Replacing Circuit Breakers

So I'm going to replace a couple of circuit breakers today and I have a couple quick questions.

The breakers in question are Siemens and mounted in a Square D panel. Should I be able to replace these QP breakers with 50 and 100 Amp Homeline breakers? I've found the direct replacement for the bottom breaker but I can't find any reference to the top breaker using google.

The panel is probably about 20 years old and you can see from the picture the Siemens breakers don't fit very well. On top of that, the bottom breaker trips about 3x a day now. The bottom breaker feeds a newer Square D panel with 2X15 amp and 1x20 amp breakers in a garage, none of these have tripped.

Also, do they make low temp breakers, I'm not finding much with breakers this size? This panel is in the middle of a field but these breakers all seem to be rated to 40. It doesn't seem to me like it's tripping due to temp since my understanding is that the lower the team the less likely the breaker would trip due to heat.

Attachment 62991

If it is a Square D panel, get breakers that are compatible to the panel. The top breaker appears to not be seated correctly, or is mismatched to the panel.

Home Depot will carry Square D compatible two pole breakers.
As far as the one breaker tripping 3X Dailey, you may have other problems than a weak breaker, you need to check current draw on the load side of the one that is tripping.

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Originally Posted by SideShow Bob

As far as the one breaker tripping 3X Dailey, you may have other problems than a weak breaker, you need to check current draw on the load side of the one that is tripping.

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This is what I was thinking, and I know nothing about home electrical.

Mr. Breaker in Highlands Ranch will do R&R on old breakers and lots of new old stock.

Your tripping that breaker because your load is too high on that circuit. The reason the breakers aren't tripping on the garage panel is that the load on those individual circuits aren't too much for that point in the circuit, but it's too much for the main coming out of your main panel. Picture one man holding up 3 people each holding 50lbs. While the individuals holding the 50lbs can handle the load, the one man trying to carry all 3 of the others is too much for him.


You really need to determine the draw on that circuit and modify the main panel accordingly. Too much load on a circuit with a failure to trip the breaker could be devastating. While it's been 30+ years since then, I had extensive residential wiring training but I know my limitations and won't attempt breaker panel work on my own. It's too easy to put my home at risk, violate local codes, etc.

OK, so I'm learning a lot here but no closer to the issue. I went and bought one of the Klein clamp meters to test with.

I'm getting 245 volts on the breaker which I think is fine.

When I test the hot wires on 200/400A it shows 0, when I drop to 2/20A it shows .07 on the black and .04 on the red. I know they should be similar, is that close enough? Do those numbers make sense?

There is very little on the circuits, a couple of lights and a garage door opener is all that is attached to the circuits in the house. There is no correlation between the garage door opener being used and the breaker tripping but I'm going to do some testing and see what measurements I get when the door is opened and closed.

Here's a picture of the inside of the panel in case it might lead to some other suggestions.

Attachment 62994

Tested with every light and every device plugged in turned on, got a steady state reading of .8. Opened and closed the garage door and maxed at 4.8A. That was on the 2/20 setting.

IMHO, breakers can age and relax over time and number of trips and become unstable. If it were me, I would replace the breakers with Square D and then see if you have any other issues.

I also had an issue with one of those dual/shared breakers in my RV. They put the A/C and something else on the same breaker pair. It would always trip when only the A/C was running on a really hot day (100* +) when we were out on the lake. Nothing like coming back to the RV to find it at 130* internal. Replaced the dual breaker with two singles and haven't had an issue since.

If you Amp draw's do not exceed 80% of rating it could be a "weak" breaker.. Most manufacturers state the breaker is designed to only work once. that doesn't mean they will only work once but they will get weak due to varying factors. that's how it was explained to me buy guys that rebuild breakers out at MillerCoors

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Originally Posted by brutal

IMHO, breakers can age and relax over time and number of trips and become unstable. If it were me, I would replace the breakers with Square D and then see if you have any other issues.

I also had an issue with one of those dual/shared breakers in my RV. They put the A/C and something else on the same breaker pair. It would always trip when only the A/C was running on a really hot day (100* +) when we were out on the lake. Nothing like coming back to the RV to find it at 130* internal. Replaced the dual breaker with two singles and haven't had an issue since.

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This is NOT recommended when you have 240V appliances on those circuits (like well pumps)... because it would pop one leg of the 240V, but the other leg would still be hot. The 2 are joined specifically drop both sides of the 240V. if the circuits serve nothing but 120V, then they shouldn't be joined.