Furnace sized based on air handler required for cooling?
I’m new to furnace and AC terminology so before I ask my question I had to figure out why AC units talk about tons. It’s not tons of air. I just learned why they use tons to describe air conditioner capacity from:
Basically it takes about 12,000 BTU/h to melt a ton of ice. So to determine an AC capacity in tons take the rated cooling capacity and divide by 12,000.
Now that I got that out the way I’m trying to correlate furnace size and air handler size to the heating and cooling requirements.
Typically you need more volume of air to cool the house than to heat it. So the cooling requirements determine the size of the air handler. However the air handler comes with the furnace. So the air handler size determines the furnace size. This logic forces me to buy a furnace of a much larger capacity than I need.
Why can’t you size the air handler independent of your furnace? Is it a cost issue in that a furnace comes with an air handler so it’s much cheaper to deal with an over sized furnace than to buy right sized furnace and air handler independently?
Here is what my HVAC design guy set up for my house. The manual J shows I have a heating load of 53,400 BTU/h and a cooling load of 36,400 BTU/h (3 ton). So they are recommending a Lennox furnace with 85,000 BTU/h output and a Lennox AC unit and coil with a 47,000 BTU/h cooling capacity (4 ton) both at 2000cfm.
Is there a way for me to match my furnace to be closer to 55,000 BTU/h and my cooling equipment closer to 40,000 BTU/h?
I guess I don’t understand why my HVAC contractor is recommending he installs equipment so over sized.
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