Running HVAC linesets underground
Running HVAC linesets underground
(OP)
I would like to relocate our A/C compressor/condensor unit approximately 25' from its current location. This will allow me to construct a patio as well as reduce the amount of fan noise transferred into the house. I would like to run the liquid and vapor lines under ground in a PVC conduit. When I had a local HVAC contractor look at the work he recommended we NOT run the lines underground. He said there is an increased chance of the compressor ingesting liquid refrigerant.
Can somebody speak on the validity of this statement? If this is a real problem can I engineer around it with a liquid trap or sufficient incline of the vapor line? I'm not ready to give up on this idea yet.
Thanks in advance,
Tom Moritz
Can somebody speak on the validity of this statement? If this is a real problem can I engineer around it with a liquid trap or sufficient incline of the vapor line? I'm not ready to give up on this idea yet.
Thanks in advance,
Tom Moritz





RE: Running HVAC linesets underground
RE: Running HVAC linesets underground
Tom Moritz
RE: Running HVAC linesets underground
Let's assume 1/2 the refrigerant charge condenses in the suction line during the off cycle (Say 3-4 lbs R-22??) The system starts; will the compressor draw this liquid up the suction line, into the compressor, accross the motor, into the valves?? I doubt it.
More likely the refrigerant will simply boil off in the suction line as the compressor reduces pressure.
RE: Running HVAC linesets underground
RE: Running HVAC linesets underground
If I understand the problem of underground DX lines correctly it's an issue of lower conductive heat flux in soil vs. convetive air. This could result in chilling the air in the PVC sleeve and surrounding soil sufficiently to prevent vaporization of any refrigerant that migrates through the expansion coil or prevent condensation of refrigerant in the suction line as the pressure rises while the compressor is off. The larger the system the more this is a problem. We have a 4-ton AC system, not very big.
Thanks for the feedback.
Tom Moritz
RE: Running HVAC linesets underground
I don't think that conductivity of the sorrounding material is too detrimental to the DX lines. Pressure drop and corrosion issues must be considered. Suction accum should be installed. Is foundation shifting/soil movement the real reason why the big guys are not recommending this approach?
regards,
RE: Running HVAC linesets underground
From Trane Engineers Newsletter — Vol. 27, No. 4
You can read the entire thing at Split systems and interconnecting refrigerant lines: As equipment evolves, so must piping practices by Paul Solberg, 1998, volume 27-4 (revised Oct 2001).
To the OP I agree more with chilled on the technical aspects for your unit size. Just keep in mind that you have the very real possibility of having to tear your entire patio up to fix a problem with the refrigerant lines. Overall, I would be with DrRTU (& Trane) and avoid them at all costs.
RE: Running HVAC linesets underground
I your case, a 25’ of run under an inaccessible area is asking for a compressor reliability issue. The line run sounds like a large percentage of the line length.
RE: Running HVAC linesets underground