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Discussion Starter · #1 ·
Hi, I recently started having an issue with my electrical system at home. Well, it's been close to a year now. Basically if I run the dryer, the power to my whole house shuts off. Now, it doesn't "trip" any of the breakers in the box, it just shuts everything off. I have to manually flip the main breaker into the off position and wait a few seconds before flipping it back on.

I thought maybe it was a bad breaker, so I replaced it. No luck. Thought maybe it was the dryer. Tore it apart and looked for any signs of a short, no luck. My in laws had just purchased a new washer/dryer set and still had their old ones so I took the dryer and tried it out. No luck.

I have an old breaker box and they apparently don't make the main breaker anymore and there are no viable replacements. Is there any way to check and see if it is in fact the main before I pay an electrician to replace the whole box?

Oh, and the other day my fiance plugged in a space heater, one of the ones that kind of looks like a radiator, and it cut the power off as well. If that helps at all.

Box: Cat. No. QOC-20M Series 6
 

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Have you checked the bolts that attach the bus to the main? They are usually in a couple pieces and bolted together. Still the main would have tripped. It sounds a little like the main breaker is worn past the point of protection. Or, also kind of sounds like the service is way too small for the load. Like one of the old 60 amp services. I saw a panel a long time ago that the bus bars were almost burned in half, and would do the same thing as you described. The service was way overloaded or undersized for the load.



I would replace all that with a new, larger Square D QO service entrance and panel.


Andrew
Handy Andy In Mt Airy NC
 

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If you have an IR thermometer check for any hot spots on the busses or breakers.

Breakers have a thermal trip component to them. If they get heated from a hot loose connection it can cause the breaker to trip lower than it’s rated trip point.






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Discussion Starter · #6 ·
If you have an IR thermometer check for any hot spots on the busses or breakers.

Breakers have a thermal trip component to them. If they get heated from a hot loose connection it can cause the breaker to trip lower than it’s rated trip point.






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I don't have an IR theometer but the panel feels warm, as does the breaker switch. Not hot to the point of discomfort but defiantly noticeably warmer than if we hadn't run the dryer at all... Is there an easy way to check for a loose connection on the main breaker?
 

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Discussion Starter · #7 ·
Have you checked the bolts that attach the bus to the main? They are usually in a couple pieces and bolted together. Still the main would have tripped. It sounds a little like the main breaker is worn past the point of protection. Or, also kind of sounds like the service is way too small for the load. Like one of the old 60 amp services. I saw a panel a long time ago that the bus bars were almost burned in half, and would do the same thing as you described. The service was way overloaded or undersized for the load.



I would replace all that with a new, larger Square D QO service entrance and panel.


Andrew
Handy Andy In Mt Airy NC
I can check when I get home, I'm worried the breaker is just too worn. And I've had this dryer for 5 years, if it was too much load, wouldn't it hsve staryed happening 5 years ago?

I
 

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The first thing I would do is check all connections to the bus as well as the wires that connect to the main breaker. You will need to disconnect the power outside which may require pulling the meter. This is dangerous and could be fatal if not done correctly. This might not be a DIY job if you are not comfortable and familiar with this kind of work.
 

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Next time before you open up the dryer or any other appliance, try unplugging it then check. No need to dig around in the dryer until you know for sure that where the problem lies.
 

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if the entire panel is warm you have a really bad connection somewhere (bad bus under breaker,...), get an electrician check that before panel caught in fire
 

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Lots of good advice above. Since you don't have an IR thermometer, try using
senses of sight (looking for anything loose or discoloured by heat), smell (think
everyone knows what overheated electrical wires etc smell like), and feel (already
mentioned the panel feels warm - you can safely touch each plastic breaker parts
to isolate hot spot(s)).
Who knows what you'll find, but my guess is still that the main breaker will
need to be replaced.
 

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We had a similar issue at our previous home. One of the main breaker lugs had a stripped out setscrew. There was no way to tighten the cable properly.

I'm an avid DIY guy, but in this case we called a professional who replaced the main.
 

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Discussion Starter · #13 ·
Lots of good advice above. Since you don't have an IR thermometer, try using
senses of sight (looking for anything loose or discoloured by heat), smell (think
everyone knows what overheated electrical wires etc smell like), and feel (already
mentioned the panel feels warm - you can safely touch each plastic breaker parts
to isolate hot spot(s)).
Who knows what you'll find, but my guess is still that the main breaker will
need to be replaced.
If you look at the main wire on the right it's clearly discolored, I assume from heat?
 

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If you are talking about the white one going to the main it does not look like its been hot to me.



Those are some pretty stout wires going to the stove :)


If It was mine I would check all the connections and then replace the main.
 

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Sounds like a weak main breaker. What's it's amp rating?
It should be 100 amp. They only used one main breaker with that box, Q12100TF.

It’s an obsolete breaker, no replacement from SQ D.
Its advertised on the US used/recertified market in the range of $225-400.
 

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If you have an AC voltmeter measure the voltage from the bare wire of each incoming feeder to the main breaker and the bottem end of the bus bar for the corresponding phase. A loose connection will have a voltage drop. This is the V* I situation that caues the self heating. The heat ius conducted into the breaker and it lowers its trip point. I doubt this is a weak breaker, rather a heated up breaker by a loose feeder screw.


To confirm this, turn on your heavy load appliances and make a voltage measurement with the probe wedged into the bare feeder wire (not on the lug the strands of wire) and then at the bottom of the panel. Then kill the heavy loads and do the same measurement.


You really shouldn't even see 0.5 Volt of AC across this point. If there is 60A on that phase and a 0.5V drop then 30W of heat is at that bad connection. If its 2.0 VAC and 60A then we are up to 120W of heat..... you'll probably smell melting plastic.....
 

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Yea I see them refurbished for $200. That bad part is you can buy a square D homeline panel with main and a few breakers for $115. Not sure but you might be able to to buy the rest of the breakers you need and still be cheaper than the obsolete breaker.
 
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