Replyyou check the defrost termination?
Professional Member*
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
Professional Member*
you check the defrost termination?
Regular Guest
Put it in defrost and see what it gets up to.
Professional Member*
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.
Professional Member
What is the customer resetting?Originally Posted by socotech
If you find that out, it will lead you to a likely cause...
Professional Member*
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.
Professional Member
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?
Professional Member*
They unplug the main power cord for a while then plug it back in.
Professional Member
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.
Professional Member
Sounds like to me you already have determined atleast part of the problem with the hot air recirculation across the condenser coil.
Professional Member* / ARP Committee
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.
Officially, Down for the count
YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET
I know enough to know, I don't know enough
Why is it that those who complain the most contribute the least?
MONEY CAN'T BUY HAPPINESS. POVERTY CAN'T BUY ANYTHING
Professional Member
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?
Professional Member
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.
Professional Member* / ARP Committee
We have had numerous issues with the relays on the grasslins welding shut or stuck open ONLY on True freezers. From what I understand, it happens during the inrush of current on startup. The older True design had a Paragon timer. This is from memory, so forgive me if I'm wrong. When True first changed over to Grasslin, they were wired the same way. After having problems, I believe the factory installed a relay in the electrical compartment. The grasslin timer energizes a relay, and not the compressor directly. If you have a unit without a relay, I'd recommend the Paragon
Officially, Down for the count
YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET
I know enough to know, I don't know enough
Why is it that those who complain the most contribute the least?
MONEY CAN'T BUY HAPPINESS. POVERTY CAN'T BUY ANYTHING
Regular Guest
If it gets down to _20f .. you probably don't have a refrigeration problem , but rather a control probelem. Thermostat sticking, defrtost timer sticking, defrost termination sticking,loose wire, burnig (going bad ) overload on compressor, burning (going bad ) contact on timer. Afew things to check. You may have to baby sit it to catch it. I also do not like the Graslin. The Paragon ued to be "bulletproof" but I think that all of thagt stuff is foreign made now and the foreigners do not have "high quality " in their vocabulary.
Professional Member
Now I got ya, makes scene.
I do the same to MR4 controllers. (install external relays)
Good ole mechanical time clocks had nice contacts...these electronic time clocks have crappy relays.
Professional Member*
Im going with defrost termination switch , or t stat
Professional Member
Make sure the self closing door hinges are working. Because something I've often seen is the customer gets in a hurry and the doors don't get shut all the way, this causes the evaporator fans to turn off, and they don't really notice until the box is already at 35*f, although this still doesn't really explain 80*F box temp.
I agree like everybody else says, probably defrost termination switch is not terminating (or it is, and the timer solenoid or release relay has failed) causing it to stay in defrost for much longer than necessary until box gets so warm.
Professional Member*
Just a follow up. I did go and babysit the unit for a few hours and definatly air recirculation problem. Air into condenser getting up to 106 degrees after about two hours of operation and 74 degree ambient. Put a box fan near condenser and it works fine all day. I wonder whats going to happen when its 100+ this summer.
Regular Guest
Is your compressor hot upon arrival? What happens when your unit goes into defrost?
