12x12
8.5' high
2 outside walls
Old double pane pella casement windows approx 30"Ć40" x 2
Wood fram, brick and cedar shake
16 adult plants in various stages
OK so the room is calling for 8,000 btu empty. That's calculated to keep the room 72 degrees/50% rh on a 99 degree humid Missouri summer day.
You have by my math 2636 watts of light
exhaust fans are 116 watts
I would guess about 100 watts for circulation fans
Thats 2,852 watts (92% of which are lights) which is 9,725 btu
Combined with the 8,000 btu that gets you to about 17,000. So you would want to probably round up to at least a 2 ton (24,000 btu) that also doesn't account for plant humidity, you could add a dehumidifier which should pretty well eliminate that.
How would room size play into that formula and is there a way to include it to be able to pinpoint actual BTU needs?
I like to size my cooling with a minimum of 20% headroom. I don't want my compressor working full blast 24/7. That will get you a dead compressor in week 7 of flower......yippee......
Also, how do you secure accurate info on the units? I've bought MS units that claim to be 2 tons and turn out to be 18,000 when the HVAC tech shows up. Is there a way to push past dealer claims and get to the truth?
Room size is tricky, I have computer software that does that for me. You can use some "rules of thumb" like x square feet per ton, but that's dangerous as not all square feet are created equal. For instance a four seasons room with 3 walls entirely of windows will have a way bigger load than a room in the center of the house with no exterior walls even at the exact same square footage.
The only way to know the unit size is the model number. Most manufacturers put the btu rating in the model number. A ton of cooling is 12,000 btu, units are sold in half ton increments so your looking for a multiple of 6 usually. 018, 030, 042 something like that. The other thing is that you have to go by the
unit model number not the compressor. Often times a 3 ton (36,000 btu) unit will have a 30,000 or 32,000 btu compressor, but they still put out 36,000 btu (at least per the manufacturers anyway)