Easystart functionality built into RV AC units?

[Strador]

Pardon my greenness. I am 100% a newbie when it comes to RV’ing. I have a 33 ft class C, 30 amp, that has a single AC unit. The fan in the bedroom is pre-wired for a second unit, so it should be easy to install, I live in Arizona so the second unit would be nice to have.

Obviously, the issue is power, or more specifically startup power. I have been working with the math and 30amps is enough to run 2 AC units once you get past that huge initial startup draw. In doing some reading it would appear it should work just fine using products like easystart or softstart.

I guess my question is, why are RV AC manufactures not including easystart/software capabilities directly into the unit? Or, are there actually units out there that does this and I can’t find them? It would seem like this would be a no brainier especially with the RV power limitation?

[JoeH]

ktmrfs wrote:
For that reason RV's with Two AC units on a 30A system come from the factory with a switch allowing one or the other AC unit to operate, but not both.

We had a 36' 1999 Pace Arrow Vision that had 2 roof AC units and was a 30 amp hookup. We used that RV for 14 years running both AC's, we are in Florida and traveled to the south west often so the AC's were in constant use. . Never had a problem and there was no "switch". The PA did have an EMS that would shed loads as needed.

[dedmiston]

Thanks for all the kind and informative responses to this new member. I appreciate it.

[otrfun]

Strador wrote:
. . . I guess my question is, why are RV AC manufactures not including easystart/software capabilities directly into the unit? Or, are there actually units out there that does this and I can’t find them? It would seem like this would be a no brainier especially with the RV power limitation?

If you're referring to a Micro-Air Easy Start (MAES), RV a/c manufacturers probably don't make them standard equipment because they cost $250-$300 each. As much as they would like to manufacture (and install) a MAES themselves (in-house), they cannot because the MAES is a patented device. However, some RV TT/camper manufacturers do offer it as an option.

A MAES's primary purpose in life is to make an RV a/c unit easier to start with a smaller generator (by reducing the a/c's LRA). A MAES serves no useful purpose if you're powering your RV a/c with a properly functioning, dedicated, commercially powered =>15a circuit (i.e., shore power) or a larger generator.

FYI: the MAES only functions when the compressor starts, for less than second. After that it ceases to function until the compressor starts again. The MAES has *no* effect on (and will not reduce) the continuous current draw of an RV a/c.

[dougrainer]

Strador wrote:
Pardon my greenness. I am 100% a newbie when it comes to RV’ing. I have a 33 ft class C, 30 amp, that has a single AC unit. The fan in the bedroom is pre-wired for a second unit, so it should be easy to install, I live in Arizona so the second unit would be nice to have.

Obviously, the issue is power, or more specifically startup power. I have been working with the math and 30amps is enough to run 2 AC units once you get past that huge initial startup draw. In doing some reading it would appear it should work just fine using products like easystart or softstart.

I guess my question is, why are RV AC manufactures not including easystart/software capabilities directly into the unit? Or, are there actually units out there that does this and I can’t find them? It would seem like this would be a no brainier especially with the RV power limitation?

To answer your last question. Some RV OEM's do install a Pulse type system for running 2 AC's on 30 amp. But it is RARE for BOTH to run at the same time. It gives you the option to run the Front AC during the day and then running the bedroom at night where you want to stay cool. Doug

This is a system Jayco installs. Other OEM's also use it

http://www.precisioncircuitsinc.com/wp-content/uploads/2016/10/00-10050-000-Power-Control-System-Mid...

[dougrainer]

When you have 30 amp service, you can only run 1 Roof AC. You do not state year model of RV
Roof AC---- pulls about 14 amps on HI FAN COOL. So 28 amps, leaving you 2 amps to run everything else.
Power Converter ----pulls about 1 to 3 amps depending on DC load
Refer pulls 2.5 to 3.0 amps
Water Heater IF equipped with 120 element----11 amps. Not usually on a 30 amp RV
Microwave depends on Wattage but 7 to 10 amps.
So, you install that 2nd AC. Well, you will not have room for the extra required 20 amp breaker for it in the 120 breaker panel. RV AC units require a dedicated 20 amp breaker. USUALLY, the Rear Bedroom prewired roof vent that wire goes to the GENSET. That requires at least a 5000 to 5500 watt Genset which probably was not optioned on your RV. You probably have a 4.0kw Genset.

[wa8yxm]

30 amps is JUST enough to run two A/C.s and nothing else. like the converter charging your batteries.

I would run the 2nd A/c off a 2nd power source like the parks 20 amp outlet.

[Strador]

Thanks everyone for all the feedback, appreciate the info sharing.

I watch a video of a guy that wired his second unit to a separate plug on the outside of his rig. Thinking that might be the best option to go that route. Not sure I want to bite off going from 30 to 50 amps at this point.

[valhalla360]

ktmrfs wrote:
Two typical Max draw for many AC units is 13.5A or more so running two violates that.

It's important to remember that an air/con unit will try to draw roughly the same wattage regardless of voltage.

So if you have a 1600w continuous draw per unit:
- At 120v, you would need 13.3amps (26.6amp for 2)
- If the voltage drops to 110v, you now need 14.5amps (29amps for 2)

And as it happens, on the hot summer weekends when you really need 2 units, everyone is running their air/con so voltage tends to sag, meaning your amp draw goes up. So what works in a practice run on a cool weekday may fail when you really need it.

Also don't forget you need to kill off everything else running.
- Fridge that's another 2-3amps
- 40amp (12v) battery charger that's another 4-5amps
- Cell phone/laptop bricks that could be 1-2 amp.
- TV/Microwave in standby but off could be another 1/2 amp.

TurnThePage's idea of running a second line to a separate 20amp outlet on the pedestal and running a smaller air/con unit directly off that is a better idea if you don't want to upgrade to 50amp.

[TurnThePage]

EasyStart type devices are great. Other options include selecting a lower BTU unit, or even wiring it separate from the rest of the RV so that it's on its own power plug.

[ktmrfs]

Two typical RV AC units draw enough current that by NEC it's not code allowed. Max draw from a "dedicated" device is limited to about 80% of max rated current. So on a 30A circuit your allowed 24A from dedicated devices. Max draw for many AC units is 13.5A or more so running two violates that. For that reason RV's with Two AC units on a 30A system come from the factory with a switch allowing one or the other AC unit to operate, but not both.



Now there are some newer units that draw around 11A, so in theory you'd be OK, but not much else running.

Next issue is starting current with one unit already running.
Without easy start, you'd need the breaker to handle a short term 50A load or so. Not likely happen w/o the breaker tripping

for a DIY install on a 30A unit, the easy start would definetly help. On my install with easy start, max current draw on startup is down around 20A, so the question is, with one unit running and drawing 13A, could the breaker handle a 20A several second surge? Maybe, if nothing else was on

Overall, IMHO NEC code requirements and common sense lead me to say I personally wouldn't try to run two AC units on a 30A system even with easy start. I'd convert the trailer to 50A. But then, many of the places we go are limited to 30A service, so I'd still be stuck, and when dry camping, same thing.

I just turn the AC unit on when temps hit about 74 and let it run. It will keep my trailer comfortable. If I wait till temps are in the upper 70's inside, the AC can't bring the temp down, it's able to hold a temp but not bring it down in a reasonable time.

[2oldman]

Strador wrote:
I have been working with the math and 30amps is enough to run 2 AC units once you get past that huge initial startup draw.

That's one of those 'looks good on paper' things, but in reality you're likely to burn up your plug.

[Neil_Citro]

Strador wrote:
Pardon my greenness. I am 100% a newbie when it comes to RV’ing. I have a 33 ft class C, 30 amp, that has a single AC unit. The fan in the bedroom is pre-wired for a second unit, so it should be easy to install, I live in Arizona so the second unit would be nice to have.

Obviously, the issue is power, or more specifically startup power. I have been working with the math and 30amps is enough to run 2 AC units once you get past that huge initial startup draw. In doing some reading it would appear it should work just fine using products like easystart or softstart.

I guess my question is, why are RV AC manufactures not including easystart/software capabilities directly into the unit? Or, are there actually units out there that does this and I can’t find them? It would seem like this would be a no brainier especially with the RV power limitation?

I have a 50 amp fifth wheel so I think it is different, but my understanding in the 30 amp motorhomes is they run on one thermostat (mine has two separate thermostats). When one thermostat controls both, then I think it ensures that they do not try to start at the same time, which is how you can get away with 30 amps for two units. As stated, keep an eye on the voltage and make sure you do not run too much. Tripping the breaker is not a big deal, you can just reset it, but if the voltage drops too low bad things happen to the AC units.

[valhalla360]

Because it costs money and generally they aren't needed. A 30 amp outlet is plenty to start a single air/con and a 50amp outlet is plenty to start 2 air/con units (or even 3 units).

It's really only when you try to use an undersized generator or overload a 30amp outlet, where these units really become useful.

Also running 2 air/con units is pretty marginal on a 30amp outlet. Keep in mind, 30amps is the nominal rating. Continuous output is limited to 80% or 24amps. You see a lot of burnt up 30amp plugs from people who think they have 30amps, so they are going to use 30 amps.