ReplyFor what it's worth, remove the defrost circuit and put a new temp control in it. I wouldn't try to reengineer it. I've done it before with Perlick glass chillers changing them into bottle coolers.
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I have a small 1250 btu McCall under counter two door reach in. Uses a 1/3 hp compressor & R404. Our restaurant manager at this location asked me to fix it to be a cooler for coffee creamers, beer glasses, etc. I think this unit has a small refrigerant leak too. But I haven't pressure tested it yet or took a real hard look for a tiny leak. I think I added a very small amount of 404A five months ago but now it's running high temps.
What's the opinion here? Can this unit be re-sized for med/high temp use using the same compressor, a new properly sized cap tube, dryer and a new thermostat & possibly converting to R134? This is pending I can find a repairable leak if it fails a n2 pressure test. I was think a Ranco constant cut-in A12-701 for a stat inserted into the evaporator. Also, the cost of labor is not a big consideration. This company hates buying new equipment.
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For what it's worth, remove the defrost circuit and put a new temp control in it. I wouldn't try to reengineer it. I've done it before with Perlick glass chillers changing them into bottle coolers.
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X2, I've seen and done this a few times. Then if they want to go back to it being a freezer just hook the defrost back up and put the old temp control back in.Originally Posted by 2sac
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Avoid a coil sensing thermostat. Since it is a freezer with cap tube, the coil may run colder than if it were designed to be a cooler and it may not behave like you hope. Just install an air-sensing thermostat, like a 1609101 White Rodgers in the return air. Leave defrost intact, no reason to disable the defrost! (Especially with air sensing thermostat).
I had a coworker try to convert several Delfield undercounter freezers into coolers, by installing A12-700's in the coils. Didn't work, cycling off prematurely. He had to try to rig it up by not really sticking them in the coil, and the boxes still do not work right to this day, will pull down to 20*f and not cycle on until 55*f. (This particular unit also cycled the evaporator fan with thermostat, which just made the situation worse) Sad!
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Before doing anything be sure to warn the customer that it will be hard on the compressor because of the higher pressures, higher amp draw, warmer suction gas in which to cool the compressor, and frequent short cycling due to it now being oversized.
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I would still disable the defrost heaters, even if an air sensing stat is used. With the unit now being greatly oversized, it should run short enough cooling cycles with enough off time to prevent ice buildup.
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I guess my way of looking at it is, the potential downside of NOT having defrost, is a possible freeze-up. The potential downside of leaving defrost intact: Nothing. Plenty of walk-in-coolers are set-up for electric defrost, and some Traulsen coolers even use electric defrost.
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+1 Good advice.
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One downside could be that the defrost fan delay switch might cause wacky operation of the evaporator fans due to the colder evaporator temperature that it will be looking for. You might want to at least jump that thing out. If you do jump out the defrost fan delay, though, it will be even harder on the compressor due to the hot evaporator coil when coming out of defrost.
If you have enough time to spend on it, I would jump out the fan delay switch, and rewire the time clock to work like a standard cooler defrost without the heaters.
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If you added 404a five months ago and now it's running high temps, could be a plugged cap tube and not a leak. Agree you should do a N2 test. Running the compressor at higher than design temps will be hard on it.
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I agree. Replacing the cap tube was part of my plan as mentioned earlier since I believed (at the time) it could have a partial restriction. I didn't like the way this unit worked last time I was checking it out. Honestly wasn't sure if it was low or restricted. Cap tubes can be head scratchers for sure. A previous tech had opened it up so it wasn't factory. I'll know more today when I look at it. Thanks everyone for the input. And I will stay away from the A12-701 & use more of a standard temp controller.
Gonna be 56F today so I'll roll this sucker out the back door and have better light & space.
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Another good point by AmmoniaDog, you will definitely need to disable fan delay. I totally forgot about that. And as far as diagnosing the unit, the most surefire way to diagnose a small unit like that is to recover, pull quick vacuum and weigh in the charge. If it now starts working (as a freezer) then it was low on charge. If it still doesn't work, more likely a restriction.
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It's done & working good.
Did this job yesterday, hooked up my stubby gauges before doing anything. Pressure was good but freezer still wasn't cooling below 45-50F, had to be restricted cap tube. I ruled out a leak. Reclaimed 12oz 404, installed new 68" Supco #2 cap tube along with Sporlan 032 cap dryer. Leak checked with N2, evacuated & charged 12oz R134. This old McCall had a standard 8145 timer, I set it up for (2) 12 min defrosts 12 hrs apart. (May not have been necessary but figured it couldn't hurt for what this cooler will be used for. I may disable if need be next time I visit or if I receive any complaints.).
Low side pressure 8psi, high side 90psi, ambient out back (worked outside) at the time was 55F. Installed a new Ranco temperature controller ETC-111. (This is the only temp controller I use, always carry one or two and replace older spring style Ranco or Penn when necessary). Once it was cooled down, the refrig unit will only need to run for about 5 mins . CI@39f, CO@36f My SH at the compressor was quite high at about 35F. But the unit was only cycling for a short time. Probably would have come lower. I would of set the temp controller to 35F but the unit continues cooling after cycling off.
Couple of thoughts. I realize the SH is high & the suction is low but working with an evaporator about 2x the size I think this will work out. The Supco chart indicated 79" #2 for medium temp, 39" #2 for high temp. for a 1/3hp pump. When do you use the medium temp length and when do you use the high temp length? I took 10" off of the high and went with it. Maybe I could of went shorter?
I really like the ETC-111 and/or the A419. I am done with Ranco spring style T-stats. The time you save setting temps is worth the extra $10 you pay. And the little extra wiring is never an issue for me.
(How many times did you have to climb in and out of the walk-in freezer to make sure your dif is set properly on an old Ranco? PIA)
I guess I did re-engineer, we'll see how it's working in a week or so.
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I would normally use the med. temp lenght for a cooler running this temp. Is that right? I thought the high temp. was for A/C or a cooler that ran 50 or above.
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Interesting experiment. I don't think most people would have the balls to change refrigerants like you did, it's good to think outside of the box sometimes.
A few things that I am curious about, though... I know that some compressors are designed differently for different refrigerants and applications. There might be a bunch of compressors that have a 1/3 hp motor, but they might have a different piston and/or crank size depending on what refrigerant and/or temperature they will be running. Did you do any checking to see if your compressor was rated for high/medium temp with R134a? If it is rated for low temp only, you might be causing problems by running it with such a warm suction temperature, since it is designed to be cooled by the refrigerant.
How warm was the compressor shell? How was your amp draw? Did you keep the defrost heaters and/or fan delay? Did you warn the customer that this was an experiment and that the compressor might not last long?
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Ammoniadog. I am the in-house & only service tech for a company in which owns 30 P Huts. I am the boss, the parts man, and service tech of my one man department.The unit is useless to us at this location as a freezer. And it was about 10 yrs old & original compressor. Someone opened it up once about a yr ago, installed taps & a Sporlan dryer but didn't change the cap tube. This puzzles me.
The unit ran much warmer with R404. A previous refrg tech company to me actually wired the condenser fan to run continuous. I wired it back to normal operation. The compressor was running much cooler yesterday, the head of the compressor was at best warm temp. I did not bother checking amp draw with so low head psi. And I didn't actually check R404 vs R134 but I have seen many small compressors of this size in some of my equipment with a label showing R134/R404. Is this really a concern with fractual compressors with POE? And my compressor ratio hasn't really changed. My biggest concern is with the low suction, I was hoping to see closer to 20psi which may actually happen come summer when the kitchen heats up. I'll check on it later in the week and run it thru a defrost to monitor box temps. But I don't see an issue with the electric heaters, All of my Traulsen VPS120's Make/Prep Tables all have electric defrost with fan delays.
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You don't want to run the heaters in a cooler. Plus you have to have the fans wired to run full time. The fans are the coolers defrost.
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Re-read the last sentence of the part that you quoted above.
I agree with you that heaters aren't needed in most coolers, and especially in this situation, however they are used sometimes. Some coolers do use the same type of defrost cycle as a freezer. Usually ones designed for high humidity (like a retarder) or for maintaining temperatures close to, or slightly below 32 degrees (like a beer cooler). In these situations, the fans do shut off during defrost and they usually have a fan delay afterwords.
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I will go along with the retarders. Aren't sure if below 32 degrees is a cooler or not. In any case there are exceptions to everything, along with special applications.
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All of the Traulsen prep tables I see running R404A use electric defrost. Temps in the coil drop to about 12F and the doors are opened often in a busy kitchen. In fact, I was thinking what you wrote above, I eliminated the defrost cycles on a unit last summer in an attempt to have better cooling. I was back two days later with iced evaps. I felt just a little bad...
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