might result in something overheating. What, exactly, DOES the gadget detect? |
#20
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AFCI and UPS?
On Feb 21, 12:15 pm, "John Gilmer" wrote:
A "series" fault is, exactly, what? My hope is that the gadgets detect a loose connection that might result in something overheating. What, exactly, DOES the gadget detect? Often bedrooms have devices plugged in using a two wire (zip cord) extension wire. The bed continuously rolls over that wire until eventually the wire arcs - causes a fire. AFCI will detect that short and cut off power before an arc can cause a fire. This is why AFCIs are required for all bedroom circuits. However, if you use a real Christmas tree, then the outlet that powers lights on that tree should also have an AFCI so that a short and resulting arc in Christmas tree lights do not create a fire. A Christmas tree fire created when his wife only turned on lights took out the entire house - killed almost all pets - in but 5 minutes. These are arcs that kill and that an AFCI quashes. |
#21
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AFCI and UPS?
John Gilmer wrote:
Starting in the 2008 code AFCIs will be required on all 15 & 20A 120V residential branch circuits. Coincidentally these will be the new AFCIs that include series arc detection that aren't yet on the market - large numbers of devices with inadequate field experience will be installed. In this instance perhaps you aren't hard enough on the NEC. It will be interesting if all the panel manufacturers even have the new AFCIs by 2008. At least the AFCIs out there now have a track record. Advice about not volunteering sounds much better for the new AFCIs. I guess I don't understand WTF is going on. A "series" fault is, exactly, what? My hope is that the gadgets detect a loose connection that might result in something overheating. What, exactly, DOES the gadget detect? You can view arcs as being of 2 kinds. One is from a hot wire to a neutral or ground wire. This is called a parallel arc. The possible arc current is the available fault current which can be very high. w_tom describes a fire source from a parallel arc. AFCIs now detect only parallel arcs. The other kind of arc is from a loose connection, like a worn out receptacle that loosly grips a plug. This is a series arc; it is in series with the circuit. It is not a "fault" as it is not across the source. AFCIs now look for high current pulses, maybe 60A. The current in a series arc is limited to the load current, and that is far too low to be detected by AFCIs now sold. As I said previously, detecting a series arc at load current levels is probably not easy and differentiating from "normal" arcs (switches, brush motors) is probably very difficult. Waveform "signatures" are used now, and analysis should be much more sophisticated in series AFCIs. I was surprised when I learned AFCIs detect only parallel arcs, but fault is the F in AFCI. Starting 1-1-08 the NEC requires AFCIs installed (produced?sold?) to detect both series and parallel arcs. I heard SquareD just announced them on its web site - don't know if they are actually available. And when the 2008 NEC comes to your turf, AFCIs (the new ones) will be required on all new 15 & 20A 120V residential branch circuits (except alarm panels). The NEC (and UL) refer to the AFCIs used now that are parallel only as "branch/feeder AFCIs" and the new series-parallel ones as "combination type AFCIs". I'm sure it was obvious from the name which ones detected parallel and which detected series arcs. Far as I know, AFCIs sold now are also required to have 30mA ground-fault detection. (This is not the same level as the 5mA detection of a GFCI.) I think the logic is arcs may go from H-N to include ground if a ground is present. There is an interesting paper at: http://www.eatonelectrical.com/unsec...ESTIGATION.PDF on "glowing connections" (series arcs) at receptacle binding screws that may (or may not) eventually cause a trip with a parallel AFCI on the ground fault function. Devices can obviously be made with both AFCI and 5mA GFCI detection. I believe they will have 2 test buttons. AFCIs came out of work done at UL sponsored by the Consumer Product Safety Commission, which was interested in reducing the number of fires. An interesting paper from the Consumer Product Safety Commission on AFCIs is at: http://www.cpsc.gov/volstd/afci/AFCIFireTechnology.pdf It explains the rationalle for using AFCIs, and why normal circuit breakers aren't adequate. It also describes how AFCIs work. It is technical enough you may like it. -- bud-- |
#22
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AFCI and UPS?
w_tom wrote:
On Feb 21, 12:15 pm, "John Gilmer" wrote: A "series" fault is, exactly, what? My hope is that the gadgets detect a loose connection that might result in something overheating. What, exactly, DOES the gadget detect? Often bedrooms have devices plugged in using a two wire (zip cord) extension wire. The bed continuously rolls over that wire until eventually the wire arcs - causes a fire. AFCI will detect that short and cut off power before an arc can cause a fire. This is why AFCIs are required for all bedroom circuits. However, if you use a real Christmas tree, then the outlet that powers lights on that tree should also have an AFCI so that a short and resulting arc in Christmas tree lights do not create a fire. A Christmas tree fire created when his wife only turned on lights took out the entire house - killed almost all pets - in but 5 minutes. These are arcs that kill and that an AFCI quashes. More simply stated, they detect when something causes an arc, e.g. a spark and they then open the ckt. |
#23
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AFCI and UPS?
You can view arcs as being of 2 kinds. One is from a hot wire to a neutral or ground wire. This is called a parallel arc. The possible arc current is the available fault current which can be very high. w_tom describes a fire source from a parallel arc. AFCIs now detect only parallel arcs. Why bother? That type of arc will also trip the breaker. Seems to me that NEC has "outsmarted" itself. The other kind of arc is from a loose connection, like a worn out receptacle that loosly grips a plug. This is a series arc; it is in series with the circuit. It is not a "fault" as it is not across the source. AFCIs now look for high current pulses, maybe 60A. The current in a series arc is limited to the load current, and that is far too low to be detected by AFCIs now sold. As I said previously, detecting a series arc at load current levels is probably not easy and differentiating from "normal" arcs (switches, brush motors) is probably very difficult. Waveform "signatures" are used now, and analysis should be much more sophisticated in series AFCIs. I was surprised when I learned AFCIs detect only parallel arcs, but fault is the F in AFCI. Starting 1-1-08 the NEC requires AFCIs installed (produced?sold?) to detect both series and parallel arcs. I heard SquareD just announced them on its web site - don't know if they are actually available. And when the 2008 NEC comes to your turf, AFCIs (the new ones) will be required on all new 15 & 20A 120V residential branch circuits (except alarm panels). The NEC (and UL) refer to the AFCIs used now that are parallel only as "branch/feeder AFCIs" and the new series-parallel ones as "combination type AFCIs". I'm sure it was obvious from the name which ones detected parallel and which detected series arcs. Far as I know, AFCIs sold now are also required to have 30mA ground-fault detection. (This is not the same level as the 5mA detection of a GFCI.) I think the logic is arcs may go from H-N to include ground if a ground is present. There is an interesting paper at: http://www.eatonelectrical.com/unsec...ESTIGATION.PDF on "glowing connections" (series arcs) at receptacle binding screws that may (or may not) eventually cause a trip with a parallel AFCI on the ground fault function. Devices can obviously be made with both AFCI and 5mA GFCI detection. I believe they will have 2 test buttons. AFCIs came out of work done at UL sponsored by the Consumer Product Safety Commission, which was interested in reducing the number of fires. An interesting paper from the Consumer Product Safety Commission on AFCIs is at: http://www.cpsc.gov/volstd/afci/AFCIFireTechnology.pdf It explains the rationalle for using AFCIs, and why normal circuit breakers aren't adequate. It also describes how AFCIs work. It is technical enough you may like it. -- bud-- |
#24
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AFCI and UPS?
On Feb 22, 7:08 pm, "John Gilmer" wrote:
One is from a hot wire to a neutral or ground wire. This is called a parallel arc. The possible arc current is the available fault current which can be very high. w_tom describes a fire source from a parallel arc. AFCIs now detect only parallel arcs. Why bother? That type of arc will also trip the breaker. If that were true, then the Christmas tree fire would not have taken out the entire house in only five minutes. A conventional circuit breaker trips after the fire has started. This fire is why AFCIs are now required for bedrooms - where an sleeping occupant has the least warning time; where such a fire can be most fatal. |
#25
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AFCI and UPS?
John Gilmer wrote:
You can view arcs as being of 2 kinds. One is from a hot wire to a neutral or ground wire. This is called a parallel arc. The possible arc current is the available fault current which can be very high. w_tom describes a fire source from a parallel arc. AFCIs now detect only parallel arcs. Why bother? That type of arc will also trip the breaker. Seems to me that NEC has "outsmarted" itself. A short circuit will trip the breaker but this is an arc. Ideally the breaker would trip "instantaneously", but that takes a lot of current. The available fault current in an extension cord may not be high enough to trip a breaker on "instantaneous". If it is high enough, the arc is not necessarily continuous and the breaker still may not trip on "instantaneous". And an arc is not a short circuit - the current will be less than the available fault current. That often leaves the breaker in its inverse-time mode. With a constant load of 30A on a 15A breaker, for example, the breaker may not trip for 2 minutes. The time delay likely with an arc leaves opportunity for the arc to start a fire. AFCIs were developed to detect an arc and provide a fast trip. The NEC requirement for AFCIs was based on research done by UL for the CPSC. When the research was done AFCIs didn't exist. The CPSC, UL and the NFPA (author of the NEC) think parallel AFCIs can prevent a significant percentage of fires with electrical causes, estimated at 40,000 per year. The information above is a part of that contained at http://www.cpsc.gov/volstd/afci/AFCIFireTechnology.pdf The link contains a more detailed explanation of why circuit breakers aren't adequate. -- bud-- The other kind of arc is from a loose connection, like a worn out receptacle that loosly grips a plug. This is a series arc; it is in series with the circuit. It is not a "fault" as it is not across the source. AFCIs now look for high current pulses, maybe 60A. The current in a series arc is limited to the load current, and that is far too low to be detected by AFCIs now sold. As I said previously, detecting a series arc at load current levels is probably not easy and differentiating from "normal" arcs (switches, brush motors) is probably very difficult. Waveform "signatures" are used now, and analysis should be much more sophisticated in series AFCIs. I was surprised when I learned AFCIs detect only parallel arcs, but fault is the F in AFCI. Starting 1-1-08 the NEC requires AFCIs installed (produced?sold?) to detect both series and parallel arcs. I heard SquareD just announced them on its web site - don't know if they are actually available. And when the 2008 NEC comes to your turf, AFCIs (the new ones) will be required on all new 15 & 20A 120V residential branch circuits (except alarm panels). The NEC (and UL) refer to the AFCIs used now that are parallel only as "branch/feeder AFCIs" and the new series-parallel ones as "combination type AFCIs". I'm sure it was obvious from the name which ones detected parallel and which detected series arcs. Far as I know, AFCIs sold now are also required to have 30mA ground-fault detection. (This is not the same level as the 5mA detection of a GFCI.) I think the logic is arcs may go from H-N to include ground if a ground is present. There is an interesting paper at: http://www.eatonelectrical.com/unsec...ESTIGATION.PDF on "glowing connections" (series arcs) at receptacle binding screws that may (or may not) eventually cause a trip with a parallel AFCI on the ground fault function. Devices can obviously be made with both AFCI and 5mA GFCI detection. I believe they will have 2 test buttons. AFCIs came out of work done at UL sponsored by the Consumer Product Safety Commission, which was interested in reducing the number of fires. An interesting paper from the Consumer Product Safety Commission on AFCIs is at: http://www.cpsc.gov/volstd/afci/AFCIFireTechnology.pdf It explains the rationalle for using AFCIs, and why normal circuit breakers aren't adequate. It also describes how AFCIs work. It is technical enough you may like it. -- bud-- |
#26
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AFCI and UPS?
If that were true, then the Christmas tree fire would not have taken out the entire house in only five minutes. A conventional circuit breaker trips after the fire has started. This fire is why AFCIs are now required for bedrooms - where an sleeping occupant has the least warning time; where such a fire can be most fatal. Huh? Unless there is something to limit the current, arcs tend to ramp up in current demands. Perhaps I am missing something here but I would be hard pressed to create an "arc" between HOT and NEUTRAL (or ground) that would NOT trip a conventional breaker. A "direct" arc would not have anything to limit the current. |
#27
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AFCI and UPS?
A short circuit will trip the breaker but this is an arc. Ideally the breaker would trip "instantaneously", but that takes a lot of current. A lot? With a 15 amp breaker, a 30 amp arc should cause a trip within a few seconds. The available fault current in an extension cord may not be high enough to trip a breaker on "instantaneous". Oh! Now we are speaking the same language. Is the NEC worried that some of that crappy lamp cord has enough resistance to limit current flow to less than, say, 30 amps when subject to essentially a direct short? If it is high enough, the arc is not necessarily continuous and the breaker still may not trip on "instantaneous". And an arc is not a short circuit - the current will be less than the available fault current. An arc is quite close to being a short circuit. To a good approximate, an arc can be modeled as a "short" with a fixed voltage drop that stays about the same regardless of current. That voltage drop is only a few volts but even if it were, say, 20 volts, the line cord would have to soak at 100 volts and to get a 100 volt drop in a line cord would take enough amps to trip a breaker. That often leaves the breaker in its inverse-time mode. With a constant load of 30A on a 15A breaker, for example, the breaker may not trip for 2 minutes. That long? OK, then why not require breakers that "magnetic trip" at a current closer the the rating for bedroom circuits? Or require a shorter "heat" trip time? The time delay likely with an arc leaves opportunity for the arc to start a fire. AFCIs were developed to detect an arc and provide a fast trip. The NEC requirement for AFCIs was based on research done by UL for the CPSC. When the research was done AFCIs didn't exist. The CPSC, UL and the NFPA (author of the NEC) think parallel AFCIs can prevent a significant percentage of fires with electrical causes, estimated at 40,000 per year. Just WHAT is that "significant percentage?" If it's only, say, 10% then I say the AFCI is a WASTE. |
#28
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AFCI and UPS?
On Feb 23, 9:57 pm, "John Gilmer" wrote:
Perhaps I am missing something here but I would be hard pressed to create an "arc" between HOT and NEUTRAL (or ground) that would NOT trip a conventional breaker. A "direct" arc would not have anything to limit the current. Remember another parameter - time. Conventional circuit breakers trip after significant energy has been dissipated at the arc. To better appreciate how circuit breakers and fuses work, lean about a famous 'I squared t' rule. Does a 20 amp circuit breaker trip or fuse blow immediately when current is 25 amps? No. Visit application notes from fuse manufacturers such as Littelfuse to learn that 'I^2t" rule and to appreciate why fuses / circuit breakers don't trip fast enough to quash an arc. Notice how long it takes a 20 amp circuit breaker to trip when conducting 25 amps. |
#29
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AFCI and UPS?
John Gilmer wrote:
A short circuit will trip the breaker but this is an arc. Ideally the breaker would trip "instantaneously", but that takes a lot of current. A lot? With a 15 amp breaker, a 30 amp arc should cause a trip within a few seconds. Might help if you read http://www.cpsc.gov/volstd/afci/AFCIFireTechnology.pdf hereafter called "the paper". The paper quotes the UL standard as only requiring a trip in 2 minutes at 200% of rated current. Looking at the time-current curve for SquareD breakers, at 200% a trip can take 40 seconds. Breakers work on a thermal element to trip and it takes longer the lower the overload - hence "inverse-time element". They also have a magnetic trip for "instantaneous". The available fault current in an extension cord may not be high enough to trip a breaker on "instantaneous". Oh! Now we are speaking the same language. Is the NEC worried that some of that crappy lamp cord has enough resistance to limit current flow to less than, say, 30 amps when subject to essentially a direct short? From the paper: UL field tested 1,590 receptacles in 80 dwellings to determine the available fault current at the receptacle. 16% of the receptacles would likely not trip on "instantaneous" with a short at the receptacle. 44% of the receptacles would not trip on "instantaneous" with a short at the end of a 6' of #18 cord. For a SquareD breaker, a 15A breaker may require up to 11 times the rated current to trip "instantaneously". That is 165A for a 15A breaker. More than 16% of the surveyed receptacles would not supply 165A. Not tripping on "instantaneous" puts the trip on the inverse-time curve. And this was for a short. An arc reduces the current further, slowing the trip. "Crappy" #18 is widely used for extension cords and appliances. If it is high enough, the arc is not necessarily continuous and the breaker still may not trip on "instantaneous". And an arc is not a short circuit - the current will be less than the available fault current. An arc is quite close to being a short circuit. To a good approximate, an arc can be modeled as a "short" with a fixed voltage drop that stays about the same regardless of current. That voltage drop is only a few volts but even if it were, say, 20 volts, the line cord would have to soak at 100 volts and to get a 100 volt drop in a line cord would take enough amps to trip a breaker. An arc may involve material that has been carbonized - which can run on a lower current. And "parallel arcing faults have erratic current flow" which reduces the current value. That often leaves the breaker in its inverse-time mode. With a constant load of 30A on a 15A breaker, for example, the breaker may not trip for 2 minutes. That long? Yes - see above. OK, then why not require breakers that "magnetic trip" at a current closer the the rating for bedroom circuits? Or require a shorter "heat" trip time? Lower "instantaneuos" ratings can cause nuisance trips for motors and lights which draw about 6x full load when they start. This is covered in the paper - it was considered. The time delay likely with an arc leaves opportunity for the arc to start a fire. AFCIs were developed to detect an arc and provide a fast trip. The NEC requirement for AFCIs was based on research done by UL for the CPSC. When the research was done AFCIs didn't exist. The CPSC, UL and the NFPA (author of the NEC) think parallel AFCIs can prevent a significant percentage of fires with electrical causes, estimated at 40,000 per year. Just WHAT is that "significant percentage?" If it's only, say, 10% then I say the AFCI is a WASTE. I would say 10%, 4,000 fires a year, would be well worth it. Consider deaths and injuries. And the cost of medical for burns and cost of building loss, which of course we all pay for. There was a "cost-benefit" analysis done - so the requirement for AFCIs in bedrooms had some grounding, if you'll excuse the expression. I think the extension to all 15 & 20A circuits is a lot more questionable. Particularly since the new series/parallel devices are barely on the market (if at all) 10 months before they are required for widespread use. Incidentally - parallel arcs were considered more dangerous than series because the current availble was much higher than a series arc. -- bud-- |
#30
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AFCI and UPS?
"w_tom" wrote in message oups.com... On Feb 23, 9:57 pm, "John Gilmer" wrote: Perhaps I am missing something here but I would be hard pressed to create an "arc" between HOT and NEUTRAL (or ground) that would NOT trip a conventional breaker. A "direct" arc would not have anything to limit the current. Remember another parameter - time. Conventional circuit breakers trip after significant energy has been dissipated at the arc. To better appreciate how circuit breakers and fuses work, lean about a famous 'I squared t' rule. Does a 20 amp circuit breaker trip or fuse blow immediately when current is 25 amps? No. Visit application notes from fuse manufacturers such as Littelfuse to learn that 'I^2t" rule and to appreciate why fuses / circuit breakers don't trip fast enough to quash an arc. Notice how long it takes a 20 amp circuit breaker to trip when conducting 25 amps. 1) Why would anyone want a 20 amp circuit in a bedroom? 2) All this ASSumes that suddenly, in the middle of the night, a fault occurs that draws more than 20 amps but less than, what, 30 amps. A "magic short" as it were. But this "magic short" is supposed to have the "signature" of an arc. What we have is a 4 kW heat source. In the several minutes it takes to trip the breaker, this "magic short" is supposed to set the house of fire without setting off any of the smoke detectors. Frankly, it "reads" like Bull Sh*t. I suspect that some "wise guy" is making BIG money from this nonsense. Slight OT: Some 30 years ago I used the then relatively new SOFT contact lenses. Every evening I took them out and cleaned them and they boilding them in a salt solution. I had no problem for over a year. I made the salt solution from little tablets given by the optician and mixed it with bottled distilled water in a small bottle than held the correct amount of water. BUT, the federal government decided that commercial "distilled" water mixed with salt pills (which cost about $.01 each) wasn't "safe." It ordered the "salt" pills (of a premeasured size) off the market and essentially forced contact lens wearers to use a "commercial" solution that, amoung other things, user a Mercury compound as a preservative. My eyes were quite sensitive to the Mercury so I gave up on contacts. BUT the "rest of the story" is that the bureaucrat responsible for the silly rule had relatives who were in the business of "packaging" the mercury preserved contact lens solution. The bureaucrat ended up doing some hard time but that didn't do me any good. When "they" decided that R-12 was bad for the ozone hole, the makers of R-12 quickly had EXPENSIVE replacements. IOW: it was the BIG chemical companies who are behind the "ozone hole" nonsense. |
#31
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AFCI and UPS?
"Bud--" wrote in message .. . John Gilmer wrote: A short circuit will trip the breaker but this is an arc. Ideally the breaker would trip "instantaneously", but that takes a lot of current. A lot? With a 15 amp breaker, a 30 amp arc should cause a trip within a few seconds. Might help if you read http://www.cpsc.gov/volstd/afci/AFCIFireTechnology.pdf hereafter called "the paper". The paper quotes the UL standard as only requiring a trip in 2 minutes at 200% of rated current. Looking at the time-current curve for SquareD breakers, at 200% a trip can take 40 seconds. Frankly, that's "gud enuf." Your AFCI causes a lot of problems to protect us from "magic shorts" which draw from 100 to 200% of the breaker rating and have the correct "signature. Breakers work on a thermal element to trip and it takes longer the lower the overload - hence "inverse-time element". They also have a magnetic trip for "instantaneous". So? The NEC would have specified a class of breakers with the "magnetic" trip point closed to the rating and a shorter time constant for the thermal trip. That would have solved the problem cheaply....But NO! |
#32
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AFCI and UPS?
On Fri, 23 Feb 2007 21:57:50 -0500, "John Gilmer"
wrote: If that were true, then the Christmas tree fire would not have taken out the entire house in only five minutes. A conventional circuit breaker trips after the fire has started. This fire is why AFCIs are now required for bedrooms - where an sleeping occupant has the least warning time; where such a fire can be most fatal. Huh? Unless there is something to limit the current, arcs tend to ramp up in current demands. Perhaps I am missing something here but I would be hard pressed to create an "arc" between HOT and NEUTRAL (or ground) that would NOT trip a conventional breaker. A "direct" arc would not have anything to limit the current. The resistance of the conductors would limit the current. -- Mark Lloyd http://notstupid.laughingsquid.com "Unlike biological evolution. 'intelligent design' is not a genuine scientific theory and, therefore, has no place in the curriculum of our nation's public school classes." -- Ted Kennedy |
#33
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AFCI and UPS?
On Sat, 24 Feb 2007 07:19:11 -0500, "John Gilmer"
wrote: "w_tom" wrote in message roups.com... On Feb 23, 9:57 pm, "John Gilmer" wrote: Perhaps I am missing something here but I would be hard pressed to create an [snip] 1) Why would anyone want a 20 amp circuit in a bedroom? Electric heater as well as lamp, TV, fan etc... could be too much for 15A. [snip] -- Mark Lloyd http://notstupid.laughingsquid.com "Unlike biological evolution. 'intelligent design' is not a genuine scientific theory and, therefore, has no place in the curriculum of our nation's public school classes." -- Ted Kennedy |
#34
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AFCI and UPS?
John Gilmer wrote:
"Bud--" wrote in message .. . John Gilmer wrote: A short circuit will trip the breaker but this is an arc. Ideally the breaker would trip "instantaneously", but that takes a lot of current. A lot? With a 15 amp breaker, a 30 amp arc should cause a trip within a few seconds. Might help if you read http://www.cpsc.gov/volstd/afci/AFCIFireTechnology.pdf hereafter called "the paper". The paper quotes the UL standard as only requiring a trip in 2 minutes at 200% of rated current. Looking at the time-current curve for SquareD breakers, at 200% a trip can take 40 seconds. Frankly, that's "gud enuf." Fires can easily start in 40 seconds of parallel arcing. And parallel arc doesn't necessarily cause a trip in 40 seconds. Breakers work on a thermal element to trip and it takes longer the lower the overload - hence "inverse-time element". They also have a magnetic trip for "instantaneous". So? The NEC would have specified a class of breakers with the "magnetic" trip point closed to the rating and a shorter time constant for the thermal trip. That would have solved the problem cheaply....But NO! "Lower 'instantaneuos' ratings can cause nuisance trips for motors and lights which draw about 6x full load when they start. This is covered in the paper - it was considered." Faster thermal trip would probably be an ever bigger problem with nuisance trips. -- bud-- |
#35
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AFCI and UPS?
"Bud--" So? The NEC would have specified a class of breakers with the "magnetic" trip point closed to the rating and a shorter time constant for the thermal trip. That would have solved the problem cheaply....But NO! "Lower 'instantaneuos' ratings can cause nuisance trips for motors and lights which draw about 6x full load when they start. This is covered in the paper - it was considered." Faster thermal trip would probably be an ever bigger problem with nuisance trips. This is getting circular. The AFCIs are required in "NEW" construction. So far as I know, there isn't any requirement that they be retrofitted in existing homes. Yet the justification for them (over a more effective solution) is that a "new" bedroom would have a room air conditioner and an electric heater, neither of which (so the claim) could work on a 15 amp circuit. No matter how you slice it, it's still .... Again, I bet is 2 or 3 jails the "real reason" will become known. Odds are that when someone checks our who benefited from the rule someone might end up in jail. |
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