[asa32sd23]

hello, i live in a condo in south florida, Ft Lauderdale.

i have a central AC unit that is cold water system. the condo building provides 2 lines into the coil/air handler and maintains a chilled water system for all units in building.

the coil/air handler if a low profile concealed unit that sit above the ceiling, its about 38 inches wide, 10 inches tall and about thickness of fins with coils is about 2 1/4 inches. the rest is the casing, place for the electric heating coil.

i am not an hvac guy but decided to replace the unit myself... my question is, when i disconnected the air handler/coil from water supply and return, i noticed that there is water pressure in both lines

i thought 1 was the supply (with water pressure) and the other is the return(no water pressure)

how can both lines have water pressure, is this normal, a specific type of system? my condo is 1 bedroom, 850 sqft.

thanks for any help understanding this issue for me.

 

[eggs]

Good question. The condo does not chill water, run to your space and let your unit dump it down the drain. The water goes back to the chiller where a pump is moving the water around. If the chiller is exactly the same elevation as your unit, then they can run very low return pressures. This is not possible when you have several elevations with multiple units. In order to push the water from the chiller up to lets say 3 floors, that is about 36+ feet. It would require a minimum of 18 psi to over come gravity. So yes, there will always be pressure on both sides.