Using two roof a/c units on 30 amps

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Wristpin

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Joined
Oct 17, 2010
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47
Location
London, KY
We are considering trading for a 2014 Heartland prowler 289 fifth wheel that has 30 amp service and only one roof top A/C unit, I think we will need another A/C unit in the master bedroom at a later time.

My question is will the 30 amp service run two roof top A/C units?

Thanks in advance for any advice you can share with me.
 
Yes you can run two A/Cs on a 30 amp service but you won't have any power left over for anything else. It might pop the breaker when one of the A/Cs starts up. I have a 32 foot class A with one A/C and a 30 amp service. I live in Florida. I bought a nice large fan that I put in the hallway between the living room and the bedroom which I use to blow the cold air into the bedroom when I need it. Works just fine. Cheaper than adding another A/C.

It would also be possible to add another A/C and put it on a 20 amp circuit all by itself with a heavy duty extension cord. Then you would plug the trailer into the 30 amp outlet and the A/C into a 20 amp outlet.
 
Is there a electrical box in the ceiling next to the opening where the AC would go? If there is, I would think that when they designed the rig, they took that into consideration that someone would in time add a second AC and that the 30 Amp would handle it. Someone correct me if I'm wrong!!!
 
Wristpin said:
My question is will the 30 amp service run two roof top A/C units?

Thanks in advance for any advice you can share with me.
Click to expand...

It depends on if you have a good clean 30 amp supply, and if you are willing to let one get going before starting the second one. We keep our 30 amp service plugged into our home 30 amp outlet and run both AC's when we are packing or working in the mh. When we do that, we only turn on one, and let it run for a few minutes before firing up the second. You will probably find that at some parks it will work, and some it won't. As Tom suggested, it wouldn't be a major deal to run a separate 20 amp cord. When we run ours, about the only other electrical we have going is the fridge and the converter. You wouldn't be able to use any high amperage appliances at the same time.
 
Our converter can draw up to 1,000 watts depending on the condition of the batteries.  If that kicks in with 2 air conditioners running, something has to give.  In our case on a horribly hot midwest day, it was the power post end end of the 30 amp cord.  I knew better, but being overheated (me, not the cord) can lead to dumb choices.  In a perfect world, you could probably get away with it.  But any weak link, like a loose outlet, will do you in.
 
SeilerBird said:
Yes you can run two A/Cs on a 30 amp service but you won't have any power left over for anything else. It might pop the breaker when one of the A/Cs starts up. I have a 32 foot class A with one A/C and a 30 amp service. I live in Florida. I bought a nice large fan that I put in the hallway between the living room and the bedroom which I use to blow the cold air into the bedroom when I need it. Works just fine. Cheaper than adding another A/C.

It would also be possible to add another A/C and put it on a 20 amp circuit all by itself with a heavy duty extension cord. Then you would plug the trailer into the 30 amp outlet and the A/C into a 20 amp outlet.
Click to expand...
We have 2 AC units on our roof with only a 30A power cord. I added a20A extension cord to run the rear AC out to the pole (like SeilerBird suggested). It works great.
 
30A is 30A, and two 13,500 or 15,000 btu a/c units will each consume 11-13 amps (depending on brand and model) while running. So yes, they could both run on a single 30A source. The problem is that the start-up amp load when the compressor turns on will momentarily take the 11-13 amps up to 22-26 amps and that is almost sure to trip the 30A source breaker if anything else is running, especially the other a/c.  You would have to have the fridge and water heater on LP instead of electric and the battery charger turned off as well.

In short, it is a crap shoot at best. If you really need two a/c's in regular operation, go for 50A upgrade on the trailer, or plan on adding a extra 20A circuit for the second a/c and hope the park supply has an extra 20A available via the power pole. Typically a site with a 20A and 30A outlet has a single 30A feed as the supply to both outlets.
 
My two C's run to the same 20 amp fuse. I can run them both but only for a short time before the fuse pops or if the wife forgets and turns anything else on. My plan is to rewire and put them both on a new 20 amp fuse and the ac's will be the only draw on the fuse. My motorhome is 30 however I run most of the time with a 50 amp adapter.
 
Theories are wonderful things. In theory one can run 2 A/C units on a 30 amp circuit. In actual practice it almost never works for me. I have 3 AC/heat pump units on my MH and have tried repeatedly to run 2 at a time. Invariably someone wants to use the microwave, we forget to turn off the electric hot water, we forget to turn off (or even worse back on) the inverter/charger, the coffee pot, the electric grill, etc.

If I was using 30 amp outlets on a regular basis, like you are set up for, I'd definitely go for a separate circuit for the 2nd A/C unit. I wouldn't even bother to try it on the 30 amp circuit you have.

Ken
 
Thanks guys for the great information
After reading all the input I've made my decision
I'm going to run a seperate heavy duty extension cord and plug it into the park supply.

Great forum and I'm proud to be a member!!
Thanks again
 
I have a 50 amp rig, What I did was electrically "Break out" the bedroom A/C. instead of connecting directly to the breaker it now connects to an INLET (plug) in a compartment on the outside, there is an OUTLET (Actually a 12 ga extension cord) next to it that IS powered by the original breaker.  I might add I recently "T" connected a special 20 amp outlet (Different from all the others) for a space heater on this same inlet.

(I mean, I don't use both heat and A/C at the same time)

Now... If on a 50 amp sige the outlet and inlet connect togethere

On a 30 amp site (or on a 30 amp RV) the plug (inlet) is connected by a 12ga power cord to the park's 20 amp outlet.

Works great, has for years.  Only problem I have had is the wire nutted connection between the flexible cord and the romex (Solid copper) I re-did it soldering this time and no problem since, this is where the "T" is soldered on as well.
 
My experience in a fifth wheel is that anywhere near bedtime, you turn on the bedroom AC and turn the other one off.  The cold air from the bedroom drops and takes care of the rest of the trailer just fine.
 
Years ago, on a '92 Bounder, I installed a "black box" that I bought at Camping World. It would run one AC for about 10 minutes, then shut it down and run the other one the same, then repeat and repeat. It kept the rig cool at front and back. I don't know who made it, but if there is something on the market similar, it would be worth looking at.

Bill
 
My '96 Win Adventurer has two a/c and 30amp service. However, I cannot even attempt to run them both. A switch box up front allows me to apply power to one or the other but not to both. Was not aware other similar rigs were different - as I read of attempts to run both when hooked to shore power.

However, when running my 5kw genset I "can" run both at the same time.

 
I realize this is an old thread but  rather than start a new thread I thought I would add my 2 cents.  My 1996 Four Winds XL has 30 amp service connection but can run both air conditioners off the generator but only 1 through a 3 position selector in the bedroom when on the 30 amp shore connection . There is 2 transfer switches,  one under each night stand in the bedroom. The one on the drivers side for switching the 30 amp circuit on the Generator or the shore power connection to the coach circuit breaker panel.  The passenger side transfer switch will switch the power from the 3 position switch rear air to the  20 amp generator leg to the rear air.

I see 2 options to run both airs at a campground that has a 3 outlet pedestal (15 amp, 3o amp and 50 amp.. 
1. install a 50 amp breaker panel and shore connection, disable the 3 position switch and rewire the rear ac transfer switch to the second leg on the 50 amp panel. wire the rear ac into the new 50 amp panel..
2. Install an additional transfer switch in line to the rear ac and add a 15-20 amp shore power wire  with 20 amp breaker  to the connect to the campground pedestal.

Option 2 allows you keep all the original equipment with out modifications.  You can also up grade at the pedestal if 15 amps is not available  or is tied into the 30 amp connection, by using a 50 to 30 adaptor and 30 to 15 amp adaptor.
 
You can make a manual transfer switch for the rear a/c using a basic double pole, double throw switch. Just switch rear a/c from the genset to the new secondary shore power line when needed.

Your best bet is to use the 50A source and feed the 30A off one side and the 15A secondary off the other. That way you are balancing the load somewhat. In many power pedestals, both the 30A and the 15 A outlets are pulled off the same side (leg) of the 50A supply. That probably means you would make your own Y adapter, with a 50A male and 30A & 15A females on the legs of the Y.

Of course, the campground is gonna charge you for 50A service if you do that, whereas you might escape notice using the just 30 & the 15 outlets.
 
Instead of a transfer switch, just install a 20 amp socket and plug in the line going to the rear air conditioner.  The socket comes from the existing wiring, the plug goes to the air conditioner.

Put it somewhere convenient, like inside an outside compartment.

When you're on the road, the air conditioner plug stays in the socket and is powered from the existing circuit just as it is now.

When you pull into a campground, unplug the rear air conditioner from the socket and plug it into it's own heavy duty 20 amp extension cord.  If you plug it into a campground 20 amp outlet the campground breaker will protect the a/c and cord.
 
That is how 30 amp rigs were wired.

A company that no longer exists it appears was PSRV (Power Soltions RV)  they sold a device that let you use the park's 20 amp outlet to run the 2nd  A/C.  They charged 99 dollars as I recall which is way over priced.

Curreent hookup on your 30 amp RV

Breaker-Switches-Breaker on generator----------------------A.C.
With their mod
All that left side stuff---------Outlet/inlet=20 amp beaker---------A.C.

Use a 12ga outdoor rated extension cord and pull the outlet off the inlet (They put the outlet on a pigtail.. I did it the other way around) Plug extension cord ONTO inlet and into 20 amp outlet on pedistal.. That's all folks.
 
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