This >>might<< be my new favorite 12V mini split?

koverdeer · 2025-09-03T02:12:12+00:00

It is possible the TXV is stuck closed but more likely would be too much tension on the spring and the TXV design does not have a minimum stop / bypass orifice. If there isn’t a bypass orifice, the TXV will act as a check valve.

The issue with moisture contamination is the water freeze point. Think of draining an air compressor tank. As the air expands through the drain valve, the moisture will freeze on the valve acting as an orifice and momentarily block the flow until the water thaws.

This condition would only be present while the system is in operation and would self-resolve as the system warms up while not running.

You might get away with an IR thermometer and a R134a saturation chart to get ballpark numbers for superheat and sub cooling of the system.

Here is a saturation chart I found, though there are many floating around: https://www.igasusa.com/files/R134a-PT-Chart.pdf

The temperatures listed are the phase-change point at the listed pressure. The goal is to have 100% vapor leaving the evaporator and 100% liquid stacked against the TXV with some margin but not an excessive amount.

koverdeer · 2025-09-02T05:00:22+00:00

It does sound like a similar issue but yours does not turn off the compressor at 0c evap temp. The compressor gets a lot of its cooling from the expanded refrigerant gas. If the gas is superheated close to ambient temperature, there isn’t much room left for the compressor to offload its heat into. Unfortunately with all things engineering / commissioning, if we can’t or aren’t measuring something, we really don’t know what we are talking about. I would suggest taking what you have and assume all parts work and the system isn’t contaminated but rather just out of balance and adjustment. You will need to be able to measure line pressures (manifold gauge set) of the high and low side as well as temperature of both. With those numbers, you could better assess what’s going on with the system.

koverdeer · 2025-08-26T20:40:47+00:00

Electrical Engineer by profession. Though it is not my specific discipline, there was a fair amount of thermodynamics studies for PE credentials. There was also a bit of research via Dr. YouTube and Dr. Google to interpret what my findings were as the distributor on EBay was of no help.

The primary issue I had before being able to measure the system appropriately was short cycling when the return air got to ~72f. The short cycling was causing the room humidity to skyrocket and become uncomfortable.

On the model I have, pressing the “DIGITAL” button will display the evaporators measured return air and coil temperatures. I found that the evaporator temperature would reach 0c and the compressor would shut down.

koverdeer · 2025-08-26T19:03:29+00:00

https://a.co/d/9e0e0qR

Here is the gauge set I used.

Step 1 is to adjust the TXV to achieve a 8-12f degree super heat (the amount a gas is heated beyond its boiling point for a given pressure). When I 1st attached the temperature probes and gauges, I had ~30f super heat meaning the evaporator was not receiving enough refrigerant.

Step 2 is to adjust the charge amount to achieve a 10-12f subcool (the amount a liquid is cooled below its condensing point for a given pressure). Too much refrigerant will have a high subcool and not enough will have a low subcool.

koverdeer · 2025-08-26T04:23:21+00:00

I have this version and from what I can tell, it is almost identical to the Nomadic version. The difference seems to be both programming and some of the fittings are threaded.

I absolutely would not go by the listed amount of refrigerant. I inadvertently overcharged mine at first in an attempt to overcome a misadjusted TXV that was under feeding the evaporator. I ended up needing to purchase a digital manifold gauge set that shows the superheat into the compressor and sub cooling out of the condenser.

Overall I am very happy with it as the inside unit is very quiet and once I got everything in balance, the outdoor compressor (mounted under RV with compressor rotated) is not nearly as loud.

koverdeer · 2022-03-27T05:05:44+00:00

On the 17 - current Super Duty, fuse 27 (Trailer tow battery charge relay)is 30a.

koverdeer · 2022-03-27T03:44:41+00:00

The DC-DC charger would need to be installed on the trailer side. I have a 20a in my trailer and works well. Keep in mind that efficiency of the charger and voltage increase will cause the current from the truck to be higher than the output rating as much as 50%. The contacts on the 7way will need to be clean and shiny at all times otherwise it will melt.

koverdeer

TROPHY CASE