dimming lights, loosing power to half of room


Old 08-28-07, 03:04 PM
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Join Date: Aug 2007
Posts: 4
dimming lights, loosing power to half of room

We have been having issues with the electrical in our new house for almost a year now. We have had two electrical contractors that work for the builder come out as well as the power company to check on things and we keep having issues. I'm hoping someone out there will have an idea of what the problem is and how to resolve it. Here's what we have experienced:
When the upstairs air handler is coming on the lights dim.
On more than one ocassion half of a room goes dark while the other half stays lit in a storm that takes out the power.
We have GFIs in the breaker box for the bedrooms upstairs and anytime that we change a light fixture etc. we trip the GFI. Now when there is a fluctuation in the power, one of the bedrooms and the smoke detectors, but not to the bathroom will loose power and we have had to go to the box and flip the breaker to full off and then on. Now this doesn't work and the power won't come back on to one of the bedrooms and smoke detectors. The electrician took out one of the GFIs and replaced it with a regular breaker to give us power again. Sorry to be so long. Thanks for any insight.
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Old 08-28-07, 03:10 PM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
I think you will find that the breakers for the bedrooms are AFCI breakers. and NOR GFCI breakers. It sounds like they did their job, and tripped. The AFCI breaker should have been replaced with a new AFCI one, not with a regular one. get that guy back and have him try a new AFCI breaker.

I suspect that the electrician who wired the house did so on the cheap, and back stabbed the receptacles and switches. Have you checked for and (if found) fixed this?
Old 08-29-07, 03:10 AM
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Join Date: Aug 2007
Posts: 164
The dimming lights problem is because the contractor put the lights on the same circuit as the outlet your airconditioner's on. When the compressor kicks in, you get a voltage drop that dims the lights. Unfortunately putting lights and outlets on the same circuit is a common residential practice because it's all about getting it done cheap. I'm against it because your problem is a common one. I agree with Bob about the AFCI. If you had a GFCI breaker the bathroom would've been on it too. You tripped out the AFCI by changing a light bulb because you didn't turn the light off first. As you screw the bulb in and it starts to make electrical contact, it causes a small arc. The AFCI is designed to trip at the slightest arc fault. plugging in any appliances that are already switched on will cause this too. I'd throw a fit and see if you can get that contractor back there to seperate the lighting circuit from the outlets. At least get them to put an AFCI breaker back in.
Old 08-29-07, 09:48 AM
Join Date: Dec 2006
Location: orange county
Posts: 285

Interesting and usefull info about AFCI circuits and the necessity to turn of the light switch before screwing in the bulb. I would have never known. Split system A/C are on two circuits. The C/U is on a 240v circuit. The air handler is generally on a 120v dedicated circuit. (unless it also has strip heating). I'm embarrased to say I'm not certain wether the NEC requires this 120v circuit to be on a dedicated circuit. I have always done so, but I know a lot of HVAC contractors tap of a general purpose branch circuits for the air handler.

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