AC Box questions - ducting, fans, ect.

[rr14]

Hi guys. I have a 5000 btu goldstar ac that is setup to cool my grow chamber. I made an ac box for the box of the unit and am venting it out of the room. I constructed the ac box of 1/2" wood. I made it about 3" larger than the dimensions of the ac unit. Behind the unit, there is approx 3" of space for air flow. I have a 4" duct sucking out of the top right and it's hooked up to a 4" dayton fan.

I drilled 16 3/4" holes in the bottom side and left side of the box for air to enter the box. Being that I'm using a 4" fan, is this enough holes to get the airflow I need across this thing?

I did some quick calculations to compare the area.

for the 4" fan, area of ducting equals pie (r) squared. So it would be 3.14 (2)squared.

I came up with 12.56 square inches of area.

For the 3/4" holes, I came up with 3.14 (.375) squared for .441 which equals right around 7.5"

I'm thinking I need a few more holes, maybe a few of larger diameter like 1".

Also, the ducting with my temp guy said 125 or so at one point. What is the temp limit of the flexible ducting from home depot. I have the black one, not the aluminum looking one. The label didn't say a max temp for this stuff.

 

[rr14]

okay... so I just went downstairs and added a 1 1/4" hole on the bottom left of the box. I think this should get the intake area closer to the exhaust.

 

[rr14]

oh yeah, the fan is connected to the temp controller so that the fan is only one when the ac is on.

 

[rr14]

update, I ran the ac all night and the ducting temps got up to 135. I'm going to pickup some dryer ducting today after work.

 

[morrisgreenberg]

i would go with 6in duct fans pulling air, did you biuld the box over the side vents? i build my boxes all the way up to the side slit vents so i didnt have to mess with them not getting enough, the problem is 4inch hole may be too small, the bigger the better when air flow is involved, i have a 12kbtu and run a 6inch and it barlet does the job, the job it does well but it gets hot, dont worry about the ducting getting hot, thats the idea, see how much heat would be in the area, especially the heat that would get sucked right back into your intake vents on the sides

 

[rr14]

yeah, I think the 4 in was too small. The efficiency of the ac unit went way down to wwhere it wasn't cooling the room enough. I'll try 6" next.