Low-temp freezer will not reach setpoint
I am a licensed HVAC&R Tech with 11 years experience, but I do not have a lot of experience with walk-in freezers. I am new to this forum.
I have a small 6X6 that will not reach a setpoint of -15 degrees. To the best of my knowledge the unit was maintaining temp before a compressor failure 3 days ago. I was able to get an exact replacement for the compressor. After intallation, it pulled down very slowly, but there was a good deal of moisture in the box (floors and walls) and it has been very humid (around 70 percent with temps in the high 80s to low 90s). With all of the moisture, I was not too concerned that it was pulling down a bit slow, and I was at the end of the day.
I checked on the unit this morning, after 14 hours of run time, and it was hovering around 9 degrees. By this afternoon, a full 24 hours running, it never went lower than 2 degrees. I was replacing a compressor on another unit - so I did not have much time to check this one out again. I did get the following information:
-15 Ice Cream Freezer - R-404A
Box Temp: 2 degrees
Suction Pressure: 20 psig (Sat. of -15 degrees)
Ambient Temp around condensor: 95 degrees
Discharge Pressure: 330 psig (Sat. of 124 degrees)
Suction Line Temp at Compressor: 32 degrees (it is not very easy to get a temp at TXV bulb while it is running as you have to drop the fan housing to get to it)
Compressor amp draw: 9.5 (Rated RLA of 11.4)
I also did try to do a quick pump down (but it is not a pump down system - just to clarify) to check the compressor even though it is new. It took a few minutes to even approach zero, and I could not wait long enough for it to get all the way down (which it did not).
Any suggestions? I am just stuck, and I find it hard to believe that a new compressor is bad.
I realize that I posted this in the wrong place. Sorry - I was pretty tired.
You need to get your superheat dialed in. As close to the bulb as you can get.
Need more info.... model numbers
Isn't sanity just a one-trick pony anyway? I mean, all you get is that one trick, rational thinking, but when you're good and crazy, well, the sky's the limit!
It is in the correct forum, now.
Originally Posted by minghex
I don't have as much experience as most other guys here, but...
Isn't your suction pressure a little high? You should set it 7-10 degrees *cooler* that your walk in's set point. You should have a suction psi of about 13...not 20. I think...
There is one red flag- you should be able to pull into around a 12-15" vacuum and hold it with the compressor off.
Originally Posted by minghex
Both suction pressure and superheat seem to be high.
Experience is what you have an hour after you need it.
the old method of pumping a compressor down into a vacuum to gauge its condition can be misleading sometimes. your best next step on this compressor is to get the model number, get a compressor performance chart for it (if it is a copeland you can get it off the web, or your supplier of that compressor can provide it) plot your suction and discharge(at the compressor) and compare amps to see if it is efficient. I remember once having a brand new ice cream freezer compressor that took a while to pump to 4 inches and i thought it odd, but a compressor curve showed its plotted readings dead on and it was way out of its operating parameters even close to 4 inch vaccum suction.
Is your sight glass clear?
Emerson has a program that can do that for you in real time.
Originally Posted by r404a
Emerson Product Selection Software