Household electricity mystery

[DaveC426913]

TL;DR Summary

Can circuit breakers just ... stop working?

A year or so ago, I had a licensed electrician come in and retroactively fix up some of my wiring (My amateur fingers did nothing near the panel, just extensions to existing lights and outlets). He ran new cable and installed a couple of new breakers for them.

My basement has been gutted to the cinderblocks - so all lines from the panel are open to inspection.

Last week, due to an unrelated issue, I went down to tripped/reset a few breakers. I may or may not have tripped/reset the one in question. I can't be sure because they are poorly labelled.

When I finished, a specific circuit would not come on - the living room lights, foyer and front door external lights - the ones he fixed for me. I cannot be sure this is only one circuit, but it's a good assumption.

Shy of cracking open the panel itself, or inspecting behind the main floor walls, I can't find any reason for them not to work.

I've reset every breaker in my panel, to no avail.

There are only three possibilities, as I see it:
1] A fault in a line in the walls,
2] A fault inside the panel
3] A dead circuit breaker.
The third one is the only one I can check without calling the electrician back.

Do circuit breakers just ... fail?

 

[jrmichler]

Yes, they do. They also can randomly trip for no reason. The breakers are plugged onto a buss, and a (usually one) wire is connected to each breaker. A problem with one circuit is usually due to the breaker or the wire to the breaker. It's possible that the screw was never tightened and the wire came loose. If not that, probably a dead breaker.

A friend had both of those problems on multiple circuits, so his son and I put in a whole new service entrance panel.

Suggestion: As long as you are flipping breakers, that's a good time to label them.

And shut the power off before opening the panel.

 

[DaveC426913]

OK, so it would be worth my while to try simply replacing the/a circuit breaker before taking the big step to open up the panel and get zappy.

So I should be able to just swap different breakers (of same configuration!) to test that- like swapping bulbs in a string of Christmas lights...

 

[berkeman]

Have you tried measuing the voltage at the failing outlets and fixtures? If you have a loose connection, you may still see a small AC voltage there instead of zero Vac. Does your DVM have leads that are slim enough to fit into the wall sockets safely?

EDIT/ADD -- turn off all loads on that circuit when you do the DVM test, so no light bulbs pull down the voltage.

 

[DaveC426913]

Have you tried measuing the voltage at the failing outlets and fixtures? If you have a loose connection, you may still see a small AC voltage there instead of zero Vac. Does your DVM have leads that are slim enough to fit into the wall sockets safely?

EDIT/ADD -- turn off all loads on that circuit when you do the DVM test, so no light bulbs pull down the voltage.

I have one of these wall pluggy things.
Not sure if it will read a partial voltage.

I guess I could get a proper multimeter off the boat...

 

[berkeman]

I have one of these wall pluggy things.
Not sure if it will read a partial voltage.

Those are probably neon bulb indicators, so it won't indicate low voltages.

I guess I could get a proper multimeter off the boat...

Sounds like part of the plan!

 

[jrmichler]

So I should be able to just swap different breakers (of same configuration!) to test that- like swapping bulbs in a string of Christmas lights...

Before going that far, I would check for loose connections.

This panel has the main disconnect on the bottom right. I'm used to seeing it top center. When it's shut off, the two screws clamping the incoming wires are electrically hot. Everything else is off. Each breaker has a wire coming out clamped under a screw. Tighten the screw on each and every breaker. If anyone moves, it was too loose. Make sure that each wire is actually under, and clamped by, a screw. That includes the neutral connections, the white wires connected to the buss bar on the right side. And the ground connections, the bare wires connected to the other buss bar on the left side (not shown).

If everything looks good, and you feel confident, turn the main breaker on, and touch voltmeter probes to the breaker output and one of the buss bars. If no voltage, replace the breaker. Be very careful because the breakers are clipped onto electrically hot buss bars.

 

[StandardsGuy]

OK, so it would be worth my while to try simply replacing the/a circuit breaker before taking the big step to open up the panel and get zappy.

So I should be able to just swap different breakers (of same configuration!) to test that- like swapping bulbs in a string of Christmas lights...

A common problem is a wall receptacle with the push-in wires. Go to the room with the problem and see if there is one receptacle that is working. If the next one in line is not, then pull the first one away from the wall and check if the wires can be pulled out. I like to replace these with ones with screw-down terminals.
I think you have to open the panel to replace a breaker. First I would see if all ground wires are tight (white wires). This is not dangerous. Any discoloration indicates a hot spot.

 

[hutchphd]

Probably not the problem here but be aware that GFCI receptacle when tripped will cut power to the rest of the circuit downstream of that box. I have earned many brownie points knowing this...

 

[Tom.G]

Probably not the problem here but be aware that GFCI receptacle when tripped will cut power to the rest of the circuit downstream of that box.

And even if not tripped, those GFCI's have a MUCH higher failure rate than a breaker!

 

[rbelli1]

First I would see if all ground wires are tight (white wires). This is not dangerous.

The ground wires are the un-insulated ones.

The white wires a neutral wires. In a live system they should be considered dangerous as they are current conductors. In a fault condition (which this post is discussing) they can have full mains voltage on them.

BoB

 

[StandardsGuy]

The ground wires are the un-insulated ones.

The white wires a neutral wires. In a live system they should be considered dangerous as they are current conductors. In a fault condition (which this post is discussing) they can have full mains voltage on them.

BoB

You are correct. The white wires are the neutral ones. The bar they connect to is connected to the bar with the bare ground wires. They won't have any voltage under any circumstances if the main breaker is turned off. Even with it on, a plastic handled screwdriver should be sufficiently safe.

 

[rbelli1]

They won't have any voltage under any circumstances if the main breaker is turned off. Even with it on, a plastic handled screwdriver should be sufficiently safe.

I agree.

However if a loose neutral is causing the failure and a load is connected to the circuit then the white wire will be at mains voltage when the breakers are on.

BoB