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  1. #1
    Join Date
    Oct 2012
    Location
    Virginia
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    2

    Undersized Liquid Line

    What impact would an undersized (1/4") liquid line have on a 2T 410a goodman heat pump's pressures in heat mode? I know it would cause elevated head pressure, but to what extent? (500+ psi w/ 65F OA & 70F IA) Indoor coil is clean, checked both pistons,changed out dryer, airflow is good and I'm Still getting a gradual increase in head pressure until it reaches 500- 600 psi. Runs normally in ac mode. Should I be looking a little more closely at the reversing valve? Any help would be greatly appreciated.

  2. #2
    Join Date
    Dec 2010
    Location
    Virginia
    Posts
    355
    That a tough one. I would think that the head pressure would build up in ac mode leaving backing the refer up in the condenser. So in heat mode samething but it would be backing up at the indoor unit and already metered by the time it gets to the outdoor unit ( where the high pressure switch is). Ofcourse I find a lot of times the way i view things tend to be the opposite.

  3. #3
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
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    6,039
    piercing valve at indoor unit will tell precisely how much.

    Airflow.....good. check.

    Id bet you are overcharged. This is a 5mm coil goodman unit. very charge sensitive.

  4. #4
    Join Date
    Oct 2012
    Location
    Virginia
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    2
    Quote Originally Posted by SBKold View Post
    piercing valve at indoor unit will tell precisely how much.

    Airflow.....good. check.

    Id bet you are overcharged. This is a 5mm coil goodman unit. very charge sensitive.
    I also recovered & weighed in the charge....sorry I forgot to mention that.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,910
    Quote Originally Posted by Kookster View Post
    I also recovered & weighed in the charge....sorry I forgot to mention that.
    R410A, 1/4" liquid is .19oz per foot, 3/8" liquid line is .54oz per foot. So factory charge would be an over charge if your line set is 15 foot. Over charge is what the head slowing climbing indicates. A bad RV wouldn't cause a slowly rising head.
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  6. #6
    Join Date
    Mar 2012
    Location
    Birmingham Al
    Posts
    224
    weighted in charge to factory? if your liquid line is undersized did you compensate for this? if so how much?

  7. #7
    Join Date
    Feb 2006
    Location
    Float'N Vally, MS
    Posts
    1,825
    Quote Originally Posted by Kookster View Post
    What impact would an undersized (1/4") liquid line have on a 2T 410a goodman heat pump's pressures in heat mode? I know it would cause elevated head pressure, but to what extent? (500+ psi w/ 65F OA & 70F IA) Indoor coil is clean, checked both pistons,changed out dryer, airflow is good and I'm Still getting a gradual increase in head pressure until it reaches 500- 600 psi. Runs normally in ac mode. Should I be looking a little more closely at the reversing valve? Any help would be greatly appreciated.
    I may be wrong, but the velocities are higher with 410a than 22. Your liquid "may/should" be flashing before it hits the expansion device with an "even higher" velocity with the smaller 1/4' line. To get the charge where it will not trip the high pressure in the winter, may leave you short in the summer........
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  8. #8
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,627
    1/4 liquid line is ok for a 2 ton ,i suspect you are not moving enough air through the indoor coil
    We really need change now

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