# Strange residential problem



## knowshorts (Jan 9, 2009)

I got a weird one. Customer called me a couple days ago. Digital clock was blinking like there was a loss of power. The next day power was lost to same clock and tv in kitchen. Customer went outside to look for any tripped breakers. None were found. Turned on exterior light and nothing. Went over and tried exterior 240 air compressor. Started real slow then powered up to full speed. Then everything started working fine. This scenario has been going on for about a week and according to the customer, it's migrating to other areas in his house. 

Panel is a 1965 era Square D all in one. 100 amp. With the old school QOT horizontal tandem breakers with conductor stab holes. Everything in the interior of the house is off of this panel. Below main panel is a little 3r sub feeding the garage and exterior compressor and convenience outlets. The main for the sub originates from the main panel above. 

My original thought was a burnt main. Pulled the meter, main, and all breakers to look for heat damage. Everything looked pristine. Voltage was good across all terminals. Re-tightened all terminals that I could. That's all I had time for yesterday. 

It happened again this morning. The customer turned on his air compressor to fix it, prior to calling me. I can see a breaker starting to fail and intermittently cutting out, but why would the air compressor be the magic fix? And this is starting to effect multiple circuits. 

Besides replacing all the existing breakers, what am I missing here? I don't think a panel upgrade/replacement is necessary due to the bus being in excellent condition.


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## 480sparky (Sep 20, 2007)

If the power comes back on, I seriously doubt the circuit breakers tripped then magically reset themselves.

Are all the items that lost power on the same circuit? If so, I'd suspect something in that circuit.

If they're not, then are the circuits that loose power on the same phase/leg? If so, I'd start looking at that side of the service. It could be anything from where the main attaches to the bus bar all the way back to the POCO transformer.


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## knowshorts (Jan 9, 2009)

I believe they are on different circuits. I haven't been in the house yet. I don't know about the same leg either, because, I only had access to the exterior. Temporarily losing a leg did cross my mind, that's why I checked the main first. If it was a problem with the POCO wouldn't they know immediately because of their smart meter? 

One more thing to add, customer has added no additional load, and this apparently is happening at various times during the day and night. No pattern.


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## Dennis Alwon (May 9, 2009)

Sounds like a classic bad connection eiher at the main breaker or at the poco side of things. Very often it is a poco problem.


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## oliquir (Jan 13, 2011)

already had a similar problem look at neutral connection, i had bad connection and i had about 100V on 1 side and 140V on other side, voltage were varying depending on load balancing between the 2 legs.


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## jza (Oct 31, 2009)

Sounds like a break in the neutral conductor too me. Last time I ran into such a thing, it was on the power companies side, buried underground.


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## guest (Feb 21, 2009)

Same as above, but investigate a bad connection on one of the hot legs. You need to take your voltage readings with a load applied, no-load voltages are frequently o.k. even through marginal connections. 

Places to look for one leg lost:

Meter stabs
Meter socket connections
Main breaker connections and stabs
Try cycling the main breaker (if present) and listen when under load for hissing, buzzing or crackling sounds
Make POCO look closely at connections at BOTH ends of the service drop

You WILL find a bad connection somewhere, keep looking. And DO NOT let the customer keep using the compressor to restore loads, they are asking for a fire or burned-up appliances. 

Recheck your voltages under load, if the voltage rises above no-load on one leg and drops on the other, open neutral. (I don't think so in this case.) 

If the voltage stays close to nominal on the leg that's good but drops on the bad leg, then it is a bad hot connection.

EDIT: Noticed you already checked meter and connections, so get the POCO off their butts as the problem is likely in their drop connections. If that customer is on their own transformer, it is also possible the transformer is bad.


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## 480sparky (Sep 20, 2007)

mxslick said:


> ...............Meter stabs..........


That's a very easy one to miss.

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_​


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## kaboler (Dec 1, 2010)

Don't forget that customers are idiots. Who knows what is really going on.


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## Bkessler (Feb 14, 2007)

knowshorts said:


> . If it was a problem with the POCO wouldn't they know immediately because of their smart meter?


That's miht be a bit optimistic. If I have one that I suspect might be a poco issue I call them or have the customer call and say there is flashing power, that gets them out there asap and sometimes I have the problem fixed before they arrive, and sometimes they verify that there end is okay while I am there. Actually the latter happened twice and the utilities guys were fine with my actions. My icebreaker is "can I have your meter lock key please? I'll trade you my linemens for them". It usually gets a chuckle.


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## Jbird66 (Oct 26, 2010)

You are trying to find a needle in a hay stack with the power back on. 

I would tell the customer next time it happens instead of going to the air compressor go to the telephone and call me! You might even want him to call the POCO at the same time. If you can get there once with it not working you can nail it. I would be very suspect of something on the POCO side of things also but until you can get more clues you do not have enough information to decide yet.


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## jwjrw (Jan 14, 2010)

I'm changing a panel this morning that had a bad main breaker. The original complaint was half the house had no power until she cut the heat on. When she cut the heat on everything worked. I told her to call poco first. They wouldn't come out until after she had an electrician come out. Turns out this time they were right. The bus is burnt on one phase and breaker melted. I relocated the main so she would have power until I got back to change it.


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## Frasbee (Apr 7, 2008)

Sounds like they called the wrong professionals.

Give them this number, they do good work.


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## knowshorts (Jan 9, 2009)

I went back over there yesterday afternoon. Was able to meet homeowner and get inside the house. I pulled the meter again and checked the meter jaws. Perfect condition. I was able to determine that the circuit feeding the clock, tv, and the computer where on the same circuit and on B phase. All lights happened to be on A phase. Coffee maker, fridge, and microwave on A phase. All other B phase circuits in the house were not being used or 240 volt loads. So if it was the POCO dropping the B phase, customer only noticed it on the 3 outlets and not anywhere else. 

I had the customer call the POCO and they told him they couldn't get out till Tuesday, since it wasn't an emergency and it was a union holiday. The customer has a monitored T1 line on A phase, so I swapped that circuit with the one B phase circuit. So if the POCO drops B, I will have a time stamp on it, and if the circuit with the clock, tv, and computer drops, then I will know it's in that circuit somewhere.

I don't know if this could at anywhere be related, but 1/2 the house has GFCI outlets. I asked why, and the homeowner said the original owner replace all 2 prong non grounding outlets with GFCI's. But half the house didn't need them, because they had a ground already. Who wires a house 45 years ago with half the outlets with grounds and the other half without?

Customer is not a typical dumb ass customer. He happens to be the CEO of a company I do work for, and has consistently awarded me over $100K in work over the last 3 years. So without this guy and his growing company, who knows where I'd be. 

What bothers me the most is that I really do like troubleshooting things. Finding problems and fixing them. I am used to a commercial environment, where you can identify a problem and actually physically see the problem. If this is a POCO problem, I can't see it and I have no control over fixing it.


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## 480sparky (Sep 20, 2007)

knowshorts said:


> ........ Who wires a house 45 years ago with half the outlets with grounds and the other half without?......


Someone who is dead or retired.



knowshorts said:


> ....What bothers me the most is that I really do like troubleshooting things. Finding problems and fixing them. I am used to a commercial environment, where you can identify a problem and actually physically see the problem. If this is a POCO problem, I can't see it and I have no control over fixing it.


This is not a 'residential' problem. This can happen to ANY service or circuit. Wire & breakers & boxes & devices do not know the difference between 120/240 1-phase and 120/208 3-phase.


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## RePhase277 (Feb 5, 2008)

What you got there is a bad connection somewhere on one of the hot legs. I have seen it occur on bad main breakers. But most often it is on the POCO side.

What has happened is the 240 V load has bridged the two "phases" and allowed them to form a series circuit. The air compressor starts slow because it is starting on 120 V, when it is up to speed there is very little voltage drop across it and the loads on the dead phase get almost full voltage. I bet that if you turned off all the breakers on the phase that is still working, and measured voltage on the bad phase, it would be zero or nearly so.


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## SparkYZ (Jan 20, 2010)

Turn off any two pole breakers, and check the voltage on bad phase. I also think the 240v loads are backfeeding the bad phase.


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## Josue (Apr 25, 2010)

Frasbee said:


> Sounds like they called the wrong professionals.
> 
> Give them this number, they do good work.


:laughing::laughing::thumbsup:


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