I have 2 AC's on my RV currently and I spend a lot of time in the Southwest where it can get to 110 120. 2 AC's won't cut it so I have decided to add a 3rd unit.I welcome your experience and comments on my plan.I will mount the 3rd unit where my kitchen vent is located.Run a wire to my current thermostat for controlRun AC power from the unit to the rear of my RV, in the closet area where my washing machine used to be. I will add a breaker in line, and connect to the 120v outlet in the closet.I will also run another AC line from that closet out to my electrical bay, so I can connect the 3rd unit directly to a 30 Amp shore power seperate from the rest of the RV, which would be connected to the 50 amp service.I hope to accomplish the following:When going down the road with the genny on I can run both front AC units and the 3rd will be plugged into the washer circuit.When parked I can run all 3 units with the 3rd unit plugged into 30 amp at the pedestal and the rest of the RV to the 50 amp. This way I won't overload the RV's electrical system.In the end I will have 3 15000 BTU Dometic units that I can run off shore power, and 2 15,000 btu units i cn run off genny power (7500 w Onan).Have I thought of everything ?

Have I thought of everything ? Yes I guess so. But have you thought of cleaning the coils on the two existing units? I've been out west and the killer south and 2 do the job no matter how long the coach is.I have to admit after venturing out of my element of the Midwest I was amazing how those coils get fouled up with stuff. I had them cleaned and could not believe how much colder that AC unit worked.I now have the coils cleaned as a routine maintenance when in the south.Pillow inserts in all the vents and cover the shower skylight drastically cuts down on how much heat comes in too. Just saying.

JCat wrote:I have 2 AC's on my RV currently and I spend a lot of time in the Southwest where it can get to 110 120. 2 AC's won't cut it so I have decided to add a 3rd unit.I welcome your experience and comments on my plan.I will mount the 3rd unit where my kitchen vent is located.Run a wire to my current thermostat for controlRun AC power from the unit to the rear of my RV, in the closet area where my washing machine used to be. I will add a breaker in line, and connect to the 120v outlet in the closet.I will also run another AC line from that closet out to my electrical bay, so I can connect the 3rd unit directly to a 30 Amp shore power seperate from the rest of the RV, which would be connected to the 50 amp service.I hope to accomplish the following:When going down the road with the genny on I can run both front AC units and the 3rd will be plugged into the washer circuit.When parked I can run all 3 units with the 3rd unit plugged into 30 amp at the pedestal and the rest of the RV to the 50 amp. This way I won't overload the RV's electrical system.In the end I will have 3 15000 BTU Dometic units that I can run off shore power, and 2 15,000 btu units i cn run off genny power (7500 w Onan).Have I thought of everything ?Sounds like you have a plan and know what you're doing, assuming that you can get through the walls and such with the wiring.#12AWG is all that's needed and the total load for this extra unit should be under 15amps. This said, I question your reference to the 30amp service on most pedestals, when a 20amp will do. Naturally in lieu of a 20amp outlet, the 30 can be used with an adapter.Also, you might consider a self contained unit that requires no thermo wiring to your existing thermostat and possible one with a remote control.Done right, you should be able to run all three from the genset as well. I would double check that the washer/dryer circuit is private though.

Another thought; a guy I know put a portable free standing unit in his living room. Added a vent and the drain hose. He could run it off the inverter while driving, no genset while driving.

I did a similar install in my kitchen vent opening. instead of tying into exist thermostat I bought a self contained 15k btu Coleman AC with heat pump. I hard wired it to back and in electrical bay I installed a 30amp breaker and box with plug to run to camp ground pedestal. Only thing I cannot do is run it while on road but have not needed it yet. The 3rd AC is a great adder It has reduced our heater use and keep us cool in the hot Texas summers.ctc

Not sure why you are adding a separate 30 amp circuit that will allow you to plug into the 30 amp outlet on the outside power pedestal. Just add another breaker to you inside 120 ac panel. That way you can all three ACs when traveling. We have three ACs on our Phaeton. All are powered through our 50 amp power cord. No overloading issues.

Adding a 3rd AC Unit | Good Sam Community

JCat
Explorer III
Apr 13, 2015
You are correct tropical.

The cord will connect to a 20 amp breaker before it connects to the 30a power at the pedestal.
tropical36
Explorer
Apr 11, 2015
JCat wrote:
Update: Had the AC guy out and talked to Customer Service at Mandalay.
The washer wiring gauge will not handle the AC as it is a 15a circuit.
The EMS in the RV will not be able to balance the load and would require an upgrade (per Mandalay) even if I add a 20A breaker and circuit.

I will add the AC, and run a wire on the roof down to a 20A breaker box and then a cord to the 30A pedestal connection.

So I will have the AC working only when parked.

I doubt very seriously if a running A/C draws close to 15amps and the starting current won't hurt or trip the breaker with it's built in power curve. As for your EMS, what does it know except for when you exceed the set current draw and it will then shed whatever loads you tell it to. I have mine to shed the air and only the air. In addition, I've installed a dual power adapter for the rear air, that I can unplug and re-plug into a separate outlet on the pedestal, so you could do that and wire your third one straight in to the breaker box if you can get to it and many have run extra AC wires inside the AC vents. They stay nice and cool in there, as well. Whatever you might do, be sure and put some breaker or fuse protection out front somewhere, unless you're going to use a min. of #12awg and will only be plugging into a 20amp outlet on the pedestal. You could even make yourself up a portable breaker box when plugging into any outside source, where you're not fully protected downrange and for the size wire that you're using.
JCat
Explorer III
Apr 10, 2015
Update: Had the AC guy out and talked to Customer Service at Mandalay.
The washer wiring gauge will not handle the AC as it is a 15a circuit.
The EMS in the RV will not be able to balance the load and would require an upgrade (per Mandalay) even if I add a 20A breaker and circuit.

I will add the AC, and run a wire on the roof down to a 20A breaker box and then a cord to the 30A pedestal connection.

So I will have the AC working only when parked.
holstein13
Explorer
Apr 10, 2015
Executive wrote:
I run all three of my 15,000 Units off 50amps with no problems. You should be able to also. IMO, you're over thinking this. Keep it simple and enjoy your coach..Dennis
I agree. I also run all three of my 15,000 units off of 50 amps with no problems. Of course I used to trip the breaker when the A/Cs were running and I added the washer, dryer and dishwasher on top of the electric water heater elements and the battery charger. Then the wife would cook dinner on our induction range.

Since then, I adjusted the power management software to shed certain loads in case I go over 40 amps.

If you don't have a load management system, maybe the separate breaker is a good idea.
Executive45
Explorer III
Apr 09, 2015
I run all three of my 15,000 Units off 50amps with no problems. You should be able to also. IMO, you're over thinking this. Keep it simple and enjoy your coach..Dennis
Busskipper
Explorer
Apr 09, 2015
JCat wrote:
I have 2 AC's on my RV currently and I spend a lot of time in the Southwest where it can get to 110 120. 2 AC's won't cut it so I have decided to add a 3rd unit.

I welcome your experience and comments on my plan.

I will mount the 3rd unit where my kitchen vent is located.
Run a wire to my current thermostat for control
Run AC power from the unit to the rear of my RV, in the closet area where my washing machine used to be. I will add a breaker in line, and connect to the 120v outlet in the closet.

I will also run another AC line from that closet out to my electrical bay, so I can connect the 3rd unit directly to a 30 Amp shore power seperate from the rest of the RV, which would be connected to the 50 amp service.

I hope to accomplish the following:
When going down the road with the genny on I can run both front AC units and the 3rd will be plugged into the washer circuit.

When parked I can run all 3 units with the 3rd unit plugged into 30 amp at the pedestal and the rest of the RV to the 50 amp. This way I won't overload the RV's electrical system.

In the end I will have 3 15000 BTU Dometic units that I can run off shore power, and 2 15,000 btu units i cn run off genny power (7500 w Onan).

Have I thought of everything ?

Just a thought -- Have you looked at an LG Mini Split System? Depending on size and location this might be an interesting option.

Just a thought.

BOL,
tropical36
Explorer
Apr 08, 2015
holstein13 wrote:
I like the idea of the separate 30 amp plug for when you are parked. You are far less likely to trip the breaker that way. I did a similar install with my old gasser and it worked out great. I agree that you don't need 30 amps however. 20 amps would work fine.

That's fine, but did you in fact run #10awg (30amp) wire or maybe something smaller like #12awg (20amp) or #14 (15amp) wire.
If not the #10 and considering the enclosed run to the A/C unit, I would most certainly be using a breaker of the proper value and you shouldn't be having any tripping problems, anyway.
holstein13
Explorer
Apr 08, 2015
I like the idea of the separate 30 amp plug for when you are parked. You are far less likely to trip the breaker that way. I did a similar install with my old gasser and it worked out great. I agree that you don't need 30 amps however. 20 amps would work fine.
John_S_
Explorer II
Apr 08, 2015
I can run my fridge and three AC units on with just my 50 amo shore cord. If you wanted to put a second line in to be able to run two ACs on 30 amps that is different but I have never tripped the pedestal except at Disney and that was just the charger alone. The pedestal was bad.
tropical36
Explorer
Apr 08, 2015
lunch surfer wrote:
I did a similar install in my kitchen vent opening. instead of tying into exist thermostat I bought a self contained 15k btu Coleman AC with heat pump. I hard wired it to back and in electrical bay I installed a 30amp breaker and box with plug to run to camp ground pedestal. Only thing I cannot do is run it while on road but have not needed it yet. The 3rd AC is a great adder It has reduced our heater use and keep us cool in the hot Texas summers.

ctc

I just gotta ask as to the why of the 30amp breaker and if you indeed used #10awg wiring for this? Because if anything smaller, like #12 maybe, then this wiring isn't properly protected. Even if you used the #10 for possible voltage drops or for whatever other reason, you should have still used a 20amp breaker.

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