Intermitten (shuts off randomly) power to one side of electrical bus bar

What could be the problem?

  • Bad contact to main breaker

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  • Replace 2-pole 50 amp breaker

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phillipa1972

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This is an apartment complex. The service panel has two rings, or meters, and 2 Murray 2-pole 50 amp breakers. The service panel is about 25 to 35 years old. Each 2-pole 50 amp breaker services a subpanel in each apartment. No issues with apartment A, but problems with apartment B.

I took a voltage reading off of the two legs from Southern California Edison (SCE) going into the main service 100 amp breaker for each of the apartments. All four read 117 volts. Two for each apartment.

I then went into the subpanel and took a reading directly from the two main wires coming from the service panel for apartment B, only one has 117 volts. Other is completely dead. Went back to the main 2-pole 50 amp breaker. Switched it on and off but still one "dead wire" at the subpanel. I then switched the 2-pole 50 amp breaker with apartment A's 2-pole 50 amp breaker. Still had same issue with the apartment A breaker that I just hooked up to apartment B. Put original Apartment B breaker on apartment A and no issues with apartment A. Seems like both 100 amp main breakers are fine.

The "dead wire" in the subpanel randomly shuts off and on. Time frame is about every 30 minutes or so. This is even with the HVAC off so that is not the issue. The contacts for the main 2-pole 50 amp breaker are not scored but I don't have access to see where the "dead wire" hooks up to the main 2-pole 50 amp breaker contact because it is right behind the electrical service meter.

So I'm thinking that the contact I can't see may be loose or bad.

1) Do I need to contact SCE to have them remove the meter?
I know how to replace the whole dual service panel if necessary but I'm not a licensed contractor.

2) Do I need to be a licensed contractor to replace the panel if necessary? This is in California.

Any suggestions on further diagnostics would be helpful.

Thank you,

Phil
 

Jadnashua

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First order of business, make sure that all of the connections are tight. Look for corrosion, arcing. This includes the internal bus bar. It's possible that the supply wiring is damaged somewhere in the run as well. That won't always trip the breaker. Is the wiring copper or aluminum? IF aluminum, it can be a bad connection, but not look like it, if the wrong method/materials are used.
 

WorthFlorida

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Does each apartment have an electric water heater? Since the timing appears to be about 30 minute intervals something might be cycling on and off like a water heater drawing a lot of current, creating heat. A good tool to buy is an infrared thermometer. (http://www.homedepot.com/p/General-...ximum-Temperature-608-Degree-IRT206/100651817). With every breaker switched on and no loss of power to that one line, check temperatures at each breaker, near the buss bars and any connectors. The one area that you cannot see check the temperature in the general area. If you find one connector or breaker to be at a much higher temperature then you have an area to look into. Any corrosion with current running through it will generate a lot of heat. If there is a water heater, run the water so as to allow the heater to switch on.

Yes, you will need a licensed electrician to replace the panel and if the power that feeds the panel cannot not be switched off the meter needs to be removed. All power companies have procedures on removing meters. All meters have a tag and to remove the meter the tag needs to be cut, but it needs to be replaced by the power company. If the power company finds a tagless meter it indicates tampering that can lead to extra charges. It can also indicate that work was done and may insist on an electrical inspection or a signed off permit.

Since this is an apartment dwelling any electrical work done by a non licensed person could jeopardize your insurance liability should there ever be a claim due to electrical problems, fire, shock, etc.
 

Dilan

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Honestly I'd hire a licensed electrician, with it being an apartment complex and all, it would put the liability out of your hands if something were to go wrong if you hired a professional.

If by "dead wire" you mean that one leg isn't working on the subpanel then my guess would be a loose connection between that breaker and the subpanel. Also check the cable itself. Apartment complexes sometimes use aluminum service cable for their sub panel connections. With aluminum wiring you have to use a special paste and breakers with aluminum rated contacts (have silver stripe instead of bronze near terminal) to get a solid connection. I'd say visual inspection of the wire but that's only for parts you can access. You might be looking at a new run if it's not at either end.
 
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