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Old 08-31-2015, 10:26 AM   #1
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Air Conditioning on 30 amps verses 50 amps

We took our new Flagstaff 832 IKBS to a campground this weekend only to discover our spot was 30 amp instead of 50 amps. We used an adapter between shore power and coach, but because it was so hot, 98 degrees, we ran both units, a 15000 btu and a 13500 btu, keeping the amperage usage at around 31 amps with everything else running off gas or the breaker shut off completely like the microwave, but never got the inside below about 85 degrees. Now at the dealership it was hooked up to 50 amps and freezing cold inside when it was just as hot outside. My question is am I just screwed on this unit when its that hot outside or will 50 amps really make that much of a difference on the Airs efficiency? Thanks.
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Old 08-31-2015, 10:36 AM   #2
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Even through you were max out power wise, It wouldn't have made a difference even being on 50 amp. If you were not tripping the 30 amp at the pedestal. You were getting everything it could put out. As far as the dealer he could have had it on before it got hot inside and it kept up. In short you need to get it on earlier before you get all that heat gain inside. The voltage only has a relation to your windings. If the compressor is running you will still get the same BTU, but you do stand a chance of burning a winding. In the business it is called FLA (full loaded amps)
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Old 08-31-2015, 11:12 AM   #3
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To prevent damaging the AC units when on 30amp recommend using one or the other not both. Later RJD
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Old 08-31-2015, 11:24 AM   #4
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You can run both a/c's on 30 amp (at least I can do it), but you need to monitor the voltage. With an EMS if the voltage gets too low the power will be shut off to protect the a/c units. The OP could have been operating on a low voltage situation, thus not cooling efficiently.
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Old 08-31-2015, 11:40 AM   #5
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You can run both a/c's on 30 amp (at least I can do it), but you need to monitor the voltage. With an EMS if the voltage gets too low the power will be shut off to protect the a/c units. The OP could have been operating on a low voltage situation, thus not cooling efficiently.
Low voltage will not effect the cooling. It's going to run at FLA. there is also a 10% plus or minus built in. If the voltage got to low the compressor would shut down on internal overlaod. Low voltage will cause heat to the windings, the compressor will still run until it heated up enough. It's not wise to run both on 30 amps FLA on a 15000 btu is like 15 or 16 amps and 13,000 btu it's like 14 or so I would need to look it up to give you the real #'s but those are close. FLA also includes your blower motor and condenser fan. The largest drop in temp can only be between 15 and 17 degree difference in the unit r/a and supply. If the inside was 80 when he turned it on the best he will get would be around 65 coming out of registers. At 70 degrees inside he could get down to 55 degree air coming out. Big difference from when a person starts his a/c.
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Old 08-31-2015, 12:21 PM   #6
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We recently did what ACEINSPP suggested - ran one or the other AC unit when we had only a 30 amp hookup and it worked well. Ran the front living area during the day, then turned it off and ran the bedroom at night. 106 degrees outside during the day and we were cool inside.
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Old 08-31-2015, 12:39 PM   #7
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We do the same as CindyB above. If it's just the Mrs. and I it works fine. If we have someone sleeping downstairs, we run that unit and I have a fan mounted where the tv goes in the bedroom that circulates enough air to keep us cool upstairs.
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Old 08-31-2015, 12:54 PM   #8
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How did you run both units?
Almost always each a/c is on its own 50 amp leg .
Once you went dogboned to 30 amp one a/c should not have worked.
But I guess it's possible.

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Old 08-31-2015, 01:04 PM   #9
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How did you run both units?
Almost always each a/c is on its own 50 amp leg .
Once you went dogboned to 30 amp one a/c should not have worked.
But I guess it's possible.

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Ron, the adapter bridges (or jumps) the single 120 volt hot leg to both L1 and L2, when hooking a 50 amp 120/240 up to a 120 30 amp outlet. The 30 amps is shared on both L1 and L2 in the RV.

This was what got our buddy Bombdoc in trouble, if you recall that evening we were trying to get it figured out. He had used an adapter for his 50 amp RV to hook to a 240 volt 30 amp 3 wire outlet instead of a 120 volt 30 amp outlet.

Here is a schematic showing this:

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Old 08-31-2015, 01:11 PM   #10
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That is correct, and running draw on both a/c's is usually around 26amps. I still argue, if voltage drops the compressor will not be as effective.


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Old 08-31-2015, 01:11 PM   #11
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You can run both a/c's on 30 amp (at least I can do it), but you need to monitor the voltage. With an EMS if the voltage gets too low the power will be shut off to protect the a/c units. The OP could have been operating on a low voltage situation, thus not cooling efficiently.
The OP says he was drawing 31 amps so guessing he had some kind of surge protector to tell this. If the voltage dropped to low it is possible both AC units could run but one of the compressors could have become locked out. It could run but only the fan would operate so iit would not do any cooling. That would be my guess as to what happened.

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Old 08-31-2015, 01:59 PM   #12
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Thanks for your replies everyone, I use a Progressive Industries Surge protector which did save me a few months ago from a 105 volt park problem. It shows as high as 34 amps being used when both units are running wide open, voltage drops to as low as 119 volts. I have a digital electricians thermometer that I used and the air coming out the vents was about 65 to 71 degrees, so I took the inside covers off and shot my meter straight into the fan on each unit. The 13.5 unit stabilized at 15 degrees F and the 15 unit at 25 degrees F. I think the units are working just fine, but I was hoping the 832IKBS would handle hot weather much better than it did from a cooling stand point. I will be hooking to a 50 amp outlet this weekend and will update my post IF that makes any difference. Thanks again.
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Old 08-31-2015, 02:06 PM   #13
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Most breakers are designed for 60 to 80% load as opposed to running 100%. Running 2 AC'S when the voltage drops increases the current. Eventually something will give and either a connector or wire will burn off.
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Old 08-31-2015, 05:46 PM   #14
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Relative humidity makes a big difference in the discharge air temperature. Air conditioning 101.
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Old 08-31-2015, 06:25 PM   #15
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Most breakers are designed for 60 to 80% load as opposed to running 100%. Running 2 AC'S when the voltage drops increases the current. Eventually something will give and either a connector or wire will burn off.

So at 60-80% load on a 30 amp breaker, you're saying they should "blow" at 18-24amps? If that is the case, we are all in trouble.


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Old 08-31-2015, 06:31 PM   #16
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And the next thing we will hear is my air does not work. Probably blew it up and want to blame the manufacture. Later RJD
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Old 09-01-2015, 01:01 AM   #17
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Ron, the adapter bridges (or jumps) the single 120 volt hot leg to both L1 and L2, when hooking a 50 amp 120/240 up to a 120 30 amp outlet. The 30 amps is shared on both L1 and L2 in the RV.

This was what got our buddy Bombdoc in trouble, if you recall that evening we were trying to get it figured out. He had used an adapter for his 50 amp RV to hook to a 240 volt 30 amp 3 wire outlet instead of a 120 volt 30 amp outlet.

Here is a schematic showing this:

Great diagram.
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Old 09-01-2015, 04:57 AM   #18
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Most breakers are designed for 60 to 80% load as opposed to running 100%. Running 2 AC'S when the voltage drops increases the current. Eventually something will give and either a connector or wire will burn off.
That's only in Canada.. If the power got to low he would trip the breaker and also go off on internal overload. You don't want that. The unit has to shut down fan and all and some times it can take up to 24 hrs to reset.. I never condemend a compressor unless it showed a dead short. I would go back the next day and re-ohm the windings to see if they reset or still showed open on my meter, meaning you burnt up the internal overload...
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Old 09-01-2015, 05:00 AM   #19
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That is correct, and running draw on both a/c's is usually around 26amps. I still argue, if voltage drops the compressor will not be as effective.


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AquaMan you can argue all you want. The SEER rating will not drop from voltage. That's like saying if my unit is gettig 125 volts it will be cooler. It doesn't work that way. also his unit didn't go off on internal overload, per the OP's reading. The truth is sorry to say that is all he can expect. I'm sure he doesn't want to hear that. If he's in Florida he better set it low in the morning to try and just keep up from the heat gain and humidity...One of the biggest complaints are cooling and heating an RV......
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Old 09-01-2015, 09:33 AM   #20
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So at 60-80% load on a 30 amp breaker, you're saying they should "blow" at 18-24amps? If that is the case, we are all in trouble.


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Line voltage breakers (household type) are designed to instantly trip at 100%, but at 80% they heat up and will eventually trip if the load stays there long enough.

Below that they should not get that hot enough to trip, unless it is getting old and weak. Then it is time to replace it. Yes, they do go bad in time.

I have also seen them go bad so they will not trip. If we had a receptacle we could not ID the breaker for we use to just short out the receptacle, then go see what breaker tripped. It was quicker than putting a line tracer on it. I did that one day and watched the wires start to smoke! No breaker tripped! Went and got the signal line tracer, fixed the problem and changed the breaker.

Jim
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