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  1. #1
    tonymjr is offline Regular Member-Bad Email address
    Join Date
    Jul 2004
    Posts
    68
    Worked on a Trane SFHCC55 rtu and noticed a 40lb psi drop thru coil. 280 @ dis. svc valve, 240 @ drier inlet, 235 at drier outlet. SH and SC ok unit operates ok. System has 2 circuits with 2 14ton scrolls. Any ideas on the psi drop?

  2. #2
    Join Date
    Jul 2002
    Location
    NorthEast
    Posts
    811

    Cycle rate of an A.C. unit

    Some people set the HVAC equipment schedules to enter occupied mode 3 hours before bussiness hours.
    It waste energy.
    If a unit is properly sized and working properly,
    shouldn.t a comfort level be reached within 15 to 20 minutes
    The un occupied temp very rarely excedes 84 Degrees

  3. #3
    Join Date
    Apr 2004
    Location
    Rossville, GA
    Posts
    104
    Tony i've noticed this with trane before on commercial packaged equipment 20 tons and above . And with my coils cleaned found this same 40 psid @ condenser. It's a good reason not to check subcooling @ the discharge port. Good finding.

  4. #4
    Join Date
    Feb 2002
    Posts
    79
    I have seen similar things on Carrier's. Could not believe the 40# drop across the condenser. What is a normal drop.
    Ray

  5. #5
    Join Date
    Mar 2003
    Posts
    1,877
    saturated condensing temperture which is needed for subcooling is checked on the liquid line after condenser not on discharge line (hot gas line)

  6. #6
    Join Date
    Aug 2003
    Posts
    242
    It is normal to have a 40# pres drop across a large commercial air cooled condenser.

  7. #7
    Join Date
    Feb 2002
    Posts
    79
    Thanx TXTRANEMAN.
    I never realy looked at that.
    Ray

  8. #8
    Join Date
    Apr 2004
    Location
    Rossville, GA
    Posts
    104
    It is normal to have a 40# pres drop across a large commercial air cooled condenser

    Why? We know how critical liquid and suction pipe sizings apply. Someone could be easily fooled if your not experienced. 40 psid across condenser coil just seems high. But ultimatly, when your compressor superheat and subcooling are in range of manufactors specs your protected. Is this Tranes standard and if so on what sizes does it start to apply? 5 tons and over?

  9. #9
    Join Date
    Aug 2003
    Posts
    49
    Compare your readings with performance data. It should be in a plastic envelope attached to the unit.
    Just as a reminder, performance data sheet is not a charging guide, you can only compare your reading with those graph and see if your unit performs in a recomended range. If it is not in the accepted range, then you have to follow the recomended charging procidure for that spesific model. Although you can contact trane support engineers and they would give you step by step procedure to check that unit.
    TRANE: 800-880-8726
    I'm learning

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