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SESK: Stuff Everyone Should Know · sesk.info/epa-poe-oil-moisture

On an HFC system with POE oil, why should line set caps stay on until you connect them?

POE oil absorbs moisture very quickly.

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  1. The caps hold the factory charge
  2. Open tubing can freeze shut
  3. POE oil absorbs moisture very quickly ✔

Why: Polyolester oil, used with HFC refrigerants, soaks up moisture fast. Lennox says to keep the refrigerant system closed as much as possible, and warns that leaving lines open means extra evacuation to remove moisture.

Huh, didn't know that: POE is short for polyolester, the oil type used with many HFC refrigerants.

The dad joke
POE oil is thirsty. It will drink any moisture within reach.
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References

Answer: POE oil absorbs moisture very quickly. Polyolester oil, used with HFC refrigerants, soaks up moisture fast. Lennox says to keep the refrigerant system closed as much as possible, and warns that leaving lines open means extra evacuation to remove moisture.

  1. Lennox installation instructions 508844-01 (R-454B split system) www.lennox.com/dA/eb5bdb59f2/508844-01b.pdf
    absorb moisture very quickly
    Checked 2026-10-10.

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