I like 40 and 34 better. Havnt worked on a random defrost so im no help there. A regular timer will work fine, Grasslin makes a nice one.

 

Put your flame suit on... your gonna need it. I'll give you some usefull info before you get berated.
Refrigerators don't neccessarily need a defrost time clock. Many times, they are a bandaid to a problem. Cut that differential back to 5, say 40 and 35. 41 is the highest refrigeration temp you should see. Way too many factors involved here. good luck.

 

This is a walk-in not a refrigerator. People are in and out of them allowing tons of humidity in. This freezes on the evap. just like in a refrigerator, which also uses a defrost timer btw.

 

i feel comfortable knowing a WIC has at least one, 1 hour defrost cycle per day when store is closed & nobody is there .. i agree with ar_hvac_man about grasslin clocks .. i keep a DTMV40 in the truck at all times !

 

Did I say a clock was wrong? I said it does'nt neccessarily need one, just because it's a walk in. I'm in a high humidity area and have walk ins with no defrost clocks. I have more with them than without though. Just making it clear, that it's not definitely required like a freezer. I'm going to leave the rest alone, I don't like to argue.

 

Set your low pressure control if it is adjustable to shut off about 34* and to come on about 40* this will shut the condensing unit off and hold it off till the ice melts no matter what the tstat is set at our how long they prop the door open. This usually works.

 

All the WIC we deal with stay set at 35-39. 40 max.

We don't have defrost timers on any of them. The simplist thing to do is check the system out after you have thawed it out and then check gaskets, hinges, and closers. Then watch everyone walk in and walk back out without closing the door tight.

Usually what I do is me and the manager sit in a corner and watch. after about 10 minutes of the manager seeing first hand what the staff is doing, they get the picture.

We try not to add a defrost cycle unless its absolutely neccessary. Not to mention, most our customers are too cheap to pay to have one installed.

 

We try not to add a defrost cycle unless its absolutely necessary. Not to mention, most our customers are too cheap to pay to have one installed.

Why not, other than cost?

I do keep a Grasslin on the truck. But for this I would put in a cheep paragon, no electronics, defrost for an hr and 15 min at midnight to one fifteen.

No adjustable pressure ctrl. on this one, all the cheep fixed type, HP Ctrl, LP CTRL and Fan Ctrl.

 

what's your saturated suction when the room's down to temp and the coil is clean?Set your LP to cut out about 6 or 7 degrees saturated equivalent lower and cut in at about 38F saturated. I'm using saturated temp as you didn't give the gas type.
Set up this way, the system will normally cycle on the thermostat but if it starts to ice up and won't pull temperature the ice on the coil will stop the airflow, causing the pressure to drop. The compressor will shut down on LP and stay off till the coil reaches about 38F at which time it should be defrosted. It will also do a cyclic defrost every time it goes out on thermostat.
Or you could just fit a defrost timer.
I always use one with a battery backup. That way if you loose power for a few hours your 45 min defrost set to end 2 hours before the busy period doesn't migrate to the middle of the heavy use period.
Still set your LP to cut in at 38F to give a cyclic defrost.

 

No adjustment on the LP control. Factory preset snap action type.

 

What condition is the evap coil in? The "off cycle defrost" will not do the job if the coil is in poor shape and has low TD.

 

The whole set up is 2 years old. New building and all new equipment. The business was closed down last fall, and re opned 6 months later with new owner. I already had to replace the LP control on the WI freezer, it was making the contactor chatter, so it fried the contactor as well. Now the WI cooler I think the LP control is fine, just got froze up on a busy day with high humidity. I don't have the numbers for the controls on the cooler in front of me, but it seems to be running fine so far. As far as replacing the LP control, it will cost them much more than a timer. No way to isolate the existing LP and is is brazed into the suction line at the compressor. I replaced the one on the freezer with a Jonson Controls, but had to pump the low side of system out as there are no isolation valves. That means more time and parts. So they will get a timer on Monday.

 

That CU sounds like a RDI/Kolpak is that correct?
A sweat on LP,HPand FC without a king valve.

 

Yea, not sure on th brand, but that is the set up. Ment to get there today and never made it.

 

Have you had any problems with ranco controls. I quit using ranco because I had several fail after just two years service on pilot duty circuits (no more than 3 amps).
Switched to johnson controls but found the calibrations way off. Tried digital temp controls, but they kept getting knocked out by power surges. Finaly switched to danfoss. Thought they ehere cheap looking but have had good success so far. They do have one great advantage you can see the points and can tell if they are burnt or opening and closing. You should check them out.

 

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Have you had any problems with ranco controls. I quit using ranco because I had several fail after just two years service on pilot duty circuits (no more than 3 amps).

was your differential set to close, causing excessive wear on the contacts?

2 years is a lot of cycles!



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