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Half of my house without power with no tripped circuit breakers

Half of my house without power with no tripped circuit breakers

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  #1  
Old 05-08-19, 10:49 PM
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Half of my house without power with no tripped circuit breakers

The master bedroom and middle bedroom of my 3 bedroom home, 2 bathrooms, also kitchen ceiling light and garage light are without power. None of the breakers have flipped.

It happened right after changing a light bulb in the kitchen’s ceiling fixture as pictures show. It worked, but after I put the glass cover on it, the circuit breaker (the blue one on top of the panel) tripped. I reset all the circuit breakers in ON position, tested with a multimeter and get 120V of EACH of the breakers from top to bottom.
Also tested GFCI outlets inside and outside with exception of one GFCI outlet in the garage that doesn’t trip when reset button pushed as it doesn’t get any power right now. No Idea how to test it when there is no power to that GFCI. Other GFCI outlets in the garage where washer and dryer are hooked up and GFCI in the kitchen are working. I removed that kitchen ceiling light fixture to check the wires, no visible damage, no burned wires.

Sounds like perhaps we've lost one leg of the power, if so where is it?

I read that 90% of time it's a problem of the utility’s transformer, right? But why it happened after we changed a light bulb in the kitchen?

Questions:

1-How to test that one suspected GFCI outlet that doesn’t trip or reset when pushed?
2-How to test/know if there is a problem with utility company’s side?
3-What would be the most common problem in this situation?

In the past, we changed the light bulbs at the same kitchen ceiling light fixture with no problem at all.

Thanks for advice

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Last edited by PJmax; 05-09-19 at 12:02 AM. Reason: cropped/resized pictures
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  #2  
Old 05-09-19, 12:08 AM
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Check for 240vAC at the two lugs on the 100A main breaker in that panel first. If you don't have the 240v present on the main breaker...... proceed below.

You have a picture there with the poco side of the meter open. Check for 240vAC at the two lugs where the wires are connected. BE CAREFUL...... this is non protected wiring. You don't want to short anything to ground. Safety glasses are a good idea too.

If you don't have the 240v here...... call the power company's emergency repair number.
 
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  #3  
Old 05-09-19, 12:36 AM
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When you say you get 120V at each of the breakers, are you measuring between each breaker output terminal and neutral or ground? If so, that's the correct voltage you should see. However, if you're measuring between the output terminals of adjacent breaker positions you should get 240V, not 120V (which would indicate that one of the two phases is disconnected). Both terminals of the blue handled breaker will have the same voltage because it's a tandem breaker occupying one spot.

Did you turn off and then reset the 100A breaker? It's possible that only one side of the 2-pole breaker could have tripped. If so this would shut off one of the phases and therefore half of the branch circuits. It would be best if you replaced the panel cover before switching the 100A breaker off and on.

The bare ground wires look very close to the output terminals of the tandem breaker. This is another possible cause of this breaker tripping besides the light fixture wiring you mentioned.
I just noticed that Pete responded before me as I write this so follow his lead.
 
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Old 05-09-19, 01:07 AM
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I get here 240V as marked in the picture. This is an indicator that 240V is present an the panel, correct?

If so, what could be the problem?
 
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Old 05-09-19, 08:42 AM
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You've confirmed that you have 240v at the panel. The supply is good.
You've confirmed all the breakers have output. The panel is good.

That leaves you with a problem circuit. You will need to ID everything on that circuit. See if anything is still working on that circuit. You will have to go from location to location to check. There is no easy way to diagnose the problem. It could be the connections at a device is bad if the push-in connections are used. It could be a splice in a junction box.
 
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Old 05-09-19, 09:38 PM
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A suggestion is to go to the non-GFCI outlets that are not working and measure the AC voltage from the narrow slot (hot side) of the receptacle to the hole for ground. This check is to confirm that the hot side is not being powered. However, if you see 120V then perhaps an open neutral conductor could be causing your problem.
 
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