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Old 08-24-2011, 07:20 PM   #1
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Can inverter run a/c

Is it possible to run a roof A/C off an inverter while driving down the road? If it is possible, what would be needed in the way of batteries, alternator, and inverter? Just wondering if this is possible so that I would not have to run generator to run the A/C............thanks in advance...........ronspradley
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Old 08-24-2011, 07:24 PM   #2
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I would say no the a/c pulls to many amps for a inverter
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Old 08-24-2011, 07:30 PM   #3
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No. You have to run the generator. It's much cheaper and practical.
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Old 08-24-2011, 07:44 PM   #4
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In our 2000 DSDP I had CW install a 2500 watt inverter, they didn't split the circuits and I could run one 13.5 heat pump off the battery, for about 20 min. That fully depleted the batteries (U-2200's) and the inverter went into low voltage warning and shut down. So it is possible. Would I recommend it? NO WAY!!!! Our alternator can put out 160 amps, but trying to run a heat pump or A/C would certainly shorten it's life and put quite a strain on the engine.
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Old 08-25-2011, 09:06 AM   #5
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Theoretically . . . yes! Practically . . . no!!
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Old 08-25-2011, 09:25 AM   #6
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Theoretically . . . yes! Practically . . . no!!

+1

Both the inverter and the alternator would be close to max ratings - not good for a long happy life. Also, the genny needs to be used regularly to be happy.
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Old 08-25-2011, 10:05 AM   #7
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Theoretically . . . yes! Practically . . . no!!
+2 Your battery capacity is the week link here. The air conditioner would draw about 130 amp/hrs from you batteries and even a 160 amp alternator could not keep up with that demand.
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Old 08-25-2011, 10:31 AM   #8
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It depends on the size of your inverter, the draw of your a.c. and how long you run it based on your batteries. You can do the math but it the end I think you will find the answer will be No.
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Old 08-25-2011, 02:52 PM   #9
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Not practical

We thought about doing the same thing as we had an extra set of VRLA batteries that would allow an additional 400 amp hour capacity.

The thought was the batteries were free, we had the space, and with the dash air needing R12 charging the only cost would be the inverter, and the size of the batteries with the alternator capacity would give us a few hours of run time.

The starting current of the compressor exceeds the surge capacity of most common inverters, one would need a minimum 5K constant duty inverter with a 100% surge rating to even consider it.

And is the roof AC is needed, IE it is hot, then the starting current is going to be even more.

We tested a 2.5KW inverter connected directly to our house battery (2x8D) which has a CCA capacity of 3000 amps, and the inverter simply would not start the compressor on a cold day in the winter.

Since then we have discovered "Hot Shot" which is a direct replacement for R12, same price as R134 so the HVAC will be repaired when we get time.

Until then, run your generator, if you are traveling at 60 MPH down the road and your generator uses 1 gallon per hour (will be less but this is easy math), your generator cost is 60 miles per gallon, the difference in performance of you engine with the ac running may be small or large, but on a hot day at cruising speeds or graded the generator is likely less expensive to run than the dash air, and the result will be that the whole coach is cool instead of just the front.
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Old 08-25-2011, 04:08 PM   #10
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TQ60 Warning Some hot shot is propane
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Old 08-25-2011, 06:06 PM   #11
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my onan uses inverter technology to run the whole coach
it runs both a/c units jest fine
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Old 08-25-2011, 08:48 PM   #12
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Thanks for all the information. My generator runs on propane so I am limited by the amount of propane I carry in the single attached tank. Was just trying to see if there was a viable alternative. Back to the drawing board................

lets see, if I get a Nissan Leaf as a toad, can I use the power generated when pulling it behind the MH..................clearly I have too much time on my hands.................................ronspradle y
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Old 08-25-2011, 08:54 PM   #13
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Originally Posted by ronspradley View Post
Thanks for all the information. My generator runs on propane so I am limited by the amount of propane I carry in the single attached tank. Was just trying to see if there was a viable alternative. Back to the drawing board................

lets see, if I get a Nissan Leaf as a toad, can I use the power generated when pulling it behind the MH..................clearly I have too much time on my hands.................................ronspradle y
Yep, propane gen is a problem. Our first DSDP had one, a Genejunk 6,200 watt unit. In 5 days, high desert (although not that high at about 2,700') in 90 weather we used 2-10 gallon tanks and most of our 40 (32 usable) gallon on board tank.
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Old 08-25-2011, 10:09 PM   #14
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OK - gotta ask - - - -exactly WHY do you not want to run the genny?
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