breaker response time

When a breaker is tripped, it's always the main breaker, not the individual breaker. Shouldn't the individual breaker be tripped first?

This is troublesome because I then have to turn off all individual breakers with the main breaker on and flip each breaker to see which one causes the trouble.

Reply to
Lenny Jacobs
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Not necessarily, but I had one main breaker rated at 100 amps that would trip at about 70 amps. The sub breakers would never trip.

Reply to
Taxed and Spent

It sounds like you either have a bad main breaker, a burned up bus connection or you are running at so close to capacity that one more thing puts you over without exceeding the capacity of that branch circuit. Either buy a clamp on ammeter or pay a sparky to analyse your panel loading. Sometimes the PoCo will do that for free and call it an energy audit.

Reply to
gfretwell

What is the rating of the main breaker? What is the load? if the main is 100 and you have a bunch of 20A breakers pulling 15A the group would trip the main.

You should do some analysis to see if you are overloading the panel. If you added Central AC, larger water heater,dryer, electric range, they may not be a problem individually but together, too much for the main.

Reply to
Ed Pawlowski

If you have a full panel - say even 21 breakers - all 15 amp, all loaded to 80%, you have a 252 amp draw - no branch breakers are overloaded, yet you are 25% overloaded on a 200 amp main breker.

Reply to
clare

Note, in case you are possibly unaware of this, that you want to count on how many amps are being accounted for by CB'ers on each side (or ones using both sides (poles?) ).

Reply to
Bill

Thanks for the reply. That's no the problem. I can always trace the problem to one single breaker and flip it. That solves the problem for quite a while. When it is dry season, there is no breaker problem. When the four month raining season comes, some breakers would trip. I don't know if it is due to moisture or underground short circuit. I flip those offending breakers and everything is good, except I don't have garden lights and others which I have yet to figure out what they are. There are so many breakers in the box. I don't know which one is for what.

Reply to
Lenny Jacobs

That sounds like a worthwhile project for you. There are tools to help.

Reply to
Bill

One of the best things I ever did was label each circuit on my breaker panels. As I recall, ~50 circuits took less than a couple hours. Now get to it!

As far as popping you main breaker, you'll need a meter like this to solve that mystery:

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Reply to
Troy

That ain't supposed to happen . When an individual circuit overloads that breaker and only that breaker is supposed to trip . Either you have a defective main or the wrong amp rating . Or maybe you've got way too big breakers on the individual circuits . Most mains are 100 or 200 amps , 30 or 40 amp breakers for stoves/water heaters/dryers , 20 amp for most outlet circuits and 15's for lighting .

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Snag

Reply to
Terry Coombs

See Clare's post. If you have a panel full of breakers and most are loaded near the max, you can be at the main breaker limit. Turn on one more load, add 5A on a circuit that is already pulling 9A, or even on a circuit that wasn't drawing anything, and it will trip the main. Someone else pointed out that if the load is unbalanced, you could also exceed the max on one leg in a similar way. It;s unusual, but so is his problem.

Another question is if the problem is being caused by the addition of a normal additional load or a dead short. A dead short can exceed both the main breaker and the individual circuit breaker at the same time. Normally just the individual one opens, but it's possible that he has a fast response time main and a slower response time individual breaker. I tend to doubt that though, those kind of shorts you'd think you'd know and they would not be intermittently happening again. breaker, not the individual circuit breaker.

Reply to
trader_4

+1
Reply to
trader_4

I can always trace the

Are these standard breakers or GROUND FAULT INT GFI breakers?

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Reply to
makolber

Theoretically possible but that's not the case here. Every year, when the raining season comes and the main breaker is tripped, I can always trace to the same sub-breakers that cause the problem and turn them down. They are not tripped all at the same time but they are always the same four breakers that have the problem.

I studied the breaker box and found that it's not like what I usually saw in the US. It has a 75 A main breaker labelled Ground-First FL Main (this is a two-story building). There are two 63 A breakers labelled Ground FL Main and another two 63 A breakers labelled First FL main. Looks like this is a three-tier system. It is the same 63A breaker that is tripped during raining season.

Usually, there are only no more than 10 lights on, two full-height and a half-height refrigerators constantly on (doesn't mean the compressors are constantly running), and a ceiling fan, a water heater. That's it. Seems to me there is absolutely no reason a breaker would trip with a load like this. That's why I suspect the culprit is moisture or underground cable getting short circuited due to rain. Now, two breakers are turned down. During dry season, all breakers are up.

By the way, this is 220 V.

Reply to
Lenny Jacobs

That is what I'd expect but that's not what is happening here.

I have 10 lights on, a water heater on, three refrigerators on, a ceiling fan on. How can these trip a 63A (220 V) breaker? It must be short circuit of some sort. But why is a main breaker tripped, instead of a sub breaker?

Reply to
Lenny Jacobs

How do you identify which one caused it? Does it immediately trip the main again when you put the offending breaker on, ie the fault is still there? If so, if it's not intermittent, I would think you'd immediately further track down what the source of the fault is.

Do you really mean tripping or that it's something on that 63A breaker that causes the main to trip? You said the main was tripping, not the other breaker. Also this picture is different than what I think most of us were envisioning, which was a typical main panel with individual branch circuits, not a main that feeds what appears to be two subpanels, That shouldn't really matter though.

What do you believe the total load normal load on it is, just before it trips? What's going on at the subpanels when this happens, those 63A breakers must feed subpanels of some kind. Anything tripped there? As to why the 75A trips first, it makes more sense now. Breakers have curves as to how fast they trip versus the size of the fault. Different breakers will have different curves and they are not exact. What you have is a 63A breaker and a 75A both exposed to an overload. Additionally, you don't tell us what else is on that main panel besides the two 63A breakers, but if there are other circuits, then the 75A is seeing whatever the 63A one is, plus those other loads. With other loads, no surprise it trips first. Even without other loads, if you present a major over load to both, the 75A might trip first if it's curve is slightly different.

I think most of us were envisioning that you had a big main breaker, eg 150A and then smaller breakers, eg 20A that feed those other circuits.

Where are you? We were assuming this is US.

Reply to
trader_4

Get busy and map the breakers!!!!

Reply to
clare

I noticed up above that the OP says he's got a 220V system ... And a different layout of main/sub panel breakers than I'm accustomed to . Yes , I did see Clare's post , and he makes sense . Lot of other info in the OP's responses , and I haven't a clue what his problem is .

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Snag

Reply to
Terry Coombs

Where are you ? I haven't a clue what your problem is , from your responses above you have a totally different setup from what I have here - 110/220 single phase from a grounded center tap transformer .

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Snag

Reply to
Terry Coombs

Then replace the damned things, they are not doing their job. There is NO WAY the main should kick before the branch circuit protection

OK - Euro system. Different problems. No "load balance" issues. 2 "main breakers" in the building. One never trips. The other trips when it is wet outside. You have external lighting circuits on that main. You most likely have leakage in those 2 circuits, not enough to trip the branch breakers, but enough to load the main heavily enough that the rest of the loads, combined with the circuit leakage, overloads the main. Find out what is on the circuits in question and get those circuits checked and fixed - or permanently disconnected.

Reply to
clare

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