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Hey Ed, How Does the Design Series Account For Blower Heat?

In This Edition of “Hey Ed,” Ed Talks About Accounting for Blower Heat

Hey Ed, how does the design series account for blower heat? In a way that might surprise you, or maybe not. When we are populating the worksheet or the computer fields doing a load calculation you'll come to a line where it will ask you about blower heat, the design series, or Manual J® in particular, looks at it one of two ways. It will ignore it if the manufactures expand a performance data deducts the heat that comes from the blower motor from the capacity of the air conditioner, or if that is not mentioned that being the discount for blower heat in the expander performance data. Then we're gonna calculate it if you want to go as far as find out how many watts it's consuming and multiply that by 3.412 to determine how many BTUs that blower motor adds to the heat gain of the structure. Go ahead and do it. There is a 1707 I believe BTU default in Manual J® that will add to it. The interesting part for lack of a better way to describe it for me is 100% of the electricity consumed by the blower turns into heat. Either when we take electricity and turn into kinetic energy where the actual friction of the air moving down the ductwork 100% of the water that motor turns into heat and that's the way I see it.

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

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