AC box with a 6" vortex.

[yamaha_1fan]

I built an AC box to route the exhaust of my AC outside. The AC is 24K BTU, the box is roughly 18" high, 27" wide and 24" deep. My calculations make it about 6.5 cubic feet. The vortex is rated at 449 CFM.

The vortex is mounted inline pulling air out of the box and pushing it outside, roughly 15 feet, maybe 7 feet of ducting on both sides. The 6" ducting runs to a 5" outlet. The ducting is really hot after just a few minutes of the AC running. Plus there is a leak in the box and I have air pushing out the box, where I thought I would have suction.

So why is this A/C pushing out so much air, that the vortex cant pull it out fast enough? Granted I may have some loss through the ducting and the outlet being reduced. But a 449 CFM fan dumping a 6 foot cubic box should be emptying the box every few seconds, even with the reduced output.

Only the rear is covered, the sides are still wide open and exposed.

So what gives? is this plan flawed or do I just need a MUCH bigger fan?

 

[Albert Hofmann]

Hey Yam-

This is just a guess, but...What are the specs on the AC...because 24000btu is a huge window unit (approx 2 tons). If I had to wager a guess, I would say that a 6" vortex doesn't move enough air. I bet the compressor on fan settings on that thing are more than 450cfm. Step up to an 8" vortex and try to eliminate the reduction at the exit point.

albert

 

[Guest 18340]

I'm with 'Hofmann on this one. Thats a decent size unit so i imagine the fan thats in it is pretty powerful, must be in order to cool off the coils.
I have a 5k btu joint that im gonna do similar to what you did (box, open sides of unit, 6" vortex sucking hot air, etc) and I'm wondering if I'll need a bigger unit.
Please let me know what you ended up doing to rectify the situation. Heat is a major problem for alot of us and ANY info on controlling heat is important. Peace, Evl...

 

[OgreSeeker]

Yamaha,
What do you mean by the rear is covered (is the back of the ac tight against the back of the ac box)? Is the ac working properly or is it cycling a lot? Does your duct seem hotter than it should be...it is common for it to get really hot.
Your 24k btu unit probably puts out around 600cfm so you'll need to move at least that amount of CFM to properly exhaust the hot air.
Sounds like you need more air flow.

 

[yamaha_1fan]

well now the A/C wont blow cold. I checked on it this morning and the room was hot, well over a 100 degrees. I shut off most of the lights, and unplugged the A/C and am hoping it will cool down and reset. It comes on and blows, just not cold. Did I burn up the compressor in one night doing this?


NEVER MIND ABOUT THE COMPRESSOR. I left it unplugged for about 45 minutes and it seems to be working fine now. I know I probably didnt do it any good but hopefully it will be OK.

 

[yamaha_1fan]

Yamaha,
What do you mean by the rear is covered (is the back of the ac tight against the back of the ac box)? Is the ac working properly or is it cycling a lot? Does your duct seem hotter than it should be...it is common for it to get really hot.
Your 24k btu unit probably puts out around 600cfm so you'll need to move at least that amount of CFM to properly exhaust the hot air.
Sounds like you need more air flow.

Yeah the box goes around the outside of the AC and slips on about an inch. Its pretty tight and I taped it up but most of the tape came loose due to the heat. The ducting was so hot, you could barely keep your hand on it.

 

[hoosierdaddy]

The sides of the unit that are taking in air...are you using air that has been cooled already, or do you have a separate intake air supply? Even if you get your flow problems worked out, which you definitely have with the 6" going into 5", using the air that has been cooled by the unit is a gross waste of energy and will continue to be a problem.

 

[yamaha_1fan]

No, the unit is mounted in a wall like it normally would be, with the first 4-5 inches through the wall. The intake is outside the room, in the garage. I simplyy boxed in the rear to direct the hot exhaust outside.

 

[DIGITALHIPPY]

,my guesses are that the back of the box is too short and the airflow inside the box is too constricted. id get a 8" can-max or somthing that can move more air. i dont feel the 6" is enough. the leaks suck too. get some caulk and fill-em-up. id also put the fan on the outside pushing into the box, the exhaust is very hot and thoes fans dont like air more then 120-140F otherwise the motors burn up. a left->right airflow or a bottom->top airflow patterns IME seams the best.
GL yamaha

 

[Guest 18340]

yamaha 1fan, Thats EXACTLY how i plan on setting up my ac, exactly the way yours looks in your pic. Shit man, now i'm wondering if my set up will work. I plan on using that same 6' vortex as you. I'm in Florida and its hotter than hell and i desperately need this to work.

 

[OgreSeeker]

DIGITALHIPPY is right on. You are suffering from inadequate air flow and to much constriction around the ac. Your picture doesn't show the size of your ac box but I'm sure it needs to be bigger. You need to leave at least 4" clearance all the way around the ac and you'll need a larger fan.
Does your ac blow cool air after it's allowed to cool off? If not then you may have already done some damage (hope not).
I'll say it again...adequate air flow is essential when constructing an ac box. If your plan lacks a good fan then you may as well throw it in the can (I made a funny).

 

[hoosierdaddy]

Where do you get the box needs to be 4" larger than the AC, Ogre?

The ducting needs to be sized to the smallest orifice in the air flow (here we go again...)
which is the housing around the fan internally. If your duct is as large as the back of the unit, forget an extra 4", you are golden. Why the extra 4"? I see no goo reason that can be explained to need that.

What IS needed is a larger duct. This ducting is essentially only 5" in diameter, since the exit orifice is only that big. If the exit port is enlarged it will get better and better with what he has now. Making the box bigger is a worthless venture, and the 5" exit is what matters, and with that you could make the box 10 inches bigger on all sides and it wouldn't do squat.

yf1, is there any chance of you being able to run regular rectangular duct (like central air in the house) from the unit to your outside? If you can, then the fan of the unit alone will probably push the air out just fine.

 

[yamaha_1fan]

Heres the box. Obviously the back is now off to allow the AC to work, which by the way is working fine now. I just went in the room and its nice and cool after the lights went off.

I also have the lights pushing into the box as well

I really dont know how I could vent outside. That exterior wall is all brick above the foundation AND faces the street. Its also where my meter is so a big ass 10" hole with hot air coming out near the meter is not high on my wish list.

I was thinking of cutting holes in the garage door and putting grills over them and building a rectanguar duct over and down and out the bottom of the garage door on the left side.

 

[hoosierdaddy]

Those two ducts running into your box...? Are these going to your grow room?
And if so, why are you sucking the cool air back into the hot exhaust. This was your problem.

 

[yamaha_1fan]

Those two ducts running into your box...? Are these going to your grow room?
And if so, why are you sucking the cool air back into the hot exhaust. This was your problem.

Thats hot air coming from the lights. The lights are cooled via air from another part of the basment, through the lights and out into the garage. I am not pulling air out of the room itself.

The goal was to channel all the heat out of the garage. Thats why all the heat is going into the box.

If I exhaust just the AC, I am still dumping the hot air from the lights into the garage.

I tend to believe this hot air building up in the garage is heating up the rest of the house. Obviously the main level is on top of this garage, and I have the finished basement on the other side of the non pictured wall. All this heat has to be affecting it somehow.

 

[hoosierdaddy]

Having only a 5" exit port, I would imagine the AC fan is probably trying to push hot air back to your lights and out that way also. I assume the air from the lights is just passive and no extra fans pushing on them? You could add some Suncourt inlines to the 6" lines from the lights and that would help with the air flow. But you are going to have to open up your exit. I'd say try going from the box to 8" and out, although 8" stuff is harder to access sometimes.

Either bigger fan or larger ducting. I'd say both.

 

[yamaha_1fan]

you assume wrong. There is a 6" vortex pushing on each one.





Bigger fan, bigger ducting. I suspected that 5" outlet wasnt going to work. It was so handy already there. I think there used to be a gas appliance above and that was an exhaust for it.

 

[hoosierdaddy]

Just an idea, but you could mount a power roof vent (Lowes $60-$90) and duct to it.
They are in the 1500cfm range and provide a nice big opening that would allow you to run larger duct to it, say 12", and just build a box around it like you have your AC.
Many of the power roof vents have temp/rh sensors for control.
Something like that in your gables would solve your issues I think, and not much coin to boot. Probably get it done for cheaper than a good new fan, which still may not cure the issue well without increased duct size.

 

[Whatever]

Just so I'm clear before I provide any input...are the 2 ducts I see in one of the latter pics in the garage, where the back of the ac hangs out, that are coming thru the wall and feeding the ac 'cooling' box the same 2 lines you show inside the veg/flower space cooling the lights? Is what you show inside the veg/flower space spread apart the intakes and then the fans pushing air through the hoods/lights from those intakes then out the ducts, almost on top of each other, blowing the exhaust into that an 'cooling' box and 1 449 6" Vortex, the 1 fan hanging in the garage, pulling that hot air out of that box and dumping outside the garage? How many watts is this circuit trying to cool?

 

[yamaha_1fan]

I know what you are going to say, its just too much heat. Truth is the ducting was getting super hot before the lights even came on. So the design was flawed to begin with

Yes you are correct, those 2 6" fans inside the room are pulling air in and pushing through the hoods and outside into the garage. Each light is 1000W, so each run is 3k and a total of 6K. The 3rd set of lights are not air cooled.

I think my best option is to build a rectangular box and dump it out the bottom of the garage door. I already bought some grills for the door. That would be alot less suspicious then a huge hole in the wall.

I cant get to the attic. This is in the basement and I have 2 stories above me and I would have to go through my living room, not a good idea.