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  1. #1
    Join Date
    Jul 2013
    Location
    Victoria, BC
    Posts
    2

    In a Mental Vacuum

    Hello Everyone

    I've just joined this great site and this is my first post. I've come across this heat pump that has me absolutely stumped. First of all some background. This is a four-year-old York condensing unit (3 phase) with a Lennox indoor unit and a York coil replacing the original fitted with a Danfoss TXV. The condensing unit is one story above the evaporator and there are no risers or traps. This is R-22 by the way.
    When I first was called to this job, I found that the compressor had burned out (open windings). I was able to get a warranty compressor, which I then installed. I cut out the original filter/drier, as well as an external one and installed a freshie. I pressure tested, vacuumed and recharged. When I hit the power, it took about 10 seconds for the low side to go into a vacuum. I thought, "great the TXV is plugged", but somehow I just didn't buy it. To test this I recovered the gas, valved off the lineset and sent nitro through the high side only. Sure enough my low side guage rose right along with the high side. But as a matter of practice, I replaced the TXV to totally eliminate that possibility. The new TXV made absolutely no difference.
    I tried the unit in heating and it basically goes into a vacuum as well. In heating, the low side king valve port reads about 250 psi, the high side king valve port reads about 110 psi and the low side suction port reads about 20 psi. There must be some kind of restriction, but why does nitro fly through with no problem and there's no evidence of any oil slugging. Anyone encounter anything similar to this?

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,910
    Might have a clog/restriction in 1 or 2 of the indoor coil's distributor lines.
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    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    Jul 2013
    Location
    florida
    Posts
    2
    is there a suction drier between the reversing valve and the compressor? is the reversing valve sticking between modes? is the outdoor unit metering device(heating mode) clean and not sticking?

  4. #4
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    Ran into a Carrier system before that had something like 4 pounds of refrigerant listed on the nameplate
    split system.... similiar to a mini-split.... had a compact evap/fan section hanging from the section with no duct on it
    around a 20 ft line set....
    it would go into a vacuum real quick too
    we pulled the piston, checked for kinks, and all kinds of hair pulling
    only to find out.... if you download the install directions for the unit, it says to add another 6 pounds or so
    ARGHHHH

    Doubt thats what you have..... it just came to mind reading your post


    On another thought.....
    any kind of strainer just before the txv?
    Extend to others the grace that God has given you.

  5. #5
    Join Date
    Jul 2013
    Location
    Victoria, BC
    Posts
    2
    There is no suction line filter/drier and the reversing valve seems to be working. With the machine stopped, pulling the O wire deactivates the solenoid and refrigerant can be heard as it equalizes. The outdoor metering device is an orifice. I could see that being plugged up all right. However, in heating pressure at the suction line king valve is about 250 psi and only about 110 psi at the liquid line king valve. Then its 20-30 psi at the low side suction port. I would think that a clogged orifice would cause some really high pressures downstream of the clog.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,910
    Not if its a clogged distributor line at the indoor coil.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

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