50 amp MH, plugged into 30 amp, ok to run 2 ac units??

[supercub]

Something new for me. My motorhome has 50 amp service, however I'm currently plugged into a 30 amp outlet. Both my air conditioners are running. Is this ok to run both on 30 amps? Thank You
Brian

[dougrainer]

For ScottG. I looked up the breaker info at work from the NEC. Doug

Circuit Breaker Ampere Ratings

Circuit breakers have an ampere rating (typically marked on the end of the operating handle). This is the maximum continuous current that the breaker can carry without exceeding its rating. As a general rule the circuit breaker’s ampere rating should be the same as the conductor’s ampacity.

[phillyg]

I know some folks have reported running two ACs on 30a. Perhaps their RVs have a load shedding feature. I have two 15k ACs and I've tried this summer to run both, and it ain't happening. If yours seems to be working, I say "carry on."

[Hank_MI]

MrWizard wrote:
i haven't had a NEC code book in many years
is that 'residential' or commercial/industrial ratings

Pretty sure that applies to commercial/industrial wiring. I don't believe there is any such language in the NEC related to residential wiring. Normally with residential wiring AC compressors will cycle on and off. Electric water heater and fridge, same thing. Is it possible for both AC compressors to run continuously for 3 hours, yes but that is not typical in residential setting. Commercial/industrial wiring code is different. Interior lighting may remain on 24 hours a day. Air handlers of other equipment is also expected to run for extended periods. Hence the difference in the code between commercial/residential and residential.

Monitoring the voltage is a different subject. NEC assumes the supply can handle the load without a voltage drop. We all know that may not be the case in many campgrounds so monitoring the voltage is a good idea.

[Captain_Happy]

And here's something else to consider. When voltage goes down, amperage goes up. And yes a 30 amp breaker is only good for 24 amps continuously. So, when one of your A/C units goes to **** don't bitching about it.

[Acampingwewillg]

I knew when this topic was posted that it was trouble! There's real world and there is textbook....I happen to be a little of both. I know for a fact that I have run BOTH of my 15,000 BTU air's on 30 amp power and I happen to be blessed with a voltage/amp meter's on one display when connected to 30 amp and two display's when on 50 amp in the motor home. In 30 amp situations, I may or may not use my auto-former but always use my Surge Guard(over/under voltage protection too).

There are a ton of scenario's that say it can't be done yet it is done. I don't sit on top of my voltage meter's watching it as the compressor's go on and off generally because if I'm using both AC's , it's HOT and the compressor's are mostly on. My Refer is residential and it stays on, my batteries are generally already charged so the inverter/charger stays on. I will admit that I did just replace my front air(after 15 year's)...oh it's still work's but decided I wanted the Atwood ducted model instead of my Carrier non ducted.
Soooo, have at it and tell me how it can't be done and that I'm ruining my electronic's!

OH...there has also been plenty of times I couldn't do it also...more times than I could actually but if Hot, I'm always willing to try while keeping a close eye on things. 🙂

[dougrainer]

ScottG.
Sorry, I DON'T LOOK UP info to prove you wrong. YOU do that. I have been an RV Technician for 38 years(still am) and I have NEVER seen any technical info for what you state as it pertains to RV's. Remember, until about 20 years ago All RV's were 30 amp. You want to post misinformation, it is up to YOU to prove you are right. Just not "someone" on the Internet told me. Doug

[Sam_Spade]

RLS7201 wrote:
you should be good to go until the breaker trips.

The problem with that IS......that what "should" happen often is not what DOES happen.

A marginal connection/splice anywhere along the line can cause heat and fire before the breaker trips.

It is NOT a good thing to do. The fact that you might get away with doing it does not change that.

[SCVJeff]

I can do it IF the batteries aren't charging, WH, fridge all on LP. Both A/C's on pull 24A combined when ext temp is ~106. Vin= 113

[time2roll]

https://jadelearning.com/jadecc/courses/UNIVERSAL/NEC05.php?imDif=2508

Again this does not directly apply to an RV because everything is on a timer or thermostat. However we all know the air can easily run 12 hours continuous in Summer.

210.20 should get you to the language.

[RLS7201]

Lantley wrote:

RLS7201 wrote:
If you are plugged into a 30 amp receptacle, protected by a 30 amp breaker and you monitor your voltage, you should be good to go until the breaker trips.

Richard

It's not simply a breaker/current issue. What is the voltage? operating at low voltage will damage the A/C unit.
He will need to pay attention to the voltage. Both units will work....
until they don't!

If you're going to quote me, read my post carefully and completely.
I did note voltage needs to be monitored.

Richard

[MrWizard]

i haven't had a NEC code book in many years
is that 'residential' or commercial/industrial ratings

and yes there are different codes for different applications
at least there used to be some differences, when i was pulling wiring back in the 80's

man old age is a pain, trying to remember this stuff

IIRC an RV is residential and that 30amp pedestal only has (2) breakers
a 30 and a 20
so even pulling 28 amps or so, you don't have the the heat build up you have in an industrial setting with a stack of breakers feeding a stack of pump motors or machinery
that will run run mostly 24/7

still i would probably run only (1) a/c at a time and alternate them as needed

[ScottG]

dougrainer wrote:

ScottG wrote:
As another recently pointed out to me, a 30A outlet is only intended to deliver 24A max continuous.
I think if you go out and check the plug, it may be quite warm. You should also check the voltage inside your RV. It could be very low.

OK, Please state where you get this information. It is WRONG. A 30 amp RV shore Power plug is rated at 30 amps and 30 amps continuous. Doug

When a fellow gentleman member of the forum forrected me in one of my posts, I did a little search and verified the 24 number he stated.
Don't believe it? Look it up for yourself.
Here's a little hint to the correct answer; CB's are sized to 125% of the expected continuous current load...

[time2roll]

NEC says supply should be 125 percent of load for a continuous load appliance. continuous is > 3 hours.
Does not really apply for an RV but if operating as such the issues still exist.

[dougrainer]

ScottG wrote:
As another recently pointed out to me, a 30A outlet is only intended to deliver 24A max continuous.
I think if you go out and check the plug, it may be quite warm. You should also check the voltage inside your RV. It could be very low.

OK, Please state where you get this information. It is WRONG. A 30 amp RV shore Power plug is rated at 30 amps and 30 amps continuous. Doug

[Lantley]

RLS7201 wrote:
If you are plugged into a 30 amp receptacle, protected by a 30 amp breaker and you monitor your voltage, you should be good to go until the breaker trips.

Richard

It's not simply a breaker/current issue. What is the voltage? operating at low voltage will damage the A/C unit.
He will need to pay attention to the voltage. Both units will work....
until they don't!