Adjusting TXV superheat.

[270wsm]

worked on a 1 year old walk-in cooler today. Two evaporators, R-22. Who ever installed it didnt bother to check TXV superheat. It was way off. So I atempted to adjust it properly. I have only had to adjust a couple in my shrt career as a tech and i seem to have the same problem every time. The superheat would go up and down from 20 down to 0. I made sure to wait 15 minutes between adjustments and I made 1/4 turns each time. I could not get the valve to quit hunting. Refrigerant charge was good. Anyone have any tips for adjusting a TXV?

[Andy Schoen]

Tip 1, 2, 3, 4:

Make sure the cooler is running near design temperature before making the final adjustment.

It doesn't make much sense trying to to determine proper superheat adjustment when the cooler temp is high. All you can do here is make sure suction pressure is up and you're not flooding.

Tip 0: Make sure you understand and can measure superheat.

[Freezeking2000]

I have found the same thing. Sometimes you just never get then to stop hunting. Insulate the bulb it will help.

[270wsm]

I do know how to check superheat and the box temp was around 40*. Thats pretty close to design temp.

[Andy Schoen]

Originally posted by ace12
I do know how to check superheat and the box temp was around 40*. Thats pretty close to design temp.

Then you know more than most when it comes to adjusting TEVs.

[icemeister]

If you were to survey every guy that walked into the typical supply house with the question, "How do I properly check superheat?"......more than half will say, "Superheat, What's that????"

[270wsm]

I agree Ice. I like to try to stay on top of the game. i strive to be the best teck i can possibly be, thats why I get on here and read just about every night and ask questions whenever i donk know something.

[the mojo]

ace12, Keep repeating to yourself Temp above SSV,Temp above SSV. Years ago had a newbe do a job w/ me and had to travel up North to Houghten Mi. He would not stop talking. After 2 hrs. of yak ,yak I got a word in edgewise. With one simple question how much do you know about TXVs ? Then it was my turn in a short time he crapped out. He has his own buisness now every once in awhile we run into each other thanks bud for the lecture it helped alot.

[vzcooler]

Hello, I am new here,but I like talking about this stuff,one thing you may want to check is the position of the bulb itself, I got a guy that works with me who thinks superheat is a certain hot day in August, also that it is ok to use compression fitting on line sets, and that a bulb is ok on top of a suction line.

[freezerfixer]

sounds like the valve is oversized. I replaced one the other day and misread the model number of the coil and put in too big of a cartridge. (sporlan "Q" body valve kit)
the valve could never find its happy spot.
my superheat would be 20 degrees and then the valve would open up and drop to no superheat at all within seconds.

anytime i build a valve, if i am between two sizes of orfices, lets say a 1 1/2 or 2 ton, i always go with the smaller size.
i may have to open the valve a little, but at least I'll have a more consistant superheat.

[selfemployed]

Originally posted by vzcooler
Hello, I am new here

If no one has welcomed you to the site consider it done

[Andy Schoen]

Originally posted by freezerfixer
anytime i build a valve, if i am between two sizes of orfices, lets say a 1 1/2 or 2 ton, i always go with the smaller size.

On a well designed evaporator with a properly sized refrigerant distributor and even air flow across the coil, having a somewhat oversized TEV shouldn't be a problem.

Unfortunately, this is not often the case.

[freezerfixer]

Originally posted by Andy Schoen

Originally posted by freezerfixer
anytime i build a valve, if i am between two sizes of orfices, lets say a 1 1/2 or 2 ton, i always go with the smaller size.

On a well designed evaporator with a properly sized refrigerant distributor and even air flow across the coil, having a somewhat oversized TEV shouldn't be a problem.

Unfortunately, this is not often the case.

yes, i agree. it just seems like i have had more problems with oversized valves than ones that were a little undersized.

i was talking to a friend of mine that works for another service company the other day about superheat and he said "I have never had to check superheat like you do."
i think he is more of a "beer can cold" kind of guy.