Dimming lights


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Old 04-25-21, 08:00 PM
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Dimming lights

Hello,

I have bought a house and I would like to get an opinion on a potential electrical problem. I am attaching a drawing of the electrical wiring which is slightly complex because there is a NG generator acting as a backup of the grid.

The problem is that when a large appliance (e.g. dryer, AC condenser unit, etc.) starts, my lights in the house are dimming.
I first thought that the problem was related to the capacity of the breaker (70amps) installed for the subpanel (where the AC unit is connected); however, the breaker for the dryer is on the first panel and the lights on the subpanel still dim when the dryer cycles.

Thanks for the help!
 
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Old 04-25-21, 08:48 PM
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Do they dim when running on generator?
 
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Old 04-26-21, 03:17 AM
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Or is it just a momentary dim when power source switches?
 
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Old 04-26-21, 04:53 AM
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Unusual arrangement. Normally the utility power and generator power input to the transfer switch directly via breakers and the transfer switch connects one of the inputs to all the loads. Can you add the common and ground actual wiring to your sketch or another sketch? What is the load on breaker 7? You state breaker 9 is empty. What is the status of breakers slots 3, 4, 8, 10-13, 15 and 22? What breakers power the lights that are dimming? Do the lights dim when either input source is powering the loads (photo 2 in your sketch)?
 
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Old 04-26-21, 06:43 PM
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joed I have never started the NG generator as there is evidence that an electric arc occured in the transfer switch and my guess is that this generator has not run for at least 5y.

Norm201 Dim occurs when large equipment kicks in (dim for about 1 sec). This large equipment can be connected to the main panel or subpanel, the result is the same.

beelzebob The breaker for the NG Generator can only be a max of 70amps per spec sheet (16kW of max output power). I can add the ground to the schematic but what would be the link with my problem? I am asking because the house is from 1955 and I have quite a few plugs that are ungrounded.
I do not know the load on breaker 7 but can check. I could not find what the purpose of breakers 3, 4, 8, 10-13, 15 and 22 were but there is quite a bit of outside electric wiring (lights for plants, plugs, etc.) that some may be for that.
The breakers 16, 19 and 21 have lights that dim when the dryer starts (breaker 5) or the AC starts (breaker 25).


I can send pictures of each of the panel if that helps. I numbered them for that purpose.

Thank you all for the help!
 
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Old 04-27-21, 09:27 AM
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The question should be do the lights served by the main panel dim, or only the lights served by the subpanel? If only the subpanel, then I would suspect the transfer switch contacts are corroded/damaged (you said it shows signs of damage).

If all lights (both those served by the subpanel as well as those served from the main panel) dim, then I would suspect poor contact where the cables from the meter connect to the main panel. It's not unusual for those to corrode or loosen over time. Unfortunately, it's not a safe repair unless you have the proper tools and know what you're doing - a job best left to an electrician.

(If it were me, I'd have him check the generator, and if it works (may only need a new battery), I'd replace the guts of the transfer switch and get that system working again. Never know when you'll need it!)
 
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Old 04-27-21, 12:09 PM
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I have just checked and the problem occurs to all the lights (on main panel and subpanel). For the transfer switch, I am attaching a picture of what I think was an electrical arc in the past.

Thanks!!


Zoom in of the other picture
 
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Old 04-27-21, 12:12 PM
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Also for the poor contact where the cables from the meter connect to the main panel, I am attaching a picture of the main panel. Thanks!!

 
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Old 04-27-21, 04:12 PM
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The photo of the transfer switch shows the neutral bus has 3 wires connected via lugs. One is from the main panel or meter box, one is from the generator and one is to the subpanel. I can't see more than 1 lug connection for the common wire in the main panel so I assume the neutral wire in the transfer switch is connected to neutral bus lugs in the meter box. There must also be a neutral wire from the main breaker panel connected to a lug on this neutral bus. A loose connection at this neutral bus could be a source of the dimming as it is common to both panels.
 
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Old 04-27-21, 05:34 PM
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You are right, the transfer switch shows the neutral bus has 3 wires connected via lugs, one is from the main panel, one is from the generator, and one is to the subpanel. However, in the main panel, there are two wires on two neutral buses, one to the transfer switch as you said (to the left), and the other from the meter box (to the right).
 
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Old 04-28-21, 04:22 AM
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Not sure how to interpret your statement there are 2 neutral buses in your main panel. When manufactured, a main panel contains one neutral bus and one ground bus. If the neutral bus gets filled to capacity, an expansion can be added by clamping it to the original neutral bus. I would make sure the lugs on the neutral bus wires in the meter box, main panel and transfer switch are tight. Make sure the tightening tool is insulated except for the tip and wear good gloves or call an electrician.
 
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Old 04-28-21, 09:46 AM
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A transfer switch will arc when it switches if there are any electrical things running at the time. It's hard to see, but I think that switch is probably ok.

Since the next things to check are in the main breaker panel (and cannot be disconnected by you) then I think the safest thing to do is call an electrician who has the right tools and protective gear to do the job safely. He or she can check the condition of the transfer switch at the same time.

Personally, I would do it myself, BUT I have the right equipment and have wired (to code) about a dozen houses. And I still would be nervous. Let that be a guide.

 
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Old 04-28-21, 10:40 AM
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I think you nailed the problem. The wire on the left side coming from the meter and going to the main breaker seems slightly disconnected compared to the wire on the right side. Iíll have an electrician fixing that. Thanks everyone for all the comments and help!!
 
 

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