Lights dim when vac/dryer etc. turn on. New panel

[Itsjustdirt]

A friend just had a new 200 a panel installed, new supply wire from the pole, new wiring (12-2) throughout the house.

When a shop vac or clothes dryer is turned on in the house, all the lights dim briefly.

I thought for sure that would not happen with all new wiring/panel. What gives?

 

[teamextreme]

Lights dimming when a large load is turned on is somewhat normal, however, if it's very pronounced or worse than before, then check the main connections at the panel and at the weatherhead, especially the neutral. I had a service call once for this symptom and found a really loose neutral connection at the weatherhead (someone made the connection using the clamp of a 2-screw romex connector ).

 

[wyliesdiesels]

Could be a loose connection.

I had this problem in a house i used to rent.

Would turn on garbage disposal and lights would dim.

So i hooked up my meter to mains and one leg was dropping to 100v.

I called PoCo and troubleshooter came out. Discovered a very hot wire at a splice on a pony pole. Had to make another secondary splice to fix the issue.

If youre comfortable taking voltage measurements in a live panel, check what the voltage is both with appliances off and when starting.

It could also be normal or the transformer is undersized or overloaded.

Every house Ive live in has had dimming lights when the AC starts. but those are large loads...

 

[BillK]

He needs to call the power company first. I have a 200 amp service in my 40 year old house and I have never seen the light dim when I turn on the clothes dryer. Its on is own breaker and really should not affect the others unless something is happening to the supply voltage. Same with the electric oven.

 

[ard]

I had the same situation- running a 240V40A table saw in the shop, the lights dimmed.


Traced it to a bad leg on the transformer out on the pole. POCO's issue

Initial poco agent insisted "you need an electrician'. Finally I talked to someone w a brain and they rolled a truck. (You could see the voltages at the main connection, so it wasn't my wiring.). Guy used an IR gun to measure the transformer from the ground, said "yep, it's bad"

Rolled two trucks out on 12/31. They mentioned it was triple time if it went past 5PM.

They were done a 5:20.

 

[Jim greengo]

Lights dimming when a large load is turned on is somewhat normal, however, if it's very pronounced or worse than before, then check the main connections at the panel and at the weatherhead, especially the neutral. I had a service call once for this symptom and found a really loose neutral connection at the weatherhead (someone made the connection using the clamp of a 2-screw romex connector ).

 

[ard]

Lights dimming when a large load is turned on is somewhat normal,

.

Actually, how much **IS** normal?

Is there a spec on this? How much voltage drop can one see on a poco feed and still be considered 'normal'?

Typically each poco (and/or the utility commission) will have a spec on the voltage range- say 120V+/- 3.6V (or whatever). Do they need to meet this no matter the draw up to the rating of your panel? Or the design rating of your loads at the time of install???

Would be a useful concept to understand...

 

[sberry]

They usually do meet this and even better. I was surprised when I had them run a load on a 100A, long chain fed a long way in town and it pulled 130 with 1 volt drop. I couldn't believe it was that good.
I had another in the same neighborhood we had a problem with on 1 leg, they gave me a little shate about it, couldn't find it, worked till the wind blew. Finally drops in the parking lot one day.