12V Mini-split Air Conditioner Install

boathealer

[Cross-posting – thought some would like to know.  Sorry.]

This is a summary of my installation of a Chinese “parking air conditioner” – a mini-split system with variable speed compressor.  I can’t get the photos to post in any kind of order, so you’ll have to just assign an interest level along with the text.  Probably a lot of TLDR for those not interested……

I took a chance on an ebay $500 air conditioner.  These are prolific on both eBay and Amazon in the $400-800 range.  I chose the particular model, assuming most were the same level of quality and function, based on the outside unit being able to fit on the cage just in front of the “tub” locker on the tongue.  In addition, the inside fan unit had to fit in the existing microwave cabinet location somehow, with connections in a logical location.  This one had a perfectly-sized inside unit also.  I figured it was worth the (relatively) low cost to find out if it would work out.

When the unit arrived, the outside heat exchanger fit perfectly as measured in the front tray.  Without exact plans ahead of time to route the high- and low-pressure hoses and electrical, I started looking for a path into the cabin. 

I finalized a plan going under the trailer frame, into the void above the corrugated plastic, and up into the wall between the head and cabin.  I had to cannibalize the existing foam duct channel to make room for the hoses.  The small panel/cutout on the wall next to the microwave just happened to be perfectly lined up with the inside fan unit where the hoses would need to enter. 

However, it turned out that the 11ft hose and electrical lengths that came with the unit were about 2ft too short.  Then began a tedious 5-week nightmare of finding someone to make longer hoses, trying to adapt non-compatible (with Chinese) fittings, and on and on.  In the end, I bought another set of end fittings from a supplier on eBay, new 14ft raw hose, and a handheld hydraulic/AC crimping tool and made my own hoses.

I had read reports about the wiring to the outside unit being a bit undersized for the current required, in lengthening the electrical connection cable, I upgraded the power wires to 6AWG.

Finally, after seeing the red cover of the unit sitting on the outside of the camper, I decided it was not going to work.  I took the whole thing apart and sanded/painted the enclosure with black Rhino liner spray paint.  I think it looks much better now.

For the inside unit, I took the face frame off from the microwave compartment, and cut the sides back so that it wouldn’t stick out so far into the space,  I think I cut about 6-7” off and then put the face framing back on.  The inside blower unit screwed right onto the face panel and fit perfectly.

Having all the right parts, now, I started assembling.  Routing the hoses was pretty straightforward and getting them attached to the blower unit and it mounted up on the new panel frame was easier than I thought (it is quite light).   I did have to dig out quite a bit of the foam duct from inside the wall (through the TV bracket opening).  I covered all the metal parts of the hose connection fittings with insulating pipe foam to keep them from sweating condensation.  I found a plastic vent cover to fit over the old air conditioner duct outlet hole that looks pretty nice.

Outside, I put a HDPE panel down under the heat exchanger to keep driving rainwater from being forced up into it.  I also mounted it to some stiff rubber pads to cut down on noise/vibration.  I covered all the outside fittings and hoses with insulation/tape/UV protection.  NOTE: the red wire in the lower right corner of the photo is the tow-vehicle charging connector that is still under construction.

The connections (and some others from the lithium battery bank in the tub) run under the transverse frame member and the up into the covered cavity back to the entry point through the floor in the drivers side wheel well locker where I have put all the battery charging/electrical components.  I found some HUGE HDPE spiral wrap to cover all the exposed wires and hoses going into the compartment under the trailer.  I ran the condensation drain hose out through the floor and then through a new hole in the corrugated under-cover.  I tilted the fan unit ever to slightly to the right so the drain water would exit easily, but will still have to mind the level of the camper at each setup where I want to use the AC.

I installed a 50A breaker and a cutoff switch on the lower bench face panel before connecting to the batteries.  With everything hooked up, and my 1200Ah battery bank up and running, it was time to charge the system with freon (it doesn’t come charged).  I went to YouTube University and figured out how to charge one of these systems, bought two cans of freon and a $50 set of gauges on Amazon, and got it done!!

Lastly, Lisa made us a WONDERFUL Sunbrella cover for the outside unit for travel and when not being used.

So as of now, without a lot of long term testing, it works FANTASTIC.  Cools the camper down immediately in the current Florida 95 degree, 90% humidity weather!  Once the set temperature is reached, it cycles from slow to fast compressor speeds every minute or so continuously.  I ran it for about an hour and it averaged 200-250W (15-20A) in order to maintain 70 degrees inside the camper with it 95 degrees outside (under cover).  The compressor fast-slow cycles were around 2A to a maximum of 32A (400W).  With an average of 20A running and 1200Ah of battery – well, you do the math…..

There is now a HUGE amount of storage space where the old air conditioner was!!

Anyway, as of now, I’d rate this project a 9 out of 10 success!  All-in (not including batteries, etc.) including HVAC tools (that I’ll probably never use again) was about $1000 and about 20 hours of my labor.  I will report back on long-term use in the future (if I can remember).

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SIDE NOTE: Before the 100th person asks why I put 1200Ah of lithium battery in the camper:

1)      Because I could 
2)      Because there was room in the tub
3)      Because I took out the propane system and want to run the 900W mode of the Alde on batteries occasionally
4)      Because my camper is also going to double as a home backup generator – I put a transfer switch on the shore power inlet to OUTPUT inverter power that we plug into the house for backup power (fridge, TV, select outlets….)

jimcenname

Thanks for the great post. How did it change the tongue weight? I'd like to check out the specs, can you share the brand or a link to it? Thanks!

boathealer

Tongue weight, mostly from batteries, went from ~230lbs to ~340lbs. 

The AC I bought is here: https://www.amazon.com/gp/product/B0CY8GGB21 - there are HUNDREDS of versions of them on both Amazon and eBay, probably all pretty much the same.....

Maxcamp

Thanks for the detailed posting! 
I'd be very interested to have you read the output air temps with an instant read thermometer.  Above 55F and below 72F are commercial duct balancing guidelines.  How is the noise and airstream comfort when sleeping?  

 Some of us have looked hard at replacing the loud ducted AC with a split 12v truckcab system.  We use our microwave frequently including on inverter power.  Inside unit could go in 320s rear cabinet above feet, with cabinet modifications.  Might be uncomfortable to sleep with it blowing on us.