Running two A/C's on 30Amps?

[JamieGeek]

"Regular" A/C's, not high efficiency ones:

https://www.youtube.com/watch?v=1mCeNRODDxc

(This would also mean that you could run one off a normal 15A household circuit.)

Link to the "Easy Start" unit.


I don't have any affiliation with either RV Geeks or Micro Air...just saw this video pop up on youtube and thought it would be of interest to the fellow RV'ers here.

[Chance]

Jamie, as you may recall, a few mid-size motorhomes have started coming from manufacturer with two 11,000 BTU/hr Power Saver A/Cs which are power by 30-Amp electrical service or a 4,000-Watt Onan generator.

Anyway, even after the A/Cs are started, it would pay to use as little power as possible on air conditioning so that other items in the motorhome can be operated at same time (albeit nothing power hungry). Running two standard 13,500 A/Cs will leave very little excess, if any. So, in my opinion, not as practical.

While doing research on Airxcel, I saw that they will be introducing additional Power Saver models that may be of interest to some looking to upgrade to two A/Cs that can run off their existing electrical. Those with shore power can always run an extra extension cord, but if trying to power from 4,000-Watt Onan while boondocking, it may make sense to buy more efficient air conditioners.

I haven’t seen electrical performance specs yet, but I’m curious if the smaller 11,000 Power Saver will be as efficient as the standard size. The Mach 10 line is much lower and a better aesthetic fit on smaller RVs. I like the idea of more efficient “and” low profile. Whether these will need a soft start we’ll have to wait for specs.

Originally Posted by Airxcel

A 15,000 BTU capacity Power Saver unit has been added to the medium profile lineup and an 11,000 BTU capacity Power Saver unit has been added to the low-profile lineup, commonly known as the Coleman-Mach 10.

[TurnerFam]

we can run both of our roof 13.5kw units while on 30amp with no issues, but only recognizing that trying to add too much else can trip a breaker, usually the shore breaker since they can tend to be old, weak, and overly sensitive after so much usage by campers plugging and unplugging on an almost daily basis.

but, last year during the heat of the summer, and while on 30amp campground service, we ran both simultaneously, ran several small electric fans around the coach, watched satellite TV, and had the residential fridge on as well. When we wanted to use the microwave, we just cut off the front a/c unit while we needed it. We used the propane for Water Heating, and cut the 'SHORE MAX' setting on the Battery Charger/Inverter down to 5amps, for only a small trickle charge, if anything.

We later went to our local campground, which has much older 30amp receptacles and breakers, and had an issue with tripping it while using both a/c units - I called the manager over, told him the breaker needed to be replaced, and all was back to normal once the new breaker was installed.
He honestly could not believe that I could run both a/c units at the same time on 30amp service, but there they were, both running just fine. Once his jaw came up off the ground, and after working there for many years, he pronounced that I must have some special 'magical' air conditioners since he had always been 'told' that you couldn't do that, and no one should even 'try' since it might 'explode', or something.
What nonsense.

Sometimes we get confused by 'what' we are doing, versus 'what' we CAN do, if we do things correctly and in the right order, as far as electrical usage goes. The 'phantom' electrical draws, such as electrical water heaters, battery chargers, and the like, sometimes get in the way of our understanding of how 'much' we can do when 'only on 30amp service'.... a tripping breaker is not a sign that something is 'wrong', it's a sign that we are trying to use too much for that size wire, that size breaker, for those things we want to power. The tripping breaker is really our sign that we have to rethink what and how we are doing things, especially when doing many things at the same time.

Usually HOT weather, or COLD temperatures, lead to these 'great' learning experiences!

[Chance]

Yeah, agree 100%. We shouldn’t compare performance or results unless conditions are the same. That’s a major flaw with Internet wisdom.

The nice thing about the motorhomes that have 2 X 11,000 Power Savers is that they include Power Management system that supposedly sheds one of the A/Cs automatically if owner runs microwave or other high-current item.

Other variables to consider are that A/C will draw more current at higher outside temperatures due to higher condensing pressure, and also that if shore power supply is at lower voltage, that too will result in higher current. A/Cs are often rated at 115V but electrical power supply can easily vary from 110V to 120V or more, which can be the difference.

With 13500 BTU/hr Power Savers pulling just over 10 Amps, it will be interesting to see how little the new 15,000 PS pull. Let’s hope the days of A/Cs requiring ~ 20 Amps is in the past.

[JamieGeek]

Originally Posted by Chance

...
The nice thing about the motorhomes that have 2 X 11,000 Power Savers is that they include Power Management system that supposedly sheds one of the A/Cs automatically if owner runs microwave or other high-current item.
...

That system is called an "Automatic Energy Select Switch" (datasheet). My Axis has one connected between the Microwave and the 120V heater on the water heater--when you use the microwave the water heater is cut out. (Although I would bet with the A/C system it may be more involved so that the compressor isn't simply cut off at a moments notice.)

[Bob Denman]

I think a simpler solution for us 30 amp folks, is to just get a 15K BTU single a/c, and throw in a heat pump for those chilly mornings...

[Chance]

It’s not the same. Not even close.

Two 11,000 BTU/hr A/Cs at 22,000 total are almost 50% more cooling than a single 15,000. While a single 15000 may be OK for smaller rigs in hot and humid weather, once you start getting around 28~32 ft in length, a single unit may not keep up depending on owner temperature tolerance.

[Bob Denman]

Are you carving ice sculptures on the kitchen counter?
Our single a/c unit does a "better than fine" job of keeping us out of the beer cooler, until a reasonable time of day is attained.

[JamieGeek]

Originally Posted by Bob Denman

Are you carving ice sculptures on the kitchen counter?
Our single a/c unit does a "better than fine" job of keeping us out of the beer cooler, until a reasonable time of day is attained.

Park your guy out in the desert in the AZ sun and lets us know...

[Bob Denman]

We might have to move "Beer-Thirty" up to a more reasonable time of day...

Truthfully: I have no interest in trying to live inside a pizza oven...
I'm good up to about 100 degrees. After that: the game is called off due to excessive sweating...

[Long & Winding road]

I have a feeling that the RV industry will have some advances in several key areas (Finally).

The amp draws on AC units, Frigs, microwave etc will get lower since everyone is trying to run stuff on inverters and litium batteries.

Cheaper litium batteries installed in most coaches from factory. Larger Hybrid inverters/converters. Medium size solar array from factory (like 500 - 700 watt range).

Hybrid drivetrains in B's, B+ and C RV's.

Self driving? or at least semi autonomus?

Can wait.

[Bob Denman]

Everybody is trying to do the same stuff that they've always done...

... But with less power usage!

[Chance]

Originally Posted by JamieGeek

Park your guy out in the desert in the AZ sun and lets us know...

The real issue is thinking that because a 15,000 BTU/hr A/C is adequate for a small 24-ft Class C, that it should also suffice for rigs larger than say an Axis/Vegas.

Additionally, there are people who camp in Death Valley, or park at a beach in the afternoon sun along the Gulf Coast in July or August. I would bet that most in 28~32 foot Class As who try it with single 15,000 A/C won’t be too happy except at night when cooling loads go way down.

In my opinion Thor should consider offering 2 X 11,000 PS on larger Axis/Vegas. I would even pay for the option on a 24.1-size motorhome. Preferably ductless — one in middle of living/kitchen area and other in bedroom. That would yield a high level of efficiency and also flexibility.

[The Gritz Carlton]

Originally Posted by Chance

The real issue is thinking that because a 15,000 BTU/hr A/C is adequate for a small 24-ft Class C, that it should also suffice for rigs larger than say an Axis/Vegas.

Additionally, there are people who camp in Death Valley, or park at a beach in the afternoon sun along the Gulf Coast in July or August. I would bet that most in 28~32 foot Class As who try it with single 15,000 A/C won’t be too happy except at night when cooling loads go way down.

In my opinion Thor should consider offering 2 X 11,000 PS on larger Axis/Vegas. I would even pay for the option on a 24.1-size motorhome. Preferably ductless — one in middle of living/kitchen area and other in bedroom. That would yield a high level of efficiency and also flexibility.

Agree...max A/C capacity and dual unit capability should be built into every unit. You can turn them off but you can't make em cold on demand.

[Pete'sMH]

Maybe it would be good to have that as an option on all factory orders. For coaches being delivered to the hottest regions it might be good but I live in Indiana and have no real interest in paying for dual air or even the infrastructure to support it. If I visit 100 degrees I may bring along a freestanding portable air conditioner but my 32 fr class A has been entirely satisfactory in the high 90s. For most of the country 2 units simply isn’t necessary.

[The Gritz Carlton]

Originally Posted by Pete'sMH

Maybe it would be good to have that as an option on all factory orders. For coaches being delivered to the hottest regions it might be good but I live in Indiana and have no real interest in paying for dual air or even the infrastructure to support it. If I visit 100 degrees I may bring along a freestanding portable air conditioner but my 32 fr class A has been entirely satisfactory in the high 90s. For most of the country 2 units simply isn’t necessary.

...dual unit capability should be built into every unit....

With buyers of RV's running all over this country for the best deal, regional building would not work. It's more the humidity on the 90 degree plus days that we battle...not the dry heat alone. Most vehicles (cars and light trucks) built today have a universal wiring harness installed that will accommodate all options. If you order heated seats, it's plug-n-play. Ordering $100K+ RV and skimping on another $800 A/C doesn't make much sense to me. Build them with two A/C's or with one A/C and pre-wire the unit for a second unit if opted for by the buyer would not cost Thor much more money. The 30A to 50A changeover could be plug-n-play also. The aftermarket conversion is 5 times that cost. There is a threshold driven by size that includes many upgrades but most units sold are not in that category.

[JamieGeek]

Well this has been a bit of a surprise LOL: Not a single comment about the Easy Start unit reducing the surge current at startup (and the noise).

Seems to me that is the biggest reason its difficult to run two A/Cs off 30 amps. I've been able to run the A/C in all our RV's off the 15 amp circuit (not all at once ) in the garage if I'm careful about what else is running on that circuit when the compressor kicks on. The Easy Start guy may fix that (and also kill the startup noise which my wife hates).

[The Gritz Carlton]

Sorry Jamie...we're old and our "brain train" has a tendency to takes dirt roads often. Personally, I'm not a fan of downsizing. Finding 50A power hasn't been an issue for me as I trip plan and travel around the coach configuration. This system might be a good back up option for those unexpected circumstances of only have 30A available on a 95 degree day but I see that as a very rare circumstance and not enough to modify my energy sucking rooftops! Down here, where you can cut the humidity with a butter knife...all those funny noises are like someone bringing you coffee in bed. I have run one A/C on 15A at the house but it's a risky chance you might damage the compressor. If I were doing this often, this Easy Start system would be great...for one unit.

[Chance]

Wiring from breaker box to bedroom ceiling for a second A/C is the very minimum that should be included.

The biggest advantage I see to this middle ground of running 2 efficient and perhaps a little lower-capacity A/Cs on standard 30-Amp service is that it eliminates the need for the larger, heavier, and higher cost generator, which can also burn more fuel at light loads. The generator is one item that’s much harder and expensive to upgrade (i.e. — going from 4,000 to 5,500 Watt Onan).

As long as the RV isn’t upgraded to 50A and larger generator, the cost shouldn’t be more than about $1,000 installed. And in my opinion, having 2 X 11,000 Power Savers in lieu of a single 15,000 has other advantages beyond extra cooling capacity that makes that a deal.

While driving it should make running front A/C from alternator and an inverter much easier.

At night while boondocking the rear A/C in bedroom should be enough, making it more fuel efficient to power one 11,000 BTU from 4,000 generator than a 15,000 BTU from a 5,500 generator.

For those who like portable generators, a single 2,200 Watt Honda or similar can run a 11,000 PS.

I’m not suggesting that having a standard 50A service with two large A/Cs isn’t great on larger rigs, but for about $1,000 I would gladly pay for the option on any motorhome the size of an Axis 24.1 or larger, particularly when bedroom can be isolated from rest of unit.

[Bob Denman]

If you are truly looking to minimize power usage...

http://www.thorforums.com/forums/att...1&d=1559824871