Mitsubishi PUH-10MYF-EUS

Hi guys,

We are having a bit of trouble with this R22 split ducted system, In cooling it seems to be working fine most of the time, though we did see the suction temp drop to -8 for a bit but then did go back to 2 degrees. The ambient temp is 16 degrees celsius.

The customer has reported the issue in heating the supply air temp is 27 degrees celsius and the return air intake is 22. In cooling the supply air is 12 and return air intake 20.

Running in cooling the Discharge temp is 40 degrees celsius (207 PSI) and suction most of the time around 0 (58 PSI). but in heating the discharge is only at 30 degrees celsius (158 PSI) and the suction is at 12 degrees celsius (90 psi)

The evaporator/condenser coils and filters are clean. The Evap fan is running. The condenser fans start at full speed then reduce after maybe 1 minute.

We suspect that this is a refrigerant issues, reversing valve issue or compressor issue.

Any help would be appreciated.

Hey mate
Looks like it might be SOG but you nee to collect more info.
Check all this in heat mode;
You have low delta T across indoor coil of 27c minus 22c=5c degrees.This is too low.
Check Delta T across outdoor coil on heat mode. Should be around 6C
You mention discharge temp of 40 deg (207 PSI) i think you mean SCT saturated condensing temp.
Discharge temp should be measure with a clamp type thermometer on the discharge line straight out of the compressor.
You can do a pump down test on compressor to check its health. Do this on cooling.

Hi,

Thanks for the Response yes SCT sorry. Not sure what you mean by SOG? I will get back and take as many readings as possible.

SOG is slang for short of gas.
Assuming this is a fixed speed compressor unit? I know its on R22 but there’s a few first generation inverters on R22.
Also check compressor amps against RLA.
Reversing valve; do a g**gle search on ``testing heat pump reversing valves`` look for the article from ACHR news. Its a handy resource.

Yes That is in my mind but I am a bit confused as to how there is a high suction in heating? Compressor amps are fine.

Have you checked the temperatures across the four-way valve?

Lower pressures due to SOG can mean that the valve does not fully change over giving mixed temperatures.