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Wire roof air conditioner to inverter

Burgboy

By Burgboy
in AC, Heating, and Cooling

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timaz996

timaz996

Posted
Posted

You are going to want a 3000 W inverter and you’re also going to want to put a soft start on the AC that you’re going to wire to it and you’re gonna want at least 400 amp hours of battery power to run that AC for an hour maybe an hour and a half with a soft start. I have 700 W of solar and a 3000 W Victron multi  II With 400 amp hours of lithium. I only have mine set up to cool down the bedroom after traveling all day if it’s warm in the evening so it won’t run more than 45 minutes or an hour. I don’t ever intend to run my AC off the batteries during the day.

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Guest Ray Davis

Guest Ray Davis

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Posted (edited)

Powering the roof A/C with an inverter is possible but not practicle even with 1K solar. The run time would be very low so it wouldn't be useful.  Your inverter doesn't look factory to me and I can't see the wattage.  Even if you install more battery capacity you will have to recharge them, I don't believe solar will keep you going.  That leaves the generator which was there all the time to run all your elect appliances.                                              We had a member, Bill Groves ( RIP ) who was very inventive, he installed a small window A/C in the bedroom window. He powered it with his inverter, and said it would keep them comfortable at night.  Somehow, Bill was able to install it so you couldn't notice it from outside.  Bill was an elect engineer, he must have concluded powering  his roof air with his inverter wasn't practcle.

Bill was a smart and cool guy,  I miss him.

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Dr4Film

Dr4Film

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Posted
27 minutes ago, Ray Davis said:

We had a member, Bill Groves (RIP) who was very inventive, he installed a small window A/C in the bedroom window. He powered it with his inverter and said it would keep them comfortable at night.  Somehow, Bill was able to install it so you couldn't notice it from outside.  Bill was an elect engineer; he must have concluded powering his roof air with his inverter wasn't practical.

Bill was a smart and cool guy, I miss him.

I miss him also! I almost bought his coach but luckily, I did not as the 2006 Dynasty I did purchase is exactly what I was looking for, so it was a blessing in disguise for the deal not to go through.

Bill also had his entire roof loaded with solar panels AND he had 8 AGM 6 VDC House batteries. The small window AC he had installed used very few amps to keep it running all night. He only used it at night.

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W7BE_Bob

W7BE_Bob

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I'd suggest running temporary wiring from the AC (perhaps the panel) to the inverter so you can how it works. A 15A 120V AC will require about 165A draw from 12V batteries which is a lot and as pointed out the run time will be short. 1000W solar is a help but you'll likely get about 66% output at noonish, say 700W or 700W/12V = 58A, so 1/3 from solar and 2/3 from the battery. Of course less for the rest of the day and none at night. 

Knowing the inverter watt rating, the battery Ah size and the AC draw would be helpful. Plus the cable size and length to the battery are factors as the voltage drop on the cables  can be significant. 

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W7BE_Bob

W7BE_Bob

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Bill Groves had 4 6V and one small 12V (for the chassis) in each of the 2 battery trays, so yes very clever. He likely had limtited starting power for cold northern weather. With his small window AC he found a solution for his needs. 

Also if you run the AC on day 1 and start with discharged batteries on day 2 then the run time is reduced. 

In reality if you want longer AC run times then consider a large lithium battery bank configured for 48V with a 48V inverter, 48V charger and a DC to DC converter (48V to 12V) for the 12V draws. 

 

 

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Rocketman3

Rocketman3

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You can run the A/C from the inverter but there is a LOT of things to be aware: (one of my next projects will be to re wire at the transfer switch so I can use the air conditioner)

 

The A/C will do much better on lithium than lead. You will need a larger battery bank. At 540ah of lithium I would consider mine barely adequate. 
 

Your batteries need to be able to support the draw. Leads can only be down to 50% (you will need a battery monitor). Lithium’s bms’s can prevent enough amps from flowing. 
 

You will need a soft start ($300) on the standard air conditioners. I just replaced my bedroom A/C with the Rec-Pro. It comes with the soft start built in. It also uses a bit less power than the standard RV A/C’s. 
 

a few other items- even with my 1220w of solar - I only get about 800w so it makes it so I will be able to use it longer - but it won’t complete support it. I added a 30amp Dc-Dc charger to charge from the alternator (had to break the connection from the alternator to the house bank when I added lithiums).  I hope to be able to run the rear A/C during the day when traveling-we will see… I figure I can run it for one or two hours a day and still have my batteries hit 100% that day when boondocking. 
 

If I need to run A/C’s all the time… I figure run the one off batteries for a while - the start the generator- run both and recharge the batteries- then go back to just one on batteries. 
 

Because these pull a lot of power you probably want to make sure all electrical connectors are done right. 

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Burgboy

Burgboy

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Thanks for the replies everyone. On that note since this doesnt seem very doable with the limited space we have.

Has anyone had luck replacing a roof ac unit with a swamp cooler?

Or installing a swamp cooler anywhere? Should it face a window? Pull air in through wet cloth? 12 volt pump recommendations?

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Burgboy

Burgboy

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My thermometer shows 30% RH in my rv atm i think a swamp cooler is viable. Just not sure on best way to configure it. Anyone here build one to mount? Limited on space so prefer a unit i can get off the floor. Probably will use an engine fan for 12volt

20220610_183554.jpg

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trailmug

trailmug

Posted
Posted

Agree with the general sentiment on the thread already.. Even with 8 GC2 batteries for 860Ah on the Sig, the microwave (roughly the same load as an A/C) on our inverter pulls the DC voltage down into the dubious range (10.5-10.8V) on anything but a full charge, and the sine wave starts to suffer, which will cause motors/compressors to run hot and appliances without switching power supplies to groan (our refrigerator lights flicker). I wouldn't want to do it for an extended period.

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Dr4Film

Dr4Film

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Devices that draw high amps are not designed to be powered from the Inverter & battery bank. It will eventually ruin the battery bank, inverter and the device itself.

If we need to use ANY high amp device, we ALWAYS start the generator if not on shore power. That includes, microwave, coffee maker, hair dryer, rooftop AC's ceramic heaters, air compressor, etc.

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