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Split system aircons

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Split system aircons

Postby jasonjason » Sat Mar 17, 2012 4:02 pm

G'day

Im interested in installing a couple of splits in my bus and wanted to know other peoples thoughts are or what others have done.
I went into a 12v shop in adelaide and the lady told me I cant run splits off an invertor and solar panels, but on motorhomeconversion.com.au he has 2 in his bus running from batteries.

I will probably install 4 x 12V 200Ah batteries to give me 24V @ 400Ah, 6 x 24V 200W solar panels on the roof, and also a 5kVA genny for backup

LG split aircons
Cooling capacity 2.5kW
Heating capacity 3.2kW
Cooling running current 2.7A
Heating running current 3.3A

12 hours a day running is only an average of 40Ah a day

Solar panels at 75% efficiency should give 900W total or 37.5A per hour average 6 hours of sun a day giving 225A a day

As far as I can see i shouldnt have any trouble. What do you think?

Jason
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Re: Split system aircons

Postby ax8 » Sat Mar 17, 2012 9:26 pm

The problem with air con is not the running current but the start up current but it can be done.
Also as it needs a bigger amp draw on start up it may effect battery life but it would be best to speak to someone who is running their air con off batteries.
Also 2.7 amps 240v is 27 amps at 24v.

cheers Al
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Re: Split system aircons

Postby plough » Sun Mar 18, 2012 7:08 am

How big is the bus, 2 split systems sounds big. We have a 1.6kw split mounted in ours, Its mounted up above the front of the bus right behind where the bus route and number would of normally been displayed. The outside unit is mounted up under the chassis, with the hot water system and generator.
I will grab some figures on its start up power and running usage later today as I have a meter here to measure it. Anyway we use ours running off an inverter, but only when driving along, never tried it from the batteryies, it would run as the inverter is 2400w with 3000w surge, but the poor batteries and I only have 200amps hours of agm batteries. Also on batteries before you buy, get a price on lithium batteries instead of the AGM. This year will be a big thing for lithiums as they look to take over the market for deepcycle batteryies, just as they have for cordless power tools. The weight difference alone is amazing, EG
◦A 305Ah (9 cell) AGM Battery bank in the Karavan has 50% x 9×35 = 152Ah usable and these weigh 100kgs with connectors
◦A 168Ah (4 cell) Lithium Battery bank in the Karavan has 90% x4×42 = 151.2 Ahr usable and these weigh 25kgs with connectors
So 75kgs lighter
http://www.camp4ever.com/article/new-ki ... field-test
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Re: Split system aircons

Postby plough » Sun Mar 18, 2012 8:26 am

I have those reading from our AC. A bit different to what I thought would happen. I can only guess that the AC has a soft start built it to it as the power levels were low in start up and then slowly went up as the ac was running.
First up, it was 2watts on standby,
Fan only, 30 watts on start then back to 20 watts,
Cold, 650 watts starting then it slowly climbed to 776watts or 4amps, the ac then reached 17deg in the bus and then turned off.
For hot, 855watts starting up then it ever so slowly climbed up 1 watt at a time about every few seconds up to 1340 watts or 5.8 amps. It then shut down as it reached 30 deg in the bus.
I guess it would climb right up the the rated 1.6 Kw if it was cooling or heating long enogh before reaching the set temp.
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Re: Split system aircons

Postby scott101973 » Sun Mar 18, 2012 9:49 am

i ran a 3hp (7.2k) inverter on the old bus off generator, batteries and 240v no problems with any.
the inverter has a soft start so it didnt have any issues.
on the new bus i have just bought 2 1.5hp (3.2 k) inverters, one for front one for rear.
found the one a/c bolted to the rear of the desto was great for the fron half of the bus, but was not so great on a hot day down the back.

both buses are ex school buses, about 38 foot.
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Re: Split system aircons

Postby jasonjason » Sun Mar 18, 2012 5:43 pm

Thanks Al, I forgot to convert it to 24v, thats changes things a bit.

Thanks plough Its great to get some tong readings to see the actual usage.
My bus is an Austral Tourmaster (12.5m long x 2.5m wide - 31m square to cool/heat)
Cooling seems pretty reasonable
30W for the fan is 1.25A @ 24v
776W for comp. is 32A @ 24v
So running for several hours a day is definately possile and if set at a little higher temp the cycle time wouldnt be great

Would like a split in the front half for traveling/daytime usage (mostly while the bus is running), then another in the rear for the sleeping area (to cool before going to sleep)

For heating I may go for a webasto diesel heater as they seem to be more efficient.

I also checked out the link to the lithium batteries. Very interesting read. Will see if I can get a price on some and see what the difference is compared to gel batteries.

Thanks scott. It seems most people run them using gennies to top up thier batteries. Will definately need one for backup i think.
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Re: Split system aircons

Postby wes » Mon Mar 19, 2012 7:49 pm

Being an air Cond mechanic i just did the calc's at an overrated figure and got 4.8kw for the whole area.
cal was floor area x 150watts ie 32x150 = 4800 or 4.8kw
Would therefore recommend the Mitsi heavy industries unit.
i have their 10kw ducted and on a 35 degree day only draws 9 amps..
http://www.mhiaa.com.au/products/srk/SRK50ZJS.aspx
Hope this also helps..
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Re: Split system aircons

Postby jasonjason » Mon Mar 19, 2012 9:53 pm

Thanks wes, but I reckon it might just be a bit big.
6.8A run current on 240v is 68A run current on 24V
would give me about 3 hours out of my batteries without running tv's or reefers or other gadgets the kids have lol
i didnt know thats how you worked out aircon size (meters square x 150W). Pretty simple really :)

Being an aircon mech which brands do you find the best? (most reliable, parts avilable, not necessarily the cheapest)

I was thinkng the smaller units as i can put a thermal curtain between the living area and the sleeping area and effectively cut the floor space in half.
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Re: Split system aircons

Postby wes » Thu Mar 22, 2012 7:55 pm

Hey jason.
The 6.8amps would be when the system has ramped up to full load.generally it will only draw 4-5 or even lower depending on conditions etc..
you could probably use the 3.5 as per link below as it is closer to the more realistic load of your vehicle..
generally stick to any of the main reputable units and mhiaa offers 5 years warranty.
http://www.mhiaa.com.au/products/srk/SRK35ZJXS.aspx
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Re: Split system aircons

Postby wannawagon » Mon Apr 02, 2012 10:11 pm

will a modifed sine wave inverter work ok for a/c units?, inverter and non inverter?, also will a 3000/6000watt inverter (modified sine wave) work on a 1.5 hp unit ok (non inverter technology)
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Re: Split system aircons

Postby plough » Fri Apr 06, 2012 1:10 pm

Thats a good question. I have a post about failed inverters on the CMCA web site.
What I can tell you is what ebay items will not work.
Ebay item Item number: 230723072518 2000W CONTINUOUS POWER 12VDC-240V AC SINE WAVE INVERTER
worked for about 5 minutes then went "pop", never worked again. Was given a full refund.
Then this other better unit I got Item number: 390386230855 Pure Sine Wave Power Inverter - 2500W / 5000W
After the first unit failed I wanted to try this unit before I drilled holes and mounted it in the bus. It ran perfectly for a full week in the garage at home, so then I mounted it in the bus.
First night away, after less than 1 hour I smelt burning plastic. I opened the compartment to see smoke comming out of the inverter. Another failure.
When I got home I pulled it apart and there was a fire inside it where the heatsink joins onto the some big black thing. The sad part was the inverter was only pumpong out a small 60watts to run a fridge and it still almost burned my motorhome down.
So now I'm ready to try a 3rd inverter.
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Re: Split system aircons

Postby plough » Sat Apr 28, 2012 4:57 pm

Back on to that second inverter from ebay item number : 390386230855 Pure Sine Wave Power Inverter - 2500W / 5000W.
As mentioned on my above post it caught fire, and if left for much longer may of destroyed my motorhome. Anyway the inverter was sent back to the seller for replacement / repair. They sent out a brand new one this week. I thought I had just better give it a test run for a few days before I mount it back in the bus.
So I connected it to a 12v battery and then the output to my small bar fridge that draws about 400w on startup then back to 80w when the compressor is runningm then back to about 2w when idle. So I turned on the fridge.
The inverters cooling fans operated for about 30 seconds and then stopped, its ment to do this as the manual says the fans are multi speed and turn on and off when required.
Well guess what.
The fans didn't come on again and the inverter went bang and then up in flames. So back to the seller once again.
It seems this model has a seriouse cooling fault.
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Re: Split system aircons

Postby downunder1811 » Thu Apr 17, 2014 9:57 am

Hello Guys, I am trying to figure out how you can run an AC unit while driving with invertor i am thinking the same thing but thought i would have to spend thousands on a generator like a Onan Cummings unit.. Can you please explain how you go about doing this, what battery bank you have, what type of invertor you run and how you charge batteries back up (guessing alternator) I am very interested on how you have done this....Also how do you find running a house unit in a bus, I have been told to many things and dont know what to belive any more.....

regards
allan
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Re: Split system aircons

Postby kelvin12 » Fri Apr 18, 2014 7:49 am

Allan,

You won't run a domestic type a/c from your batteries or if you do it won't last long power wise. A/c's suck up quite a bit of power and it won't take long before you flatten the batteries. You might be able to on a very large lithium battery pack, (but they are really expensive) and a big solar array up top or the alternative is to run the generator when you are underway. A/c's, washing machines, freezers are pretty well a caravan park deal unless you run the generator daily. AGM batteries only allow you to take them down to 50% before they start self destructing, and its not long before they are unusable. They are also extremely heavy with a decent AH rating. Lithium on the other hand can go way down but you still need a means of powering them back up again to get a full charge. Petrol generators are noisy enough but diesel really bad.

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Re: Split system aircons

Postby downunder1811 » Fri Apr 18, 2014 8:23 am

thanks kelvin, from reading storys above the are seemin to run this from invertors, i was thinking the sames as you would need generator to do this..
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Re: Split system aircons

Postby kelvin12 » Fri Apr 18, 2014 4:14 pm

The start up is the killer even the inverter models, when it ticking over its not to bad but when it kicks over again the current draw is really high and that kills your batteries. Check out this site for good info on lithium batteries if you plan on going this track, Bill has done heaps of work in this regard http://www.motorhomeconversion.com.au/ I am running 560A/H's of AGM's myself mainly due to the budget looking real sick at this stage, but don't plan on running a/c's from them. Just not practical without running generator or being park up.

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Re: Split system aircons

Postby scott101973 » Thu May 15, 2014 8:24 pm

Ok my bus ran 2 domestic splits easily on solar/batteries. I used lg units 400w draw each, 2.6kw solar and 580ah lion batteries - with Victron charge controller and Victron inverter charger.
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Re: Split system aircons

Postby rustbucket » Fri May 16, 2014 9:47 am

I am the Bill referred to above.
If you want to run INVERTER (soft start) aircons you MUST get Lithium Iron Phosphate batteries.
My original build was to be 1200 Ah of lead acids to give me 600 Ah of useable power. Then LiFePO4 batteries came along and I did some homework
The original LA pack I was to install would have weighed 1.2 tonnes.
I now have 800 Ah of Liths which weigh a bit over 200 Kg
That still gives me the same capacity, for about the same price (going rate from the right seller is around $1.50 per Ah) I was lucky and picked up mine for $1 per Ah.
Sitting in the coach the other day after registration, it was a bit warm so flicked on the bedroom inverter one, left it running for over 2 hours, the battery pack when I switched it on was sitting at 26.5 and when I switched it off was still 26.5 The capacity of these things is amazing.
They will also recharge as quickly as you like.
We use 2 x Rich electric DC-DC chargers from the 240 amp bus alternator (70 amps each) and have 2 Kw of solar on the roof which gives around 60 amps at 24 V on a sunny day.
Thats 200 amps going into the batteries and they lap it up. Do that with LA batteries and they would boil, then melt.
Current draw of the aircons when the outside unit cycles off (room down to temp) is minimal, will have a look if you need the figures
Some of the guys that have been using them for several years now have gone all electric, no gas at all
We have one split in the area above the driving cab, we can seal the area just behind the cab (when the 2 slideouts are in and it only has to handle that very small area when travelling, and is running off the solar and alternator anyway. When stopped, open slides, close passage door and it easliy handles the front half of Vanishing Point. Vehicle must be well insulated of course.
Cheers
Bill
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Re: Split system aircons

Postby kelvin12 » Fri May 16, 2014 5:40 pm

That's a lot of panels up top. Enough to power a small country town......

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Re: Split system aircons

Postby Toolman » Tue Jun 03, 2014 2:06 pm

Bill where did you find was the best place to buy Lithium batteries as I am building a similar system to yours
Thanks,
Kevin
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Re: Split system aircons

Postby rustbucket » Wed Jun 04, 2014 7:33 pm

Kevin,
There is a guy in Mackay who sells quite a few, does a good job of strapping them as well if needed and because he moves them always has fresh stock. Some of the other resellers have stuff years old. Ask them for a production certificate of their stock, some you will never hear from again (experience)
Definitely get Winstons though, more capacity than sinopolys, I only bought my sinopolys because, at the price, I can afford to toss them a bit earlier (if still on this mortal coil)
Do your homework though, expensive monitoring systems are not necessary and can be dangerous, you must monitor at cell level. Easily achieved once you get some knowledge.
I am using a Super Combi and Rich solar reg, but my whole monitoring system outside that is about $100 worth.
I also get free hot water from any excess solar via low voltage elements, works a treat in conjunction with the rest of the system.
Cheers
Bill

PS if you need his contact PM me.
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Re: Split system aircons

Postby Toolman » Wed Jun 04, 2014 8:46 pm

Bill

Thanks for that. I must be on the right track as I had already decided on the Winstons
There is a mob down in Perth that convert cars to Electric that I have been talking too
I will also use a Super Combi and I want to run a Hitachi Multizone split system with a couple of Cassette units in the front hatches
I only need to run them for up to an hour off batteries, as if I am stopped longer I will run the generator
Cheers,
Kevin
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