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09-16-2020, 08:38 PM
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#1
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Member
Brand: Thor Motor Coach
Model: Windsport 27B
State: Tennessee
Posts: 80
THOR #14933
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Running 2ac's on 30amp
Have a 50amp MH, thought could only a single ac unit on 30amps, first time at 30amp hookup and both work. I realize probably can't run much else with both units running however to just cool the MH on a hot day works great. Is this typical or is there anything special maybe on pedestal?
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09-16-2020, 08:59 PM
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#2
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Senior Member
Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
Posts: 1,797
THOR #20289
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I don't think you have any special power supply, but I do think you got lucky and maybe you have a robust pedestal supply that doesn't sag with lots of amps. Any of these will probably make it unworkable:
Low pedestal voltage. Low voltage pulls more current and you are already running at the limit.
Starting both compressors at the same time. The inrush current will probably trip the breaker before they start.
David
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09-16-2020, 09:27 PM
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#3
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Senior Member
Brand: Still Looking
State: Texas
Posts: 6,187
THOR #2121
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There’s probably more variation in current between different sizes and models of air conditioners, particularly when adjusted for operating temperatures, than there is between 30A breakers (provided breakers are good).
Just saying it’s likely more about air conditioner loads than breakers.
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09-16-2020, 09:43 PM
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#4
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Senior Member
Brand: Thor Motor Coach
Model: Thor Ace 33.1
State: Illinois
Posts: 1,266
THOR #20274
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Quote:
Originally Posted by mrgscooter
Have a 50amp MH, thought could only a single ac unit on 30amps, first time at 30amp hookup and both work. I realize probably can't run much else with both units running however to just cool the MH on a hot day works great. Is this typical or is there anything special maybe on pedestal?
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There is a chance your air conditioners have a soft start built in. This allows 2 ac units to run at one time. If you pull the side panel off the ac unit and see a capacitor you don't have a soft start. I'm going to install them on mine. Its called Micro-Air. https://youtu.be/soP0uZFd0nQ
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09-16-2020, 09:47 PM
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#5
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Senior Member
Brand: Thor Motor Coach
Model: Forest River Forester 235
State: Indiana
Posts: 4,884
THOR #6826
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Quote:
Originally Posted by mrgscooter
Have a 50amp MH, thought could only a single ac unit on 30amps, first time at 30amp hookup and both work. I realize probably can't run much else with both units running however to just cool the MH on a hot day works great. Is this typical or is there anything special maybe on pedestal?
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Typical AC will draw about 14A so yes it can work. But they draw much more at start up so if both happen to cycle on at the same time you might trip the pedestal breaker. Isn’t a fatal event though. Just try again, one at a time.
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09-16-2020, 09:52 PM
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#6
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Site Team
Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 14,386
THOR #7035
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So what size are your A/Cs? In a factory installed dual A/C installation in a 27B coach they are probably less than 13.5K BTU units so two 11K or 9.2K BTU A/Cs can easily be run on 30 amps.
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Ted & Melinda
2016 ACE 27.1
2016 Chevy Sonic Toad - Selling
2020 Chevy Colorado Z71 Trail Runner Toad
2024 Chevrolet Trax 2RS - Soon 2B TOAD
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09-16-2020, 09:53 PM
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#7
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I Think We're Lost!
Brand: Still Looking
Model: Tiffin Wayfarer 24 BW
State: New York
Posts: 22,195
THOR #8860
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I'd say that you're pretty lucky: congratulations!
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09-16-2020, 10:05 PM
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#8
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Senior Member
Brand: Still Looking
State: Texas
Posts: 6,187
THOR #2121
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Quote:
Originally Posted by 16ACE27
So what size are your A/Cs? In a factory installed dual A/C installation in a 27B coach they are probably less than 13.5K BTU units so two 11K or 9.2K BTU A/Cs can easily be run on 30 amps.
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The newer 29M has 15,000 BTUH standard, and optional dual 13,500 BTUH.
Unless they are running in desert conditions, many models can pull less than 13 Amps each, and some energy efficient ones a lot less. Basically, an A/C can pull less than a microwave, so running two at once isn’t that different than running microwave and one A/C simultaneously on 30A service. And that’s extremely common. I don’t see the big deal as long as both A/Cs don’t start together, or other loads are on at same time.
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09-16-2020, 11:18 PM
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#9
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Senior Member
Brand: Keystone
Model: Sprinter
State: Florida
Posts: 1,422
THOR #15553
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Quote:
Originally Posted by mrgscooter
Have a 50amp MH, thought could only a single ac unit on 30amps, first time at 30amp hookup and both work. I realize probably can't run much else with both units running however to just cool the MH on a hot day works great. Is this typical or is there anything special maybe on pedestal?
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Nothing special. Any 30 amp will run 2 a/c but NOTHING else.
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2011 Keystone Sprinter 323BHS. Retired Master Electrician. All Motor Homes are RV's. All RV's are not Motor Homes.
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09-17-2020, 01:48 AM
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#10
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Senior Member
Brand: Thor Motor Coach
Model: Hurricane 29M
State: Texas
Posts: 2,727
THOR #11781
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I'd say lucky you. I have had 30 amp pedestals pop when the microwave was used at the same time as 1 air conditioner.
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Lt Keefer
2018 Hurricane 29M
CHF, Saf-T-Plus, SumoSprings
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09-17-2020, 02:31 AM
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#11
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Senior Member
Brand: Still Looking
State: Texas
Posts: 6,187
THOR #2121
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Quote:
Originally Posted by Lt Keefer
I'd say lucky you. I have had 30 amp pedestals pop when the microwave was used at the same time as 1 air conditioner.
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Maybe you’re the unlucky one.
Seriously though, we use the microwave extensively and run it for extended periods to heat dinners while the A/C is going full blast, and it hasn’t been a problem in our own RV or in numerous rentals we’ve traveled in. The only times I recall a problem was when we had A/C, microwave, and wife used hair dryer. That combination trips breaker pretty fast.
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09-17-2020, 11:01 AM
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#12
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I Think We're Lost!
Brand: Still Looking
Model: Tiffin Wayfarer 24 BW
State: New York
Posts: 22,195
THOR #8860
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Chance,
You didn't say what you were plugged into (if at all); or the amperage capacity of the RV that you were in.
(Just trying to make sure. that the comparisons are valid... )
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09-17-2020, 12:24 PM
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#13
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Senior Member
Brand: Still Looking
State: Texas
Posts: 6,187
THOR #2121
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Quote:
Originally Posted by Bob Denman
Chance,
You didn't say what you were plugged into (if at all); or the amperage capacity of the RV that you were in.
(Just trying to make sure. that the comparisons are valid... )
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Always 30-Amp at campground pedestals all over the country. We’ve also successfully powered the microwave and A/C simultaneously from Onan 4,000-Watt gasoline generators on various motorhomes. The generator has a much easier time if you start the A/C first, let it run a few minutes, then start using microwave as needed. Start-up current can be a lot of load on generator, but a breaker doesn’t have the same mechanical limitations of a generator.
The key here is to consider that all air conditioners and cooling conditions are not the same and will load a 30-Amp breaker differently. The newest air conditioners can have higher Energy Efficiency Ratio (EER) which means they will use less power and therefore current to deliver the same 13,500 BTU/hour of cooling. Also, air conditioners require more power and current when it's warmer inside and or outside. Cooling in 90 F weather requires much less power and current than in 105 F weather. Likewise, it takes more power when it’s 90 F inside motorhome than when it’s 80 F inside.
I’m not saying it’s not possible or even likely to trip a 30-Amp breaker under right conditions when trying to power “two” A/Cs, but just because some can’t, it doesn’t mean others will have similar problems.
The Devil is in the details. And let’s not forget that various manufacturers are installing dual 11,000 BTU/hr Power Saver air conditioners in mid-size motorhomes with 30-Amp and 4,000-Watt generators. Also, the difference between 11,000 and 13,500 BTU/hr Power Savers is not that great.
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09-17-2020, 12:35 PM
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#14
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I Think We're Lost!
Brand: Still Looking
Model: Tiffin Wayfarer 24 BW
State: New York
Posts: 22,195
THOR #8860
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Thanks: just had to check..
But now i have to wonder how microwave and air conditioner power usages may differ...
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"What: me worry?"
Good Sam Member 843599689
Current coach: Tiffin Wayfarer 24 BW
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09-17-2020, 12:43 PM
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#15
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Senior Member
Brand: Thor Motor Coach
State: Georgia
Posts: 2,585
THOR #4735
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30amp service is not always '30amps' maximum, as breakers are not 'exact' is how they react to HEAT(amps) flowing thru them - some will react quicker, such as when the breaker is old, overused, weak, etc, making the RV owner think they have somehow 'used' too much power - the reality is that there is no 'exact' same reaction because there are too many variables.
Yes, your own appliances will determine how 'much' amperage you draw at any given moment, and microwaves are not all of the 'same' amperage draw variety - some are 900watts, while other larger ones are 1100watts, etc. How 'long' you have that appliance operating comes into play. The outside 'ambient' temperature also plays a factor, a BIG factor in very hot weather, where the wires, especially those shore power cords exposed to sunshine, can certainly cause a breaker to trip sooner than 'normal'.
There are a lot of factors when it comes to RV power, but yes, you can easily run two 13.5kw a/c units at the same time on 'only' 30amp power, IF the breaker is new or reacting correctly, and IF you are also aware of your other large draws, such as electric water heaters, microwaves, and even the Converter/Battery Charger.
Power is power, there is no 'you can't do this, you can't do that' answer = in many cases you may be able to successfully do what you wish, while the next stop may not be so kind. It's the nature of the 'mobile' environment and the many various 'electrical' power sources and devices we use along the way.
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the Turners...
two Campers, two Electric cars
former diesel pusher traveler
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09-17-2020, 01:00 PM
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#16
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I Think We're Lost!
Brand: Still Looking
Model: Tiffin Wayfarer 24 BW
State: New York
Posts: 22,195
THOR #8860
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__________________
"What: me worry?"
Good Sam Member 843599689
Current coach: Tiffin Wayfarer 24 BW
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09-17-2020, 01:33 PM
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#17
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Site Team
Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 14,386
THOR #7035
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Quote:
Originally Posted by Chance
Maybe you’re the unlucky one.
Seriously though, we use the microwave extensively and run it for extended periods to heat dinners while the A/C is going full blast, and it hasn’t been a problem in our own RV or in numerous rentals we’ve traveled in. The only times I recall a problem was when we had A/C, microwave, and wife used hair dryer. That combination trips breaker pretty fast.
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Yeah, A/C and MW should easily be doable.
Rule of thumb is 2 major appliances at a time in a 30 amp RV.
Lotsa people forget about the silent third major appliance - the water heater on electric - that would break the camel's back.
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Ted & Melinda
2016 ACE 27.1
2016 Chevy Sonic Toad - Selling
2020 Chevy Colorado Z71 Trail Runner Toad
2024 Chevrolet Trax 2RS - Soon 2B TOAD
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09-17-2020, 01:45 PM
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#18
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Senior Member
Brand: Thor Motor Coach
Model: Forest River Forester 235
State: Indiana
Posts: 4,884
THOR #6826
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Also lots of time people have the water heater running on electricity and forget that it can use 6A or so.
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09-17-2020, 02:00 PM
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#19
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Senior Member
Brand: Still Looking
State: Texas
Posts: 6,187
THOR #2121
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Quote:
Originally Posted by Bob Denman
Thanks: just had to check..
But now i have to wonder how microwave and air conditioner power usages may differ...
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For what it’s worth, air conditioners have improved in efficiency far more than microwaves as far as I can tell, so relative power usage has changed over the years.
When I tested my Class C, both the 13,500 A/C and microwave pulled around 13+ Amps (more or less). That’s around 1,500 Watts each.
Microwaves today still require around 1.5 Watts of electric power for each Watt of cooking power rating, so a typical 1,000-Watt microwave uses around 1,500 Watts of power.
Older air conditioners, particularly 15,000 BTU/hour sizes, often required close to 2,000 Watts and even more in desert conditions. Those large and inefficient units plus a microwave could easily trip 30A on a hot day. It’s simple math.
By comparison, modern air conditioners, particularly the 13,500 BTU/hr size, can be more efficient than years ago and require much less power; and much less than many microwaves.
Attached is claimed efficiency specs for 13,500 Power Saver. Two of those on a 30A service leaves plenty of spare capacity for smaller loads.
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09-17-2020, 02:22 PM
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#20
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Senior Member
Brand: Still Looking
State: Texas
Posts: 6,187
THOR #2121
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P.S. — It’s kind of sad that manufacturers keep installing low-efficiency air conditioners just to save a little on initial costs — all driven by the price-point wars. Not only would it help owners, it would help reduce load on campgrounds also.
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