Our Mitsubishi heat pump

Our Mitsubishi heat pump

We installed a state-of-the-art Mitsubishi M-Series FE18NA heat pump that is rated at 21,600 Btu/hour for heating and 18,000 Btu/hour (1-1/2 tons) for cooling. Marc Rosenbaum, P.E. ran heat load calculations showing peak heating demand (assuming –5°F outside temperature) about 23,000 Btu/hour, assuming the air leakage we measured several months ago, before the house envelope was completed. If the air leakage ends up being cut in half from that measured level, the design heat load would drop to a little over 19,000 Btu/hour.

We think the FE18NA model will work fine for nearly all conditions, but we are also installing a small wood stove—the smallest model made by Jotül—for use on exceptionally cold nights.

The indoor unit of our heat pump is about 43” long by 13” tall by 9-3/8” deep and installed high on a wall extending in from the west wall of the house—next to an open stairway to the second floor; it is controlled with a hand-held remote. The outdoor unit, installed just off a screen porch on the west side of the house is 35” tall by 33” wide by 13” deep. It is under an overhang and held off the ground by granite blocking.