Cause of 55a coach breaker repeatedly popping

[John Stephens]

I just got back from a two-week trip to Illinois to attend a funeral. The coach was taken out of storage here is SW Florida and readied for the trip, and everything appeared to be working.

While in Illinois, we encountered cold weather, with the nights getting down to 36 degrees. I anticipated this and got the propane tank filled before leaving town. The first night it got cold, we had electric and water hookups in a campground. I moved the slider switch on the thermostat to "gas heat," knowing the heat pump would be worthless in temps that cold. The furnace came on, and hot air was dispensed, so I know the burner ignited, but the furnace would not come back on when the temp reached the set point on the thermostat. We had to buy a space heater the next day.

Three days later, I tried the furnace again, and this time, it worked like a champ. I couldn't understand what made a difference other than the weather wasn't quite as cold.

On the last day of our trip, we were back in Florida, and it was warm enough to need the a/c. That evening while parked in a Cracker Barrel, it got cool enough to turn the a/c off. I slid the switch to "off," and everything in the coach went dark. I tracked down the main 55a breaker popped - the one that oversees nearly every 12v item in the coach.

Long story short, that evening and night, the breaker popped four times. This told me that either the breaker had gone bad, or more likely, it was trying to tell me I had a short somewhere, and it was only doing its job. I thought back to when this issue began, and realized it was when I had slid that slider switch on the thermostat to "off." So I slid it back to "a/c" and set the set point high enough that it wouldn't come on. Over the course of several hours of driving home with the generator recharging the batteries that had gone dead since the converter couldn't do its job, the breaker never popped again. This tells me there was a short in the thermostat that the slider switch was causing.

I'm now wondering if that could have been the problem with the furnace not wanting to come on when the set point was reached. I have had issues with that switch for years, having to make sure it's in the exact correct spot to get the a/c to turn on. I'm also wondering if it's time to install a new thermostat. I'd like to get the opinions of the people on this forum before I spend the money on a new one because I'll go digital this time.

 

[John From Detroit]

You do need to find the problem The furnace is a major power sucker.
One thing you can do if you have a short is get a 12 volt INCANDASCET drop light (Trouble light) you know the old cord with the caged lamp on one end and normally a plug on the other you use working on the car. Only this one has battery clamps instead of a plug

Hook it across the breaker while it's tripped. Now if there is enough current draw (About 10 amps if it's a 100 watt lamp) the light will be bright. You can not poke around trying to make the light go out with relative safety. When you find something that when poked or wiggled makes the light go off and on. BINGO.

 

[CharlesinGA]

I'm confused, as a 55 amp breaker (which in iitself is odd) would indicate a 120v AC device, then you start discussing the furnace (a 12v DC appliance)

When I have time later tonight, I will look at the wiring diagrams and see if anything makes sense.

Charles

 

[Ray-IN]

The slider switches on those old 'stats get corroded and do crazy things. A spray can of contact cleaner(plastic safe) cleans them up, just remember to unplug the 12V first, on the back of the 'stat. Reattach the plug after you slide the switches to both limits several times to wipe off the residue.

 

[CharlesinGA]

OK, From the wiring diagrams, the coach batteries supply the battery disconnect relay which when turned on (salesman's switch) passes power thru to the 55 amp breaker which is the round, white push button one in the entrance step box. This 55 amp breaker supplies the two rows of 12v house circuit breakers via an isolated stud near the converter, which is the same point the converter connects into the system.

Remember the batteries can push as much as 55 amps thru to the two row breaker panel, and the converter can push as much as 55 amps back thru the 55 amp breaker to the batteries, Its a two way street.

You haven't replaced the converter with a larger unit have you?

Link to your wiring diagrams and install drawings.

I would also consider disconnecting all batteries, and unscrewing the breaker panels, both the one at the step and the two row house breaker panel and verifying that the screws on the back are all tight (don't get crazy with them, but you need to make sure you don't have anything working loose. (My '07 WBO View had screws half out of the breakers, hanging by only one thread, the screws are very short any how, and if they overlap two buss bars and run a screw thru them to the breaker the screw is not long enough, it barely catches. Basically, they cheap out and while they should use one continuous bar, they sometimes use two shorter bars and overlap them). The isolated stud connection near the converter needs checking also. High resistance can cause the breaker to pop if you are drawing heavy loads.

At this point, IDK.

Charles

 

[John From Detroit]

I'm confused, as a 55 amp breaker (which in iitself is odd) would indicate a 120v AC device, then you start discussing the furnace (a 12v DC appliance)

When I have time later tonight, I will look at the wiring diagrams and see if anything makes sense.

Charles

Many RVs have a main breaker for the 12 volt system.. 55 is a common size.

 

[woof-n]

I moved the slider switch on the thermostat to "gas heat," knowing the heat pump would be worthless in temps that cold. The furnace came on, and hot air was dispensed, so I know the burner ignited, but the furnace would not come back on when the temp reached the set point on the thermostat. We had to buy a space heater the next day.

Long story short, that evening and night, the breaker popped four times.

Over the course of several hours of driving home with the generator recharging the batteries that had gone dead since the converter couldn't do its job, the breaker never popped again.

55 AMPs is a lot of DC to trip a breaker. It is not an instantaneous trip but a sporadic trip. Meaning something is causing it.
You implied you have two sources heat from your coach. Propane furnace and electric heat pump? is the heat pump AC or DC?

Were you on shore power when you when the breaker tripped? Do you know what your battery voltage was at that time of the trip and was your DC systems under load when you tripped?
You said that you ran the generator on the way home to charge the batteries because the converter did not do its job. That is a serious flag. I suspect that you have at least one bad battery pulling the other batteries down. If the converter is fused through the fuss block you could have excided 55 amps trying to charge the dead batteries and run your furnace? This is just a guess. The very first thing I would do have the batteries tested. If bad or marginal, replace them. Second thing is test the converter and verify the operation. Good Luck

 

[Alan_Hepburn]

Remember the batteries can push as much as 55 amps thru to the two row breaker panel, and the converter can push as much as 55 amps back thru the 55 amp breaker to the batteries, Its a two way street.

Just a minor clarification: amps don't get "pushed" by a source; they are "pulled" by a load.

 

[John Stephens]

55 AMPs is a lot of DC to trip a breaker. It is not an instantaneous trip but a sporadic trip. Meaning something is causing it.
You implied you have two sources heat from your coach. Propane furnace and electric heat pump? is the heat pump AC or DC?

Were you on shore power when you when the breaker tripped? Do you know what your battery voltage was at that time of the trip and was your DC systems under load when you tripped?
You said that you ran the generator on the way home to charge the batteries because the converter did not do its job. That is a serious flag. I suspect that you have at least one bad battery pulling the other batteries down. If the converter is fused through the fuss block you could have excided 55 amps trying to charge the dead batteries and run your furnace? This is just a guess. The very first thing I would do have the batteries tested. If bad or marginal, replace them. Second thing is test the converter and verify the operation. Good Luck

Woof-n: The heat pump is AC. The furnace uses DC to run the blower. The breaker tripped while I was on the road using the generator. It was impossible for me to tell what the battery voltage was when the trip occurred because I didn't know it occurred until the batteries were dead from not being charged by the converter. The converter wasn't charging them because it wasn't getting any power from the generator after the breaker tripped. The converter is three years old and in good condition. The batteries are brand new, and dedicated deep cycle. They charged back up to 13.6v by the time we got home. They are currently holding 12.8v two days later.

Since the breaker hasn't tripped again since I moved the slider on the thermostat, and since I have researched this particular thermostat and found others with similar problems as I have experienced with it over the years, it is easy for me to assume it was the cause of the breaker tripping because although the a/c and heat pump are AC, the thermostat and EMS board are DC. When the breaker tripped, I had no EMS. Because of this, I have ordered a new digital thermostat to take its place, and will install it as soon as it arrives. It can also easily be assumed this slide switch was the cause of the furnace not kicking on at the set point.

To everyone who has responded - thank you very much for your thoughts and opinions. I have always been able to count on this group when I have a problem, and am always happy to return the favor when someone else needs assistance.

 

[DonTom]

I'm confused, as a 55 amp breaker (which in iitself is odd) would indicate a 120v AC device,

120 times 55 amps=pops at around 6,600 watts. expected load around 5KW. What in an RV needs that type of AC power?

~12.7 volts times 55 amps=Pops at around 700 watts. Expected load perhaps 20% less. More within reason. I would expect a 55-amp breaker to be a 12-volt breaker.

-Don- Reno, NV

 

[SCVJeff]

While there’s lots of guessing going on without going after this with the proper diagnostics, they’re just guesses. While a DVM is a must IMO, my most used meter is an amp clamp that works on both AC & DC. An Amp clamp is the last word and will easily tell you the real load through that breaker.

Since everyone’s guessing, here’s mine: It’s entirely possible you have a soft breaker; it sure wouldn’t be the first time and would explain a lot. You’d really have to work on finding 12v@55A worth of load on that coach. It wouldn’t surprise me if you found that breaker heating up from a poor (loose) spade screw behind the panel

 

[CharlesinGA]

120 times 55 amps=pops at around 6,600 watts. expected load around 5KW. What in an RV needs that type of AC power?

~12.7 volts times 55 amps=Pops at around 700 watts. Expected load perhaps 20% less. More within reason. I would expect a 55-amp breaker to be a 12-volt breaker.

-Don- Reno, NV

It a 12v DC circuit breaker, not AC.

While there’s lots of guessing going on without going after this with the proper diagnostics, they’re just guesses. While a DVM is a must IMO, my most used meter is an amp clamp that works on both AC & DC. An Amp clamp is the last word and will easily tell you the real load through that breaker.

Since everyone’s guessing, here’s mine: It’s entirely possible you have a soft breaker; it sure wouldn’t be the first time and would explain a lot. You’d really have to work on finding 12v@55A worth of load on that coach. It wouldn’t surprise me if you found that breaker heating up from a poor (loose) spade screw behind the panel

I agree. Those small circuit breakers are the same type used in many General Aviation aircraft (think Cessna) and having worked on them, I know, the breakers do go bad, more so that a typical home breaker.

Charles

 

[John Stephens]

It a 12v DC circuit breaker, not AC.


I agree. Those small circuit breakers are the same type used in many General Aviation aircraft (think Cessna) and having worked on them, I know, the breakers do go bad, more so that a typical home breaker.

Charles

I replaced that 55a breaker about three or four years ago because it had gone bad. Now, I'm being told it's nearly impossible to find one. I doubt this one has gone bad, if for no other reason than its age. I'm convinced I have a short in my thermostat because after I slid that switch back to "a/c" from the "off" position, the breaker stopped tripping. If that switch has gone bad, which I am pretty sure it has, it would also explain why my furnace wouldn't work when needed a couple of weeks before and then DID work a fe days later. That switch has given me issues for years because it had to be in just the right position for the a/c to engage, and I had given consideration up to a year ago to buy a new digital thermostat. But then, it started working without issue whenever I needed the a/c, so I decided not to buy a new one. Now, it's giving me problems with more than the a/c setting. I have a feeling it was shorting out when set to the "off" position, and that was what was causing the breaker to continually trip that one night. The new thermostat is arriving today and I'll install it tomorrow. If the breaker doesn't trip anymore, we'll know the thermostat was the problem.

Thanks for your thoughts and opinions on this matter.

 

[CharlesinGA]

If you need a breaker, a 60 amp aircraft breaker would be a good substitute.

If close in depth so the buss bar connects, then it could be shimmed with washers on the neck of it to push it back some. If not, a heavy copper strap could be formed to connect it to the other two that are connected together.

60 amp breaker from Aircraft Spruce

 

[DonTom]

Now, I'm being told it's nearly impossible to find one.

If you cannot get by with a 50-amp breaker, then use a 60-amp.

-Don- Auburn, CA

 

[John Stephens]

If you cannot get by with a 50-amp breaker, then use a 60-amp.

-Don- Auburn, CA

Unfortunately, in order to have it fit on the breaker panel and be easily reset, it will have to be a button breaker similar to the one pictured in Charles post.