Sanhua sec-612

[davidk]

Hello all,

I've built two custom air conditioners for a special vehicle. The units are equipped with single phase 230V compressors and a Sanhua SEC-612 controller for the EEV. Everything works just fine except one thing: After compressors stop, the pressure tends to equalize between condenser and evaporator. After one minute or so the controller shows "PST" meaning it sees the pressure sensor as shorted due to high pressure feed from condenser. In this situation the controller fully closes the EEV and the equalisation can't continue. As a result, the compressor won't start unless I wait a very long time. Do anyone knows if there's a setting I missed that will leave the valve open?
If I power cycle the SEC controller one or two times, during initialisation it will open the valve and will allow pressure equalize and I can start the compessors.
I use R410a refrigerant and the refrigerant setting is correct in the controller (as I said, the SH modulation works as intended) . This situation happens on both units but on one unit the error show with a delay and I'm able to start the compressors after 10 minutes.
If I had three phase compressors the starting torque would have been larger enough but on single phase there's no much torque.
Any ideas?