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  1. #1
    Join Date
    Sep 2006
    Location
    Chicago
    Posts
    474

    Thumbs down Old walk In Cooler

    Anyone remember me? Im the guy who took the 20 gas station maintenance deal 3.5 months ago. Well everythings been going fine as far as refrigeration equipment goes up until today. Job on the other hand isnt real great. Turns out one of the biggest HVAC companys in the state couldnt please the guy whos my boss. So you can figure what lifes like for me. Instead of saying see yah to the anus im stuck with him. Anyway...

    Im having trouble diagnosing stuff in the cold. Sounds like im a baby but today we didnt make it out of the teens and when market tech said I didnt know what cold was until i had worked on equipment with the condenser fan blowing on my face he was right. Now I know. So I get a call for a medium temp 6 door walk in cooler. Cooler normal runs around 35 today it was mid 40's. Unit is old no numbers on condensing unit and evap data sticker was unreadable. Sorta important for parts and stuff. But ok. Unit is R-22. Very
    simple. Thermostat, LLS pump down, Low pressure control, TXV, Semi-herm comp. no defrost clock just off cycle defrost.

    So I get there and unit is cycling on low pressure. Kind of strange since the site glass was full. Found a flare that was leaking so I tightened it up. I go to add refrigerant and get to 30 psi suction side and 168 psi high side both measure at service valve on comp. Ok so I add more refrigerant because its still to low pressure although the site galss is full. I then get to a point where this isnt working and its time to stop adding. Cause nothings changing. SH, SC same.

    At this point suction is at 30 psi or 10 degrees at serivce valve and superheat is 12 or 22 degrees at suction valve. Head presure is at 168 and did not change while I added refrigerant. Subcooling was 30 measured at reciver outlet. But you cant take these numbers as 100% accurate cause its 18 degrees outside and its got the condenser blowing on it. Yet all this is looking like crap the cooler gets to temp of 35 and shuts off. Now on the off cycle things get interesting. I watched on my guages as unit pumped down which it did. Then the pressure slowly rised to 25 psi which is the high event setting and cycled the unit on until 5 psi which is the low event. So Im thinking the LLS selenoid is probably leaking since its continuously cycling on while on the off cycle. I was gonna pump down and replace the selenoid but the king valve was leaking when the cap was removed(bad). These pressure just dont make sense to me. I learned in school that a cooler at 35 degrees should have a coil 15 degrees colder or about. So it should be more like 20 degrees.

    At this point Im frozen cause Ive now worked since 4:00 am this morning in the cold with nothing to eat all day. So with the unit acting like this I probably can expect the coil to be an ice ball. Right? I dont believe you can have a medium temp cooler with that temp coil and just off cycle defrost.

    Well I guess theres really only 2 parts to replace the TXV and the LLS. Guess someone could have mis adjusted TXV. Both coils clean and unit pulls down to temp just worrried about ice.Just not nice when you have no king valve. In the cold I just wanted to hit it with a hammer and go home.

    Let me know what you pros think. Something will probably come to me but I just cant think of anything right now. Thanks, Dan

  2. #2
    Join Date
    Oct 2007
    Location
    The rainy state
    Posts
    172
    sounds like a head pressure problem to me. the unit might be overcharged now. does the unit have a headmaster or a condenser fan cycling control?

  3. #3
    Join Date
    Jun 2005
    Location
    Las Vegas NV
    Posts
    1,139
    Quick question to start. At 17 degrees ambient and the condenser fan still running, does this unit have any type of flooded condenser or fan cycle control for low ambient conditions?

    With those pressures it might be that the low ambient control is not working. With the HP staying at 168 and it's a flooded condenser type it might still be undercharged.

    What's the scoop?

    Also, is it a factory outdoor unit or a condensing unit with a aftermarket cover. This info would help in determining the accessories it might have. The compressor number would be helpful.
    Last edited by powell; 11-29-2007 at 09:21 PM.

  4. #4
    Join Date
    Nov 2005
    Location
    Haymarket VA
    Posts
    642
    you need to pump head up to push thru txv .headmaster ? fan control ?
    stil long way to go my friend .
    good to hear from you
    http://www.hvac-talk.com/vbb/showthr...ght=headmaster
    Last edited by sarpanch2001; 11-29-2007 at 09:16 PM. Reason: add

  5. #5
    Join Date
    Jun 2005
    Location
    Las Vegas NV
    Posts
    1,139
    Quote Originally Posted by chilly123 View Post
    sounds like a head pressure problem to me. the unit might be overcharged now. does the unit have a headmaster or a condenser fan cycling control?
    chilly, you beat me posting But we're headed the same direction.

  6. #6
    Join Date
    Nov 2005
    Location
    Haymarket VA
    Posts
    642
    Quote Originally Posted by powell View Post
    chilly, you beat me posting But we're headed the same direction.
    my truck also behind you

  7. #7
    Join Date
    Oct 2007
    Location
    The rainy state
    Posts
    172
    sorry powell just got lucky

  8. #8
    Join Date
    Jun 2005
    Location
    Las Vegas NV
    Posts
    1,139
    Quote Originally Posted by sarpanch2001 View Post
    my truck also behind you

  9. #9
    Join Date
    Sep 2006
    Location
    Chicago
    Posts
    474
    Oh sorrry about that guys. All my systems have a head master. Im so used to them i didnt even think to tell. its just a condensing unit with a generic sheet metal conver. And yes I do have a long way to go. This system is so basic as far as controls go. Head masters are simple I studied them long ago. But question is how do u determine what head should be when cold outside. Is it based on system charge? After quite a bit of refrigerant nothing changed an ounce. System has two reciever tanks so i think it can hold a bit. Thing that kind of throws me off is the totally clear sight glass right from the start. This was my worst day on the job so far.

  10. #10
    Join Date
    Jun 2005
    Location
    Las Vegas NV
    Posts
    1,139
    Quote Originally Posted by dangpgt97 View Post
    Oh sorrry about that guys. All my systems have a head master. Im so used to them i didnt even think to tell. its just a condensing unit with a generic sheet metal conver. And yes I do have a long way to go. This system is so basic as far as controls go. Head masters are simple I studied them long ago. But question is how do u determine what head should be when cold outside. Is it based on system charge? After quite a bit of refrigerant nothing changed an ounce. System has two reciever tanks so i think it can hold a bit. Thing that kind of throws me off is the totally clear sight glass right from the start. This was my worst day on the job so far.
    If the two receivers are horizontal, it's probably a Copeland C-Line with a semi-hermetic compressor. The flooded condenser valves would have been field installed or by a box manufacturer. I'm just thinking out loud here, trying to determine what you have. Most flooded control valves are set to bypass at 180lb (R-22 / R-502)

  11. #11
    Join Date
    Sep 2006
    Location
    Chicago
    Posts
    474
    How in the world did you know that? Your good. Very few bells and whistles on this system. Most these stores are scheduled to get bull dozed. Head master must be doing something to get 170 head today. Problem is when I get there I lose my logic and focus on how freakin cold it is out. 22 and still slightly immature. I think Ill hibernate for the winter. J/K. When Im freezing I think theres other guys out there doing the same thing. Just didnt realize how sweet it was to diagnose cars in a heated shop.

  12. #12
    Join Date
    Oct 2007
    Location
    The rainy state
    Posts
    172
    22 deg and you think thats cold. I worked 10yrs in the reno/Tahoe area. is this a unusual cold spell in your area, either the headmaster is not bypassing enough or you need to add fan cycling to this unit. you need to get your head pressure up.

  13. #13
    Join Date
    Jan 2007
    Location
    maine
    Posts
    787
    well first off before you shoot down the LLSV leaking.. Did you pump the compressor down using the suction valve, and see if it would hold?? 170 head seems to me like the headmaster may not be bypassing like it should.. Most r set at 180

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