true freezer works....sometimes

[socotech]

I have been working on a three door true freezer. It will pull down to -20f and a few hours later gets up to 80f. Have not caught it in the act. By the time i get there customer has reset and seems to be working fine. Thought it was sticking in defrost so i replaced defrost control. Got a call back today. Same problem. Any suggestions? thanks

[hvac wiz 79]

you check the defrost termination?

[lovetowork]

Put it in defrost and see what it gets up to.

[socotech]

I should have already provided this info, but this is a model T-72F. It is located in a mobile catering trailer. There is a three door cooler directly across fron it (cooler condenser blowing into freezer condenser). Exhaust fan does not work in trailer. I think the condenser air is recirculating and overheating compressor in the heat of the day (tripping snap disk on top of compressor). I told customer to open window and put a box fan in the door until ex fan is replaced. Also there is no service taps on condenser skid to check pressures. Condenser coil is clean. Both cond fans operational.

[Phase Loss]

By the time i get there customer has reset and seems to be working fine.

What is the customer resetting?

If you find that out, it will lead you to a likely cause...

[socotech]

Customer said when they find the box temp high, the defrost clock green light is lit and cond fans running (I know this doesnt mean the compressor is running). Also the evap fans not running during this time, but Im assuming the fan delay has them out until temp comes down.

[Phase Loss]

that description sounds like an open overload.

But what is the customer resetting? Could it possibly be a high pressure safety that's inline with the compressor?

[socotech]

What is the customer resetting?

If you find that out, it will lead you to a likely cause...

They unplug the main power cord for a while then plug it back in.

[Phase Loss]

defiantly sounds like a tripping overload.

I'm not familiar with True Freezers...But.

I would check the CRO if it has one. Also check the starting components.

[sgagne199]

Sounds like to me you already have determined atleast part of the problem with the hot air recirculation across the condenser coil.

[2sac]

FYI True freezers and Grasslin timers don't get along. Not sure if that is the problem but if you change out the clock again, use a Paragon.

[Phase Loss]

FYI True freezers and Grasslin timers don't get along. Not sure if that is the problem but if you change out the clock again, use a Paragon.

Whats the deal with this? I haven't worked on enough of them to know which clock is used more often. But how would the unit know?

[trippintl0]

FYI True freezers and Grasslin timers don't get along. Not sure if that is the problem but if you change out the clock again, use a Paragon.

Hmm.. I have to say I disagree, especially since I've started up brand new True freezers with Grasslin timers. All we carry on the truck stock is Grasslin clocks and we have never had a problem with them on True freezers.

But to your credit, I will say that when you are converting from a Paragon to a Grasslin, the terminal numbers (1,2,3,4,N,X,F) don't match up the same, and it can be a little confusing. The last one it took me a little while to think it through, but after I got it done it worked fine and hasn't had any issues for about a month now.