Condensate Temperature

Joe_55

At what return temperature does an oil-fired boiler condense? Thank you.

Constantin

IIRC, the oil-fired flue gases condense...

... at around 117°F. However, at what return temperature the flue gases will condense inside a boiler depends on the boiler. For example, the Buderus G215 and the Viessmann Vitola have no low limit for the return water temperatures while the the Burnham MPO has a lower return water temp. limit of a mere 100°F. Boilers like the Monitor FCX would probably love return temperatures below 104°F to maximize condensate extraction, but I'd double-check the Installation instructions since the FCX has two HX's, and one of them is not supposed to experience condensate.

Other boilers have higher limits, AFAIK. Thus, I would refer to the individual I&O literature to verify what temperatures the boilers can endure, how the manufacturers recommend the boiler be connected to a heating system, and how to protect them from low return temp. water, if applicable. Pump Logic, Pri-Sec, Injection-Mixing, or 3- or 4-way valves are among the different ways to do it.

Lastly, double-check the flue liners... you don't want condensation in that area either.