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Old 11-13-14, 06:30 PM   #56
jeff5may
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Has anyone seen inside the newer Zoneline heat pump PTAC units? I saw a brand new one at work today. They have a quiggle-ator in them! This device not only serves as a suction/liquid heat exchanger, but also as a charge compensator. It looks like a compressor muffler, and has cap tubes in the top and bottom of it. The wide part of the muffler is brazed to the outdoor hx line that leads to the reversing valve. I found a faraway pic of a smaller unit on display:



If I can remember, and find some time, I'll go back and stare at the rat's nest between the compressor and outdoor hx. I'll take some pics and try to untangle the maze.

These units also have a heat pipe sandwich with the indoor hx in the middle. They call it "super-dry" or something similar. The main purpose of this rig is to increase dehumidification.

Since one half of the heat pipe sandwich is upwind from the evaporator, it will always be warmer than the other half downwind. The heat pipes have R410A in them, and are connected at the top and bottom. When the unit is working as an air conditioner, the downwind hx condenses refrigerant, due to the temperature drop of the evaporator coil. This forces a pressure drop which carries over to the upwind hx. Due to the decreased pressure, the refrigerant boils out of the upstream hx and pre-cools the ambient air before it reaches the evaporator coil.

GE says this gimmick nearly doubles the amount of water the evap coil can condense from the air. They claim a 10 degree or better reduction of wet bulb temperature at the evaporator coil surface.

Now correct me if I'm wrong, but this sounds like the opposite of what we are trying to do with a suction line exchanger. Doesn't this thing shunt some of the load around the evaporator? Also, wouldn't forcing a 10 degree drop in evaporator temperature raise the effective temperature split and kill efficiency and COP?
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