Electrician Talk banner
1 - 20 of 50 Posts

·
Registered
Joined
·
99 Posts
Discussion Starter · #1 ·
Homeowner stated to me today that when her AC compressor kicks on her lights flicker. I explained a couple possible issues. Uneven load on that particular leg of the service? Possibly a poco issue with voltage? Thoughts? A common problem that I feel I need to be more educated on.
 

·
Electrical Simpleton
Joined
·
3,350 Posts
I'm gonna go with the lights are momentarily dimming due to voltage drop from the inrush current on the compressor motor.

Pete
 
  • Like
Reactions: micromind

·
Registered
Joined
·
99 Posts
Discussion Starter · #4 ·
As a side note... is your homeowner a polar bear? Who in MA is using their A/C at the moment?:blink:

Pete
Haha I don't believe its happened recently. But it could be used a heat pump as well. The lights continue to flicker as the compressor runs.
 

·
Bilge Rat
motors and controls.........
Joined
·
8,849 Posts
I'm gonna go with the lights are momentarily dimming due to voltage drop from the inrush current on the compressor motor.

Pete
Me too, and the more energy efficient it is, the higher the starting inrush.

If a 'hard start' kit is available for the unit, it'll reduce the inrush to some degree.
 

·
Registered
Joined
·
32,059 Posts
Utility transformer is undersized for the inrush-
Utility lateral is undersized voltage drop.
Issue with the panel or meter base check for high resistance connections.

Is it bugging her, I had one customer that was a train wreck over this crying when she explained it to me.
 

·
Registered
Joined
·
32,059 Posts
Make sure you have a good incoming neutral from poco and all load neutrals are tight.


Anytime you have any voltage issue in a house I would check the neutral too much to lose from an open neutral

The average electrician over tightens connections and almost all connections are over tightened.
 

·
Registered
Joined
·
60 Posts
Can't disagree with the neutral connection but, it seems to me that a bad neutral from the main would show its self on other 120v loads. e.g. icebox compressor, microwave, washer etc..
 

·
Chairman of the Bored
Joined
·
9,774 Posts
Can't disagree with the neutral connection but, it seems to me that a bad neutral from the main would show its self on other 120v loads. e.g. icebox compressor, microwave, washer etc..
not necessarily: one leg tends to die while the other gets over voltage, which doesn't always affect some 120v equipment
 

·
Electrical Simpleton
Joined
·
3,350 Posts
I certainly know that there are 120 volt condensers out there but the majority of condensers and/or heat pumps I see are 240 volt at residential settings.

Exactly how does the neutral play in a 240 volt circuit?

Pete
 

·
Registered
Joined
·
60 Posts
not necessarily: one leg tend to die while the other gets over voltage, which doesn't always affect some 120v equipment
Possible but would you agree that if one leg goes down to lets say 85-90v the lights would dim and if the other leg spikes to 135-140v the lights would brighten.
 

·
Registered
Joined
·
60 Posts
I certainly know that there are 120 volt condensers out there but the majority of condensers and/or heat pumps I see are 240 volt at residential settings.

Exactly how does the neutral play in a 240 volt circuit?

Pete
That's why my suggestion was a little PM at the unit and the corresponding discs.
 

·
Registered
Joined
·
11,762 Posts
Sounds like a loose hot. There is no way to know without going in checking this all out.

BTW, if this isn't a heat pump never run a compressor below 55*. Oil migrates out of it or something I think.
 

·
Registered
Joined
·
880 Posts
We had one just today. The original 200 amp meter/main setup had two neutral lugs one on top of the other screwed thru the grounding bus, thru the flat neutral jumper that goes to the line side, and into a 10/32 threaded hole in the back of the cabinet. The 10/32 screw was melted or broke off and the only neutral connection was from the broken off lug laying on top of the other one. The customer said lights have been dimming for about four months, they thought the house needed re-wiring! We got a new 250MCM lug and drilled/tapped for a 1/4-20 and bolted it in.
 
1 - 20 of 50 Posts
Top