100 amp to 200 amp questions

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  #1  
Old 07-17-06, 05:52 PM
pgn
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Question 100 amp to 200 amp questions

OK. I recently had service to my house upgraded from 100 amp to 200 amp service. I did this in the hopes of having some irritations fixed. The irritations are: lights dim when outside central compressor air kicks in, lights dim when inside a/c window unit kicks in, and lights dim when disposal is used. These problems weren't solves, so I'm going to make some suggestions to the electrician, but I'm not sure I'm accurate in my assumptions.

I think this may solve these problems, or maybe I'm way off base.

For disposal: currently has own circuit rated at 15 amps, will changing to 20 amps fix lights dimming (all over house) when it goes on?

For inside air. Previous owner had their unit in a separate outlet that had its own 20 amp circuit. Current place I have it is on a 15 amp shared with several other devices like TV, lamps, and computer. Will swapping these two breakers solve the problem?

Finally, for outside air: It's on a two-pole 20 amp circuit. I have an attic exhaust fan (not whole-house, just for attic area) and it has a two-pole 30 amp circuit. I can't see how the small exhaust fan would use 30 amps, whereas I can see how the outside compressor would. I'm going to suggest swapping these two.

So, what do the pros think?
 
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Old 07-17-06, 06:20 PM
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If the lights throughout the house dim whenever a high-current load starts then most likely the problem is not one that you can solve but involves the power company transformer and service to your meter.

What I would do at this point is probably not a DIY project but I would connect a recording voltmeter to the incoming power supply, preferably at the input connections of the main circuit breaker. This recorder could either be a peak/valley recording digital meter or a chart recorder. I would record the voltage supplied to the house for no less than 24 hours and as much as practical I would make notes as to the times and conditions of any light dimming activity.

If this analysis shows a significant dip from the "nominal" supply voltage, especially with different high-current loads having the same effect, then there is a voltage regulation problem from the power company. This could be from an undersized transformer serving you or undersized service cables to your meter.

If only a single unit in your house causes the problem then it could be a fault in that particular unit.

I suggest that you contact your power company and explain your concerns, they will probably run the 24 hour voltage monitoring themselves.
 
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Old 07-17-06, 07:17 PM
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dimming lights

disposal on dedicated is best. a/c also should be on dedicated. do not bump up breaker if wiring is not upsized. that will not make problem go away. have electrician amp-probe each leg to see what the draw is. uping to 200 should have given you plenty of room. try moving light breaker up or down one spot first. sounds funny but it has worked in past.
 
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Old 07-17-06, 07:30 PM
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DO NOT go swapping breakers around for larger ones!
Only use breakers appropriate for the circuit and corresponding wire sizes.

The lights dimming is unfortunately a very common occurrence and is even found in new homes. It is usually a POCO issue but can be local to the house as well.
A slight dimming is even normal and acceptable with regards to air conditioning and refers/freezers.
 
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Old 07-17-06, 10:13 PM
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My house is brand-spanking-new. It has a 200A service and is wired, inspected and accepted to 2005 NEC. The transformer on the pole is new as well. The lights dim a bit when the central A/C kicks on. I never gave it a second thought - I consider this is normal.

Joe Michel
 
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Old 07-18-06, 01:00 AM
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If the lights momentarily dim and then return to normal when a high current load comes on it is normal. If the lights dim and stay dim all the time the high current load is running it is not normal.
 
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Old 07-20-06, 07:48 PM
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Originally Posted by furd
If the lights momentarily dim and then return to normal when a high current load comes on it is normal. If the lights dim and stay dim all the time the high current load is running it is not normal.
Thanks for the clearification, Furd. Yes, the lights dim for a second, then return to normal.

Joe michel
 
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