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Integrated RV HVAC system with hydronic heating and 12V A/C

4612 Views 34 Replies 9 Participants Last post by  eranrund
I’m new to the forum and plan to order a Transit Cargo van, 144” wheel base, dual rear wheels, high roof, extended/long body, AWD and convert it to a class B RV. I've spent the last 2 months on this to develop requirements and come up with a conceptual design of the system. For the HVAC system, I plan to run a hydronic heater and an under van mounted 12V compressor & condenser for HVAC use with a rear heater/A-C unit (not coupled with the vehicle) when not driving. The heater would also provide hot water through a heat exchanger. The compressor would be powered by a 600 AH 12 volt lithium battery bank and about 800W of solar on the roof. Don't really want to put AC on the roof. Has anyone on this forum already done this on a Transit? Any suggestions or advice? I am really lacking geometric information of the underside of the van to place the A/C components - and tanks for that matter. There is a separate topic for tank placement that I have started to sort through.
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In our van we have a Rixen hydronic heat system for hot water and air. For AC we use Cruise-&-Comfort 12v system. The Rixen system works very well at high altitude and sea level. We will be testing the AC system this summer. I calculated if you run the AC system for 3 hours at 40 amps draw will drain 120Ah. Important to size your system for the typical needs. Our insulation is, thinsulate with EZ cool air gap on ceiling, and ceramic coating on all windows.
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Thanks. A few more questions:
1)what is your fan set up?
2) do your windows open for ventilation?
3) Do you have solar on the roof?
4) What color is the van, I think this matters for the thermal model. White vs. color vs. black. Not sure how to evaluate, but a test would be worth a lot.
  • the C&C system we have is : HD-12L Mobile 12 Volt DC Air Conditioner split system. 8k
  • Fan system - maxxair as far forward as possible
  • Tern Overland roof hatch
  • Windows - AMA half sliders on driver and passenger
  • 200 watts of solar. 2 - 100W renogy panels.

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Just started my C&C install. Mounted the condenser where the spare tire was. (Spare is now mounted on a rear door tire rack and ladder combo for aluminess). I set the condenser at 20Deg angle, the minimum is 15 deg. Used 3/16" aluminum stock and bent it to the correct angle. Attached to van with 5/16" bolts and Rivnuts. Took a little while to make sure I could route the refrigerant lines up to the evaporator, but will work. Overall took me two half days to complete the install. I will put some metal screen in front of the condenser to stop any road debris from damaging the heat exchanger fins.

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Nice! Thanks for the info. Will be interesting to see how it works out for you. Keep us posted.
Finished my install of Cruise&Comfort 8kBTU HD-12L, 12 Volt DC Air Conditioner split system and wanted to share some pictures and performance data.
The Condenser is where the spare tire was and the evaporator/compressor is on the rear passenger side over a 22 gallon water tank. The refrigerant lines run thru the passenger side walls down to the channel/cavity behind the bumper and I cut a 2" hole behind the condenser to route the connections. Added R134a refrigerant, needed to buy a set of manifold gauges, fairly straightforward with instructions from C&C and a YouTube video from Login • Instagram.
The dual fan C&C condenser can be wired in parallel or in series with parallel being high power, louder and series being lower power and quieter. I was trying to see if I could use a relay to switch between parallel and series; luckily a huge thank you to going_boundless for letting me know I could use a DPDT switch to accomplish the same.
This weekend we took the van out to northern CA and ran into some high temps (+95) during the day. The unit does a great job of cooling the back of the van and we had it on during lunch and it was very comfortable.
As far a current draw and noise, I did a test today comparing parallel and series. The dB readings are with the rear doors close; the sound meter is about 4 feet back from the van and waist high.
Parallel: Current draw ~50 Amps, noise level 70 dB
Series: Current draw ~ 40 Amps, noise level 55 dB
It is much quieter in series >10 times quieter vs parallel, a good option if you are in an urban area or have close neighbors.

Condenser in spare tire location
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Final install - testing parallel and series options
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Do you think the condensor could fit in other locations underneath the van without decreasing ground clearance?

I was hoping to keep spare tire underneath while putting a gray water tank under the driver's side and condensor under the passenger side.
I think it will fit on the passenger side, the angle might need to be increased. Also the exhaust is on the passenger side so be careful not to get too close. When you place the compressor/evaporator in your design check how long the refrigerant lines need to be. I was able to use the standard size (I think it is 7 feet). If you need a different size I believe C&C will make custom length. Best is just send them your design and prosed line routing to ensure you get the correct length.
Hi @eranrund, here are some details on running the refrigerant lines from the condenser fan up to the main C&C unit in the van using the default 7 foot long refrigerant lines. No holes were drilled in the floor, we have a LWB van and the condenser is as far back under the van where spare tire was. I accessed the "channel" behind the rear bumper and run the coolant lines internally through the back of the van up through the wall cavity into the van; no floor penetration necessary. Unfortunately I did not take pictures of the internal run, but the 7 feet did work with not much to spare.
  1. Condenser install, with protective screen (1/4" stainless steel mesh folded over once). The refrigerant lines are on the left protected with pipe insulation covered with aluminum foil tape.
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  2. Penetration for refrigerant line. Used a hole saw and widen with jigsaw, then protected edge with the same material used for windows. To seal the hole cut a "cover" of expanded PVC and sealed with silicone RTV ( had a tube of the red color). It is tough to keep the RTV application neat; but has held up through the past winter
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  3. Refrigerant lines over water tank. (BTW: Pos and Neg wires are 2AWG - ran from 70amp breaker)
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  4. Overall install - from last summer:
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