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Hey Ed, Is There a Difference Between Sizing a Furnace and a Heat Pump?

In this edition of "Hey Ed," Ed discusses the difference between sizing furnaces and heat pumps.

Hey Ed, is there a difference between sizing a furnace and a heat pump? No, there isn’t. Oh wait, yes there is. There’s an enormous difference. The big difference is the furnace we size for the heat loss. The heat pump, we size it for the air conditioning requirement. And hard stop, that’s the way it’s done. At least currently, with the version of Manual S that we are still using. In the future, is there some wiggle room for putting in a larger heat pump? There will be. That wiggle room comes with the practitioner, the designer, pick the description you want to put on the person doing the work. As long as they can guarantee that we’re going to get rid of the moisture in the summertime, it’s a path that’s going to be allowable. So, when you pick that heat pump’s capacity to meet the heat loss, there is going to be a separate path for you to show or demonstrate that the equipment that you’re installing is going to be able to take care of the latent load. And that equipment could be the heat pump. That equipment could also include some sort of ancillary dehumidification. Personally, I don’t care how you do it. I want you to do it so that we can ensure that that house can maintain 75 degrees, 50% relative humidity on a design day. And that’s the way I see it.

Ed Janowiak

Ed Janowiak is the Manager of HVAC Design Education at ACCA.

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