Hello, just joined and hoping for some comments on my problems. There are 2 at the moment.

First
I want to use a Sanden SD5 compressor in a freezer system. The SD5 is normally a car aircon unit and so maybe a HBP unit and typically runs at a suction of 25 PSIG. My application is a freezer with a suction of 2 PSIG even going to minus 1 PSIG i.e. LBP. This is going to put the compression ratio way up and may overheat the unit? Does any one have experience of this type of usage and what the actual compression ratio is? I will only run it at 1800RPM so it's running at 1/3 of it's max RPM.

Second
The SD5 usually uses 5GS oil which is pretty thick and I want to use 3GS oil instead, I know the makers would frown on this but.....
Having changed the duty to a freezer the oil will be subject to temperatures as low as -20C and so in a small trial I put some 3GS and 5GS in a small pot and stuck it in a freezer, the 3GS was still quite viscous but the 5GS was solid. So here the problem lays, if I use the 5GS it will freeze in the evaporator and starve the compressor but the 3GS will flow back to compressor but may be a little thin at operating temperatures expected.

I obviously did not try a refrigerant/oil mixture in the freezer test but would have liked to - it would show how the mixture would react which is very realistic. Does any one know how the viscosity of the oil changes with refrigerant present. Will it work?

Thanks - Betldrive