Keep tripping main breaker RANDOMLY... sometimes after a week!

[aaron7]

I feel a long confusing post coming... please read the whole thing before replying!

1979 Shasta Class-C

We're full timers and not having power is very, very bad!!

Since we've bought it we've had problems with the main breaker tripping randomly.

Doesn't matter if you have anything on or even plugged in; seems to just be at total random.

Sometimes it'll go a week without issue, sometimes it'll do it once a day, and sometimes it'll pop every hour!

We've replaced the breaker (P20) with a new one hoping it was just weak. Wasn't easy to find! No change.

There is only one other breaker and that's strictly for the air conditioning unit.

I've removed all the 12v fuses from the converter to isolate the system and it still happens.

I've disconnected the fridge at the back; both 12v and AC.

Nothing is plugged into any outlet.

We do not use the water in the camper so the water heater is not used.

We don't have LP (leaky tank) so the furnace is not used. Did work fine before the LP was depleted.

Everything else functions fine. Fans, lights, all outlets, etc.

Disconnected the house battery in case it was shorted (though it's 6 months old); no change.

Also does not seem to be temperature related. Happened in the summer, happened the other night when it was 30 out. Morning, noon, night... doesn't change.

At this point everything points to either the DC converter itself or a bad connection somewhere in the AC lines that's causing resistance and building up heat till that breaker pops.

Once the breaker has tripped it cannot be reset till you wait around 10 minutes. If you try and reset it before then it trips immediately. Also points to something getting hot.

I do see the main line feed to the plate the breakers mount to is melted at the end though that could be old.

I put a good fan on the converter insides hoping that was the problem... also not the case.

Problem is... I have no idea where to start.

Aside from gutting the damn thing, how the heck do I troubleshoot this further???

[Gary RVRoamer]

You can stop fiddling with the fuses and battery 12v stuff because that can't trip the 120v/20A breaker. Even a direct short there would not cause a trip because your converter cannot draw anywhere near enough current to trip that breaker. I suppose the converter itself could be internally shorted (intermittently) though. It is probably fed via that breaker if the only other one is for the a/c.

More likely, though, you have a tiny short in the 120v wiring downstream from that breaker. A stray strand of wire that occasionally touches as it heats/cools or a brief air current moves it, or some of that dust I see in the pictures crosses two wires and a spark jumps. You might try vacuuming all that dust & dirt away for starters (do it with shore power disconnected, just to be safe).

Are you sure the water heater electric mode (if it has one) is turned off? If not, it is heating water whether you actually use any or not.

[Skip426]

I'm thinking your next step would be to hook an independent battery charger to the coach battery, so you have 12v lights etc. , and disconnect the 110v supply from the converter/charger coil.
Without being there with a volt meter, to test 110v power flow, best guess for place to disconnect would be the white wiring cap in the second to last picture, next to the coil.

Of course , as Gary says , best time to do that would be with shore power disconnected.

[aaron7]

Yes I understand it's very dusty! That's only recent due to the fan I put on top of it thinking it was a heat issue. I'll be sure to vacuum it all out!

The water heater is about 6 years old but I do believe it's LP only. If it also has electrical power I don't believe it's connected.

I do believe you are correct in thinking it's in one of the AC lines though. But since there's only one breaker for EVERYTHING AC I'm not sure how to go about tracing lines!

[Mentor]

Originally Posted by aaron7

Yes I understand it's very dusty! That's only recent due to the fan I put on top of it thinking it was a heat issue. I'll be sure to vacuum it all out!

The water heater is about 6 years old but I do believe it's LP only. If it also has electrical power I don't believe it's connected.

I do believe you are correct in thinking it's in one of the AC lines though. But since there's only one breaker for EVERYTHING AC I'm not sure how to go about tracing lines!

Change the 30 amp breaker that keeps tripping, they too get old and tired, unable to keep up.

[okcnewbie]

After looking up your breaker ( P120GF ) I would do the following just to eliminate the breaker itself.
Disconnect the output from the breaker and hook it up to something like a small heater. If the heater runs for ever than you know it's not the breaker.
If it is the breaker it looks like it might be cheaper to put in a new breaker box and breaker.
You could go the other route. Totally bypass the original breaker. Wire in a separate 20 amp breaker and see if the wiring in the trailer causes it to trip.
Be careful.

[okcnewbie]

I don't think it can be converter but if you find you need an old Magnetek 6300 you could PM me and we can find one really cheap.

[George Schweikle]

aaron7, I used to work in circuit breaker and panelboard design and remember just a little of that long ago activity.

Like most RV's, you have a circuit breaker designed for residential use. These trip for two reasons; SHORT CIRCUIT trips magnetically, quickly, and THERMAL trips when a bimetal strip becomes hot from excess current and trips the breaker mechanism (sometimes this takes some time, depending on the load). Your reset sequence indicates a thermal (non-short circuit) overload, and the continued problem with a new breaker indicates the problem isn't the breaker itself.

Somewhere there is an intermittent load that is beyond the capacity of the breaker (what amperage is the breaker?). What is happening is that the load isn't a short circuit, rather something just beyond the current carrying capacity of the breaker. It finally trips, then the current is off until you can get the breaker to reset, then the cycle starts again Since you have turned off all loads in the coach the problem is elsewhere and could be the "melted" connection to the breaker itself. Can you show this in a picture?

You mentioned there are only two breakers, and these are likely from one of the major manufacturers (Square D, GE, Siemens, ITE, etc.) and converter manufacturers use these in their combination products. It may be that you can replace the section of your converter that contains your breaker mount and connections, although the company that made the breaker and mount may be out of business which is why you had such a hard time finding a breaker.

Whatever the mysterious excess load on the breaker, it may be right at the thermal calibration limit, and this setting may be varying just enough to change the duration of trip times. The thermal calibration is actually a range or window defined by Underwriters Laboratories. Again, seeing a picture of the breaker(s), and connections may reveal something.

Originally Posted by aaron7

...Sometimes it'll go a week without issue, sometimes it'll do it once a day, and sometimes it'll pop every hour!.



We've replaced the breaker (P20) with a new one hoping it was just weak. Wasn't easy to find! No change....

Once the breaker has tripped it cannot be reset till you wait around 10 minutes. If you try and reset it before then it trips immediately. Also points to something getting hot.

I do see the main line feed to the plate the breakers mount to is melted at the end though that could be old...

[RW8804]

Have you tested that you are getting clean power from the post?

[wa8yxm]

YOu said you used a 20 amp breaker but even with everything off it trips (or is the A/C on)

First, is your rig a 20 or 30 amp (Compare the power plug) if it's a 30 then the main breaker should be 30 amps.

Second: the A/C... When was the last time you did any cleaning on the coils. Epically the condenser.. On my coach (50 amp) one of the A/C's (13.5 amp normal draw) started popping the 20 amp branch breaker.. Turns out it was Seriously overdue for some tender loving cleaning.

I took the business end of the 150PSI huffer-puffer up there (Air compressor hose with jet nozzle) and blew the CR** out and suddenly the draw is back down to 13.5 (from 21 when the breaker tripped by measurement).

And as for that power converter/charger.. You should consider an upgrade. That is a very old unit, and the new ones are lighter, more efficient, Quieter and treat the battery better as well. Just so you know

I like Progressive Dynamics Intella-power units with charge wizard

[spritz]

Mine does the same thing but it only happens in the mornings with nothing on. Its 30 amp brand new outlet on the S&B (dedicated) Some times it just trips the main on the MH and sometimes it blows the breaker in the S&B Your not alone.
Thanks I'll watch for comments.
Thanks,Tim

[TQ60]

Measure voltages...

Or...

Disconnect all load wires and wait...

Connect them one at a time and measure voltages to see if and how they drop voltage.

Only connect one at a time.

If one drops more than rest see why.

If no issues then hook up all but one and rotate the non connected until it faults.

Or...

Get a clamp on ammeter and measure current draw on every wire and perform normal troubleshooting and repair.

[wa8yxm]

Originally Posted by okcnewbie

I don't think it can be converter but if you find you need an old Magnetek 6300 you could PM me and we can find one really cheap.

What are those worth now days about 2¢ per pound?

[cwit]

I think it is your 5 th picture it shows the breaker on the bottom of it. Behind the breaker is 2 wire lugs. The lower one looks like it got hot and melted the insulation and maybe some of the wire. The wires are black in color.