# 1930s house, new service, old clad wiring, dimming lights



## borzym60 (Nov 6, 2014)

I have a house with newer service and main box, all new breakers, which are tied into the old existing metal clad/BX wiring and some newer romex. 

When heavy appliances turn on, despite being on a entirely different breaker, all the lights momentarily dim no matter what room your in.

Is this a grounding issue because the ground is carried through the metal sheathing around the clad wiring which is old and deteriorating? 

The house has 100a service at the main.


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## wildleg (Apr 12, 2009)

no .


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## macmikeman (Jan 23, 2007)

It is not all that unusual to see that on 100 amp services in old houses, small poco transformer coupled with distance to house and a few other factors could be dropping the voltage when motors or large loads are energized.


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## duaneb (Nov 4, 2014)

had similar problem found bolt in meter socket connecting the neutral was deteriating causing unbalanced loads


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## retiredsparktech (Mar 8, 2011)

macmikeman said:


> It is not all that unusual to see that on 100 amp services in old houses, small poco transformer coupled with distance to house and a few other factors could be dropping the voltage when motors or large loads are energized.


I've seen, where just the service was changed from 60 to 100 amps and the service drop POA was OK, the utility would just reconnect, the new service feeders to the existing drop. I gauged the wire and it was something like #7 aluminum. I know that the drop is in free air and has more ampacity, but I believe it has too much voltage drop, under heavy loads.


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## pete87 (Oct 22, 2012)

Get rid of that Old Refrigerator you got . It will drain Hover Dam when it cycles .







Pete


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## The_Modifier (Oct 24, 2009)

> *About borzym60*
> What is your electrical related field/trade:
> contractor


Just for curiosities sake, what type of contractor are you?


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## 1.21gigawatts (Jun 22, 2013)

Record the voltage sag at the panel when these loads start, to see if it may a transformer issue. Run a temp feed to a large appliance and fire that bitch up to see if there is no dimming indicating its a wiring issue (voltage drop from high impedance)Measure the voltage at the load while running, to see if your getting voltage drop on the branch.

If these are older appliances with compressors, I would expect some dimming.


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## FrunkSlammer (Aug 31, 2013)

Only an apprentice or non electrician wouldn't know why the lights dim when a heavy load kicks on. 

This don't pass the sniff test... unless it's an apprentice.


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## chicken steve (Mar 22, 2011)

~CS~


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## North Coast Lights (Apr 20, 2011)

Check voltages at the main panel under load, and measure each leg to neutral, to make sure they are equal. I've had some interesting problems with poor neutral connections to the panel.


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