Walkin freezer temp

[mech_head]

I went to a freezer today in a building that we do all the other work in. I don't do alot of refrigeration but its a good customer and they just fired there refrig. company. Anyrate it is a keeprite evap KUCB204DED. They have the temp of the box at 17 deg. F. They have no open food, just boxes of whatever, I didn't look too close, I am going back with a new evapmotor in the next day of so. Is 17 deg. kind of random? I don't see anything else at that and they have a walkin cooler next to it off of a different system entirely.
I don't trust the co. that set it to that. They used to take care of the whole building and I have been cleaning up there crap for months now.

[gbfromsd]

0 - 10deg is more typical for food storage.

[primmers]

i would set the t-stat for 0*f or set the psi control for that temp. see if that brings it around, while your waiting for the temp to drop, make sure the coils (both) are clean.

put a set of guages on it..17*f is a bit warm for a freezer.

[mech_head]

i would set the t-stat for 0*f or set the psi control for that temp. see if that brings it around, while your waiting for the temp to drop, make sure the coils (both) are clean.

put a set of guages on it..17*f is a bit warm for a freezer.

That is a good point. The co that left did just replace the compressor. Maybe it is at 17 because something else is wrong. Well, obviously something else is wrong, all they did was replace the compressor. Apparently it had a broken crankshaft.
Condensing unit is a K300L6-HT3A-0027

[tjc76]

i do work for a commercial bakery. they set their freezer for 13*. it is strange, but not totally uncommon. what does the customer want it set for? as long as they don't store ice cream, which they probably don't or they would have called long ago, 0* will be fine for a holding freezer. as primmers said, check the coils . check superheat, typically between 20-40* at the compressor, and 4-6 at the evap for low temp (check this when box is closer to 0*) you can check subcooling, although this is not so important as subcooling "is what it is" on receiver systems. as long as it is not extremely high. obviously check for a clear sight glass. check net oil pressure. check defrost operation, time clock setting, failsafe, is x hooked up to clock? check all heaters for amp draw. document amps for everything, defrost, evap fans, compressor, cond. fans,etc... this will make it easier for you or the next guy from your co. who goes to work on the unit, they have a reference point of which to work with and can tell right away if there is a bad evap motor, def. heater, etc... check defrost termination, check fan delay after defrost. check compressor superheat after defrost, make certain there is no floodback. check many other things i have forgotten to mention. good luck

[tjc76]

That is a good point. The co that left did just replace the compressor. Maybe it is at 17 because something else is wrong. Well, obviously something else is wrong, all they did was replace the compressor. Apparently it had a broken crankshaft.
Condensing unit is a K300L6-HT3A-0027

broken crankshaft = flooded starts or slugging. check crankcase heater. also, does the site have a lot of power failures? if the power goes out long enough on low temp equipment, evap and crankcase will flood with liquid. on restart, there goes the crankshaft. sell them a phase monitor with manual reset. you have to go back after power failures and throttle the valves to restart, but it is cheaper than changing a compressor. new compressor $5000, $150 phase monitor, priceless. also, check superheat, especially after defrost.

[iraqveteran]

Freezer temps are typically at 0*

Some places like to keep the freezer a little warmer like around 5* to 10*. That is usually based upon customer preference.

If they keep ice creams products.....gotta be at 0*. Won't stay at anything higher.


And if its a DippinDots......they have to be at -40*.




Check with the manager. Ask them what temp they need for the freezer. They will tell you what the health department requires. And go from there.

Make sure the sight glass is full. And check the superheat to ensre proper operation of the TXV. Most TXVs on refer equipment is adjustable. So check that if its off.....you may be able to fix it on the spot.




Good luck and let us know what ya find. We always like to hear the success stories.

[Slatts]

Check the LLSV doesn't leak through during defrost...

[mech_head]

So I went back today and as it turns out the building operator that showed me the freezer was wrong. The thermostat was showing 17 when we got there so questioned him on it and he said that is what it was set for. I went there today and it is set for -10. Replaced evap motor and then forced the system into defrost. The heater on the drain pan doesn't work all the way across and the compressor ran the suction to -15 psig and just stayed there and stayed on. I left it for a bit to make sure that it wasn't going to shut off then I adjusted the diff on the pressure switch. I cycled it and it shuts off at about 0 then drops for a half second then stays at 0 ish. It doesn't really raise during defrost to much.
All the defrost heaters work.
The suction is at 20psig and the head is at 300. It is 404A.
Before the accumulator the suction line temp is 21
After the acc. the suction temp is 33 and after going through the filter and vibration absorber at the compressor the suction temp is 45.
At 20 psi if the box ever got to -10 that would give me high humidity, right?
I am going to insulate the suction line as much as I can. See if I can keep the SH to 20.
This system doesn't shut off.
The door has two inch rubber sweepers that run across the floor when opened - 62" door. Doesn't seal well at all. Another cause for high humidity.
The TXV bulb wasn't insulated.
found a leak at fitting at LLFD and SC was at about 4-6 deg.

[mech_head]

I went back today and changed the second evap motor. I put it into defrost and out, when it came back out the fans came on right away. Found the fan delay sticking.

Now for the questions.

I got the SH down to 18-20 deg at the compressor by opening the TXV When the box was at 0 ish. A TXV controls SH so I shouldn't have any problems with that when the box comes down right?
The box is set for -18 because they keep a tub of Ice cream or two in there. Is that right? Seems like a waste.

[tjc76]

you should be okay with the superheat, but make sure that you check it after defrost. make sure that there is no floodback. if it is flooding back, the txv will need to be throttled down.