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  1. #1
    Join Date
    Mar 2004
    Location
    Syracuse, N.Y.
    Posts
    8

    Liebert head master puzzle

    Initial call was circuit 2 HPCO. After reset I have low suction 50 psi, discharge 100 psi and flashing sight glass. R407C, 30 degrees ambient.
    Receiver upper sight glass is maybe 3/4 full.Discharge gas line warm up to tee into coil, then from tee to head master, receiver and liquid line all at roughly ambient.
    Any thoughts on this? Stuck valve, receiver heater etc. My plan is to verify heater is working first, but I really haven't had any experience with these so I thought I'd ask for help.
    Thanks
    Steve

  2. #2
    Join Date
    Dec 2001
    Location
    Phoenix, Az
    Posts
    1,247
    Sounds like the HPC isn't bypassing. The head pressure should be 185 with an 1/2 full lower sight glass.
    I carry a gun because I'm too young to die, and too old to take an ass whoopin

  3. #3
    Join Date
    Dec 2001
    Location
    Phoenix, Az
    Posts
    1,247
    Also, have you tried blocking the condenser or turning the fan(s) off to see what your head pressure does?
    I carry a gun because I'm too young to die, and too old to take an ass whoopin

  4. #4
    Join Date
    Mar 2004
    Location
    Syracuse, N.Y.
    Posts
    8
    I did run with no fans, but just to verify HPCO trip point. I was supposed to be back there today, but that got changed.
    Any way I can try to force the HPC? Thought I read something about equalizing system pressure.

  5. #5
    Join Date
    Dec 2001
    Location
    Phoenix, Az
    Posts
    1,247
    Don't know about forcing an HPC. Sometimes you can snip the cap tube on the top to get temporary usage. You might as well replace it if is the problem.

  6. #6
    Join Date
    Jun 2004
    Location
    Olean, NY
    Posts
    1,449
    I can't figure out what HPC is, help me out there?

    Sent from my MZ601 using Tapatalk
    Guinness for strength

  7. #7
    Join Date
    Dec 2006
    Location
    new england
    Posts
    619
    I think he's talking about a High pressure control (safty).
    Chaos equals cash$$$

  8. #8
    Join Date
    Sep 2006
    Location
    Ohio
    Posts
    473
    I think he means Head Pressure Control.

  9. #9
    Join Date
    Mar 2009
    Location
    Mid-Mo
    Posts
    3,595
    Was the receiver warm? Does seem that the headmaster should have been bypassing and dumping straight into the receiver. Did you check temperatures across the valve?

  10. #10
    Join Date
    Nov 2006
    Location
    Wisconsin
    Posts
    287
    I just replaced a headmaster on a liebert ds 407c unit last friday. Sounds to me like the headmaster isn't bypassing as others have said. We have had some issues with headmasters on some units from 2009. Of the 4 circuits (2 units) we have, I think 3 of them have been replaced already. Not sure if its an issue with this era of units. Units were charged and set up to liebert specs. According to the liebert manual, below a 40 degree ambient should have the bottom sight glass 3/4 full.

  11. #11
    Join Date
    Feb 2011
    Location
    Sacramento, CA
    Posts
    147
    Did you check the heater in the Lee Temp receiver? The liquid line leaving the receiver should not be ambient tempature.
    I have done so much with so little for so long, that now I can do almost anything with nothing at all.

  12. #12
    Join Date
    May 2008
    Location
    Collinsville, Tx (Texoma)
    Posts
    46
    I have never been a big fan of headmaster valves, especially dealing with them in refrigeration situations. Fan control is always better in my opinion. I didn't think that sigh glass on the receiver was suppose to be full till you were up around 250 psi head pressure. I could be wrong. It sounds like you are stacking gas in your condenser from the cold temps, if you cut that stem you will bypass the headmaster and cause more stacking at those temps. Defiantly try blocking your condenser off again and try to maintain above 200 psi, and see what your suction does.

  13. #13
    Join Date
    Mar 2009
    Posts
    10
    Quote Originally Posted by ratzo79 View Post
    Initial call was circuit 2 HPCO. After reset I have low suction 50 psi, discharge 100 psi and flashing sight glass. R407C, 30 degrees ambient.
    Receiver upper sight glass is maybe 3/4 full.Discharge gas line warm up to tee into coil, then from tee to head master, receiver and liquid line all at roughly ambient.
    Any thoughts on this? Stuck valve, receiver heater etc. My plan is to verify heater is working first, but I really haven't had any experience with these so I thought I'd ask for help.
    Thanks
    Steve
    In my opinion it doesn't sound like the headmaster is working. My understanding is that this valve is used instead of fan cycling in cold areas. The valve will open to allow high pressure gas into the reciever to "sit on the liquid" raising the liquid pressure. If it is cool outside, the hot gas line into the headmaster will be hot, as will the line out of the bottom of the valve leading to the top of the receiver.
    I would look into the situation further as to why the system was off on high pressure though to rule any other potential problems out.

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