SOURCE: normal operating pressures
Normal operating pressures will change as the freezer reaches the selected temperatures on the inside. Normals of minus 14 degrees on the inside would be around minus 4 psi on the suction and 150 pis on discharge. Now checking the pressure will require a set of guages that have been purged with the same freon before connecting with the suction line on freezer. If not purged the suction line will draw outside air into the system and cause freezing of air and moisture inside the capillary tube rendering the freezer inoperative, Hope this helps, Sea Breeze
SOURCE: inadequate cooling on walk in freezer
YES GOOD ADVISE . ALWAYS START WITH THE BASICS. IS EVAPORATOR COIL CLEAN AND CLEAR? ALL EVAP FANS RUNNING? DRAIN PAN CLEAR? IS STAT CALLING FOR COOL? IS OUTDOOR COND COIL CLEAN? IS OUTRDOOR FAN RUNNING WITH NO PLAY IN BUSHING? DO RUN AND START CAPS TEST GOOD? DOES CONTACTOR LOOK GOOD? THEN TRY TO CATCH UNIT WHEN TEMP IS ABOVE DESIRED SETTING. FIRST TEST STAT. IS IT OPEN OR CLOSED? IF BOX IS HOT AND ITS OPEN THEN PROBLEM IS STAT. IF STAT IS CLOSED AND OUTDOOR FAN IS NOT RUNNING THEN COMPRESSOR PROBABLY OVERHEATING WHEN FAN QUITS. CHECK FOR VOLTS TO FAN GOT VOLTS? FAN IS BAD. NO VOLTS? TRACK BACK TO SOURCE OF POWER ( CONTACTOR) AN R22 BOX AT 52 PRESS IS NOT TO BAD ON START UP ON A HOT BOX BUT COULD BE HIGH ON 502 408 OR R12 STUFF TYPE OF REF IS DEFINITELY IMPORTANT. GOOD LUCK
SOURCE: What is the normal operational
why yes there is. Generally speaking, the head pressure should be around the "ambient +30" rule.
That is, measure the entering air temp to the condenser, say 75 degrees. Now add 30 to that and get 105 degrees. Look at a P/T chart and see what the pressure is for that temp which is about 253 for R-404-A.
The evap on a freezer leads the load so, as a general rule, the evap temp is going to be around minus 10 degrees to get a 0 degree box. Coolers are different. So, the pressure for a minus 10 evap is around 25 or so. But the unit has to be close to operating temp. If the box is warm, naturally the pressure is higher. And what influences the pressure is whether or not it's a TXV or a cap tube system.
If a TXV and no receiver, charge by subcooling. If a receiver, fill by sight glass. If Cap tube, charge by superheat.
Hope that answers your question.
SOURCE: head pressure too low
Charge until the sight glass is full. I suspect your pressures will be be better. 12 psig is low even if the case is down to temp. I suspect once the sight glass is full you'l be runniing in the upper 20's.
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