Home>Discussions>ELECTRICAL & LIGHTING>dimming lights with new electrical
9 posts / 0 new
Last post
4squareowner1
dimming lights with new electrical

We just had an electrician update our electrical in our old house. Went from knob and tube to conduit throughout the entire house and updated our panel from 100 to 200 amps. When our A/C or dishwasher kick on, our lights still briefly flicker. It was a problem before but we assumed once we got the additional amps, it wouldn't happen anymore. Is that still common despite our upgrades? If not, what is the problem? just want to have some insight into the issue before we address with the electrician.

Thanks in advance for any feedback!

dj1
Re: dimming lights with new electrical

Question: when the electrician upgraded the panel from 100 to 200, did he/she use some of the old circuit breakers or did he/she install all new breakers? if you don't know or not sure, please ask him/her.

keith3267
Re: dimming lights with new electrical

You didn't upgrade your "amps". You increased the capacity of your circuit breaker panel, that is all. Your overall capacity did not change and I doubt it is anywhere near 200 amps. Most likely it is 62.5 amps.

Two things limit your "amps", they are the cable from the transformer and the transformer itself. This is from your utility company. If you live in a suburban or urban environment, you probably share a larger transformer with your neighbors so this is not the restriction. If you have a dedicated transformer that serves only your house, it will be much smaller and they have a tendency to dim the lights when large appliances kick on, but the lights should not flicker, just dim a little.

Transformers have losses, one of those losses is no load losses or also called iron losses. This is the amount of power they use just being plugged into the distribution circuit, even when there is no load on them, that is there is nothing turned on in the house. The larger the transformer, the larger the losses. The losses are on the utility companies side of the meter so you are not paying for them, but the utility company is unlikely to install a larger transformer for you, it cuts into their profits.

If you have flickering, then there could be a loose or corroded connection somewhere on the supply line to your house. It could be in the meter or even on the transformer itself. You should call the utility company to come out and inspect. Loose or corroded connections can cause fires, but also contribute to the other type of losses transformers have, load losses. It is in their interests to reduce those as well as they are paying for them.

Brad
Re: dimming lights with new electrical
dj1 wrote:

Question: when the electrician upgraded the panel from 100 to 200, did he/she use some of the old circuit breakers or did he/she install all new breakers? if you don't know or not sure, please ask him/her.

Could you please explain how branch circuit breakers would cause the OPs issue?

Mastercarpentry
Re: dimming lights with new electrical

Another thought here which should have been covered but might have been missed- Did the utility company upgrade the wires from the transformer to the house? Old K+T designs didn't carry that much power so smaller wires were used here. Putting a thousand amp panel downstream of them won't add to their ability to feed everything. I mention this because where I live you must specifically request this when doing a service upgrade or they will just inspect the existing wires and leave them if they're in good shape- they charge for a separate service call if you have to ask for this afterward since they were already there once gratis and could have done it then!

I live in an older part of town where the transformers and lines are nearly ancient. Mine feeds 5 houses so when any one of us applies a high load we all lose voltage! Flicker, dim and hum are normal for me :p

Phil

dj1
Re: dimming lights with new electrical
brrichter wrote:

Could you please explain how branch circuit breakers would cause the OPs issue?

Old breakers and wires sometimes have hidden issues, could be corrosion which is not visible, could be broken casing, could be bad insulator, could be a loose connection, and so on.

If you get a new panel, get new breakers, even when you get the same brand panel.

When you change your oil in your car, do you keep the old filter?

Fencepost
Re: dimming lights with new electrical

I would call the electrician and explain what you are experiencing, and ask them to come back and double-check the tightness of the connections in the breaker panel, and render an opinion on the adequacy of the incoming service from the power company.

4squareowner1
Re: dimming lights with new electrical
dj1 wrote:

Question: when the electrician upgraded the panel from 100 to 200, did he/she use some of the old circuit breakers or did he/she install all new breakers? if you don't know or not sure, please ask him/her.

I believe it's new circuit breakers but I'll ask.

4squareowner1
Re: dimming lights with new electrical
Mastercarpentry wrote:

Another thought here which should have been covered but might have been missed- Did the utility company upgrade the wires from the transformer to the house? Old K+T designs didn't carry that much power so smaller wires were used here. Putting a thousand amp panel downstream of them won't add to their ability to feed everything. I mention this because where I live you must specifically request this when doing a service upgrade or they will just inspect the existing wires and leave them if they're in good shape- they charge for a separate service call if you have to ask for this afterward since they were already there once gratis and could have done it then!

I live in an older part of town where the transformers and lines are nearly ancient. Mine feeds 5 houses so when any one of us applies a high load we all lose voltage! Flicker, dim and hum are normal for me :p

Phil

Good question - I am not sure about what exactly the utility company did. I'll have to double check.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.