running two ACs on 50 amps--update - Page 2 - Montana Owners Club

David and Jo-Anna · 07-07-2007, 02:38 AM

I'm able to run the two ACs as long as there is no other power consuming appliances running. However, if I run the hot water heater OR the washer/dryer while the ACs are running, the CG 50 amp circuit breaker pops. Based on Rich's readings with his PT50C, the 2 ACs should draw no more than 28 amps. Therefore I suspect a bad circuit breaker at the pole. I'll continue to test it in other CGs when we head back up towards Virginia.

Rich--by the way, what else does your PT50C do for you and what made you go with it?

Dick--turns out that the Big Sky that Camping World erroneously installed our washer/dryer and bedroom AC in belonged to the dealer's inventory. Dealer told me that Camping World was so embarassed at their mistake that they did not ask him to pay anything for them. LOL!!!!

ols1932 · 07-07-2007, 03:05 AM

We only have the one AC but we supplement it with one of the portable Fantastic Breeze 12V fans which we set on the floor to help circulate the air. Once in a while we run the ceiling fan also. Although this doesn't keep the inside below 88 °F when the outside temp is above 92 °F, it does keep it livable.

Orv

richfaa · 07-07-2007, 03:26 AM

The PT50C is not inexpensive,Paid 395.00 for it from a vendor ant a FCRV rally.Here are two Web sites www.progressiveindustries.net that is the manufacturer of the product and www.viprv.com this is the vendor we purchased from. This will give for much better information that I could..
We purchased because it does a in depth evaluation of your power system and a readout you can see(good for trouble shooting). It has prevented power from being applied to the camper on 3 occasions since we purchased it. One time it detected very low voltage on 1 leg (50V). We plug it into the pedestal BEFORE we apply camper power. It shut down the power to the camper here at the Colorado State Fairgrounds this morning. Don't know why but we suffered no ill effects.. Yes it is a pricy item but so was my 3400.

David and Jo-Anna · 07-07-2007, 04:34 AM

Rich--With regard to the PT50C's ability to monitor the incoming voltage and shut down in the event of a voltage problem, that sounds like what the Surge Guard does--albeit without the power readout you get. Anything else that the PT50C does that the Surge Guard doesn't?

richfaa · 07-07-2007, 04:55 AM

Features: PT50C

The 50C Is a surge guard among other things.

High Low Voltage Protection: Whenever source power falls below 104 volts, or it rises above 132 volts the EMS automatically shuts down power to the RV. Once the source power rises above 104-volts, or falls below the 132-volt level the time delay indicator flashes for the preset time and then automatically restores power to the RV.

Time Delay for A/C Compressor: Whenever source power is interrupted (by the source or the EMS), due to a fault condition, the built in time delay is activated for 136 seconds. This prevents the air conditioners from trying to start up under load. Starting up under load will burn up air conditioners.

4-Mode Surge Protection: This feature provides full surge protection L-N, L- N, L-G, L-G, L-L and N-G. Joule rating is 3640, with a response time of

dieselguy · 07-07-2007, 06:24 AM

David ... you gave me a chance to try out my new clamp on amp meter ... 11.3 amps draw on the 10 gal hot water heater. I knew it drew a moderate load as it makes the Kipor genset RPM's come up a bit. Like stated earlier ... some campgrounds have less than optimum equipment no matter what the advertised amps are. In those areas just to be safe, we water heat on propane and let the A/C have at it.

David and Jo-Anna · 07-09-2007, 04:44 AM

Well, some good news--and an additional puzzle. We arrived at a new campground yesteday afternoon, and this morning I tested the limits of the 50 amp service. I had both ACs running at the same time as well as the hot water heater. When that didn't pop the breaker, I added the central vacuum and the hair dryer, each pulling over 10 amps apiece. When that still didn't pop the breaker, I added the iron, and still didn't pop anything. OK, that tells me that the problem at the last camp site--when I couldn't run anything else if both ACs were running--was probably caused by a weak breaker at the CG pole, not by some short in my new bedroom AC that was somehow pulling too much current. That's the good news.

Now for the puzzle. When I arrived at the campground yesterday afternoon and hooked up to the 50 amp service, I couldn't get the bedroom AC to work--all I got was a quiet hum, even when I turned it on fan only and even when I shut off the living room AC. After playing around with some other tests, I unplugged from the 50 amp outlet on the CG pole and hooked into the 30 amp outlet. Now I could get the bedroom AC to work fine. I assumed that I had a bad leg on one side of the 50 amp service. This morning, I plugged back into the 50 amp service to test just what was going wrong, and everything worked fine--indeed, as noted above, I could run virtually all of my power consuming devices at the same time.

So color me puzzled. Any ideas on what was happening with my power supply??

bsmeaton · 07-09-2007, 05:47 AM

That hum sounds like you restarted the AC too fast and the compressor didn't have time to equalize. Was the AC running at any time when you hooked up? It only takes a momentary power loss to cause the compressor to lock up. Once it settles and is restarted, its fine.

Ozz · 07-09-2007, 09:48 AM

That Brad is a smart cookie....

David and Jo-Anna · 07-09-2007, 12:33 PM

Brad--as for the "hum" sound, I may well have turned the AC on the first time without giving the compressor time to "settle down." But I then waited probably about 15 minutes before trying again, and again got the hum. Plus I got the same hum when I turned the AC to "fan only." Could that be due to the failure of the compressor to equalize?? If so, just how long do I need to wait for the compressor to equalize before being able to use it in either AC mode or fan mode??

Cyrus · 07-09-2007, 01:50 PM

David,
I agree that the campground where you had the problem has a problem but you might have a problem also. Your problem and the answers you got confuse me since my understanding of 50 amp camper wiring is, you have two separate 120 volt legs at 50 amps each. You would only use the 220 volt capability if you have something that takes 220 volts like a 220 volt dryer. When you run your camper off of a 30 amp plug, with adapters you only have one leg of 120 volts. What does not work off of 30 amps, don’t try everything at once, may kick the 30 amp breaker. I have read on MOC of members only using a 30 amp cord with adapter since it is lighter and easer to handle.

My Mountaineer is wired for 50 amps but everything will work off of a 30 amp plug, one 120 volt leg. Our gun club has about 40 30 amp plugs, no 50’s and we have everything from popup’s to the biggest RV’s plug in and run for the weekend. They can’t run second AC is the only complaint I am aware of.

According to what I have read the wiring which I have for my second AC (don’t have the AC) will come off the other leg of the 50 amp plug. I have not checked this out but I have run everything off of 30 amp service with no problems.

I could be way off but this is what I have learned.

Ozz · 07-09-2007, 02:00 PM

David,
The hum on fan only without the A/C turned on is puzzling, a person would have to have instruments on the unit and system at both times to get a good answer. Troubleshooting is almost impossible remotely.
You may find a pattern, you are a bright guy, just take notes and a qualified troubleshooter will have to get to the bottom of it when you have your systems looked at.
Good luck.
Ozz

richfaa · 07-09-2007, 02:15 PM

Both of my A/C's run on the same leg of the 50 amp service. The camper came pre wired from the factory but the A/C was installed by the dealer. It would be interesting to see how others are wired??? if you can check it out.I know that both of mine are on the same leg as I can see the Amp draw on my PT50C surge guard..

sreigle · 07-10-2007, 10:38 AM

Quote:

quote:Originally posted by bsmeaton

That hum sounds like you restarted the AC too fast and the compressor didn't have time to equalize. Was the AC running at any time when you hooked up? It only takes a momentary power loss to cause the compressor to lock up. Once it settles and is restarted, its fine.

We have just one AC unit but this Montana has a built in delay for starting the AC. It will not come on until two minutes after it is turned on. David and Jo-Anna, yours is newer than ours so I'd think it has the same thing. And the second AC would work the same, or is it on a different circuit without the delay?

David and Jo-Anna · 07-10-2007, 06:54 PM

Steve--my OEM living room AC has the same two minute delay you have. However, the new bedroom AC, the one that was "humming" at me, is a Dometic low profile model and doesn't have any built in delay. When I turn the switch from off to AC, it kicks on right away--except, of course, for the other day when it just "hummed" at me. Still don't know what that was all about, especially since it did that humming in "fan only" mode as well.

Ozz · 07-11-2007, 01:30 AM

The delay feature is in the wall thermostat, so the unit mounted controls will not have one.

kmh3212 · 07-11-2007, 09:16 AM

I can run two 15,000 BTU ac units, the electric water heater, refrigerator and convection/microwave all on 50 amp service. I suspect bad breakers and or worn power outlet from lots of use as well as many overloads on the power pole. Cirduit breakers do wear out.

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