Puzzling electrical problem

[mike805]

I just installed a Dometic cu434 stove/oven on our Roughwater 41. This stove has a 12v piezo and oven light that require a 12v connection. The propane line has a remote solenoid operated from a breaker in the galley. Being lazy and not particularly bright, a combination that usually works very well for me, I piggy backed the 12v connection to the stove to the breaker switch on the propane solenoid.

This worked as planned for about 2 weeks. Starting yesterday, though, when the propane breaker is turned on it trips after a minute or so whether the stove is lit or not. The oven light is off. I disconnected the stove from the breaker and this cured the tripping issue, indicating that the fault is in the stove, which is disappointing as it is brand new. What I don't understand is, if I have a short at the stove, why does it take a minute or so to trip the breaker? Why does it not trip immediately?


My next move is to run a dedicated wire to the stove to see if the problem is indeed the stove or whether it is my wiring, but I am still puzzled by the delay in the tripping of the breaker.

[DavidM]

Does your boat have a propane leak detector that may be tripping. It is usually located somewhere near the floor under the stove. When it trips it is usually wired to turn off the propane solenoid, so if you have one it is in the same circuit as the breaker. I realize this theory doesn't quite sync with your symptoms, but who knows?

David

[oscar]

The "run a direct line and see if the problem is in the stove" approach sounds good.

For the record, a Piezo igniter is not 12V. It is non-volt. The resistance you feel when pushing the thing is the energy converted to spark.....

[Barking Sands]

https://cdn.shopify.com/s/files/1/12...98307590210399

According to the wire diagram from the manual its quite simple. I would recommend disconnecting the wires to the stove and using a digital multi meter in the Ohms setting check the resistance of the oven circuit. With the light switch off and none of the ignitor buttons pushed it should be Open. If it is not then that would indicate something in the oven itself. Did the ignitors and the light both work properly?

If the entire combined circuit is the same as the previous set up and it worked previously and the only change is the new oven and you check the new oven circuit and it is in fact open look at everything you touched closely looking for stray strands or exposed/smashed wiring. Double check polarity.

[FF]

"but I am still puzzled by the delay in the tripping of the breaker"


Most CB have some sort of built in delay so they can start motors that draw heavily on start.. Your CB small delay is normal.

[rslifkin]

Originally Posted by FF

"but I am still puzzled by the delay in the tripping of the breaker"


Most CB have some sort of built in delay so they can start motors that draw heavily on start.. Your CB small delay is normal.

Agreed. If the draw is only a little over rated current, a CB will take a little time to trip. As the current gets higher, it'll trip faster. The exact curve depends on the CB, they're not all the same.

[mike805]

Originally Posted by FF

"but I am still puzzled by the delay in the tripping of the breaker"


Most CB have some sort of built in delay so they can start motors that draw heavily on start.. Your CB small delay is normal.

Thanks, I suspected as much. The breaker is being used as a switch to activate the propane solenoid, so I imagine the manufacturer chose a breaker with a long delay. A full minute seems a bit excessive, but, on the other hand, nothing caught fire so it must be OK. Maybe has something to do with the 'degree' of the short. I haven't had time to troubleshoot with a multimeter yet but will get back when I do.

[mike805]

Originally Posted by oscar

For the record, a Piezo igniter is not 12V. It is non-volt. The resistance you feel when pushing the thing is the energy converted to spark.....

Agreed. I misused the term 'piezo' out of habit. The stove actually just uses a 12v supply activated by a momentary switch to create the spark.

[GoneFarrell]

Mike, if your meter has a clamp on feature for measuring amps put that around the line in question to see how many amps are on that circuit.

[Bud]

If it worked ok for two weeks a 12v wire might have melted and is shorting to the chassis. I would check the wires going to the spark generator and the wires going to the light switch internal in the stove/oven.

[mike805]

Originally Posted by Bud

If it worked ok for two weeks a 12v wire might have melted and is shorting to the chassis. I would check the wires going to the spark generator and the wires going to the light switch internal in the stove/oven.

That was my thought as well. However, I am unable to find a short with my multimeter. The stove is riveted together so, unfortunately, doing a visual check is not practical. Next step will be to run a dedicated wire to the stove.

[ksanders]

Regarding circuit breakers and fuses

Circuit breakers work in a concept that the larger the fault current, the shorter the time to trip is.

The curve reflecting fault current vs time to trip is defined by the manufacturer.

Right at a devices rating it may or may not ever trip.

At 1.5 times it’s rating it will trip in X amount of time

At 2X the time will be shorter

At 5X the time will be shorter still.

[FF]

I can understand putting the gas solenoid on a breaker , it should have a mechanical timer and an operating light as well.

But I have no idea why the lighting circuit should be on the same circuit.