Do u have an accumulator ? It shouldn't hunt that much. Make sure it's sized right, bulb insulated, pure liquid to it, adjust for 6-10 at coil. You should have an accumulator with that short of a line set.
Hey guys, long time first time here. First post, and thanks in advance for all the help! Had a call for a walk-in cooler. Found evap coil half iced up. Defrosted and ran unit. Everything looks fine. The only thing I didn't like was that my superheat cycled from 2F to 12F consistently. I thought it was hunting and a faulty unit, so I called another tech. He was saying that it's common on those walk in boxes because they always cycle on and off too quickly to normalize. Your thoughts guys?
As a side bar, something else happened while on site. I see someone has added a hard start cap to the compressor. I watched the unit cycle on and off on temp a few times, and it all worked well, except once where it sounded like the pistons rotated at a quarter speed or something. Could I think that the txv is hunting, causing liquid slugging on rare occasions, causing my coil to freeze up faster than the defrost can handle? There is no CrankCase heater on this, btw. Indoor condensing unit right on top of box.
Thanks a lot guys for all your help.
Do u have an accumulator ? It shouldn't hunt that much. Make sure it's sized right, bulb insulated, pure liquid to it, adjust for 6-10 at coil. You should have an accumulator with that short of a line set.
no accumulator, but now that you mention it, it would be a good point. The suction side is probably 3 foot length, total. It's a packaged walk in, with a condensing unit on top, so I 'assume' the manufacturer put in the right size txv. I checked sight glass and compared against closing the king valve (full column of liquid). I checked the bulb, it looked good. Even if someone adjusted the txv before me (wouldn't be surprised), I would imagine it should have high or load SH, but not both. I would like to say faulty txv, but I don't want to jump to conclusions.
Sounds like txv working ok to me. Are all circuits in the evaporator frosting or just a few? That could cause coil to partially freeze up.
Assuming entire coil is feeding properly, the 2 to 10 degrees super heat just sounds like normal fluctuation of a txv. Remember, it is not flooding that causes frozen up coil, it is usually starving. If that is ok then check your thermostat and defrost controls, or electronic controller if it has one.
Make sure fan blade is not on backwards
I cant tell you how many I find reversed ... pulling half the amount of air
Got a new customer yesterday , checked over everything , found 3 blades on wrong causing compressors to overheat, and another wrong Motor with wrong rotation AND blade on backwards which had a blanket of lint on INSIDE of coil .... outside looked sparkly clean but hardly any air coming out
The only time I find that acceptable would be shortly after the box/compressor started and the TEV was trying to figure out where it should be. And even at that, it should only be the superheat that is fluctuating. The actual suction pressure should only have minimal fluctuations during this time. If you see wide swings in the suction pressure, then that is a problem.
How does the system act when down at temp?
It is also possible someone put in too large of an expansion valve, or the wrong power head. I love those balanced port valves; you get a strong pull down, then tight control at temp.
symptoms? sore throat, cough, fever, loose stool?
I hate it when that happens....
What are they using to control the temp? Humidity level in box? Drain clear? Drain trapped? Which half of the coil? Top? Bottom? Middle with top and bottom clear?
How would liquid slugging cause a frosted coil? What does a crankcase heater have to do with your diagnosis?
Officially, Down for the count
YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET
I know enough to know, I don't know enough
Why is it that those who complain the most contribute the least?
MONEY CAN'T BUY HAPPINESS. POVERTY CAN'T BUY ANYTHING
bbeerme is right on the TXV. sounds like you have gaps in your box. Check all box penetrations for caulk Electricians forget to caulk inside their conduit too.