xxrobertxx
Member
I ran a dedicated line for a new FAU but when the FAU kicks on the lights in the dinning room dim alittle then come back to normal power. FAU is on a dedicated line and separate from the lights. What could be causing this?
lights dimming
- Thread starter xxrobertxx
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Service conductor undersized.
Feeder conductor undersized.
Branch circuit conductor undersized.
Loose connection in the service.
Loose connection in the feeder.
Loose connection in the branch circuit.
Wrong motor rotation (3-phase).
FAU has airflow path blocked.
Motor out of alignment.
Start capacitors bad or off-line.
Welcome to the forum.
Feeder conductor undersized.
Branch circuit conductor undersized.
Loose connection in the service.
Loose connection in the feeder.
Loose connection in the branch circuit.
Wrong motor rotation (3-phase).
FAU has airflow path blocked.
Motor out of alignment.
Start capacitors bad or off-line.
Welcome to the forum.
bakerbrotherselectric
Member
We had a service change we did about 18 months ago for two reasons, dimming when big loads kicked on , and the old panel was a FPE..
Customer had called the power company complain of the dimming prior to us doing the change. The power company sent out a service tech. who installed a device that took snap shots of his electrical system when large loads kicked on.
The results came back showing spikes of up to 180 amps, lasting up to 7 seconds. The 100amp main on the FPE never tripped. Change his panel out, but still suffered the same dimming affects. The new 200amp CH did not trip either. Only to call and talk to the power company and find out the transformers in this neighborhood where the original ones from 1974. Everyone in this neighborhood had upgraded there AC units to gigantic over sized ones, overloading the undersized transformers at the street. Every neighbor we talked to suffered from the dimming of the lights when big loads kicked on. The power company said its in the works to change out the transformers in that neighborhood. Wonder how looooonnnnnnggggggg that will take.
Customer had called the power company complain of the dimming prior to us doing the change. The power company sent out a service tech. who installed a device that took snap shots of his electrical system when large loads kicked on.
The results came back showing spikes of up to 180 amps, lasting up to 7 seconds. The 100amp main on the FPE never tripped. Change his panel out, but still suffered the same dimming affects. The new 200amp CH did not trip either. Only to call and talk to the power company and find out the transformers in this neighborhood where the original ones from 1974. Everyone in this neighborhood had upgraded there AC units to gigantic over sized ones, overloading the undersized transformers at the street. Every neighbor we talked to suffered from the dimming of the lights when big loads kicked on. The power company said its in the works to change out the transformers in that neighborhood. Wonder how looooonnnnnnggggggg that will take.
alfiesauce
Senior Member
This is a classic 'problem' that seems to come up when electricians are on sight.
I can't count the the number of times people have asked me what I did to their power because all of a sudden their lights are dimming when they start their dryer.
I calmly explain to them that this has always happend and that the only reason that they just noticed today was because I was here so they were more aware of the electrical components in their home.
Near as I can figure- large current draws drop available current to the rest of the home and thus drops the supply for brief moments. The combination dimms lights, will set UPS's a beeping, cases hardship on fragile electronics, etc. etc.
The reasons for this primarily go back to the supply authorites ability to supply the needed power requirements in the community like baker suggested.
I can't count the the number of times people have asked me what I did to their power because all of a sudden their lights are dimming when they start their dryer.
I calmly explain to them that this has always happend and that the only reason that they just noticed today was because I was here so they were more aware of the electrical components in their home.
Near as I can figure- large current draws drop available current to the rest of the home and thus drops the supply for brief moments. The combination dimms lights, will set UPS's a beeping, cases hardship on fragile electronics, etc. etc.
The reasons for this primarily go back to the supply authorites ability to supply the needed power requirements in the community like baker suggested.
- Location
- Illinois
- Occupation
- retired electrician
I would not expect that a 180 amp, 7 second spike would cause a 100 amp breaker to trip. Looking at the time trip curves for a major brand breaker, a 200 amp load will cause the 100 amp breaker to open some time between 27 and 250 seconds.bakerbrotherselectric said:
mdshunk
Senior Member
- Location
- Right here.
I highly doubt that FAU is winking the lights. I'd rather suspect its associated hermetic refrigeration compressor. If, indeed, that FAU is the lone item winking the lights, you need to hunt down a bad feeder or service connection someplace.
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