View Full Version : Fresh meat display, freezing evap. Coil…
12-27-2005, 08:11 PM
This is an old unit, converted to R22 refrigerant a while back. It has a pump down valve, but no defrost system, at least it’s not working; the wiring has been modified from a local bricklayer…
The pressure is 180/30 psi, all evap. fans are working.
The end of the evap. coil begins to frosting after a day or two, the rest is working fine.
Definitely, there is enough freon in the system, frost shows up only on the end off the coil.
No freezing on the suction line back to the compressor, (restricted air flow?)
Does this system require a defrost system? There are el. heather coils installed, but obviously not wired up right.
Some of the evap. fans have 3 wires, one wire used for slow (reversed?) motion.
Should a paragon timer be installed with compr. OFF – Fan and defrost heater coils ON?
Alternatively, should I simply get a stick of dynamite or should I wait till my customer does it...
Any help is greatly appreciated – thanks – walter.
[Edited by walters on 12-27-2005 at 08:19 PM]
12-27-2005, 08:30 PM
IS this a capillary fed system or a txv?
make sure your fans are the correct fans, and going the correct direction.
make sure the low pressure control is not sticking on, or t--stat/cold ctrl.
check the temp of the inside of the controlled space, then
see if the t-stat is satisfying?
check to see where the frosting is coming from it should be normal from the txv to the evap, did u weigh in the charge, and was the txv changed with or to the new refrigerant? what was the old refrigerant?
need to go through these type of things ,, hard to say without seeing or doing these things!
I wonder if the system was bypassed to stay running all the time? does it ever cycle off? can u see if the compressor has a control that cycles it off when the temp satisfies
[Edited by coldspot on 12-27-2005 at 08:32 PM]
12-27-2005, 09:36 PM
You have to go through the numbers. IS the unit right capacity. Is the TXV correct. Start with a subcooling measurement. Then superheat. Rewire the evap properly.
What is the history, why was it converted, what different. Had it always worked like ****, or just started to?
Most meat stuff, you'll see defrost equipped.
12-28-2005, 07:29 AM
I don't know much about this unit; the owner changed a few moths ago. The new owner contacted me instead of the previous service company, they’re 60 miles away.
The sight glass is clear, the unit cycles but is mostly ON. It has two evap. lines 12 feet long each with TXV’s. All 6 (or 8?) evap fans are running right direction and full speed, I’ve changed 2 fans on my first visit.
The air coming from evap. is about 22º F. I believe that this unit has a bypassed defrost system; the heating coils are still installed but the timer is missing. Does this system need a defrost terminator thermostat (50º ?) or is it just controlled over the timer?
Why is just the end of the evap frosting?
I’ll check the superheat today and let you know.
The butcher told me that they have a long history of problems with this cooler.
Thanks a lot folks – Y’all take care – walter.
12-28-2005, 09:30 AM
We need more information.
Evaporator Make / Mod & Sr # to begin with.
Where is the frosting, on the distributer off the X-Valve or on the U bends???
What application is this for? Packaged product, Aging Box, Med temp?
12-28-2005, 01:04 PM
This is a fresh meat display cooler, very old and probably converted a couple of times. The evap freezes on the u-bends.
I will take SH measurments tomorrow and also check the TXV's.
Thanks for your support - walter.
12-28-2005, 01:37 PM
it sure require a defrost system ....
what exactly is the problem ?
have u check the honeycomb? it have to be remove!!
is it clean?
12-28-2005, 09:23 PM
if it is an old piece of crap box that takes a day or two to frost up i would install a time clock to break pump down circuit and not worry about fan controls or heaters.
12-29-2005, 08:00 AM
I'll check the honeycomb again today, at the beginning (before freezing) the air-flow apeared to be normal.
I definitely install a timer without heather and controls - thanks t527ed and thanks to everyone too!
I'll let you know - thanks - Y'all take care.
12-29-2005, 10:48 AM
Assuming this is an open case (no doors) the evap fans should run constantly both in refrigeration and defrost. For fresh meat display, 22-24 Deg F discharge air temp is good, but it definitely needs defrost heaters and a timeclock. Check out the heaters for continuity, install a clock and hook them up. Tie in the defrost termination thermostat if there is one or add one. Overheating the fresh meat will cause it to lose its bloom or redness.
Set the clock for two or three defrost per day with a failsafe time of around 40 minutes or so. Set your case thermostat for 22-24 Deg F controlling discharge air temperature with a close differential of 2 Deg F or less. For fresh meat, I like to have the thermostat control the compressor directly and pump down only for defrost.
The evaporator coil is building up ice from the ends because whatever off-cycle defrosting time it currently gets isn't enough to completely clear the coil. The heaters and proper defrost control should eliminate this.
12-29-2005, 11:41 AM
Didn’t Hill have a case with heaters and reversing fans? If this is that type of case he will need the proper type of defrost.
Still need Make Mod & Sr.
12-29-2005, 12:44 PM
The three-wire fan motors would kinda indicate a reverse air defrost case, but the existence of defrost heaters makes me think that it may have been converted to electric defrost at some point. Those RA deals didn't always work too well.
If Hill made one with RA and heaters I'm not aware of it. Then again, I may have been absent that day. ;)
An ID on the case would certainly help us in helping.
12-29-2005, 10:47 PM
Waren Sheer had a case that fans reversed and it did not have heaters, motors only had two wires I think, I don't know how they made them to reverse maybe a relay and run capacitor? The third wire he is talking about may be a ground? easy enough to check. There must be a timer somewhere that is not working. I would find out who manufactured the case and get in touch with tech-service and have them fax you a wiring diagram.
12-29-2005, 11:15 PM
last time I opened a meat case to check the coil .... there was enough junk down in there to feed an army of vultures!
It hadnt been cleaned out in ages!
THAT can inhibit airflow.
Also if some of the sheetmetal is missing or out of place ... the fans wont draw the air correctly.
Keep it simple.
12-30-2005, 12:30 AM
Originally posted by n8ies
Waren Sheer had a case that fans reversed and it did not have heaters, motors only had two wires I think, I don't know how they made them to reverse maybe a relay and run capacitor? tom n8ies
Yes indeed Kysor Warren/ Warren Sherer had reverse air defrost cases- particularly frozen. I know that their tubs (KW) were a two wire, and a cap was wired in line; problem was that if you slapped in a 9w instead of a 9w psc it would drag all the motors down in rpm- you would only notice this if you were careful.
They used a relay in rail for reversing. Thank goodness for progress.
Who was the manuf. of reachins that the case top would open during defrost....just curious I forgot.
Hill hasnt had a rev air case for a while but they are out there= still packing a couple of those turd 3 wire motors around on my truck. They remind me of bowling balls on most sharp left turns......
WALTERS!!! Dude give us real info if you seek advice- its funny but if you want sincerity at least narrow it down...
[Edited by thegoodhumorman on 12-30-2005 at 12:47 AM]
12-31-2005, 02:45 AM
I believe it was Kysor Warren/ Warren Sherer that had the doors on the top of the multideck freezers? that opend up during defrost, I have seen some but not lately. Now that i think back it was the Warren Sherer glass door reach ins that had the doors on top that opend up during defrost I remember helping my dad install one. Can't remember if it was freezer or cooler (I think freezer)
[Edited by n8ies on 12-31-2005 at 02:51 AM]
01-01-2006, 12:34 PM
Proper meat case operation is critical in any market. Especialy if it is a multi or single deck open case. The butcher cuts it and puts it in the case and if its not working correctly he knows the very next day. They can be slicing 60 degree cheese in the service deli and not have a clue. Ice is pointing you down the proper road to victory. Airflow, defrost, and correct temp control setting are critical for the butcher to get maximum shelf life. If those are reverse air fans the wire colors should be black,white, and blue.
01-19-2006, 07:39 AM
Sorry for the late update, I am still quit busy...
Thanks everyone – a special thanks to Icemeister!
I’ve installed a timer, set to 4 cycles @ 30 min. It works just fine, but I need to clean the honeycomb on my next visit because the air distribution is not consistent.
If I discover any more problems with this old unit (open meat display), then I’ll install a second wire to hook up the defrost heaters.
Well – for now it works without any problems – thanks a lot folks!
Y’all have a nice day – walters.
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