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Heatpump piping and height

When you have a heatpump located on roof is their a min. height it must be off the roof in NJ .Same job diffrent question, 3 story building 3/8 & 5/8 line set 2 ton units, 410a,do i need an inverted trap or regular trap and if so how deep, and where, nothing specified in installation man.Dx coils down below York equipment if it matters.


  • clammy
    clammy Member Posts: 2,829
    standard stuff

    The standard things i would do is a inverted trap on the liquid and traps as per standard one by the dx coil then 1 trap for ever 8 ft of vertial height on your suction line,also as for your condensing unit i would suggest that you see if they have a wind defletion kit for the condensing unit and leg extension kit to keep the unit from getting a build up of snow and so it  has some place for any ice to to drop off during defrost if the unit is equipted with a hot gas defrost cycle ,These are just standards that i hve used in the past and it  has been quite a few years since i have installed a heat pump like 15 years or so but i would think that some installation pratices do not change much,Hope any of this helps search around and maybe download some installation instruction from other manafactures that may give you a better outline for accesssories also check the manafacture who.s equiptment you are using also check out a low ambeint kit and fan speed controller and don't for get a crank as heater other wise all your oil will end up in your dx coil peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • Your Main Concern

    Your main concern should be keeping the outdoor unit above the snow line. Things to consider with this are: (1) Is the unit located on the roof next to any parapet walls? (2) Is the unit located near any other obstructions that can cause snow to accumulate? (3) Is the roof slanted or horizontal?

    By keeping the unit above the snow line, you will help keep the coil clear and reduce the amount of defrost time needed to clear it.

    As far as the refrigeration lines go, you should always be concerned with oil return to the compressor. In the cooling mode, the indoor coil is functioning as your evaporator, so the vapor refrigerant will have to flow up to the outdoor unit. In this case, you will want to install a trap at the base of the verical run and an inverted trap at the top of the vertical run. The longer the vertical run, the more traps you will want to install. Typically, one trap for every 10 to 15 feet of vertical rise is sufficient, although installing more will not hurt much. What we always did in the field was this... If the vertical run was three stories, we installed three traps... four stories, four traps.

    Also remember, if the velocity of the refrigerant is maintained by properly sized refrigerant lines, many equipment manufacturers will tell you that traps are not needed! If the refrigerant is flowing too slowly, then you will have oil return problems. At higher refrigerant speeds, you will help ensure oil entrainment.

    Installing traps on a properly sized suciton line do not help oil return since the oil will flow properly. The one thing that a suctionline trap will do is increase the suction line pressure drop. A suction line pressure drop is typically in the 3 psig range and adding traps can increase this pressure drop to over 6 psig. A suction line pressure drop in this range can result in a loss of system capacity of up to 3%.

    If you feel you need to install a trap, keep this in mind. The length of the trap is far more important than the depth. It is the length of the trap that determines how much oil is accumulating in the trap before the liquid seal is formed. Since many manufacturers do not specify the size of the trap, I have always found that a length no larger than three or four (about) the diameter of the pipe would be appropriate. So, a 1" line would have a trap that is no longer than about 4" or so.
  • heatguy
    heatguy Member Posts: 102
    Thank you

    Just wanted to thank you both for your answers.I will put it in manufacturer's lap so to speak so if there is any issues we can state as per manufacturers recommendation's.
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