need to downgrade breaker (from 40amp to 15amp) for new hvac?
Hello,
I recently had a home inspection in preparation for selling my house. The inspector informed the buyer that I need to downgrade the circuit breaker (from 40amp to 15amp) for new hvac? He said he sees this problem a lot. My father, who does a lot of DIY including some electrical, says that if we change to 15amp when the hvac switches to aux. heat it will blow the breaker? I need to find out if this really needs to be changed, the inspector warned the hvac unit could be damaged if this isn't changed. But I don't want to have the change done if it will cause problems when the unit goes to aux heat. I'd call the hvac installer, but, clearly, they didn't think it was necessary to change the breaker & I'd really like an independent opinion on this. ALSO, is changing a breaker best left to an electrician or might this be something we could do ourselves? Thanks in advance for any input. WJ |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
If the unit has an electric heating element in it that requires a 40 amp
feeder, you don't want to change it. It may be possible that two feeds are required, one for the blower and a separate one for the heater and your father installed an improper jumper to feed both. I would call a local electrician to give a look wrote in message ups.com... Hello, I recently had a home inspection in preparation for selling my house. The inspector informed the buyer that I need to downgrade the circuit breaker (from 40amp to 15amp) for new hvac? He said he sees this problem a lot. My father, who does a lot of DIY including some electrical, says that if we change to 15amp when the hvac switches to aux. heat it will blow the breaker? I need to find out if this really needs to be changed, the inspector warned the hvac unit could be damaged if this isn't changed. But I don't want to have the change done if it will cause problems when the unit goes to aux heat. I'd call the hvac installer, but, clearly, they didn't think it was necessary to change the breaker & I'd really like an independent opinion on this. ALSO, is changing a breaker best left to an electrician or might this be something we could do ourselves? Thanks in advance for any input. WJ |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
Maybe the inspector is talking about the size of the conducter on the
breaker? If it's #8, it is correct for the 40A breaker. If it's smaller, the breaker needs to be changed appropriately. Bill wrote in message ups.com... Hello, I recently had a home inspection in preparation for selling my house. The inspector informed the buyer that I need to downgrade the circuit breaker (from 40amp to 15amp) for new hvac? He said he sees this problem a lot. My father, who does a lot of DIY including some electrical, says that if we change to 15amp when the hvac switches to aux. heat it will blow the breaker? I need to find out if this really needs to be changed, the inspector warned the hvac unit could be damaged if this isn't changed. But I don't want to have the change done if it will cause problems when the unit goes to aux heat. I'd call the hvac installer, but, clearly, they didn't think it was necessary to change the breaker & I'd really like an independent opinion on this. ALSO, is changing a breaker best left to an electrician or might this be something we could do ourselves? Thanks in advance for any input. WJ |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
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need to downgrade breaker (from 40amp to 15amp) for new hvac?
Yes, but what Bill Allerman posted is important as well. The feeder cable
must be sized for a 40 amp breaker, which would be at least #8. Look on the unit's name plate for an amperage rating or even a recommended circuit breaker size. The full load amperage will determine the size wire and breaker required wrote in message ups.com... Thank you for your responses. We didn't do any of the wiring ourselves, the breaker is the same from the prior HVAC unit (ca. 1987), I'm fairly certain the contractor who installed the hvac a few months ago didn't make any change to the breaker(s). He seemed quite competent and earnest, so I'm a little reluctant to accept the inspector's word as gospel. Either way, I'm concerned about a liability situation down the road, so I'm trying to research this prior to having someone in to make a change. The inspector stood in front of the breaker box pointing to the 40amp breaker when he made the statement, so I'm pretty certain he's referring to the breaker. The buyer read aloud a liability disclaimer based upon the inspector's report. I read all of the literature that came with the unit - an electric heat pump/air conditioning unit w/air handler. I did find this within the paperwork for the new unit (not sure if this is relative): i This unit is designed for single-phase electrical supply. DO NOT OPERATE ON A THREE-PHASE POWER SUPPLY. Measure the power supply to the unit. The supply voltage must be in agreement with the unit nameplate power requirements and within the range shown in: Nominal Input 208/240 Minimum Voltage 187 Maximum Voltage 253 /i I don't mind saying this is pretty much greek to me, but does this mean if I check the plate on the unit I'll be able to tell what kind of breaker is best (based upon the range info above)? I plan on having someone come in to make the change, if it's necessary, but I'd like to have an idea of whether it needs to be done before 'going there.' Again, thank you so much for any input. WJ |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
Thank you for your reply dpb, I missed it when I posted a few minutes ago, I lost a post somewhere, so if this one is a duplicate, my apologies. See, I think you could be right about the inspector. I'm sure he's quite knowledgable, but if he's seen this problem often, I figure hvac units are installed by certified hvac techs.. who would be more likely to be the expert? Additionally, the lack of any liability for his findings/report makes me hesitate to take his word as gospel... if he's wrong & there's a problem w/the unit after we switch to 15amp, who is liable? maybe me? I may end up telling the buyers if they want me to have it changed, I'll have it changed, but I've let them know I'm not certain it should be done. I'd contact the manufacturer, but I'm afraid of voiding the warranty. This is a new unit, installed a few months ago, installer seemed quite competent and knowledgable. |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
wrote in message .
See, I think you could be right about the inspector. I'm sure he's quite knowledgable, but if he's seen this problem often, I figure hvac units are installed by certified hvac techs.. who would be more likely to be the expert? Unfortunately, in my experience in many cases it is the inspector. Many "certified" HVAC techs take shortcuts if they can get away with it. After the #1 shortcut (inadequate evacuation prior to system charging), failing to downsize a breaker when installing a more efficient system is probably the #2 shortcut taken. Having said this a reduction is breaker size from 40A to 15A seems a bit extreme unless there was a significant change in the system (for example, the elimination of resistive heat strips in the air handler). This is a new unit, installed a few months ago, installer seemed quite competent and knowledgable. See comment above. Did the installation require a permit in your municipality? Was one pulled? Did the installation pass the municipality's final inspection? If no permit was pulled and one is required, the HVAC installer was probably a hack. Finally, are we talking about the breaker for the air handler or the condenser? Does the air handler have heat strips (aka emergency heat)? What is the make and model of the air handler and condenser, and what are the specifications for the electrical supply for each (note: should be on manufacturer's nameplate)? |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
First time posting so this is a test.
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need to downgrade breaker (from 40amp to 15amp) for new hvac?
I don't believe it's on a condenser. I think it's an air handler with
heating strips wrote in message ... On Sun, 24 Jun 2007 11:36:02 -0400, "RBM" rbm2(remove wrote: Yes, but what Bill Allerman posted is important as well. The feeder cable must be sized for a 40 amp breaker, which would be at least #8. Look on the unit's name plate for an amperage rating or even a recommended circuit breaker size. The full load amperage will determine the size wire and breaker required Nope, not on an HVAC condenser. Read the label on the condenser and size the breaker/wire accordingly You should see miminum circuit ampacity, that is the wire size based on 301.16 (not 240.4(D) so 12ga is good for 25a, 14ga 20a. Then look at maximum branch circuit over protection size and that is the breaker you can use. It will NOT be what you would think. This is for short circuit protection, not overload protection, that is internal in the compressor as a general rule. You can very well see a 40a breaker on 14 ga wire. All that said you still have to wire and protect the heater strips in the air handler like a regular circuit, using the 310.16 rating on the wire. Again that will be in the installation instructions as to what wire and breaker combo you need for each heater option size. |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
wrote in message ups.com... Hello, I recently had a home inspection in preparation for selling my house. The inspector informed the buyer that I need to downgrade the circuit breaker (from 40amp to 15amp) for new hvac? He said he sees this problem a lot. My father, who does a lot of DIY including some electrical, says that if we change to 15amp when the hvac switches to aux. heat it will blow the breaker? I need to find out if this really needs to be changed, the inspector warned the hvac unit could be damaged if this isn't changed. But I don't want to have the change done if it will cause problems when the unit goes to aux heat. I'd call the hvac installer, but, clearly, they didn't think it was necessary to change the breaker & I'd really like an independent opinion on this. ALSO, is changing a breaker best left to an electrician or might this be something we could do ourselves? Thanks in advance for any input. WJ What I have seen done a lot is for the breaker in the main panel to NOT be changed when a new unit is installed but the correct sized breaker to be installed in the disconnect box located next to the unit. Assuming the wire from the breaker to the disconnect box is properly sized this would be fine. Not something the average home inspector is smart enough to realize. The final protection for the unit is at the disconnect box. The wiring may be able to carry 40 amps to the disconnect but if that is a 20 amp breaker only 20 can pass to the unit. By doing it this way the HVAC contractor has not messed with your wiring or your breaker box and is only liable for the disconnect and the unit. It is a CYA (his A) type of thing. If that is the case a simple letter from the HVAC contractor should be enough to satisfy the "repair requirements" of the home inspection. You should offer to pay the HVAC for the time to write the letter. Most will not charge. I have never seen a home inspector argue with a licensed person who is willing to commit something to writing. Colbyt |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
Travis Jordan wrote:
wrote in message . See, I think you could be right about the inspector. I'm sure he's quite knowledgable, but if he's seen this problem often, I figure hvac units are installed by certified hvac techs.. who would be more likely to be the expert? Unfortunately, in my experience in many cases it is the inspector. Many "certified" HVAC techs take shortcuts if they can get away with it. After the #1 shortcut (inadequate evacuation prior to system charging), failing to downsize a breaker when installing a more efficient system is probably the #2 shortcut taken. .... What, precisely, is the "shortcut"? If the existing wiring is sized for 40A, the circuit breaker isn't intended to do anything but protect the wiring from short circuit faults, _NOT_ the load device, whatever it is. -- |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
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need to downgrade breaker (from 40amp to 15amp) for new hvac?
wrote in message ups.com... Thank you for your responses. We didn't do any of the wiring ourselves, the breaker is the same from the prior HVAC unit (ca. 1987), I'm fairly certain the contractor who installed the hvac a few months ago didn't make any change to the breaker(s). He seemed quite competent and earnest, so I'm a little reluctant to accept the inspector's word as gospel. Either way, I'm concerned about a liability situation down the road, so I'm trying to research this prior to having someone in to make a change. The inspector stood in front of the breaker box pointing to the 40amp breaker when he made the statement, so I'm pretty certain he's referring to the breaker. The buyer read aloud a liability disclaimer based upon the inspector's report. Then change the breaker and add into the purchase agreement a disclaimer for the inadequate breaker and lay hte blame on future breaker trips on the incompetent inspector. Include power requirements (amp draw) of the HVAC unit. Your attorney should know how to word it and lay the blame and liability squarely upon the inspector's report. Be absolutely certain to include the SIGNED (the inspector and buyer's signatures) inspection report in the closing of the house. Have fun finding a 15 amp 240 breaker! 20 is about the smallest I have seen and if you do find one, the wires might be too big to fit them into the breaker! All you need to do to replace it is to shut if off, take off the breaker box cover, unscrew the wires, pull out the breaker, put the new one in, connect the wires, replace the cover, and turn it back on. Simple job! I read all of the literature that came with the unit - an electric heat pump/air conditioning unit w/air handler. I can guarantee that it draws MUCH more than 15 amps unless it is a micro ..25 ton unit! My 2 ton requires a 25 amp breaker and it also needs the furnace! An electric heat pump plus aux heat requires even more amperage! I did find this within the paperwork for the new unit (not sure if this is relative): i This unit is designed for single-phase electrical supply. DO NOT OPERATE ON A THREE-PHASE POWER SUPPLY. Measure the power supply to the unit. The supply voltage must be in agreement with the unit nameplate power requirements and within the range shown in: Nominal Input 208/240 Minimum Voltage 187 Maximum Voltage 253 /i I don't mind saying this is pretty much greek to me, but does this mean if I check the plate on the unit I'll be able to tell what kind of breaker is best (based upon the range info above)? I plan on having someone come in to make the change, if it's necessary, but I'd like to have an idea of whether it needs to be done before 'going there.' Again, thank you so much for any input. WJ |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
wrote in message ... On Sun, 24 Jun 2007 11:36:02 -0400, "RBM" rbm2(remove wrote: Yes, but what Bill Allerman posted is important as well. The feeder cable must be sized for a 40 amp breaker, which would be at least #8. Look on the unit's name plate for an amperage rating or even a recommended circuit breaker size. The full load amperage will determine the size wire and breaker required Nope, not on an HVAC condenser. Read the label on the condenser and size the breaker/wire accordingly You should see miminum circuit ampacity, that is the wire size based on 301.16 (not 240.4(D) so 12ga is good for 25a, 14ga 20a. ?????????????????????????????????????????????????? It is a violation of code to put a 20a breaker on 14ga wire! 12ga is required!!!!!!! Then look at maximum branch circuit over protection size and that is the breaker you can use. It will NOT be what you would think. This is for short circuit protection, not overload protection, that is internal in the compressor as a general rule. You can very well see a 40a breaker on 14 ga wire. All that said you still have to wire and protect the heater strips in the air handler like a regular circuit, using the 310.16 rating on the wire. Again that will be in the installation instructions as to what wire and breaker combo you need for each heater option size. |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
Travis J beat me to the puch on the question: Is this breaker for the
outside condensing unit, or for the inside air handler? Very few condensing units call for a 15amp breaker. I have only seen a couple--certain brands of 1.5 and possibly 2 ton units. Regardless, the unit will have a maximum breaker size on the data plate, and some brands list a minimum as well. Go with whatever it says, making sure the wire is large enough. Larger wire than necessary is fine. If it is the air handler you are referring to, even the smallest heat strips made will require a lot more than 15 amps. The problem is that the airhandlers are usually ordered without heat strips, and they are ordered separately and installed when the unit is installed. You have to first know what size heat strips you have ---they can be from 3KW to 20 KW. They are sized according to the amount of heat desired, and the available power. Call the installer and get all the info from them. They may be willing to talk to the inspector and get this resolved over the phone. Our service mgr gets involved with things like this from time to time. Good luck Larry |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
"dpb" wrote in message:
What, precisely, is the "shortcut"? If the existing wiring is sized for 40A, the circuit breaker isn't intended to do anything but protect the wiring from short circuit faults, _NOT_ the load device, whatever it is. The circuit breaker is there to protect the load device and the wiring. The shortcut is that some installers don't downsize the breaker when installing a more efficient system. The NEC, most state building codes require appropriate sizing. Most HVAC manufacturers specify the maximum fuse size (MFS) and maximum circuit breaker size (MCB) for protection of their equipment. Of course the wire size has to be large enough for the intended load. Generally the calculation is: MCB = 2.25 x largest motor amps (FLA or RLA) + the sum of the remaining motor amps. |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
Mike Dobony wrote:
wrote in message ... On Sun, 24 Jun 2007 11:36:02 -0400, "RBM" rbm2(remove wrote: Yes, but what Bill Allerman posted is important as well. The feeder cable must be sized for a 40 amp breaker, which would be at least #8. Look on the unit's name plate for an amperage rating or even a recommended circuit breaker size. The full load amperage will determine the size wire and breaker required Nope, not on an HVAC condenser. Read the label on the condenser and size the breaker/wire accordingly You should see miminum circuit ampacity, that is the wire size based on 301.16 (not 240.4(D) so 12ga is good for 25a, 14ga 20a. ?????????????????????????????????????????????????? It is a violation of code to put a 20a breaker on 14ga wire! 12ga is required!!!!!!! For motors the rules change. The breaker protects the wire from short circuits, not overloads, as gfretwell said. Rather arcane rules for motors are among the reasons why electricians have licenses. It is not possible to give an answer to the OP's question without nameplate information for the equipment connected and wire size. I wouldn't necessarily trust a home inspector apply the rules. I also wouldn't necessarily trust an installer to do the electrical right - particularly if the electrical was not done by an electrician. -- bud-- Then look at maximum branch circuit over protection size and that is the breaker you can use. It will NOT be what you would think. This is for short circuit protection, not overload protection, that is internal in the compressor as a general rule. You can very well see a 40a breaker on 14 ga wire. All that said you still have to wire and protect the heater strips in the air handler like a regular circuit, using the 310.16 rating on the wire. Again that will be in the installation instructions as to what wire and breaker combo you need for each heater option size. |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
Travis Jordan wrote:
"dpb" wrote in message: What, precisely, is the "shortcut"? If the existing wiring is sized for 40A, the circuit breaker isn't intended to do anything but protect the wiring from short circuit faults, _NOT_ the load device, whatever it is. The circuit breaker is there to protect the load device and the wiring. The shortcut is that some installers don't downsize the breaker when installing a more efficient system. ... 40A to 15A more efficient???? Now THAT is one efficient system... I ain't buyin', sorry. -- |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
wrote in message ... On Mon, 25 Jun 2007 10:00:27 -0500, Bud-- wrote: For motors the rules change. The breaker protects the wire from short circuits, not overloads, as gfretwell said. Rather arcane rules for motors are among the reasons why electricians have licenses. Exactly right Bud. In fact there is a question on every inspector exam I have taken about a 115v 1HP motor with internal overload protection (16a FLA) and the correct answer is "40a breaker, 14 ga wire". I understand this is an anomally using all the exceptions and "round up" rules but it is NEC compliant. Really? That's plain nuts! Your run of the mill CB takes seconds to trip just from FLA currents. There just isn't any need to put a 40 amp breaker on a motor circuit. If there is something about the motor the keeps it from coming up to speed in a second or two then fix that. But don't put a 40 amp breaker on #14 wire. |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
"dpb" wrote...
40A to 15A more efficient???? Now THAT is one efficient system... I ain't buyin', sorry. Normally I'd agree, but if a resistive heat air handler was changed out for a variable speed heatpump only air handler, it would be completely logical. Or maybe the original breaker was oversized. |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
Travis Jordan" wrote...
"dpb" wrote... 40A to 15A more efficient???? Now THAT is one efficient system... I ain't buyin', sorry. Normally I'd agree, but if a resistive heat air handler was changed out for a variable speed heatpump only air handler, it would be completely logical. Or maybe the original breaker was oversized. I just checked Trane's documentation and all of their 1.5T and smaller heat pump systems state a MCB of 15A. It is quite possible the old system (1987 vintage, probably twice the load) had an oversized breaker installed also. |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
John Gilmer wrote:
wrote in message ... On Mon, 25 Jun 2007 10:00:27 -0500, Bud-- wrote: For motors the rules change. The breaker protects the wire from short circuits, not overloads, as gfretwell said. Rather arcane rules for motors are among the reasons why electricians have licenses. Exactly right Bud. In fact there is a question on every inspector exam I have taken about a 115v 1HP motor with internal overload protection (16a FLA) and the correct answer is "40a breaker, 14 ga wire". I understand this is an anomally using all the exceptions and "round up" rules but it is NEC compliant. Really? That's plain nuts! Your run of the mill CB takes seconds to trip just from FLA currents. There just isn't any need to put a 40 amp breaker on a motor circuit. If there is something about the motor the keeps it from coming up to speed in a second or two then fix that. But don't put a 40 amp breaker on #14 wire. FLA (full load amps) are not the problem. Starting current/LRA (locked rotor amps) are. I presume this was a typo on your part. As a rule of thumb a motor draws a current (LRA) of about 6x its FLA when it starts. Looking at a SquareD current - trip-time curve, at 6x the rated breaker current a breaker may be in it's "instantaneous" trip region - no time delay. If the motor was rated 80% of the breaker rating (more likely) the starting current is (0.8)x(6) = 5.4x the breaker rating. The trip time can be 0.3 to 2.5 seconds - not reliable. Obviously the motor current goes down as the motor accelerates. But that doesn't help in the instantaneous trip region. And in the 0.3 to 2.5 sec range there is no guarantee the motor will start. If turn up a thermostat then turn it down a refrigeration compressor it will likely not restart immediately. That causes the LRA until the motor protector opens the circuit. You would generally not want the circuit breaker to open. And high inertia motor loads increase the time to start. The NEC is really quite pragmatic. Rules like this come from field experience as well as engineering considerations. Not only can a circuit breaker be 250% of FLA, as in gfretwell's example - if the breaker does not permit the motor to start the breaker can be increased to 300 or 400% of the FLA. And as has been a couple times, the breaker provides short circuit protection for the wire, not overload protection. -- bud |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
In article , Bud-- wrote:
I have one issue with your otherwise excellent post -- this last sentence: And as has been a couple times, the breaker provides short circuit protection for the wire, not overload protection. The breaker provides *overcurrent* protection for the wire -- IOW, the breaker is sized to open if more current is flowing through the wire than it can safely handle. This does not occur solely through short circuits, but can result from overload as well (e.g. fifty 60W incandescent light bulbs on a single 15A circuit is supposed to pop the breaker, even though there is no short). -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
Travis Jordan wrote:
"dpb" wrote... 40A to 15A more efficient???? Now THAT is one efficient system... I ain't buyin', sorry. Normally I'd agree, but if a resistive heat air handler was changed out for a variable speed heatpump only air handler, it would be completely logical. Except OP specifically spoke of "emergency heat" kicking on which seems to preclude that -- or, of course, could be he just does not know what he just bought and paid for and had installed... Or maybe the original breaker was oversized. In about the same category as the above... imo, ymmv, $0.02, etc., etc., ... -- |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
Doug Miller wrote:
In article , Bud-- wrote: I have one issue with your otherwise excellent post -- this last sentence: And as has been a couple times, the breaker provides short circuit protection for the wire, not overload protection. The breaker provides *overcurrent* protection for the wire -- IOW, the breaker is sized to open if more current is flowing through the wire than it can safely handle. This does not occur solely through short circuits, but can result from overload as well (e.g. fifty 60W incandescent light bulbs on a single 15A circuit is supposed to pop the breaker, even though there is no short). Note that gfretwell and I agree on this. This is a motor circuit, not light bulbs. The rules are in article 430. The circuit breaker provides *short circuit* protection - 430 part 5. *Overload protection* is typically provided by thermal overload units in, or attached to, the motor. - or motor starter (contactor) overload units - 430 part 4. (Note that the overload protection is near the motor, not the panel.) Wire size is 430 part 2. gfretwell's nice 'worst case' example gave code citations for his calculations - would be a good place to start. IMHO article 430 is of similar difficulty to article 230 - grounding. Article 230 is the most difficult of the commonly used articles. As I wrote earlier, there is a reason why electricians are required to have licenses (in many jurisdictions). If you (and John) are appalled by the 'oversizing' of the breakers for motors make sure you don't read article 630 - welders. Particularly for low duty cycle welders. -- bud-- |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
In article , Bud-- wrote:
Doug Miller wrote: In article , Bud-- wrote: I have one issue with your otherwise excellent post -- this last sentence: And as has been a couple times, the breaker provides short circuit protection for the wire, not overload protection. The breaker provides *overcurrent* protection for the wire -- IOW, the breaker is sized to open if more current is flowing through the wire than it can safely handle. This does not occur solely through short circuits, but can result from overload as well (e.g. fifty 60W incandescent light bulbs on a single 15A circuit is supposed to pop the breaker, even though there is no short). Note that gfretwell and I agree on this. This is a motor circuit, not light bulbs. The rules are in article 430. The circuit breaker provides *short circuit* protection - 430 part 5. Right, I know -- I'm objecting to what appeared, at least, to be a general statement that breakers provide only short-circuit protection. In the specific cases you cited, that's correct, but as a general rule, it's not. -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
In article , wrote:
On Wed, 27 Jun 2007 15:43:25 GMT, (Doug Miller) wrote: Right, I know -- I'm objecting to what appeared, at least, to be a general statement that breakers provide only short-circuit protection. In the specific cases you cited, that's correct, but as a general rule, it's not. Doug I think the point was that in the case of motors on dedicated circuits the rules are different. Right, I know that. I just wanted to make sure it was understood that as a _general_ rule, breakers are there to provide overcurrent protection generally, which is not the same as short circuit protection. -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
If the unit has aux heat, it may very well need 40 amps. Read the
manual. If you have to ask, you don't have the skills. I wouldn't reccomend to open a panel box unless you've seen it done several times, and have someone experienced working with you. -- Christopher A. Young You can't shout down a troll. You have to starve them. .. wrote in message ups.com... : Hello, : I recently had a home inspection in preparation for selling my house. : The inspector informed the buyer that I need to downgrade the circuit : breaker (from 40amp to 15amp) for new hvac? He said he sees this : problem a lot. My father, who does a lot of DIY including some : electrical, says that if we change to 15amp when the hvac switches to : aux. heat it will blow the breaker? : : I need to find out if this really needs to be changed, the inspector : warned the hvac unit could be damaged if this isn't changed. But I : don't want to have the change done if it will cause problems when the : unit goes to aux heat. : : I'd call the hvac installer, but, clearly, they didn't think it was : necessary to change the breaker & I'd really like an independent : opinion on this. : : ALSO, is changing a breaker best left to an electrician or might this : be something we could do ourselves? : : Thanks in advance for any input. : WJ : |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
See if the paper work mentions the word amp, or ampacity.
Since this is greek, please leave the panel box closed. For your safety, you see. -- Christopher A. Young You can't shout down a troll. You have to starve them. .. wrote in message ups.com... : Thank you for your responses. : : We didn't do any of the wiring ourselves, the breaker is the same from : the prior HVAC unit (ca. 1987), I'm fairly certain the contractor who : installed the hvac a few months ago didn't make any change to the : breaker(s). He seemed quite competent and earnest, so I'm a little : reluctant to accept the inspector's word as gospel. Either way, I'm : concerned about a liability situation down the road, so I'm trying to : research this prior to having someone in to make a change. : : The inspector stood in front of the breaker box pointing to the 40amp : breaker when he made the statement, so I'm pretty certain he's : referring to the breaker. The buyer read aloud a liability disclaimer : based upon the inspector's report. : : I read all of the literature that came with the unit - an electric : heat pump/air conditioning unit w/air handler. : : I did find this within the paperwork for the new unit (not sure if : this is relative): : i : This unit is designed for single-phase electrical supply. DO NOT : OPERATE ON A THREE-PHASE POWER SUPPLY. Measure the power supply to : the unit. The supply voltage must be in agreement with the unit : nameplate power requirements and within the range shown in: : Nominal Input 208/240 : Minimum Voltage 187 : Maximum Voltage 253 : /i : I don't mind saying this is pretty much greek to me, but does this : mean if I check the plate on the unit I'll be able to tell what kind : of breaker is best (based upon the range info above)? : : I plan on having someone come in to make the change, if it's : necessary, but I'd like to have an idea of whether it needs to be done : before 'going there.' : : Again, thank you so much for any input. : : WJ : : |
need to downgrade breaker (from 40amp to 15amp) for new hvac?
Doug Miller wrote:
In article , Bud-- wrote: Doug Miller wrote: In article , Bud-- wrote: I have one issue with your otherwise excellent post -- this last sentence: And as has been a couple times, the breaker provides short circuit protection for the wire, not overload protection. The breaker provides *overcurrent* protection for the wire -- IOW, the breaker is sized to open if more current is flowing through the wire than it can safely handle. This does not occur solely through short circuits, but can result from overload as well (e.g. fifty 60W incandescent light bulbs on a single 15A circuit is supposed to pop the breaker, even though there is no short). This is a motor circuit, not light bulbs. The rules are in article 430. Right, I know -- I'm objecting to what appeared, at least, to be a general statement that breakers provide only short-circuit protection. In the specific cases you cited, that's correct, but as a general rule, it's not. My post was in the context of motors. Your response was general - it would have helped if it was limited to non-motors. -- bud-- |
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