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Old 04-12-2016, 02:35 PM   #1
Mini-Skoolie
 
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Aircon from an inverter?

HI there,

I have had a quick look through the threads and haven't found anyone discussing this idea in detail. I hope i haven't missed it.

I have just bought a Ford e350 7.3 diesel based school bus I’m turning into an rv. There was no aircon installed in the bus and the wife says I have to get that resolved. So, I am thinking this:

Install a high output alternator (150-200A) feeding a 250Ah deep cycle battery bank, feeding a 3kW inverter and then a domestic aircon (maybe like this one - Haier 8,000 BTU 250 sq. ft. Cool Only Portable Air Conditioner with 70 Pint/Day Dehumidification Mode and LCD Remote Control-HPRB08XCM - The Home Depot).

I’m no electrician, but here are my sums. The aircon claims 6.3A required, but I am told that a domestic aircon could draw up to 5 x on start up, so I need to prepare for 31.5AC amps although this seems ridiculously high and well past the normal fuse range. Nevertheless, 31.5A x 110V = 3465W. 3465W/12V = 289DC amps on startup. Nominal running should be 6.3A x 110v = 693W / 12V = 57.75DC amps which is easily in the range of these alternators claimed output even at idle (600rpm).

I know there will be loss in the system, and the output/demand of these items will be overestimated/underestimated respectively, and i need to keep the DC wires short, and the alternator wont last more than a few years, but I have also heard people running 15,000 btu aircons on 2,000W inverters, so my solution seems reasonable for good aircon compared to other solutions.

Does this all make basic sense or am I missing something?

Thanks,

Gyronaut

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Old 04-12-2016, 04:25 PM   #2
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Howdy. Just to throw a wrench into your thinking, check out the mini split systems. It's a small household type heat pump.
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Old 04-12-2016, 04:38 PM   #3
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look into this if you are looking at a portable floor standair-conditioner.. I talked to the gentleman through email and he states it maxxes out at about 1000watts.. however since it is variable Inverter driven the compressor speeds up and slows down as needed and since it doesnt cycle much you wont constantly surge your batteries..

Climax Air | DC Inverter Portable Air Conditioner w/ Dual Hose | Worlds Most Efficient Portable AC

these are $899 plus shipping... lead time about 3 days....



it is an Inverter style SOFT-START unit and will not have a huge startup draw like a standard unit.. its 110 volt so you can run it on a 12 volt to 110 volt inverter or on shore-power if your bus is parked at a campground.. one unit wont cool a whole large bus but it will help...

minisplits as mentioned above are great except they have a Large outdoor condenser that needs to be Located somewhere.. you wont find a mini split that can fit under the skirt on a bus..

-Christopher
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Old 04-12-2016, 06:31 PM   #4
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I have inverter mini splits that can run off my inverter. I can run both on one 15 A circuit on cool. On start up one draws about 2A very slowly increasing to about 7A.
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Old 04-12-2016, 06:35 PM   #5
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Thanks. I don't mind a split unit and could probably mount it on the back wall above the door. I had one on my boat years ago and it worked very well. However, in this installation, power consumption is the key. Im hoping there are some DC guys here who might endorse or poo poo my math.
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Old 04-12-2016, 06:38 PM   #6
Mini-Skoolie
 
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Quote:
Originally Posted by cadillackid View Post
look into this if you are looking at a portable floor standair-conditioner.. I talked to the gentleman through email and he states it maxxes out at about 1000watts.. however since it is variable Inverter driven the compressor speeds up and slows down as needed and since it doesnt cycle much you wont constantly surge your batteries..

Climax Air | DC Inverter Portable Air Conditioner w/ Dual Hose | Worlds Most Efficient Portable AC

these are $899 plus shipping... lead time about 3 days....



it is an Inverter style SOFT-START unit and will not have a huge startup draw like a standard unit.. its 110 volt so you can run it on a 12 volt to 110 volt inverter or on shore-power if your bus is parked at a campground.. one unit wont cool a whole large bus but it will help...

minisplits as mentioned above are great except they have a Large outdoor condenser that needs to be Located somewhere.. you wont find a mini split that can fit under the skirt on a bus..

-Christopher
Thanks Christopher. I had not seen these before and will contact them for their thoughts on my plan.
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Old 04-12-2016, 07:44 PM   #7
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Quote:
Originally Posted by gyronaut View Post
Thanks. I don't mind a split unit and could probably mount it on the back wall above the door. I had one on my boat years ago and it worked very well. However, in this installation, power consumption is the key. Im hoping there are some DC guys here who might endorse or poo poo my math.
where would you mount the outdoor unit? the inside unit is easy.
-Christopher
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Old 04-12-2016, 08:04 PM   #8
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where would you mount the outdoor unit? the inside unit is easy.
-Christopher
Probably outside above the rear door, with the internal unit above the door inside. It'd be a little bulky for my small bus, but if it proved to be the best option, I'd make it work. That said, this one looks like a good option if it performs as promised - Climax Air | DC Inverter Portable Air Conditioner w/ Dual Hose | Worlds Most Efficient Portable AC
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Old 04-12-2016, 08:17 PM   #9
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I've seen people mount them as you described. Apparently that configuration works quite well and obviously would be relatively easy to hook up because of the proximity of the two units.

This is a rookie question about these mini split systems. They are actually heat pumps, and heat pumps not only make AC but also make heat in the winter?
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Old 04-12-2016, 08:18 PM   #10
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depending on your timeline for A/C I plan on ordering one of these for use while im working inside my bus on hot summer days.. I'll be able to measure its performance and power usage.. I wont be ready for a couple weeks though..
-Christopher
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Old 04-12-2016, 08:25 PM   #11
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Quote:
Originally Posted by Robin97396 View Post
I've seen people mount them as you described. Apparently that configuration works quite well and obviously would be relatively easy to hook up because of the proximity of the two units.

This is a rookie question about these mini split systems. They are actually heat pumps, and heat pumps not only make AC but also make heat in the winter?
they will until it gets really cold.. a heat pump is an air-conditioner "backwards".. just like in summer your A/C blows cold inside and hot outside.. turn it to heat and it reverses the process...

the caveat is the colder it gets outside the less efficient a heat pump is.. most people that live north of orlando or so (or anywhere not on the west coast) will have a secondary source of heat.. ie electric coils or gas furnace.. if you are running your bus engine obviously you have great source of heat.. if you are on shore power you could get some heat from the mini split without using your propane.. (ie if the campground has electricity included.. you run your heatpump as long as you possibly can so you dont waste your propane.. but you will still want a furnace of some sort for those really cold nights..)...

I have run my ducted inverter splits (my home system is based on them) down to 0f outside but they struggle.. get noisy and use lots of power to push out minimal hot air... since I have natural gas main heat and gas is CHeaper than electricity I dont use the heat pumps much here at home..

-Christopher

P.S. if you install a mini split with less than 15 feet of refrigerant lines you must adjust the amount of refrigerant down to match the line lengths...
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Old 04-12-2016, 08:26 PM   #12
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Quote:
Originally Posted by Robin97396 View Post
I've seen people mount them as you described. Apparently that configuration works quite well and obviously would be relatively easy to hook up because of the proximity of the two units.

This is a rookie question about these mini split systems. They are actually heat pumps, and heat pumps not only make AC but also make heat in the winter?
I'll have to get the tape out to see if it'll fit properly before deciding. They do seem to offer some heating as well, but i doubt they'd keep us warm against a Canadian winter. The other bonus if they seem to have a soft start which is the biggest hurdle for low power options like mine.
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Old 04-12-2016, 08:28 PM   #13
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Originally Posted by somewhereinusa View Post
I have inverter mini splits that can run off my inverter. I can run both on one 15 A circuit on cool. On start up one draws about 2A very slowly increasing to about 7A.
Can i ask, how big is your inverter, battery bank and alternator is? Do you use them when you're on the road?
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Old 04-12-2016, 08:29 PM   #14
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if you are buying minisplits be sure you buy the type that say "DC Inverter" as they did make cheaper units which were standard hard start / stop compressors.. you want the inverters running R-410A refrigerant to get the soft-start and much better efficiency than the cheaper units..
-Christopher
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Old 04-12-2016, 08:31 PM   #15
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Originally Posted by cadillackid View Post
depending on your timeline for A/C I plan on ordering one of these for use while im working inside my bus on hot summer days.. I'll be able to measure its performance and power usage.. I wont be ready for a couple weeks though..
-Christopher
Thanks. That might help. I have sent the guy an email and if the BTU and power consumption range are anywhere near what he claims, it should work just fine. I'm in no rush to purchase, but i like to get my research done early.
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Old 04-12-2016, 08:35 PM   #16
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Originally Posted by cadillackid View Post
if you are buying minisplits be sure you buy the type that say "DC Inverter" as they did make cheaper units which were standard hard start / stop compressors.. you want the inverters running R-410A refrigerant to get the soft-start and much better efficiency than the cheaper units..
-Christopher
Great advice. I'd not even heard of inverter aircons before today. Thanks guys.
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Old 04-12-2016, 09:14 PM   #17
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I'd seen the inverter on some of the systems but didn't know what it meant.

Yeah, research phase here too. I'm looking to lean hard away from propane for heating purposes. I installed a wood stove but can't always use it depending on location.
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Old 04-12-2016, 10:37 PM   #18
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Quote:
Can i ask, how big is your inverter, battery bank and alternator is? Do you use them when you're on the road?
I have a 3000 sine wave inverter, but have run one on a 1500 and yes I can run one while driving. Bus alternator is 180A, my battery bank is small so will only run 1 AC for about a half hour. My generator, not quite finished is 320A DC, so should run everything.
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Old 04-12-2016, 11:18 PM   #19
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I've been watching these guys - I bought a fridge from them. They released their AC unit just a little while ago.

EcoSolarCool Solar Air Conditioner Wall Mounted
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Old 04-13-2016, 06:53 AM   #20
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I've been watching these guys - I bought a fridge from them. They released their AC unit just a little while ago.

EcoSolarCool Solar Air Conditioner Wall Mounted

I need to read up more on how this works.. standard absorption cooling was done with heating the refrigerant.. however this appears different, though they dont state what refrigerant these use..

if nothing else the fact they take 12 volts as input voltage is an advantage as you dont have the Loss in the 12 to 120 Inverter like when using a standard mini split..

cool stuff!!

-Christopher
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