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Newmar 14 · 06-18-2005, 03:34 PM

I have 50 amp service and two a/c on roof but when we are pluged into 30 amp service, seems only one a/c will function properly/. Is this normal?

Newmar 14 · 06-18-2005, 03:34 PM

I have 50 amp service and two a/c on roof but when we are pluged into 30 amp service, seems only one a/c will function properly/. Is this normal?

TXiceman · 06-18-2005, 05:27 PM

You are correct. When on 30 amps, there is not enough power to run both A/c's. The 50 amp servieis really two 120 volt circuits in parallel. When on a 30 amp plug, you are running on onlt one side of the circut and thus the second A/C will not run.

Ken

CAD-Man · 06-18-2005, 09:48 PM

TXiceman,
Did I understand your response correctly? Only one air Conditioner will run or you can only run one air conditioner at a time? When I am on a 30amp circuit with my adapter, I can run either air conditioner, but only one at a time. I usually run the front air conditioner and leave the rear air conditioner in the fan only mode during the day and then run the rear air conditioner at night and leave the front one on fan only.

TXiceman · 06-19-2005, 06:12 AM

Cad-Man, how you can run the A/C's is determined by the energy management system your coach has installed. On 30 amps you can generally run only one at a time. Some systems will let you chose front or rear A/C. When you are plugged into 50 amp service, the systems can sense this and lets you operate both at the same time. Some of the older systems had a switch that you could choose front, rear or both on the A/C depending on your power source.

There should be section on the energy management system in your owners manuals.

Ken

max49 · 06-19-2005, 01:53 PM

TXiceman , what does the AC that does'nt work "correctly" do?
I've run my 2 ACs on 30 amp and run one on 15 amp in my driveway, even with 100' 12 gauge extension cord.
If they don't trip the circuit, does this hurt any thing?

TXiceman · 06-19-2005, 02:39 PM

Have you checked your voltage at the rig? Your energy management system may hold one out on lower than normal voltage, but will allow both units if you have sufficient voltage.

Do you have a Volt-Ohm meter to read the voltage in the RV as well as at the power surce? If not try to get a plug in RV volt meter and se what it shows with no A/C and with one A/C running.

Ken

max49 · 06-19-2005, 04:36 PM

TXiceman , Yes, I just checked my voltage in the driveway from my house for the first time.
122 no load volts, drops to 108 volts at start up of AC, then comes back and settles at 116 volts. Normal???
The 5500 watt Onan holds at 120 volts w 1 AC.
I also have a "Home Depot", $500 , 5000 watt generator, to save hours on the MH generator at the races. It only carries 108 volts steady with 1 AC and reefer on.
I have "Carrier "13,500 BTU AC's in the new Damon. My 93 Class C had a newer "Hi Effiecieny" Coleman 13500 AC and I ran it on the same 15amp plug but I do remember it tripping the circuit at least once.

Retired and Happy · 06-19-2005, 05:33 PM

My M/H with 30 amp shore service has two roof A/C's and no energy management system. When I bought it used, it had a switch that allowed selecting either front or back A/C unit on shore power or both on generator power.

I changed the switch to a Pulse-Air unit to allow alternating the units on shore power and selecting either or both on generator power. This is a great device for coaches with limited shore power capability.

I am now considering adding a second Automatic Transfer Switch (ATS) in the 20 amp circuit to simulate 50 amp service and be able to run both units when proper outlets are available. I'm still studying the details on how to connect this second ATS so the Pulse-Air will still work properly and also allow maximum flexibility in power connections (30 vs 50 amp shore power outlets).

CAD-Man · 06-20-2005, 06:36 AM

TXiceman,
As far as I know I do not have energy management system. None is mentioned in the owner's manual for my RV. I have never tried to run both AC in the cooling mode when on 30 amps but as I said before, I can run one AC in the cooling mode and the second AC in the fan only mode. I can then change which AC I want to cool manually through the thermostat. So what I am saying is that either AC will cool in the 30 amp mode.

Stan Birch · 06-22-2005, 12:19 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by TXiceman:
You are correct. When on 30 amps, there is not enough power to run both A/c's. </div></BLOCKQUOTE>
Not at all sure of your reference point; but as veteran RVers, with our aged '99 Winnie; we've never experienced so much as a single fleeting hiccup in running both of our twin 13,500 BTU Power-Saver Coleman A/Cs simultaneously on a mere 15 amp circuit.

Gary RVRoamer · 06-23-2005, 05:58 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Not at all sure of your reference point; but as veteran RVers, with our aged '99 Winnie; we've never experienced so much as a single fleeting hiccup in running both of our twin 13,500 BTU Power-Saver Coleman A/Cs simultaneously on a mere 15 amp circuit. </div></BLOCKQUOTE>

Since that is not physically possible, Stan, I would guess that one or the other of the a/c units is running fan-only. Depending on the specific model, each 13,500 btu Coleman draws 13-15 amps with the compressor running, so clearly two of them cannot run together on a 15 amp circuit if both have their compressor running at the same time. [Note: energy management systems prevent both a/c's from starting their compressors simulataneously - that allows both to be "on" but not actually cooling at the same time].

The Coleman Power Saver models need only about 10 amps, so two of them might run on a 20A circuit. And Coleman also has a "Cub" model that draws only 8 amps.

Stan Birch · 06-23-2005, 02:19 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by RV Roamer:
Since that is not physically possible, Stan, I would guess that one or the other of the a/c units is running fan-only. Depending on the specific model, each 13,500 btu Coleman draws 13-15 amps with the compressor running, so clearly two of them cannot run together on a 15 amp circuit if both have their compressor running at the same time. </div></BLOCKQUOTE>
The actual specs for the Coleman Power Saver A/C is 1147 watts (9.5 amps) with outside temp at 95F. Up here in the frosty north, where temps seldom get that high, the monitor panel never shows current-draw exceeding 7 to 8 amps max when running a single A/C with our Power Saver units.

I don't think the Energy Monitor, which cuts in at 20 amps, even considers the rear A/C which is on a separate non-monitored circuit. It doesn't display any current-draw when the rear A/C is being run on it's own.

Nevertheless, I am absolutely certain that both A/Cs can run simultaneously on a mere 15 amp circuit, drawing 7 amps each. The only caveat is that you first have to set the fridge to run on propane.

HeatAir · 06-27-2005, 05:43 PM

Stan,

There is an 80% rule that applies to circuit breakers. That rule is that there should never be more then 80% of the rated capicity (load) of a circuit breaker at any time. Therefore, a 15 amp circuit breaker should never have any more than 12 amps on it. A 20 amp circuit breaker should never have more than 16 amps on it.