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Old 07-01-2013, 08:46 PM   #1
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Running AC on Generator Power

Hello all,
How long does it take for your AC compressor to stay on when on generator power? On my 2013 Interstate, I have to run the generator and wait for about 20 minutes before the AC's compressor will stay on. Otherwise, the compressor keeps shutting down (although the AC's fan keeps blowing). I'm not sure if I still need to break in the generator and/or the AC unit (I haven't needed either until now). Thanks in advance.
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Old 07-01-2013, 09:13 PM   #2
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If your temp control is set to say around 60 and the AC is trying to produce cold air, it will do so provided your gen-set can produce enough amperage. Try off loading maybe your battery charger and other small electrical loads when operating on the gen-set. If nothing else is consuming gen-set power except the roof air , then you may have a bad thermostat.
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Old 07-01-2013, 10:35 PM   #3
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I'm an owner of a '59, but I don't think they've repealed the laws of Physics.

Is there any possibility of a low voltage condition? If so, it is a high risk to your compressor. Lower voltage results in higher current, which exponentially increases heat output, risking your compressor.

Your control circuitry should prevent this problem, but a simple voltage check with a relatively cheap meter can set your mind at ease.

Starting a compressor requires a surge in current. Some on this forum use a "hard start" capacitor to give an extra boost without overloading the circuitry or generator.

Since you are under warranty -- if you see voltage below 105V -- call Airstream ASAP.
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Old 07-01-2013, 10:45 PM   #4
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Quote:
Originally Posted by FLTRisk View Post
If your temp control is set to say around 60 and the AC is trying to produce cold air, it will do so provided your gen-set can produce enough amperage. Try off loading maybe your battery charger and other small electrical loads when operating on the gen-set. If nothing else is consuming gen-set power except the roof air , then you may have a bad thermostat.
Stay Cool!
Thanks FLTRisk. There was nothing else drawing amps while I was running my AC/generator test and the thermostat was set to 78 with the outside temp being in the 90s. Though I never considered a bad thermostat, I don't think that's it because the AC fan keeps blowing - it's just the compressor that keeps cycling off after about 10 seconds of running. And when the compressor tries to kick back on after a few minutes, the generator slows down and struggles. What's weird is that the compressor stays on after I run the generator for at least 20 minutes; and then stays on. I also had close to 100% battery while performing this test. BTW, this happens whether the remote inverter switch is on Auto or Charge Only. I'm thinking it might be a tight compressor or I need to break in the generator. Anyone else experience this on a new Interstate?
Thanks
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Old 07-01-2013, 10:54 PM   #5
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Quote:
Originally Posted by 65CV View Post
I'm an owner of a '59, but I don't think they've repealed the laws of Physics.

Is there any possibility of a low voltage condition? If so, it is a high risk to your compressor. Lower voltage results in higher current, which exponentially increases heat output, risking your compressor.

Your control circuitry should prevent this problem, but a simple voltage check with a relatively cheap meter can set your mind at ease.

Starting a compressor requires a surge in current. Some on this forum use a "hard start" capacitor to give an extra boost without overloading the circuitry or generator.

Since you are under warranty -- if you see voltage below 105V -- call Airstream ASAP.
I thought of a low voltage condition too, but both batteries are new and are close to 100% charged. I haven't connected a volt meter, but the panel shows 12.8v. Could I have a defective controller? The AS dealer replaced both batteries and the charge controller when I took delivery in April of this year. Could a bad inverter cause this?
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Old 07-02-2013, 12:16 AM   #6
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Mine does what you are describing if the batteries are down in the 80% range due to the amperage taken by the charger. When the compressor kicks on the load regulator thing-a-mo-bob shuts down the a/c ... but does leave the fan running. Once the batteries get up to charge (10-20mins) the a/c works fine. If the batteries are really low I think it does this on shore power as well.
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Old 07-02-2013, 12:21 AM   #7
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My A/C on a hot day in the 90s will draw about 18 amps. The genset is good for 20, so you may need to kill everything but the A/C 'til your 20 minutes is up. On 100 degree days, I have to basically turn everything off including the inverter. Not sure why yours is working that way but I'd work w/ the dealer 'til it was working right.

What's the current draw before the compressor shuts down? The controller will start shedding load as soon as the draw goes over 20 amps.
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Old 07-02-2013, 01:06 AM   #8
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Thank you Russ and Shark. That makes sense. I will run the test again tomorrow to see how many amps the compressor is drawing (I don't want to run the generator at night and disturb my neighbor). My controller may be shutting things down prematurely or my compressor may be drawing too many amps.
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Old 07-02-2013, 06:12 AM   #9
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I was always taught to start the generator no load, let it run up for about 10 minutes add the load and to shut it down the same way. Remove the load and let it run for about 10 minutes to stabilize then turn it off.

I do agree with Russ that you may have something else loading up the generator that is keeping the AC from getting the amount of power it needs.

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Old 07-02-2013, 07:50 AM   #10
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FWIW, the Air Conditioner in my 2010 Interstate (made by Carrier) runs on 115v AC not on 12v DC. Specs from Carrier indicate full load is 13.4A. I don't know what the start current is.
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Old 07-02-2013, 08:23 AM   #11
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Also, the Onan 2.5KV generator will produce 20.8A. So, without regard to the start surge, the gen should handle the A/C just fine if there are no other AC loads. And wahoonc is correct about the recommended cycle up procedure.
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Old 07-02-2013, 09:52 AM   #12
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Quote:
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FWIW, the Air Conditioner in my 2010 Interstate (made by Carrier) runs on 115v AC not on 12v DC. Specs from Carrier indicate full load is 13.4A. I don't know what the start current is.
Starting load typically is about double the max running load, so your generator is taking a ~28 amp hit with the just the AC trying to start, this only lasts for a few seconds at most, however if something else is pulling amps you don't have enough for the AC so it goes into low voltage protection mode. Kind of hard to explain without getting very technical.

Most generators have a surge capacity to allow for this, but if you exceed the surge capacity by very much the appliance is going to go into shut down mode or the generator is going to bog down or in some cases even stop.

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Old 07-02-2013, 10:27 AM   #13
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Your genny may be putting out the proper voltage, but not sufficient amperage to keep your A/C running. I would have the amperage output tested by a generator expert to be certain that it's operating to specifications.
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Old 07-03-2013, 12:54 AM   #14
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I have the exact same issue in my 2013.

( I'd love to hear protagonist jump in with more info, but here's what my experience has been)

I noticed this problem immediately as I was living in Vegas when we bought the AS. Talked to the dealer who put me in touch with the head tech at AS and we troubleshot the issue over the phone. According to him the battered must be fully charged to the pint where the investor is not trying to charge the batteries or you will overload the generator.

When you turn of the ac, first the fan will come on for a minute, then the condensor will kick on. If you watch the meter you can see It go to about 21-23 amps and everything shuts down one by one. (Not sure the name of the gauge, but it says ac, water, coffee and something else.) after a few minutes it will try again. For me, it usually just repeats.

They had me shut off everything, change the dip switches and it still barely worked about running for about a half hour (rv had been driven for several hours when I tried ac and was hooked up to shore power prior to leaving).

Considering we use this as a touring coach, not a camper, this is a crappy system and if it wasn't for the fact that I now over in the very temperate Bay Area this would be a constant issue.

Funny enough, I actually ran into this issue for the first time in over a year yesterday. (We're having a heat wave and it was about 100 in concord). Got back on the phone with the dealer and insisted we get this worked out before we potentially move back to Vegas next year.

Apparently AS has used two different inverter brands since our was made. Not sure if this is still and issue or not in the new ones.

Again, the problem seems to be that with my model, there is no way to NOT charge the batteries until the inverter reads then as fully charged. Charging the batteries and trying to start the condenser is about 1-3 amps more then the generator can handle and some protection circuit shuts it down.

If there was a way to just stop charging while you ran the ac, it seems like it would be fine.
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