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nike123
30-04-2011, 07:19 AM
Q 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.

At 35F set temperature, 72 psig (30F evaporation saturation temperature) does not seam possible unless compressor did not worked at time of measurment.
Check your measurments again and take SH reading (both pressure and temperature) at evaporator outlet.

jakb21599
02-05-2011, 12:38 AM
At 35F set temperature, 72 psig (30F evaporation saturation temperature) does not seam possible unless compressor did not worked at time of measurment.
Check your measurments again and take SH reading (both pressure and temperature) at evaporator outlet.
That could be the case nike123. The system got knocked out by power failure and took several attempts to get the compressor started. Made terrible noises at start up. Once it finally started, it tripped on head pressure saftey a few times. then after a couple of hours once it was running i took sc and sh measurements. So does that mean this compressor is going into failure ? will valving off and seeing if it will pull a vacuum give the answer ?

nike123
02-05-2011, 08:27 AM
That could be the case nike123. The system got knocked out by power failure and took several attempts to get the compressor started. Made terrible noises at start up. Once it finally started, it tripped on head pressure saftey a few times. then after a couple of hours once it was running i took sc and sh measurements. So does that mean this compressor is going into failure ? will valving off and seeing if it will pull a vacuum give the answer ?

Yes, compressor should pull to about 0,3 Bara (absolute) very quickly and then, in 2 min period, it should not get to 1 Bara.