[rbeck]

I think he meant Dirty Power.......Power fluctuations

 

[coolwhip]

Poor ground/corroded - oxidized ground lug at panel.

 

[motoguy128]

Sorry... I meant "dirty". the "I" and "U" are next to each other on the keyboard and I type too fast. Yes power fluctuations normally caused by larger customers switching large loads on and off the grid as well as feedback from those large inductive loads. Dirty power usually has spikes in voltage as well as "blips" (sudden drops) on occasion. Not much fun at industrial settings. Even a small blip will usually take you down... and it takes hours to get back up again.

But just Dirty Power would not really explain a constant voltage sag demonstrated by the dimmed light bulb.

I'm a little dissapointed the power company and electrican didn't do something simple like measure your voltage in response to seeing the dimmed light.

 

[WhoIsThat?]

I'm a little dissapointed the power company and electrican didn't do something simple like measure your voltage in response to seeing the dimmed light.

"Light output is approximately proportional to V^3.4" for an incandescent.

So for 50% of normal light output the voltage for a 120v lamp would be 98v and (120-98)x30A = ~700W.

I'm surprised the OP doesn't smell something burning when the HVAC is on.

http://www.youtube.com/watch?v=Ozc70JPGRMQ

 

[Kevin O'Neill]

If the lights were dimming only at AC startup, I would put the compressor breaker nearest the main lugs in the panel. That helps sometimes. But it sounds like a bad connection somewhere in the system. Could be the transformer, the lateral from the pole to the house, the meter base, a breaker or any number of other things. An electrician should be able to locate it.