View Full Version : Suction Pressure

29-04-2011, 01:45 AM
Question for you guys. I have 2 systems with 404A gas. One system has 3 hp compressor with matching evaporator for it, and the other a 5 hp compressor with matching evaporator for it also. Both coolers have the same set point temp of 35F SH 30 and SC 15 at design temp. My question is this. The head pressure for both are 265 psi but on the low side, the 3 hp has 72 psi and the 5hp has 50 psi. Both were at design temp when sc and sh were taken. Why is this ? is it because the differant size evaporators ? Orfice ? Txv valve ? Both units work fine and pull down to temp fine. Just curious as to why the differant pressures. Thanks for your help

04-05-2011, 11:38 AM
was both rooms down to temp when you took those pressure readings? 50 psi would be an acceptable reading for a chiller at 2degrees (35F). 72 psi would be acceptable for a room at approx 9degrees (49F) hp reading is pretty sweet for a system on 404a.
Yes evaporator design, valves etc can all play a part in actual running pressures.