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Air handler heat exchanger output

PLUMMER Member Posts: 42
With a 12x18" water to air heat exchanger can you adjust BTU output by increasing flow and increasing fan speed. 500cfm to 1200cfm. I have a contractor telling a customer that the 70kbtu braztek exchanger is doing 120kbtu cause he turned the fan speed up and is pumping 12gpm instead of the 6-7 GPM @180 degrees that the exchanger is rated for.

I've been trying to find fixture data and performance specs with no luck so far. Braztek actually has the most detail I've found so far and surface area,flow in pounds per hour, water temp and temp differential are the calculating factors. I haven't found anything regarding air flow cfm over a fixed surface area finned heat exchanger.

Of course the customer seems to be giving the unlicensed contractor a lot of credit with his theoretical modifications and estimates. Kinda like the Home Depot isle jockey telling the customer I'm doing it wrong.


  • Snowmelt
    Snowmelt Member Posts: 1,415
    First company

    In theory he may be correct I only used a flat plate heat exchanger 4 times as an external item.

    The reason I titled the post first company is I had a job where there where 80 condo units and the association didn't know what was really going on with the units. Doing my research then can help you now.

    First thing I want you to do is go to the first company websight, go to fwa series then go to the specs as you look at it you will see that it goes from 13,000 - 60,000 all has to do with fan speed temp of water and gpm going through the coil.

    So like I said it can be done but he would have to have the spec sheet of the heating coil to do so. Also with different temp and fan speed you will have a pressure drop in the coil, that will dictate how the pump operates.