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Possible loose neutral?
All,
Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9 volts difference between phases when a 120 V 1.3 kW microwave is running. Is this excessive, or acceptable? Long story: For the past few mornings, the UPS (APC Smart-UPS 600) in my office has been switching on to battery power for a few minutes, even when the lights in the rest of the house hadn't flickered or gone out. I finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the UPS while the UPS was running and found out it was probably tripping on _over_voltage: the wall socket was delivering over 130 volts! After a bit of experimentation, I discovered that the voltage went up when the microwave in the kitchen was running, which is why it happened in the mornings when the other half was making tea. The microwave is on one of the 20 A kitchen circuits, while my office is on a 20 A receptacle circuit with a couple of other rooms. It's a GE microwave, about 10 years old, 120 V 1300 W per the nameplate. I also noticed that the voltage rise was less pronounced when the central air conditioner was running. The compressor is 240 V and is fused and breakered at 40 A. Suspecting a loose neutral, I inspected the breaker panel. Nothing looked out of place. I tried tightening all of the screws on the neutral/ground bus bar. They all took a bit of tightening - less than 1/8 turn - but none were really badly loose. I made very sure that the neutral coming in from the meter was tight at the bus bar. I have the US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus panel. It is original to the house (1969), although the breakers have all been replaced. To my knowledge, the kitchen circuits are two separate 20 A circuits with their own NM cable, not split like a Canadian kitchen circuit. After I tightened the screws, I went around in the house and made sure most things were turned off. There were still a few computers running, but the TV, stereo, lights, etc were all off. The air conditioner was also shut off. I measured the voltage between the neutral/ground bus bar and each hot lug with the microwave off and then with the microwave running, heating about 8 oz (230 mL) of water in a coffee cup. I then turned the A/C on and tried again. Results... A/C uWave left right l-r notes off off 122.5 123.2 -0.7 run 1 off on 126.3 117.6 8.7 off off 121.9 121.3 0.6 run 2 off on 126.1 116.7 9.4 on off 119.6 123.3 -3.7 on on 123.7 118.5 5.2 I know that the two sides of the service will very rarely be in exact balance, but the 8 to 9 V difference seems somewhat high. Is this considered within reasonable bounds, or should I have the power company out? Or should I chase the wiring in the house further? When I moved into the house 5+ years ago, most of the receptacles were original and back-wired. I changed all of them that are regularly used for new spec grade side-wired receptacles. Out of curiosity, I measured the voltage drop across each breaker. This was with most of the loads shut off, so it may not be too useful, but I found no breaker over 100 mV and most under 40 mV. Let me know if you need more information. Thanks for your help! Matt Roberds |
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#2
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The gain on the hot leg opposite the microwave is about 1/2 the loss on the
microwave side. This make sense because the the neutral leg is 1/2 the circuit for the microwave. Let me get this straight - you are measuring at the panel? If so, the gains and drop seems excessive. John wrote in message news:Xiroe.12325$Wr.100@fed1read04... All, Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9 volts difference between phases when a 120 V 1.3 kW microwave is running. Is this excessive, or acceptable? Long story: For the past few mornings, the UPS (APC Smart-UPS 600) in my office has been switching on to battery power for a few minutes, even when the lights in the rest of the house hadn't flickered or gone out. I finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the UPS while the UPS was running and found out it was probably tripping on _over_voltage: the wall socket was delivering over 130 volts! After a bit of experimentation, I discovered that the voltage went up when the microwave in the kitchen was running, which is why it happened in the mornings when the other half was making tea. The microwave is on one of the 20 A kitchen circuits, while my office is on a 20 A receptacle circuit with a couple of other rooms. It's a GE microwave, about 10 years old, 120 V 1300 W per the nameplate. I also noticed that the voltage rise was less pronounced when the central air conditioner was running. The compressor is 240 V and is fused and breakered at 40 A. Suspecting a loose neutral, I inspected the breaker panel. Nothing looked out of place. I tried tightening all of the screws on the neutral/ground bus bar. They all took a bit of tightening - less than 1/8 turn - but none were really badly loose. I made very sure that the neutral coming in from the meter was tight at the bus bar. I have the US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus panel. It is original to the house (1969), although the breakers have all been replaced. To my knowledge, the kitchen circuits are two separate 20 A circuits with their own NM cable, not split like a Canadian kitchen circuit. After I tightened the screws, I went around in the house and made sure most things were turned off. There were still a few computers running, but the TV, stereo, lights, etc were all off. The air conditioner was also shut off. I measured the voltage between the neutral/ground bus bar and each hot lug with the microwave off and then with the microwave running, heating about 8 oz (230 mL) of water in a coffee cup. I then turned the A/C on and tried again. Results... A/C uWave left right l-r notes off off 122.5 123.2 -0.7 run 1 off on 126.3 117.6 8.7 off off 121.9 121.3 0.6 run 2 off on 126.1 116.7 9.4 on off 119.6 123.3 -3.7 on on 123.7 118.5 5.2 I know that the two sides of the service will very rarely be in exact balance, but the 8 to 9 V difference seems somewhat high. Is this considered within reasonable bounds, or should I have the power company out? Or should I chase the wiring in the house further? When I moved into the house 5+ years ago, most of the receptacles were original and back-wired. I changed all of them that are regularly used for new spec grade side-wired receptacles. Out of curiosity, I measured the voltage drop across each breaker. This was with most of the loads shut off, so it may not be too useful, but I found no breaker over 100 mV and most under 40 mV. Let me know if you need more information. Thanks for your help! Matt Roberds |
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wrote in message news:Xiroe.12325$Wr.100@fed1read04... I know that the two sides of the service will very rarely be in exact balance, but the 8 to 9 V difference seems somewhat high. Is this considered within reasonable bounds, or should I have the power company out? Or should I chase the wiring in the house further? When I moved into the house 5+ years ago, most of the receptacles were original and back-wired. I changed all of them that are regularly used for new spec grade side-wired receptacles. It is too high but I doubt the power co will help and they may cause you more problems. I'd try to find a smart, honest electrician. N |
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ees right! run the romex to the ground on the other side of the box
from where the wires come out of the box. Romix is tricky tho, so run a wire from the one wire that is hooked to the romix in the box where the other wires are. Then hook it in somewher to an outlet somewher but not before the place where an outlet hooks to something, and make double sure you dont hook it to something that hooks to something before the box with the wires in it hooks up to the other thing. |
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Matt,
I think you have a run-of-the-mill power quality issue that your APC caught. The microwave appears to be causing the problem. Microwave tubes fire at a very high frequency and can send AC noise back into the whole system. Your APC is seeing this and reacting. Solutions: Put the APC or the microwave on a different phase (switch breakers around) and see if this helps. Otherwise, a more modern microwave with better filtering maybe in order. Jake wrote in message news:Xiroe.12325$Wr.100@fed1read04... All, Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9 volts difference between phases when a 120 V 1.3 kW microwave is running. Is this excessive, or acceptable? Long story: For the past few mornings, the UPS (APC Smart-UPS 600) in my office has been switching on to battery power for a few minutes, even when the lights in the rest of the house hadn't flickered or gone out. I finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the UPS while the UPS was running and found out it was probably tripping on _over_voltage: the wall socket was delivering over 130 volts! After a bit of experimentation, I discovered that the voltage went up when the microwave in the kitchen was running, which is why it happened in the mornings when the other half was making tea. The microwave is on one of the 20 A kitchen circuits, while my office is on a 20 A receptacle circuit with a couple of other rooms. It's a GE microwave, about 10 years old, 120 V 1300 W per the nameplate. I also noticed that the voltage rise was less pronounced when the central air conditioner was running. The compressor is 240 V and is fused and breakered at 40 A. Suspecting a loose neutral, I inspected the breaker panel. Nothing looked out of place. I tried tightening all of the screws on the neutral/ground bus bar. They all took a bit of tightening - less than 1/8 turn - but none were really badly loose. I made very sure that the neutral coming in from the meter was tight at the bus bar. I have the US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus panel. It is original to the house (1969), although the breakers have all been replaced. To my knowledge, the kitchen circuits are two separate 20 A circuits with their own NM cable, not split like a Canadian kitchen circuit. After I tightened the screws, I went around in the house and made sure most things were turned off. There were still a few computers running, but the TV, stereo, lights, etc were all off. The air conditioner was also shut off. I measured the voltage between the neutral/ground bus bar and each hot lug with the microwave off and then with the microwave running, heating about 8 oz (230 mL) of water in a coffee cup. I then turned the A/C on and tried again. Results... A/C uWave left right l-r notes off off 122.5 123.2 -0.7 run 1 off on 126.3 117.6 8.7 off off 121.9 121.3 0.6 run 2 off on 126.1 116.7 9.4 on off 119.6 123.3 -3.7 on on 123.7 118.5 5.2 I know that the two sides of the service will very rarely be in exact balance, but the 8 to 9 V difference seems somewhat high. Is this considered within reasonable bounds, or should I have the power company out? Or should I chase the wiring in the house further? When I moved into the house 5+ years ago, most of the receptacles were original and back-wired. I changed all of them that are regularly used for new spec grade side-wired receptacles. Out of curiosity, I measured the voltage drop across each breaker. This was with most of the loads shut off, so it may not be too useful, but I found no breaker over 100 mV and most under 40 mV. Let me know if you need more information. Thanks for your help! Matt Roberds |
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wrote in message news:Xiroe.12325$Wr.100@fed1read04... All, Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9 volts difference between phases when a 120 V 1.3 kW microwave is running. Is this excessive, or acceptable? Long story: For the past few mornings, the UPS (APC Smart-UPS 600) in my office has been switching on to battery power for a few minutes, even when the lights in the rest of the house hadn't flickered or gone out. I finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the UPS while the UPS was running and found out it was probably tripping on _over_voltage: the wall socket was delivering over 130 volts! After a bit of experimentation, I discovered that the voltage went up when the microwave in the kitchen was running, which is why it happened in the mornings when the other half was making tea. The microwave is on one of the 20 A kitchen circuits, while my office is on a 20 A receptacle circuit with a couple of other rooms. It's a GE microwave, about 10 years old, 120 V 1300 W per the nameplate. I also noticed that the voltage rise was less pronounced when the central air conditioner was running. The compressor is 240 V and is fused and breakered at 40 A. Suspecting a loose neutral, I inspected the breaker panel. Nothing looked out of place. I tried tightening all of the screws on the neutral/ground bus bar. They all took a bit of tightening - less than 1/8 turn - but none were really badly loose. I made very sure that the neutral coming in from the meter was tight at the bus bar. I have the US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus panel. It is original to the house (1969), although the breakers have all been replaced. To my knowledge, the kitchen circuits are two separate 20 A circuits with their own NM cable, not split like a Canadian kitchen circuit. After I tightened the screws, I went around in the house and made sure most things were turned off. There were still a few computers running, but the TV, stereo, lights, etc were all off. The air conditioner was also shut off. I measured the voltage between the neutral/ground bus bar and each hot lug with the microwave off and then with the microwave running, heating about 8 oz (230 mL) of water in a coffee cup. I then turned the A/C on and tried again. Results... A/C uWave left right l-r notes off off 122.5 123.2 -0.7 run 1 off on 126.3 117.6 8.7 off off 121.9 121.3 0.6 run 2 off on 126.1 116.7 9.4 on off 119.6 123.3 -3.7 on on 123.7 118.5 5.2 I know that the two sides of the service will very rarely be in exact balance, but the 8 to 9 V difference seems somewhat high. Is this considered within reasonable bounds, or should I have the power company out? Or should I chase the wiring in the house further? When I moved into the house 5+ years ago, most of the receptacles were original and back-wired. I changed all of them that are regularly used for new spec grade side-wired receptacles. Out of curiosity, I measured the voltage drop across each breaker. This was with most of the loads shut off, so it may not be too useful, but I found no breaker over 100 mV and most under 40 mV. Let me know if you need more information. Thanks for your help! Matt Roberds sounds very much like a high resistance in the neutral wire to the main panel to me. id give the power company a shout first. might be a connection gone bad in the meter or something. |
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wrote in message news:Xiroe.12325$Wr.100@fed1read04... All, Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9 volts difference between phases when a 120 V 1.3 kW microwave is running. Is this excessive, or acceptable? Long story: For the past few mornings, the UPS (APC Smart-UPS 600) in my office has been switching on to battery power for a few minutes, even when the lights in the rest of the house hadn't flickered or gone out. I finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the UPS while the UPS was running and found out it was probably tripping on _over_voltage: the wall socket was delivering over 130 volts! After a bit of experimentation, I discovered that the voltage went up when the microwave in the kitchen was running, which is why it happened in the mornings when the other half was making tea. The microwave is on one of the 20 A kitchen circuits, while my office is on a 20 A receptacle circuit with a couple of other rooms. It's a GE microwave, about 10 years old, 120 V 1300 W per the nameplate. I also noticed that the voltage rise was less pronounced when the central air conditioner was running. The compressor is 240 V and is fused and breakered at 40 A. Suspecting a loose neutral, I inspected the breaker panel. Nothing looked out of place. I tried tightening all of the screws on the neutral/ground bus bar. They all took a bit of tightening - less than 1/8 turn - but none were really badly loose. I made very sure that the neutral coming in from the meter was tight at the bus bar. I have the US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus panel. It is original to the house (1969), although the breakers have all been replaced. To my knowledge, the kitchen circuits are two separate 20 A circuits with their own NM cable, not split like a Canadian kitchen circuit. After I tightened the screws, I went around in the house and made sure most things were turned off. There were still a few computers running, but the TV, stereo, lights, etc were all off. The air conditioner was also shut off. I measured the voltage between the neutral/ground bus bar and each hot lug with the microwave off and then with the microwave running, heating about 8 oz (230 mL) of water in a coffee cup. I then turned the A/C on and tried again. Results... A/C uWave left right l-r notes off off 122.5 123.2 -0.7 run 1 off on 126.3 117.6 8.7 off off 121.9 121.3 0.6 run 2 off on 126.1 116.7 9.4 on off 119.6 123.3 -3.7 on on 123.7 118.5 5.2 I know that the two sides of the service will very rarely be in exact balance, but the 8 to 9 V difference seems somewhat high. Is this considered within reasonable bounds, or should I have the power company out? Or should I chase the wiring in the house further? When I moved into the house 5+ years ago, most of the receptacles were original and back-wired. I changed all of them that are regularly used for new spec grade side-wired receptacles. Out of curiosity, I measured the voltage drop across each breaker. This was with most of the loads shut off, so it may not be too useful, but I found no breaker over 100 mV and most under 40 mV. Let me know if you need more information. Thanks for your help! Matt Roberds Hello Matt, Sounds like a problem at or upstream of your panelboard. Your service voltage should stay pretty much unchanged if a smallish load like your microwave goes on or off. You could put a call in to your utility. Under the circumstances, hopefully they'd send someone to have a look for free. 130V at your outlet is pretty crazy, too. We need a second opinion but I would think that problems with a neutral connection should not show that much effect, except maybe at the end of a circuit using that neutral (ie. the circuit using the neutral or the multiple circuits using it if in fact it is shared). Again, though, a neutral problem at or upstream of your panelboard could cause this trouble. Wait for a few more opinions though. I wouldn't take my word on this stuff. j |
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On Sun, 05 Jun 2005 00:03:03 GMT, wrote:
All, Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9 volts difference between phases when a 120 V 1.3 kW microwave is running. Is this excessive, or acceptable? Long story: For the past few mornings, the UPS (APC Smart-UPS 600) in my office has been switching on to battery power for a few minutes, even when the lights in the rest of the house hadn't flickered or gone out. I finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the UPS while the UPS was running and found out it was probably tripping on _over_voltage: the wall socket was delivering over 130 volts! After a bit of experimentation, I discovered that the voltage went up when the microwave in the kitchen was running, which is why it happened in the mornings when the other half was making tea. The microwave is on one of the 20 A kitchen circuits, while my office is on a 20 A receptacle circuit with a couple of other rooms. It's a GE microwave, about 10 years old, 120 V 1300 W per the nameplate. I also noticed that the voltage rise was less pronounced when the central air conditioner was running. The compressor is 240 V and is fused and breakered at 40 A. Suspecting a loose neutral, I inspected the breaker panel. Nothing looked out of place. I tried tightening all of the screws on the neutral/ground bus bar. They all took a bit of tightening - less than 1/8 turn - but none were really badly loose. I made very sure that the neutral coming in from the meter was tight at the bus bar. I have the US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus panel. It is original to the house (1969), although the breakers have all been replaced. To my knowledge, the kitchen circuits are two separate 20 A circuits with their own NM cable, not split like a Canadian kitchen circuit. After I tightened the screws, I went around in the house and made sure most things were turned off. There were still a few computers running, but the TV, stereo, lights, etc were all off. The air conditioner was also shut off. I measured the voltage between the neutral/ground bus bar and each hot lug with the microwave off and then with the microwave running, heating about 8 oz (230 mL) of water in a coffee cup. I then turned the A/C on and tried again. Results... A/C uWave left right l-r notes off off 122.5 123.2 -0.7 run 1 off on 126.3 117.6 8.7 off off 121.9 121.3 0.6 run 2 off on 126.1 116.7 9.4 on off 119.6 123.3 -3.7 on on 123.7 118.5 5.2 I know that the two sides of the service will very rarely be in exact balance, but the 8 to 9 V difference seems somewhat high. Is this considered within reasonable bounds, or should I have the power company out? Or should I chase the wiring in the house further? When I moved into the house 5+ years ago, most of the receptacles were original and back-wired. I changed all of them that are regularly used for new spec grade side-wired receptacles. Out of curiosity, I measured the voltage drop across each breaker. This was with most of the loads shut off, so it may not be too useful, but I found no breaker over 100 mV and most under 40 mV. Let me know if you need more information. Thanks for your help! Matt Roberds I had a similar situation, but even greater voltage difference with even smaller loads. Found it to be present at the panel. Sure looked like a loose neutral in the 120/240 service. I was pretty certain it was power company connections. Called the power company. Fortunately I was an electrician in a previous career and left a note on the meter telling sparky what I thought the problem was. I was real scared that they would blow me off figuring I was some homeowner nut case. Thank goodness when they came they found the neutral loose in their meter section and fixed it pronto. Steve J. Noll | Ventura California | The Used Equipment Dealer Directory: | http://www.big-list.com | The Peltier Device Information Site: | http://www.peltier-info.com |
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#12
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mrobe:
You should immediately call up your Power Company and have them come out and check the service to your meter.... they are responsible for that... and may even check everything up to your breaker box if they are nice guys. I had a similar but more catastophic problem with a previous home I owned; it turned out that their Neutral connections were faulty from the power pole to the meter.... they did come into the home and check everything in the breaker box as a courtesy. I was blowing out light bulbs and eventually blew up a microwave oven. Don't let this go... it will not get better, but only worse to the point of destroying some of your appliances and equipment.... call your power company right away. electricitym - - - - - wrote: All, Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9 volts difference between phases when a 120 V 1.3 kW microwave is running. Is this excessive, or acceptable? Long story: For the past few mornings, the UPS (APC Smart-UPS 600) in my office has been switching on to battery power for a few minutes, even when the lights in the rest of the house hadn't flickered or gone out. I finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the UPS while the UPS was running and found out it was probably tripping on _over_voltage: the wall socket was delivering over 130 volts! After a bit of experimentation, I discovered that the voltage went up when the microwave in the kitchen was running, which is why it happened in the mornings when the other half was making tea. The microwave is on one of the 20 A kitchen circuits, while my office is on a 20 A receptacle circuit with a couple of other rooms. It's a GE microwave, about 10 years old, 120 V 1300 W per the nameplate. I also noticed that the voltage rise was less pronounced when the central air conditioner was running. The compressor is 240 V and is fused and breakered at 40 A. Suspecting a loose neutral, I inspected the breaker panel. Nothing looked out of place. I tried tightening all of the screws on the neutral/ground bus bar. They all took a bit of tightening - less than 1/8 turn - but none were really badly loose. I made very sure that the neutral coming in from the meter was tight at the bus bar. I have the US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus panel. It is original to the house (1969), although the breakers have all been replaced. To my knowledge, the kitchen circuits are two separate 20 A circuits with their own NM cable, not split like a Canadian kitchen circuit. After I tightened the screws, I went around in the house and made sure most things were turned off. There were still a few computers running, but the TV, stereo, lights, etc were all off. The air conditioner was also shut off. I measured the voltage between the neutral/ground bus bar and each hot lug with the microwave off and then with the microwave running, heating about 8 oz (230 mL) of water in a coffee cup. I then turned the A/C on and tried again. Results... A/C uWave left right l-r notes off off 122.5 123.2 -0.7 run 1 off on 126.3 117.6 8.7 off off 121.9 121.3 0.6 run 2 off on 126.1 116.7 9.4 on off 119.6 123.3 -3.7 on on 123.7 118.5 5.2 I know that the two sides of the service will very rarely be in exact balance, but the 8 to 9 V difference seems somewhat high. Is this considered within reasonable bounds, or should I have the power company out? Or should I chase the wiring in the house further? When I moved into the house 5+ years ago, most of the receptacles were original and back-wired. I changed all of them that are regularly used for new spec grade side-wired receptacles. Out of curiosity, I measured the voltage drop across each breaker. This was with most of the loads shut off, so it may not be too useful, but I found no breaker over 100 mV and most under 40 mV. Let me know if you need more information. Thanks for your help! Matt Roberds |
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wrote in news:Xiroe.12325$Wr.100@fed1read04:
Matt, I'd call my utility company and have them check the neutral from your meter back to the transformer. Had a similar situation with increasing voltages on one leg, turned out to be a loose neutral at the transformer. -- Anthony You can't 'idiot proof' anything....every time you try, they just make better idiots. Remove sp to reply via email http://www.machines-cnc.net:81/ |
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On Sun, 05 Jun 2005 00:03:03 GMT wrote:
Results... A/C uWave left right l-r notes off off 122.5 123.2 -0.7 run 1 off on 126.3 117.6 8.7 off off 121.9 121.3 0.6 run 2 off on 126.1 116.7 9.4 on off 119.6 123.3 -3.7 on on 123.7 118.5 5.2 Go back and do this test again, but this time measure everything at the breaker box entrance. That will allow you to determine whether the cause is inside or outside your house. Be careful! - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
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"operator jay" wrote in message ... snip Hello Matt, Sounds like a problem at or upstream of your panelboard. Your service voltage should stay pretty much unchanged if a smallish load like your microwave goes on or off. You could put a call in to your utility. Under the circumstances, hopefully they'd send someone to have a look for free. It sounds a lot like a loose neutral. The loose connection could be anywhere from his panel up to the service transformer, including inside his service panel. 130V at your outlet is pretty crazy, too. We need a second opinion but I would think that problems with a neutral connection should not show that much effect, except maybe at the end of a circuit using that neutral (ie. the circuit using the neutral or the multiple circuits using it if in fact it is shared). Again, though, a neutral problem at or upstream of your panelboard could cause this trouble. Wrong. I have seen much greater than 130V with loose neutral problems. Theoretically, you could get nearly 240V on one leg and zero on the other but realistically it doesn't get that bad. Have a qualified electrician check the connections in your panel to make sure they are tightened to the correct torque specifications. If that does not help, contact your utility. Most will have a device that they can temporarily put in the meter base to determine if a loose neutral exists on the service drop. They remove your meter, and plug in the device. It has two voltmeters (one for each leg) and a large load that they can switch between the legs. Simple and effective. Charles Perry P.E. |
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You have it right on. I also have seen this problem. Another characteristic
is that adding loads cause further unbalance. If you happen to have a couple of 100W lights on one circuit and a toaster on the other, the voltage distribution can get quite hairy as you indicate. -- Don Kelly remove the urine to answer "Charles Perry" wrote in message ... "operator jay" wrote in message ... snip Hello Matt, Sounds like a problem at or upstream of your panelboard. Your service voltage should stay pretty much unchanged if a smallish load like your microwave goes on or off. You could put a call in to your utility. Under the circumstances, hopefully they'd send someone to have a look for free. It sounds a lot like a loose neutral. The loose connection could be anywhere from his panel up to the service transformer, including inside his service panel. 130V at your outlet is pretty crazy, too. We need a second opinion but I would think that problems with a neutral connection should not show that much effect, except maybe at the end of a circuit using that neutral (ie. the circuit using the neutral or the multiple circuits using it if in fact it is shared). Again, though, a neutral problem at or upstream of your panelboard could cause this trouble. Wrong. I have seen much greater than 130V with loose neutral problems. Theoretically, you could get nearly 240V on one leg and zero on the other but realistically it doesn't get that bad. Have a qualified electrician check the connections in your panel to make sure they are tightened to the correct torque specifications. If that does not help, contact your utility. Most will have a device that they can temporarily put in the meter base to determine if a loose neutral exists on the service drop. They remove your meter, and plug in the device. It has two voltmeters (one for each leg) and a large load that they can switch between the legs. Simple and effective. Charles Perry P.E. |
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IMHO: Sounds that you have imbalanced circuit design within the residence
also, along with the possible loose neutral. Most moderately high current devices in the kitchens and utility areas of a residence have priority circuits specified to them, and are connected to the service in a way that they cause minimal un-balancing of the overall system. wrote in message news:KTToe.34658$Wr.31578@fed1read04... In alt.home.repair wrote: Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9 volts difference between phases when a 120 V 1.3 kW microwave is running. Is this excessive, or acceptable? All, Thanks for the advice! To clarify something that was asked a few times, all of the numbers in the chart I gave were measured directly at the breaker panel. I took the cover off the panel and put one meter lead on the neutral/ground bus bar and the other meter lead on one of the two screw terminals where the hot wires from the meter are connected. If it is a loose neutral, it almost has to be on the power company's side. My breaker panel is right on the other side of the wall from the meter... the supply wires into the breaker panel enter through the rear of the box and I presume they are coming out the rear of the meter can as well. The neutral connection to the neutral/ground bus bar in the panel appears to be tight. I will call the utility in the morning and see what they have to say. I'll post back with further developments. Thanks! Matt Roberds |
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wrote in message news:KTToe.34658$Wr.31578@fed1read04... I will call the utility in the morning and see what they have to say. I'll post back with further developments. Perhaps you have a grow op next door! N |
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"Don Kelly" wrote in message news:68Loe.1582115$6l.557950@pd7tw2no... You have it right on. I also have seen this problem. Another characteristic is that adding loads cause further unbalance. If you happen to have a couple of 100W lights on one circuit and a toaster on the other, the voltage distribution can get quite hairy as you indicate. Ditto. After a truck knocked a ground installed 240/120 transformer for my neighbor and my house, I was having trouble with lights getting bright when the furnace started. Called the utility right away, explained that they had just re-set the transformer the night before, and what my lights were doing. Service man showed up within the hour. Cut seal on meter and read voltages there. Had me just turn on the coffee pot. That load was enough imbalance that he could see there was a problem (and that it was on the utility side of the service). Whole line-crew showed up within the next hour and found the problem. A loose neutral when they re-installed the xfmr. While talking with the guys, mentioned that it was real nice of them to come out after 6:00 PM and all, but it could have waited. They replied that faulty wiring on their side is a big liability issue and they had to get to it ASAP. In the end, didn't cost me a dime. daestrom |
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Neutral failed inside pole transformer. Homeowner had a
defective earth ground. Therefore house obtained neutral through the gas meter - until gaskets eventually failed. Fortunately no one was home when the house exploded. Neutral failures and missing/defective earth ground should not be treated lightly. daestrom wrote: ... After a truck knocked a ground installed 240/120 transformer for my neighbor and my house, I was having trouble with lights getting bright when the furnace started. Called the utility right away, explained that they had just re-set the transformer the night before, and what my lights were doing. Service man showed up within the hour. Cut seal on meter and read voltages there. Had me just turn on the coffee pot. That load was enough imbalance that he could see there was a problem (and that it was on the utility side of the service). Whole line-crew showed up within the next hour and found the problem. A loose neutral when they re-installed the xfmr. While talking with the guys, mentioned that it was real nice of them to come out after 6:00 PM and all, but it could have waited. They replied that faulty wiring on their side is a big liability issue and they had to get to it ASAP. In the end, didn't cost me a dime. daestrom |
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On Mon, 06 Jun 2005 08:33:46 GMT wrote:
Thanks for the advice! To clarify something that was asked a few times, all of the numbers in the chart I gave were measured directly at the breaker panel. I took the cover off the panel and put one meter lead on the neutral/ground bus bar and the other meter lead on one of the two screw terminals where the hot wires from the meter are connected. If it is a loose neutral, it almost has to be on the power company's side. My breaker panel is right on the other side of the wall from the meter... the supply wires into the breaker panel enter through the rear of the box and I presume they are coming out the rear of the meter can as well. The neutral connection to the neutral/ground bus bar in the panel appears to be tight. That was the right way to take the measurements, and you've done the right thing in calling the utility. Your problem could be in the meter box or at the pole, but either way, they are the right ones to fix it. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
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wrote in message news  rppe.55421$Wr.10721@fed1read04...In alt.home.repair wrote: I will call the utility in the morning and see what they have to say. I'll post back with further developments. snip I called today at about 2 PM and the call center rep said that they came out yesterday and "repaired a connection at the weatherhead". To me, the "weatherhead" is the thing at the top of the conduit running up from my meter, where the wires make almost a 180 degree turn and go out through a plastic disc with holes in it. That would be it. I went out and looked at it from the ground and couldn't see anything different. I can't see my connections at the pole very well, so I'm not sure if anything changed there. I decided to retest. I measured again at the breaker panel, with most of the loads in the house shut off except as noted. The results we A/C uWave left right l-r notes off off 120.4 118.7 1.7 run 1 off on 120.9 117.8 3.1 on off 118.7 118.2 0.5 on on 119.0 117.1 1.9 off off 121.2 119.7 1.5 run 2 off on 121.5 119.0 2.5 on off 119.5 119.5 0.0 on on 120.0 118.2 1.8 The 3.1 volt spread does seem to be an improvement from the previous result, which was a 13.1 volt spread (-3.7 to +9.4). You don't look at the spread as much as the change in voltage when a single phase load is turned on verses when it is off. If the AC is 240 V, it really matters little if it is on or off. The voltages look perfectly normal now. I climbed up on the roof and inspected the connections at the top of the meter conduit. I have an insulated crimp splice on each hot wire, and a bare crimp splice on the neutral wire. I'm pretty sure that the hot wire splices weren't changed, as each one has a small crack in the insulation that has been there for a while, and I'm assuming the lineman would have replaced the insulation sleeve if he installed a new connector. I am not sure if the bare neutral splice was changed; even though I haven't inspected it carefully in the past, it doesn't _look_ brand new - there are some black spots (oxidation?) on it, and the engraved markings are easy to read because dirt seems to have accumulated in the grooves. There weren't any telltale bits of wire lying on the roof or shiny places on the wire next to the connector, either. The thing that holds the mechanical tension on the bare netural wire (basically a ramp on the wire and a mating ramp with a metal loop around the conduit) hasn't been changed. Probably recrimped the neutral connector. I'm also pretty sure that they didn't do anything to the meter. First, my lights didn't go out. Also, even though I didn't write down the serial number on the meter seal before I called, it's at least the same type of seal, and the metal loop through the meter can tab isn't shiny as I would expect with a new seal. New seals need not be shiny. They sit in a bin in the toolbox of a truck for months or years before installation. Also, he could open your meterbase, tighten the connections, and close the meterbase without ever interrupting your power, unless you have a 60amp meter base. It's entirely possible that the bad connection was at the pole and I'm mistaken about where the "weatherhead" is, or that the path from the lineman to the call center four states away is lossy and noisy. I'm curious to know what exactly was repaired, but the test results seem to show an improvement, so maybe I should just be happy. Thanks to all for the advice and assistance! Matt Roberds Charles Perry P.E. |
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wrote in message news rppe.55421$Wr.10721@fed1read04...In alt.home.repair wrote: I will call the utility in the morning and see what they have to say. I'll post back with further developments. Short version: Utility claims they fixed something and the test results are better (3.1 V difference as opposed to 9.4 V), but I'm still not sure what exactly they fixed. Long version: I called the utility on Monday afternoon about 2 PM, then hung around the house, hoping to catch the lineman and hear what he found, if anything. The utility did try to call at 7:03 PM per the Caller ID. I was in another room and the machine picked up before I did; I stopped the machine and picked up and got silence. By 9 PM I hadn't heard anything, hadn't noticed the lights going out, and I hadn't retested, so I decided to call again today (Tuesday). I called today at about 2 PM and the call center rep said that they came out yesterday and "repaired a connection at the weatherhead". To me, the "weatherhead" is the thing at the top of the conduit running up from my meter, where the wires make almost a 180 degree turn and go out through a plastic disc with holes in it. I went out and looked at it from the ground and couldn't see anything different. I can't see my connections at the pole very well, so I'm not sure if anything changed there. I decided to retest. I measured again at the breaker panel, with most of the loads in the house shut off except as noted. The results we A/C uWave left right l-r notes off off 120.4 118.7 1.7 run 1 off on 120.9 117.8 3.1 on off 118.7 118.2 0.5 on on 119.0 117.1 1.9 off off 121.2 119.7 1.5 run 2 off on 121.5 119.0 2.5 on off 119.5 119.5 0.0 on on 120.0 118.2 1.8 The 3.1 volt spread does seem to be an improvement from the previous result, which was a 13.1 volt spread (-3.7 to +9.4). I climbed up on the roof and inspected the connections at the top of the meter conduit. I have an insulated crimp splice on each hot wire, and a bare crimp splice on the neutral wire. I'm pretty sure that the hot wire splices weren't changed, as each one has a small crack in the insulation that has been there for a while, and I'm assuming the lineman would have replaced the insulation sleeve if he installed a new connector. I am not sure if the bare neutral splice was changed; even though I haven't inspected it carefully in the past, it doesn't _look_ brand new - there are some black spots (oxidation?) on it, and the engraved markings are easy to read because dirt seems to have accumulated in the grooves. There weren't any telltale bits of wire lying on the roof or shiny places on the wire next to the connector, either. The thing that holds the mechanical tension on the bare netural wire (basically a ramp on the wire and a mating ramp with a metal loop around the conduit) hasn't been changed. I'm also pretty sure that they didn't do anything to the meter. First, my lights didn't go out. Also, even though I didn't write down the serial number on the meter seal before I called, it's at least the same type of seal, and the metal loop through the meter can tab isn't shiny as I would expect with a new seal. It's entirely possible that the bad connection was at the pole and I'm mistaken about where the "weatherhead" is, or that the path from the lineman to the call center four states away is lossy and noisy. I'm curious to know what exactly was repaired, but the test results seem to show an improvement, so maybe I should just be happy. Thanks to all for the advice and assistance! Matt Roberds No your not mistaken on what the weather head is. I once had a ******* open delta service (commercial service) that lost a leg. It was dam near mid night before the line man showed. He got out of the truck with an attitude and was going to teach me something RIGHT NOW. He started spewing out the right way of testing the system as I kept my temper and held my tongue. He got the same readings as I had. Lost a phase. Then I turned on the 8 inch spot light on the roof of my service van. The light went to the transformer with one of the feeders hanging down cause the terminal on the transformer was gone. Absolute silence from the line man. They had to replace the transformer. Be happy that there is an improvement. Doubtful you will know the truth to what they really did. Never got so much as a oops from him. |
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Kudos. Not that the problem is fixed, but more important,
how you approached the problem. With intent and solutions to get it solved the first time. Others should appreciate why your attitude - how problem was addressed - was so productive. Also important: a (potentially) major problem was solved before it could happen. wrote: Short version: Utility claims they fixed something and the test results are better (3.1 V difference as opposed to 9.4 V), but I'm still not sure what exactly they fixed. Long version: I called the utility on Monday afternoon about 2 PM, then hung around the house, hoping to catch the lineman and hear what he found, if anything. The utility did try to call at 7:03 PM per the Caller ID. I was in another room and the machine picked up before I did; I stopped the machine and picked up and got silence. By 9 PM I hadn't heard anything, hadn't noticed the lights going out, and I hadn't retested, so I decided to call again today (Tuesday). I called today at about 2 PM and the call center rep said that they came out yesterday and "repaired a connection at the weatherhead". ... |
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wrote in message news rppe.55421$Wr.10721@fed1read04...I called today at about 2 PM and the call center rep said that they came out yesterday and "repaired a connection at the weatherhead". To me, the "weatherhead" is the thing at the top of the conduit running up from my meter Yup. N |
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According to :
In alt.home.repair wrote: I will call the utility in the morning and see what they have to say. I'll post back with further developments. Short version: Utility claims they fixed something and the test results are better (3.1 V difference as opposed to 9.4 V), but I'm still not sure what exactly they fixed. You did exactly the right things. For future reference: power codes require that the voltage varies no more than approximately 3-5% from a nominal 240V at the panel under worst-case conditions (ie: max power on one leg, zero on the other). Another 3-5% are permitted at the end of the circuits. [Precise values of permitted variance will change from jurisdiction to jurisdiction.] [Note all of the below is assuming you're measuring the voltages on the main bus bars. If you're measuring at a circuit-end, double them.] What that means, for example, is that the leg voltage at the panel on a given leg should drop no more than 4-5 volts even when max power on that leg, and zero load on the other. Given resistance in the neutral, _half_ of that would be the neutral "going towards" the maxed out leg, and half of that would be the maxed out leg "going towards" neutral. In otherwords, (100A panel right?), drawing 100A on one leg, zero on the other, the fully loaded side could drop as much as 4-5 volts (hot-neutral), leg-to-leg drop by as much as 2-3V, and unloaded side to neutral voltage could _rise_ as much as 2-3V. If the neutral-leg voltage varies more than half of the leg-to-leg does (see (1) below), you have a loose neutral. All that said, there are several caveats: 1) Extreme caution should be taken when taking the voltage levels off your voltmeter. There are a number of ways they can misread, and many voltmeters are simply not that accurate at measuring RMS volts. So, don't take a few volts either way seriously. 2) While voltmeters can be fooled by back EMI (line noise), for the most part it will be minor. To minimize these affects, use resistive loads (rather than motor or electronic). Ie: heaters. 3) While it may seem that you were approximately "on" those numbers, remember that your test loads were MUCH less than 100A, so the problem you were seeing was much worse than the allowable variance. Frankly, if your wiring was good, given the loads you were able to test with, I'd expect the voltage variation to be a volt at most, but, generally speaking, you can't rely on your voltmeter to that high a degree of accuracy. Most times the variation will be extremely obvious. You were on the low side of "obvious" [+] While your "fixed state" is _still_ outside of what I suggested above, it's a considerable improvement over what it was, and I'd be doubtful of taking it too seriously. That said, keep an eye on it. [+] The high side of obvious is having a lightbulb on one leg expire with a BRIGHT flash when you try to turn on something on the other leg - and that "something" doesn't work. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
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I'd recommend, you don't use a UPS, it's useless and a pain in the ass.One
friend of mine who runs a computer shop, told me that a customer had a kaputt ups after a power outage.When the power came back, the UPS went poof.All modern hard discs have an auto parking function in case of power failure, I think, and one should save everything regularly, I think. -- Tzortzakakis Dimitrios major in electrical engineering, freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr Ο έγραψε στο μήνυμα news:Xiroe.12325$Wr.100@fed1read04... All, Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9 volts difference between phases when a 120 V 1.3 kW microwave is running. Is this excessive, or acceptable? Long story: For the past few mornings, the UPS (APC Smart-UPS 600) in my office has been switching on to battery power for a few minutes, even when the lights in the rest of the house hadn't flickered or gone out. I finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the UPS while the UPS was running and found out it was probably tripping on _over_voltage: the wall socket was delivering over 130 volts! After a bit of experimentation, I discovered that the voltage went up when the microwave in the kitchen was running, which is why it happened in the mornings when the other half was making tea. The microwave is on one of the 20 A kitchen circuits, while my office is on a 20 A receptacle circuit with a couple of other rooms. It's a GE microwave, about 10 years old, 120 V 1300 W per the nameplate. I also noticed that the voltage rise was less pronounced when the central air conditioner was running. The compressor is 240 V and is fused and breakered at 40 A. Suspecting a loose neutral, I inspected the breaker panel. Nothing looked out of place. I tried tightening all of the screws on the neutral/ground bus bar. They all took a bit of tightening - less than 1/8 turn - but none were really badly loose. I made very sure that the neutral coming in from the meter was tight at the bus bar. I have the US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus panel. It is original to the house (1969), although the breakers have all been replaced. To my knowledge, the kitchen circuits are two separate 20 A circuits with their own NM cable, not split like a Canadian kitchen circuit. After I tightened the screws, I went around in the house and made sure most things were turned off. There were still a few computers running, but the TV, stereo, lights, etc were all off. The air conditioner was also shut off. I measured the voltage between the neutral/ground bus bar and each hot lug with the microwave off and then with the microwave running, heating about 8 oz (230 mL) of water in a coffee cup. I then turned the A/C on and tried again. Results... A/C uWave left right l-r notes off off 122.5 123.2 -0.7 run 1 off on 126.3 117.6 8.7 off off 121.9 121.3 0.6 run 2 off on 126.1 116.7 9.4 on off 119.6 123.3 -3.7 on on 123.7 118.5 5.2 I know that the two sides of the service will very rarely be in exact balance, but the 8 to 9 V difference seems somewhat high. Is this considered within reasonable bounds, or should I have the power company out? Or should I chase the wiring in the house further? When I moved into the house 5+ years ago, most of the receptacles were original and back-wired. I changed all of them that are regularly used for new spec grade side-wired receptacles. Out of curiosity, I measured the voltage drop across each breaker. This was with most of the loads shut off, so it may not be too useful, but I found no breaker over 100 mV and most under 40 mV. Let me know if you need more information. Thanks for your help! Matt Roberds |
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