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spidertrany2k
08-05-2011, 02:21 AM
Hello everyone,
I am air conditioner guy with basic commercial refrigeration. got a call to from him and it us usually for a/c work. but today he surprised me. took me to a vegetable case or two. tell me that it is now cool enough, check with my k meter right after the expansion valve and it was showing 62 F. i thought that was too high. i would think that the idea temp right after the expansion would be 20 and 25 F. that would probably get you about 35 to 40 F in the air. took me to a room and show me the system that runs all the cases the the supermarket. am like WTF? but i learn not to panic. after pokering around little bit i learned that the system first of all is very old. 502 refrigerant, Hussman. it has 4 compressor but one is not running breaker is on the of position. the other 3 running consistently. 2 were pulling about 20amps, but one was pulling about 25-28amps. check the pressure, low was at about 55psi, high side was about 175 - 180psi. i also learned that that they link together it looks like. so the that failed it does seem to matter at the moment because the other 3 are still running. i check the condenser fan and it total of 6 fans and all but one is not running. come to find out it was set but pressure so i moved the pressure control just see if the motor was working and it did.
so now here is my question. if the system is supporting all the cases in the supermarket. how come just the 2 cases that the veggie guy is complaining not cool enough. i like to adjust the expansion valve but it was so hard to loosen it. i don't want to kink the pipe. is there a trick to this. one guy told to me heated up first, not sure about that one. maybe all i need is better tools like 2 adjustable wrenches. also im guessing that the system is probably running on R22 because i don't think 502 is available any more. i learn that this type of system is a whole animal in itself and i understand that it is. but for now i like to see if adjusting the expansion valve will do the trick maybe it is just too dam old and clog up. please help

jpsmith1cm
08-05-2011, 07:10 AM
Racks are a peculiar animal.

The two cases could be warm for a variety of reasons.

Could be low on gas. Could be a problem with one of the control valves. Bad fans. Bad or mis adjusted txvs. Iced up.


i like to adjust the expansion valve but it was so hard to loosen it. i don't want to kink the pipe. is there a trick to this. one guy told to me heated up first, not sure about that one. maybe all i need is better tools like 2 adjustable wrenches.

Repeat after me.... Backup or you WILL @$*% UP. Using two wrenches on threaded fittings isn't optional, it is mandatory.

rmuntz
08-05-2011, 08:53 AM
Always, always, always use 2 wrenches or you will be getting out many more tools to repair the damage you did with 1 tool.

Phase Loss
08-05-2011, 09:07 AM
there's a good chance your 502 rack is running 408

spidertrany2k
08-05-2011, 10:25 AM
thanks guys. the case has no ice. i put my k meter right after the txv and it is reading 62F. normally what degree it is for vegetables?

jpsmith1cm
08-05-2011, 10:38 AM
thanks guys. the case has no ice. i put my k meter right after the txv and it is reading 62F. normally what degree it is for vegetables?

Depends.

I typically run produce at 20-24 degrees coil temp

However, depending on where you clamped your thermometer, you may get different readings.

Take a proper superheat and you'll know more.

spidertrany2k
08-05-2011, 11:33 PM
do i check the super heat at the case or at the compressors?

spidertrany2k
08-05-2011, 11:35 PM
how do verify the actual refrigerant in the system if there is nobody has a clue.

Joe Harper
08-05-2011, 11:46 PM
Check the superheat at the case. Look a foot or so after the evap outlet and you will see the pressure port.to find out what refrigerant you have you would need to take a vacuumed recovery cylinder and fill it with some liquid refrigerant (not all the way) and use your pt chart.
be aware not all txv,s on veggie cases are adjustable.

spidertrany2k
08-06-2011, 10:20 AM
thank you Joe for the advise. i will look in to it and see if i can figure it out what refrigerant that way. also, can you tell the differences between the adjustable txv and the one that is not adjustable just looking at it? do you need to open the cap off first?

ammoniadog
08-06-2011, 11:04 AM
Before messing with the txv's, make sure the system isn't low on refrigerant. Look for a sight glass on the liquid line coming out of the receiver. If it isn't full, then you need to start there. Also, make sure you are looking at the right rack system. R502 is usualy used for freezer cases. There might be another rack system, or the produce coolers might be on their own condensing units somewhere that use R22 or R12.

ammoniadog
08-06-2011, 11:18 AM
Usualy the txv will have a sticker on the powerhead that will say what refrigerant it was designed for. If the case really was designed to run on R502 (or R408) it will have a purple sticker on it and it will say R502. If it was made for R22 it will be green, and R12 (or one of it's replacements) will be a white sticker. Like I said, verify that you are looking at the correct compressor or rack that goes with his case. Also, see if the store has any of their own refrigerant stashed away somewhere. Hopefuly, if it is still using R502 or R12, they might have some old jugs hidden away in a corner somewhere.

Joe Harper
08-06-2011, 01:59 PM
About the sightglass....the sightglass need not be full. The liquid level in the glass will depend on the receiver setup and if something is in defrost.
If the txv looks like it has a flat bottom its not adjustable. If you have a pressure port in the liquid line in the case, just push on the schrader core and see if some liquid comes out.

-frozen-ocean-
08-06-2011, 07:33 PM
Be like Columbo! search hi and dry in that machine room for old job cards or anything similar. Also if you know the owner ask if can go through old invoices to see what gas they charged him for. check for system number at cases then at rack. you have to first understand how it is being controlled. It make even have a LoadMaster inside the case. Good luck! Too much possibilites that can exist.

meoberry
08-06-2011, 08:04 PM
Be like Columbo! search hi and dry in that machine room for old job cards or anything similar. Also if you know the owner ask if can go through old invoices to see what gas they charged him for. check for system number at cases then at rack. you have to first understand how it is being controlled. It make even have a LoadMaster inside the case. Good luck! Too much possibilites that can exist.

Like he said. Be prepared for allot of head scratching. I used to tell customers, Hey! this thing is older than my daughter. It will take time to diagnose. Don't let it boggle your mind it is still just a refrigeration system. It pumps freon around to remove heat. Usually you can listen at the expansion valve for hiss or gurgling which would mean that it does not have a full column of liquid to valve. Then figure out why. Low on freon or some other control slowing flow could even be expansion valve. I might try adjusting valve as long as bottom of valve is not flat to diagnose. I usually will replace an expansion valve if it is not controlling superheat the way it is supposed to. I have had to many expansion valves make me look like an a@@ over the years. :grin2:

spidertrany2k
08-07-2011, 01:34 AM
thanks ammoniadog. i really like your input. especially about there could be another rack somewhere because i do recall that the txv was gray in color but don't see a sticker on it. possibly had been removed. also, the store supervisor was the one who took me to the mechanical room and said that ''that's the rack'' but now that i think about it. he probably don't have a clue. there could another rack on the roof top. i will find out when i get the opportunity.
also thank you Joe. the txv has a nut on the bottom it was just so hard to loosen it. especially when it attach to the liquid line that is 3/8'' and no supporting. i used the 2 adjustable wrenches but did not put my full power into it because i was afraid if it slips, then i will kink the pipe then i will need alot more than just the expansion valve. not sure why it is so tough to remove the cap for it. i think it just too old and no one ever open it up before. i meant too young. still virgin :). but i was hoping i could be lucky. but just my luck i couldn't do it. so freaking sad. don't tell me try try again. i wish that there is a diagram that would show which system is supporting what cases like a blue print. but that would be asking for miracle. the only thing i find was some log sheets dated back in 1987. that don't mean crackly jack right now. im sure by now things had been modified and reroute, switch around, bypass that sort of things. i wounder what happen to the old tech. i will find out more about that when i talk the sup again.

spidertrany2k
08-07-2011, 02:09 AM
thanks ammoniadog. i really like your input. especially about there could be another rack somewhere because i do recall that the txv was gray in color but don't see a sticker on it. possibly had been removed. also, the store supervisor was the one who took me to the mechanical room and said that ''that's the rack'' but now that i think about it. he probably don't have a clue. there could another rack on the roof top. i will find out when i get the opportunity.
also thank you Joe. the txv has a nut on the bottom it was just so hard to loosen it. especially when it attach to the liquid line that is 3/8'' and no supporting. i used the 2 adjustable wrenches but did not put my full power into it because i was afraid if it slips, then i will kink the pipe then i will need alot more than just the expansion valve. not sure why it is so tough to remove the cap for it. i think it just too old and no one ever open it up before. i meant too young. still virgin . but i was hoping i could be lucky. but just my luck i couldn't do it. so freaking sad. don't tell me try try again. i wish that there is a diagram that would show which system is supporting what cases like a blue print. but that would be asking for miracle. the only thing i find was some log sheets dated back in 1987. that don't mean crackly jack right now. im sure by now things had been modified and reroute, switch around, bypass that sort of things. i wounder what happen to the old tech. i will find out more about that when i talk the sup

Joe Harper
08-07-2011, 12:59 PM
Why don't you try turning off the liquid supply to the valve. There should be a handle in the case. And pull the screen and see what's in it..

meoberry
08-09-2011, 09:51 PM
Why don't you try turning off the liquid supply to the valve. There should be a handle in the case. And pull the screen and see what's in it..

Best answer yet. If the valve is still there.:cheers:

frideman1
08-10-2011, 09:39 PM
look at liquid line manifold on rack .it is possible that your produce case cicuit is at the end of the run and the other circuits are fed first. in other words you may be low on charge. also checki your controls you may have epr valves in which case you may need more info . would like to hear more hope i can help.

Phase Loss
08-10-2011, 09:45 PM
look at liquid line manifold on rack .it is possible that your produce case cicuit is at the end of the run and the other circuits are fed first. in other words you may be low on charge. also checki your controls you may have epr valves in which case you may need more info . would like to hear more hope i can help.

backwards :)

a good rule is the first liquid branch will run warm first, because liquid will flow to the further systems first...but this not not always true, it really depends on how the store is pipped. But still it is a good rule.

When in doubt...shut off some liquid valves then sit and watch.