Two airs on 30 amp

I know a tad about power draw and amperage, I did monitor my voltage closely by external means and my 96 Vogue's built in monitoring meters. I mention the age of the motorhome only to indicate that it has no power shedding features. I ran both airs all day long in greater than 90 degree direct sunlight( little to no shade),voltage stayed at a constant 116-117 volts. I only mention this because generally, I would not even think of trying this but a employee that I know at this park had mentioned that he was running both of his air's on his older 5th wheel( no power shedding but he did turn his appliances over to gas). I listened for the compressors to kick in, thinking surely the pedestal breaker would trip but it never tripped..I can't explain it, just reporting what occurred, nothing more. My first thought also was a faulty breaker but after monitoring voltage and lack of over heating of the dog bone....I didn't have my clamp on amp meter with me but will take it along with me next month when I return their. My built in meter's have the ability to measure amp usage ....but the amp feature hasn't worked for some time. .

My final thought was that since the park was not busy, I was getting full power without the additional draw created by hundreds of airs switching on and off. Once again, normally I wouldn't think of trying this because I do have some understanding of start up amp's required and continuous load. One other thought...something that just adds to my curiosity...TT parks are not known for their state of the art upgraded pedestals....they generally use the bare minimum with little to zero maintenance.

What LarryJM said. If you look at circuit breaker trip curves, they do not trip up to 100% of rated load, even at continuous operation.

Hi,

The air conditioner compressors do not use nearly as much power at 80F outside air temp as when it is 95F or 100F outside. So the compressors are only going to draw say 70% of their full load current under such conditions.

The 300 watt load of a ice maker inside a residential refrigerator probably would push the limits on the 30 amp receptacle, and it's circuit breaker. Good thing that the camp receptacle is in good condition, some are not and can have a 10 volt drop across them. This is indicated by the dogbone adapter getting really warm, and that was not happening.

You can further shed loads by turning off your battery charger for the day, and let it recharge at night. It is only a 1-2 amp load during the day, but it might help out. In my RV, I never have my charger on (it is part of my inverter system) yet charge via the solar system.

Glad that you had fun camping!

Fred.

Do you have an EMS that might have shed loads to maintain 30 amps or less?

I would suggest checking the voltage while both compressors are running.

You are pushing up against the limits so it may or may not work but you might also be doing harm to your system even though it is working.

holstein13 wrote:

Furthermore, a 30 amp outlet can put out 30 amps for short periods of time. Each of your A/Cs can run for a short while on 15 amps so 2 times 15 makes sense.

The bad news is that 30 amp breakers are only designed for 80% draw continuous, over one hour so you effectively only have 24 amps to work with on a continuous basis.

I predict that if you continue to run both A/Cs, you will trip the breaker in a couple of hours. If you don't trip the breaker, something is probably wrong with the campground breaker and should be checked out.

On edit: I see that the high in Santa Barbara was only 81 yesterday. Were you in the shade? My guess is that both compressors were not working together for long periods. Try this again when the temperature is in the 90s and you probably won't have the same result.

Unfortunately you are confusing "design" and "the 80% Rule" adopted by the NEC in 1996. A CB is not as you believe "designed" only to operate continuously at 80%, but is designed to operated continuously at 100% under the testing conditions of it being in free air with an ambient temp of less than 104deg F. Because heat affects the number that a CB will actually trip at it is not able to accurately predict the continuous amps number it will trip when say in an enclosure so they are typically sized with the 80% rule as to the expected continuous load. Furthermore a "continuous" load is one that can expected to be drawn "uninterrupted" for a sustained period of 3 hours or more like general office lighting, and A/C operations are definitely not "continuous" if the load number includes the compressor since that cycles on an off. I could easily envision one sustaining 30A say in a pedestal when the ambient air temp is only 81 deg and it is even better if inside an RV where the ambient temp is down in the 70's.

Larry

How long did you run them and what was the ambient temperature? The real draw comes from the compressors and if both compressors weren't working at the same time, this is entirely doable.

Furthermore, a 30 amp outlet can put out 30 amps for short periods of time. Each of your A/Cs can run for a short while on 15 amps so 2 times 15 makes sense.

The bad news is that 30 amp breakers are only designed for 80% draw continuous, over one hour so you effectively only have 24 amps to work with on a continuous basis.

I predict that if you continue to run both A/Cs, you will trip the breaker in a couple of hours. If you don't trip the breaker, something is probably wrong with the campground breaker and should be checked out.

On edit: I see that the high in Santa Barbara was only 81 yesterday. Were you in the shade? My guess is that both compressors were not working together for long periods. Try this again when the temperature is in the 90s and you probably won't have the same result.