Typical operating pressures for 507 freezer

[dmd-marc]

Good evening everyone.

I was asked by a friend to check out his walk in freezer. I normally dont work on refrigeration equipment. It is another animal. Anyway, I was wondering what would normal operating pressures or temps be for a walk in freezer with R507 in it be? Normal ambient conditions are around 80-90 deg F right now. What about superheat/subcool? Customer is trying to maintain 0-10 deg

[dmd-marc]

I stopped by to take peek at it and the low side was @ 25psi but what alarmed me was that the high side was @ 275psi. Box appears to be maintaining temp but will trip low/high pressure control. Haven't witnessed it myself. Condenser is clean but facing in an awkward direction. But has been operating for years this way. Any info would be great

[mmmdave]

Those pressures look ok. You'll want to get a SCT that's 25-30 over ambient, and evaporator temp 10 degrees below box temp. Shoot for a SH of 4-6. SC doesn't mean much assuming the system has a receiver. Just make sure the expansion valve sees a solid column of refrigerant.

Now as to why the compressor is tripping... need more info, particularly why it's tripping. It could just be shutting off on the lpc on pumpdown.

[dmd-marc]

All I have been told is that the owner has to reset the combination low/high pressure control. The high pressure setting was at 375 psi and the low at 20 psi according to the owner. He resets the control by pressing in the reset butoon on top of the control.

[jim147]

What controls the cycle? If it's not shutting down, and keeps getting colder it will hit the low pressure switch. To hit the high pressure would take the fan dropping out or something strange going on.

Once it shuts down it can be hard to find the problem. Get the owner to get as much info as possible when it goes down. I know, I know, but you can try.

jim

[thermofridge]

Sounds like a dual pressure control. Most likely its tripping on high pressure. Dont think Ive seen a dual control with low press. reset.

[frigeguy]

Sounds like a dual pressure control. Most likely its tripping on high pressure. Dont think Ive seen a dual control with low press. reset.

correct, check condensor fan bearings, could be over heating going off on thermal and cooling down by the time the high reset is pushed. Condensors often look clean I always blow them out anyway. Test high pressure control.

[jeep6275]

definately blow/wash out the condensor. it can look clean and still be dirty?

does this unit sit outside? if so does it have an HPR and could it be sticking from time to time? i had this problem just the other day.

[jpsmith1cm]

Verify the setting of the control by S-L-O-W-L-Y front seating the discharge valve with a gauge connected.

If you are uncomfortable with that, remove the control and use nitrogen to test it.

Those scales are not accurate.

[dmd-marc]

The head pressure trip is set at 375/ The ambient the other day was 84 deg adn the head pressure was at 275-280psi. But that doesn't mean it isn't tripping. Just witnessing it is the issue.

[flange]

general rule of thumb is ten degree lower evap temp than desired temp in box, and head at 20-30 above ambient. we like to see subcool in the 5-10 range but all you need is solid liquid to the expansion device. I think as the other suggested, you need to first check the setting on the high pressure cutout as those scales are for amusement only. once that is correct, assume the fan motor could be an issue and keep an eye on it. only other thing I would suggest is to make sure the air off the condenser is not recircuiting.

[dangpgt97]

Change the condenser fan motor. One of my first problems in the field was a occasional head pressure trip. Never did it when I was there. Finally found the fan motor was occasionally dropping out.

Some other simple things you can verify... Can you pump the system down by closing the reciever outlet without tripping head pressure. Does it get close to the trip setting? Is the head pressure regulating device sticking open?

In this situation I might strap a data logger to some of the lines.