How do 3+ A/C's work?

[bruceisla]

Originally Posted by Steve Ownby

For most 50 amp coaches they have two legs of 50 amp power at 120. .

It is important to note the 2 legs are out of phase. They are NOT 2-120vac lines that are alike.

[PDR John]

You seem to be under the impression that the ACs always draw 20 amps, when ours pull only around 15 when running.

2 of them are on 1 leg drawing only 30 amps of the breakers total. Our electric cook top is 120 volt and so is the dryer. The highest I've seen our coach pull was 79 amps. That was all 3 ACs, the dryer and microwave. If we do draw to much the EMS will shift some smaller loads to the inverter, entertainment system and frig first. We haven't been able to pull that much at a time though, yet.


On our old coach we ran both ACs just fine on 30 amp, you just can't have them start at the same time.

[Barlow46]

Our 05 dynasty utilizes the 220v function for our stacked dryer. We have the 10kw generator that puts out 120v/220v. I think this is the transfer switch that is in our coach. http://www.generatorjoe.net/html/esco/ES350.pdf
We have never run into a problem running the 3 a/c or anything else when connected to 50A shore power or when using only the generator. The only non-electric device is the propane stove.

[FlyingDiver]

Originally Posted by bruceisla

Well ... sort of ... it's actually like 2 - 50a out-of-phase 120vac services for a total available 100a. (as opposed to a single 100a 120vac service).

A distinction without a difference, unless you actually had a single 120V circuit that needed more than 50 amps. Which you never would in an RV.

[clyon51]

Originally Posted by jesilvas

You had the EMS or whatever so that makes sense.

I know it's not 240V, but it is. I understand nothing actually uses 240V. It's two phase, three wire service. That all makes clear sense.
I'm just wondering how, or if, you can run three or more A/Cs at once.

I can't understand your confusion. The coach has 100 amp service. 3 ACs (even with all compressors running at once) will only draw 45a max. That leaves 55 amps for the rest of the coach. My 30a coach runs 2 ACs at once no problem.

These coaches also have load sheading (EMS). If ever the rest of the coach demands close to that extra 55a (such as turning on the microwave) the EMS will cut power to a secondary AC, perhaps middle or rear. When extra power later becomes available, it will restore power to that AC unit. All major AC appliances are connected through the EMS. The factory sets the priority which ones are the first, second or third to be shead if necessary.

[jamesrxx951]

Originally Posted by Steve Ownby

You are correct. A few coaches with stackable washer/dryers have used the 240 capability and a very few all electric coaches may use it for the range top but it's rare. For most 50 amp coaches they have two legs of 50 amp power at 120. By adopting this standard which uses readily available residential components it does insure that any competent electrician will understand the system. As far as the end user is concerned the 120 vac power in a coach is just like their house.

I was actually thinking about the dryer after my post. I would have to think that a dryer (even in a motorhome)would be a 240 unit. I wouldn't think that a 120VAC dryer would work very well.

[jamesrxx951]

Originally Posted by bruceisla

The service is 240/120 ... just like a house.

No .... in your ending scenario, you would need a source (the entire park and pedestal), and cord, and the entire motorhome wired in a non-standard configuration of single-pole 100a 120vac. Wire size would be huge and costly.

I did state that you would need a larger supply wire to run 100 amp service. However, the motorhome PAST the fuse box would remain the same because everything is still 120VAC unless you have an appliance that uses 240VAC.

[Dogpatch]

Originally Posted by Peralko

No EMS, just straight 30 Amps. 30 Amps will run two ACs just fine.

I don't know how you are doing it, but I can't run both my A/C units on 30 amp. Only 1 on 30 amps and 2 on 50amps.

Tried at one campground and blew the breaker 3 times. That was on my previous 03 HR Vacationer. Haven't tried yet on Dynasty with EMS.

[Stan.Birch]

Originally Posted by jesilvas

I know that 50A 240VAC is required for two A/C's, but what about more. Multiple 50A connections?

Your information is incorrect.

I have no problem whatsoever, running two Coleman 13,500 Power Saver A/Cs on a mere 20 amp receptacle. These units typically run 7 to 8 amps per unit.

[Steve Ownby]

Originally Posted by jamesrxx951

I was actually thinking about the dryer after my post. I would have to think that a dryer (even in a motorhome)would be a 240 unit. I wouldn't think that a 120VAC dryer would work very well.

All the combo washer /dryers are 120. Many of the stackable are also 120. Yes, the dry function is slower. It takes 30-50% more drying time on 120.

[clyon51]

Originally Posted by dogpatch

I don't know how you are doing it, but I can't run both my A/C units on 30 amp. Only 1 on 30 amps and 2 on 50amps.

Tried at one campground and blew the breaker 3 times. That was on my previous 03 HR Vacationer. Haven't tried yet on Dynasty with EMS.

Two 13.5K BTU ACs use about 25 amps in my 30a coach. This only leaves 5amps, so you can't run much else. If they were both 15K BTU, I'm sure the results would be different. An AC capacitor not working at 100% could also affect this.

I do know that there are 30a coaches out there that can only run one AC on shore, however can run 2 if the genny is running. This is because the 20a circuit on the genny only feeds the rear AC.

[jesilvas]

Originally Posted by clyon51

I can't understand your confusion. The coach has 100 amp service. 3 ACs (even with all compressors running at once) will only draw 45a max

Because they have 20A breakers, and are rated up to that.
I guess I ere on the side of caution and maybe I'm thinking of another electrical code? Idk. My train of thought is if it's rated for 15A, then your source needs to be at least that. If everything is rated for 150A, your source should be that.
Does my train make more sense?

[FlyingDiver]

Originally Posted by jesilvas

Because they have 20A breakers, and are rated up to that.
I guess I ere on the side of caution and maybe I'm thinking of another electrical code? Idk. My train of thought is if it's rated for 15A, then your source needs to be at least that. If everything is rated for 150A, your source should be that.
Does my train make more sense?

It sort of makes sense, but that's not how the electrical code works. The code assumes that not all circuits will be used at max at the same time. The max total load (going by branch circuit ratings) in my RV is well over 100amps, but that's all I have going in.

[clyon51]

Originally Posted by jesilvas

Because they have 20A breakers, and are rated up to that.
I guess I ere on the side of caution and maybe I'm thinking of another electrical code? Idk. My train of thought is if it's rated for 15A, then your source needs to be at least thatu.u If everything is rated for 150A, your source should be that.
Does my train make more sense?

I have no idea where you got 150 amp from. All I can say is what I said in my last post is the way it is. The EMS does not necessarily consider the breaker limit per circuit, even if it did, thats only 60a with 40 left, it monitors total amps and sheds as needed. You have heard from several 3 AC owners, what more do you want? 3 ACs use 45amps, in a 100 amp coach, so where is your problem??