Odd curiosity, any suggestions what might have caused this?

[DutchmenSport]

Parked at home, 50 amp service, never had any issues with anything electrical in my Montana High Country since we've had it.

I have a 50 amp Progressive portable EMS plugged in. Works good, no issues.

We've been using the camper 24x7 while at home for the last few weeks, sleeping in it every night, spend most of the day in it. No problems.... none!

Yesterday, we got out of bed and decided to go into the house. We were going to be in there a while, so I went ahead and shut both air conditioners off in the camper. About 2:00 pm, I figured I better flip both AC's back on so the camper would be cool when we came back out (planned about 4:30 pm).

Flipped both on, set them 69 degrees (both), everything started up just fine. No problems. I went back into the house.

4:30 rolled around, we went out to the camper. No AC. It was HOT inside, about 90 degrees. AC not running, either one. Clocks and microwave in the camper were NOT flashing, so it was not due to a power outage. I checked the EMS anyway... working just fine.

Television turned on, everything looked good, no issues with anything electrical. I flipped the AC completely off (Dometic thermostat), it went dark. I turned it back on. .... Nothing! So, I then decided to check the breakers in the electric panel.

Yep, both breakers for the AC were tripped. Just the AC breakers, one for each AC.

I flipped the breakers, turned the thermostats back on, waited about 30 seconds and both AC came back on.

I set both to 69 degrees and they have been running perfectly fine ever since. No issues at all any more.

Question? What caused the breakers to trip? If it was a power surge or a low power, I would have though the Progressive would have shut off the trailer. If the Progressive shut of the trailer, the clocks and microwave would have been flashing. Such was not the case.

If it was an over load on the entire trailer, I would have expected the main 50 amp breakers to trip. That did not happen either. I could kind of expect even, one AC breaker to trip (maybe).... but both?

So, any ideas to help solve this mystery? As I said, everything has been working perfect since, yesterday evening, through the night, and all day today. Everything still set on 69 degrees. AC are cycling on and off just fine today.

Your turn? Go for it! Any ideas?

[MandK]

Nope, I don’t know, but I hope someone does. Now I’m wondering too.
I do not know about the microwaves in our campers, but my microwave at the house has to loose power for about a minute before the clock will reset to 12:00 and flash. We have a whole house generator and if there is a power outage, the generator starts and comes up to rpm and then warms up for about 20 seconds before the automatic transfer switch kicks the load to the generator. Our microwave never looses track of time in that 20 seconds. The electric clocks in the house do though.

[WFWilson]

Licensed electrician here, without seeing first hand my inclination would be a brown out. Based on your description of very hot a voltage drop even for a few seconds would be enough to trip the ac circuits if they were running but not the main.

[Bourbon County]

I'm thinking like WFWilson, maybe the voltage was already near the lower threshold on the EMS and if your RV outlet is fed from your house you could have dropped the voltage even lower when you started turning on appliances inside the house. I'm not familiar with your EMS, but mine will turn power back on once the low voltage issue has cleared, maybe quick enough as to not knock out the clocks.

Another extremely remote but possibility, is both ACs on the Montana tried to start at exactly the same moment. The combined locked rotor current on both at the same time would have overloaded both circuits. Again, not being familiar with your EMS, I believe most are only checking the incoming power conditions, not conditions inside the RV.

[twindman]

My progressive displays previous error codes. Do you not have this option?

[Kfinnert]

I agree with WFWilson. I ran into an issue last month where the Elks Lodge I was enjoying was not pushing sufficient power 104 to 138 Volts to the outlet. As such, lines tripped. It was a head scratcher until I checked my faults and determined the cause.

When you flipped on both ACs at the same time could have caused a significant enough drop to trip the lines.

Cheers

[jeffba]

Could have a wiring issue down stream of the EMS. I have a voltmeter plugged in and watch the voltage as the AC units and other things run. it the brownout was after the EMS it will not show a problem

[ChuckS]

I would take a wild guess and state that both AC breakers tripped.. one at a time due to excessive head pressure and rotor lock amp draw trying to start compressors back up

They would not have likely both started at the same time so that is why the main feed didn’t trip nor the EMS indicate any issues ..

Start up amp draw depending on head pressure and rotor lock amp draw can be in excess of 30 amps which would of course trip only the AC breakers

Again.. it’s speculation but with my background it is what I would suspect

[Bourbon County]

Originally Posted by ChuckS

I would take a wild guess and state that both AC breakers tripped.. one at a time due to excessive head pressure and rotor lock amp draw trying to start compressors back up

They would not have likely both started at the same time so that is why the main feed didn’t trip nor the EMS indicate any issues ..

Start up amp draw depending on head pressure and rotor lock amp draw can be in excess of 30 amps which would of course trip only the AC breakers

Again.. it’s speculation but with my background it is what I would suspect

That does bring up a very unlikely scenario that might just be possible. If both units were running when you walked out, and for some reason like maybe low voltage tripped the EMS and then restored power. I'm not sure if RV units or thermostats have this feature, but most all residential units have protection from restarting too quickly under high head pressure, normally 3-5 minutes after power is restored. Both timers theoretically started timing at the same instant. If so equipped and the timers timed out at nearly exactly the same instant, the units could have tried to start simultaneously. I saw the locked rotor current rating on the Coleman units somewhere and it was 58 amps, I would imagine Dometic would be very similar. A circuit breaker should hold at this current draw for a few seconds, they do it all the time. If they did both start at the same instant, I would think they could both trip because there's just not enough capacity in the RV.