Air Conditioner Run on Inverter

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Air Conditioner Run on Inverter

September 10, 2017, 08:26:28 am

Does anyone (likely with solar) run at least one of the roof AC units off the inverter? My roof AC units will not run without shore power or the generator running. How difficult is it to change the wiring so the back roof AC can run off the inverter? I expect if rewired it may only run for 1 to 2 hours???

Thank you,

Re: Air Conditioner Run on Inverter

Reply #1 – September 10, 2017, 08:38:50 am

This possibility has been explored by many on paper over the years. Just not practical-- watts needed to run a roof A/C would require a huge solar array and very large battery bank and/or very short run time.

A roof A/C drawing even 10 amps @ 120 VAC would require about 130 amps @ 12 VDC (inverters are not 100% efficient).

Re: Air Conditioner Run on Inverter

Reply #2 – September 10, 2017, 08:39:43 am

The short answer is no. Not enough battery capacity. This subject has been discussed and tried on the bus conversion boards at length. The only folks I know who have done it successfully owned The Odyssey. Their story is here: Our Odyssey Fascinating reading.

TOM

Re: Air Conditioner Run on Inverter

Reply #3 – September 10, 2017, 08:48:52 am

I believe the "Wynns" had a successful trial.. for hours.

In the dessert. .

With 300 watt panels, soft start an lithum batteries- who knows...

Re: Air Conditioner Run on Inverter

Reply #4 – September 10, 2017, 10:11:40 am

When we had our PV system installed at AM Solar, I had them add the front A/C unit to the inverter sub-panel. Told them I wanted to play with trying to run it on inverter. They looked skeptical but did what I asked. It didn't work - would not even start the compressor - the inverter (MS2812) kicks off due to overload. I have not explored the "soft start" options available...don't know if they would help or not. We only have 2 8D-AGM house batteries, so running A/C on battery would not be feasible in most circumstances (like when parked). It was mostly just a "experiment" for my own amusement. I was thinking if I was able to get the A/C unit started on inverter, we might be able to use it when running down the highway because we would have both the alternator and the solar panels recharging the house battery bank.

We can run the front roof A/C unit on "fan" setting with the inverter. I have played with doing that to increase air circulation in the front of the coach while driving. It helps a little, but not really worth the trouble. Easier to just leave the bathroom vent open and use the "fan" setting on the dash A/C for admitting fresh air.

Re: Air Conditioner Run on Inverter

Reply #5 – September 10, 2017, 10:42:16 am

(inverters are not 100% efficient). in post by Wolfe10

What would you say a top Inverter would be how efficient/

Re: Air Conditioner Run on Inverter

Reply #6 – September 10, 2017, 10:44:16 am

I have the microAir easyStart on two new marine A/C units. 12,000 and 18,500 btu per hour. Total running amps on both around 11-12amps 120VAC. The easyStart allows me to run either unit on a honda eu2000i. Eco mode must be off to start, but once the compressor is running, eco can be turned on and the generator drops RPM to about 80%.

The reason I typed all this is because, I'm fairy certain these two units could run off a 2000-3000 watt inverter. Though, without a yard, roof, and trailer full of solar panels, you won't have enough battery capacity to run it for more than an hour or two.

Re: Air Conditioner Run on Inverter

Reply #7 – September 10, 2017, 10:45:44 am

Quote from: Bill Chaplin – September 10, 2017, 10:42:16 am

(inverters are not 100% efficient). in post by Wolfe10

What would you say a top Inverter would be how efficient/

My 3012 is peak efficiency 90%

Re: Air Conditioner Run on Inverter

Reply #8 – September 10, 2017, 10:46:40 am

Peak/best efficiency of, for example a Prosine 1800 (just happen to have specs) is listed as 89%.

Re: Air Conditioner Run on Inverter

Reply #9 – September 10, 2017, 11:33:18 am

The 50 amp (aka locked rotor amps) inrush current when it starts can be a deal buster for most invertors. A/c units for homes have been available for many years that use a soft start variable speed invertor driven compressor that the inrush current is less than 16 amps @ 120 Vac and consume about 900 watts per 12,000 btuh. So you could run one unit off of an inverter for a couple of hours, or off of the alternator while driving at peak load. The inverter driven compressor of the a/c unit converts single phase vac alternating current to DC current, and then back to 3 phase alternating current so there's probably another 3-5% of additional efficiency that could be picked up there by running off of DC and eleminating one conversion. BTW these units use 24 vdc to run the variable speed indoor evaporater fan and some also use 24 vdc to run the variable speed condenser fan. There maybe another 50 watt reduction in total unit power if the fans grow turbicles. Once the sun goes down and ambient temperature drops these units consume less than peak power so running one all night off of batteries may be feasible.

Re: Air Conditioner Run on Inverter

Reply #10 – September 10, 2017, 12:01:17 pm

I re-wired one A/C unit through the inverter - after rewiring the A/C unit with a MicroAir EasyStart. We have 1140 Watts on the roof, and a pretty gigantic 1200 AH (600 usable) battery bank. We run it for about 60-90 minute when we use it - takes a serious chunk of battery - depends on the current sun but usually about 150-200AHs total. We only use it when we already have full battery, and the heavy load seems to increase the absorb charge time needed on the bank to get it truly back to full. Usually 2 days of full sun until I feel like it's actually full again.

Re: Air Conditioner Run on Inverter

Reply #11 – September 10, 2017, 12:08:55 pm

Also, because it's been discussed above - My experience with the additional inverter power efficiency loss has been approximately 25-30% when using an A/C - according to the specs from my A/C manual and the Magnum display of energy draw on the battery itself. The higher the power draw of the appliance, the less efficient the energy conversion process is. The most comparable appliance normally used in a coach would be the microwave.

Re: Air Conditioner Run on Inverter

Reply #12 – September 10, 2017, 12:31:45 pm

I personally would be more concerned about the transfer switch contacts in either transfer switch. Inverter or coach.. Not going to name the place in Quartzite, but had to straighten out several coaches, where they wired the coach shore cord directly to the 2500 watt Heart inverter. Everything could run off the inverter. No sub panel, no nothing. On one coach, it took out the inverter internal transfer switch, even though they never ran the air off the batteries. I can only imagine those poor little contacts, with 2 roof airs running through them!

Re: Air Conditioner Run on Inverter

Reply #13 – September 10, 2017, 01:40:05 pm

Thank you for all the replies. I will remove the thought from my upgrade/renovation plans. I have gotten cold feet on installing the solar system myself and at this point am planning to have Solar Energy Systems in Nappanee, Indiana install for me.

Re: Air Conditioner Run on Inverter

Reply #14 – September 10, 2017, 02:29:07 pm

We never run any high amperage appliance on our inverter, mainly to not stress inverter and house batteries, but many do it. This includes our microwave, heater, toaster, roof air, etc.

In our opinion, keeping inverter loads below 50% of its rated capacity can extend the life of the unit.

For the record most high amp appliances have a dedicated 'home-run' Romex 120-volt cable from appliance to a circuit breaker. Moving any appliance's Romex from the main breaker panel to the inverter breaker panel is all that is needed to be able to turn on appliance when on inverter power. Also the opposite Romex cable switch can be made so an appliance can never be run on inverter.

Re: Air Conditioner Run on Inverter

Reply #15 – September 10, 2017, 03:17:46 pm

Quote from: Barry & Cindy – September 10, 2017, 02:29:07 pm

We never run any high amperage appliance on our inverter, mainly to not stress inverter and house batteries, but many do it. This includes our microwave, heater, toaster, roof air, etc.

In our opinion, keeping inverter loads below 50% of its rated capacity can extend the life of the unit.

For the record most high amp appliances have a dedicated 'home-run' Romex 120-volt cable from appliance to a circuit breaker. Moving any appliance's Romex from the main breaker panel to the inverter breaker panel is all that is needed to be able to turn on appliance when on inverter power. Also the opposite Romex cable switch can be made so an appliance can never be run on inverter.

Completely agree with you. We will make coffee in a pinch, or run the microwave briefly as to not wake neighbors. Especially if I know we are going to drive that day to charge the batts., even though we have 400 watts solar, and 3 8D's.
Most the time we dry camp for weeks, and don't want to bring the batts down early. We run the gen for about 1 hr. in the morning for blow dryer, curling iron, water heater etc. and sometimes a base board heater
I run the small 300 watt inverter in the front, 24/7 for all the TV stuff, because we record of sat. Have a samll 200 watt for rear TV, use it for an hr at night, then turn it off.
Some people think they have solar and batts, so just live it, but I try to explain you have to manage it, just like your water.
Cheers
Chris

Re: Air Conditioner Run on Inverter

Reply #16 – September 10, 2017, 08:18:35 pm

Maybe in the future. Until then use the generator or shore power.

Re: Air Conditioner Run on Inverter

Reply #17 – September 11, 2017, 12:51:07 am

Quote from: Barry & Cindy – September 10, 2017, 02:29:07 pm

We never run any high amperage appliance on our inverter, mainly to not stress inverter and house batteries, but many do it. This includes our microwave, heater, toaster, roof air, etc.

In our opinion, keeping inverter loads below 50% of its rated capacity can extend the life of the unit.

For the record most high amp appliances have a dedicated 'home-run' Romex 120-volt cable from appliance to a circuit breaker. Moving any appliance's Romex from the main breaker panel to the inverter breaker panel is all that is needed to be able to turn on appliance when on inverter power. Also the opposite Romex cable switch can be made so an appliance can never be run on inverter.

What do you consider high amp? I believe my OEM inverter was designed to run the microwave or a coffee maker, and do so all the time. But not for long in order to keep from draining the batteries too much.

Re: Air Conditioner Run on Inverter

Reply #18 – September 11, 2017, 11:47:19 pm

Tom, Pretty common to use inverter for lots of stuff, just not our style, which is to run generator for things that heat.

Re: Air Conditioner Run on Inverter

Reply #19 – September 11, 2017, 11:56:45 pm

I had a customer (jack carlisto) in the late 80's with a sister coach to Cranemans 1981(?) 40' fox on a Hendrickson Chassis that loved to add things to his coach.

I remember putting in a half dozen 8d batreries in the bays and a bunch of inverters so he could run a roof air off the batteries.

Built in a pressure washer and a set of Apollo tanks so he could wash the coach without spoting and a marine large roof spotlight.

Re: Air Conditioner Run on Inverter

Reply #20 – September 12, 2017, 12:45:03 am

My '81 has a Trace 4024 inverter. 4,000 watt continuous 11,000 watt surge. It would run 1 of my air conditioners but with just 4 large golf cart batteries not for long. But the Yanmar 13 kw generator was very frugal more so than my Powertech 10 kw so used it when ever we needed air.

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