Most efficient way to cool 8KW?

Stealthy · Jan 30, 2008

I've got two rows with 4 - 1000 watt lights in each row (total of 8kw). Room will be sealed and I will be using 8 Cool Sun reflectors with the 6" flanges.
I have two 8" Can Fans that I will be using with these lights so the duct will have to be reduced to 6" somewhere along the line.
Here's my question...
Should I run one fan per row of lights (pulling air) or should I bring in the 6" duct, push air with one fan then split / tee off this duct for both rows and then tee back to one 6" duct with another fan pulling air at the other end? Which configuration would be more efficient?
This may not make sense so I've included pictures.
Thanks guys.

Mr Celsius · Jan 30, 2008

Most efficient cooling method.

TGT · Jan 30, 2008

Very good question which seems extremely hard to answer without experience. I personally don't have much experience with cooling lights other than what I have seen so I wouldn't be too much help. But just looking at all three diagrams and using comon sense I would say number one and number three would be the best, with probably the third diagram being the choice format. It makes sense that not as much heat would build up as apose to the others as the air only has to travel through 2 hoods instead of 4. Also, with both you will get the the full power of the fans equally, so I would have to say the third idea wins hands down. That said, the most common setup would be the first and I have seen this work in the past, how efficiently I do not know - so with both I am sure you would be fine. This is just a guess as like I stated already light cooling is not my expertise, but it is very interesting. Thanks both for putting up the diagrams to make it more easy to understand. I will be watching as I too will have to use air cooled hoods for my next setup. Good luck and stay safe!

TGT

gregor_mendel · Jan 30, 2008

If you've not purchased the hoods yet, stepping up to eight inch flanges would be a more efficient way to do it no matter which drawing you follow.

I vote for Mr. Celsius's design.

yamaha_1fan · Jan 30, 2008

But pic #1 is a straight shot. Pic #3 has at least 2 90 degree turns which reduces air flow. I also wonder how does each hood get the same amount of airflow?

Not criticizing, just inquiring

BlindDate · Jan 30, 2008

Stealthy......You cannot run 4 x 1000 watts inline and expect them to get cooled by a single 8" fan. Use the layout that Mr. Celcius recommended and upgrade to 12" fans on at least 12" manifolds. Even with the air cooling your still going to need at least 10,000 BTU of air conditioning as well. Oh,and make sure you use insulated ducts. 8000 watts is no joke.

But pic #1 is a straight shot. Pic #3 has at least 2 90 degree turns which reduces air flow. I also wonder how does each hood get the same amount of airflow?

They are not 90 deg turns but manifolds.

Each PAIR of hoods gets the same airflow (TEMPERATURE FLOW RATHER).

Stealthy · Jan 30, 2008

Mr.Celsius,
Thank you so much. That diagram is a big help. I was just wondering...wouldn't most of the air entering the manifold go to the first couple of rows of lights leaving the farthest rows fighting for cool air. Probably a dumb question with a common sense answer. Thanks.

gregor_mendel,
I've already purchased the Cool Sun 6" reflectors. I've used 8" hoods in the past and I feel to much light escapes (I'm weird like that).
6" is a good compromise

although 8" would be better for cooling.

yamaha_1fan,
Yeah that's what I was wondering. Seems that all those turns/elbows would reduce the airflow dramatically??

BlindDate,
YOU ARE RIGHT!!! 8KW is no joke and that's why I'm here asking. I'd rather hear from others personal experience rather than learn from my own trial and error!!
So you don't think two 8" fans will be sufficient to cool 8kw (I do plan on using an AC unit)?

I'm not very handy/crafty so if anyone has a picture or link to show a "real" setup of Mr.Celsius diagram (large manifold w/ rows of lights attached) please post.

yamaha_1fan · Jan 30, 2008

just an idea as I am no expert or even close on this type of stuff. But how about 4 6" fans? Use pic #1 and just put put one on each end, one pushing, one pulling?

Seems the easiest to build and when you consider the bigger 12" fan and ducting, it will probably cost the same, maybe cheaper?

I use one 6" to push through 3 1000 watters and it seems to do the job. I get plenty of air out the exhaust.

Blind, I dont understand. Its still a 90 degree turn that the air has to make. The air is being pushed, then has to turn to go in the hood, then turned again to go out. Unless it gets built differently than the picture?

Mr Celsius · Jan 30, 2008

Stealthy said:
Mr.Celsius,
Thank you so much. That diagram is a big help. I was just wondering...wouldn't most of the air entering the manifold go to the first couple of rows of lights leaving the farthest rows fighting for cool air. Probably a dumb question with a common sense answer. Thanks.

Not a dumb question at all.

With a fan pushing from the intake it will cause the first to get more airflow then the second and so on until the 4th. However, you have a fan also pulling from the opposite side, therefor the "4th" hood will actually be the first hood having air pulled from it. Do you see how the fans balance each other out?

BTW to create pressure, the long duct that the pairs of hoods connect too should be 8" and the actual ducting to the hoods and in between hoods should be 6", as to create pressure. Basically, on the long duct, just have the fan attached to a 10" T

and then on the T part that goes to the hood, put an 8" to 6" reducer

.

Also, seal all your hoods cracks with metal tape, this wont allow any heat from the hoods to escape back into the room.

You aren't going to get away with cooling the entire room with just this. You will need additional ventilation; whether that be AC or another fan, this will depend on the size of the room.

Hope this helps, you can PM me anytime. Growing ain't cheap! :wave:

Mr Celsius · Jan 30, 2008

yamaha_1fan said:
just an idea as I am no expert or even close on this type of stuff. But how about 4 6" fans? Use pic #1 and just put put one on each end, one pushing, one pulling?

Seems the easiest to build and when you consider the bigger 12" fan and ducting, it will probably cost the same, maybe cheaper?

I use one 6" to push through 3 1000 watters and it seems to do the job. I get plenty of air out the exhaust.

Blind, I dont understand. Its still a 90 degree turn that the air has to make. The air is being pushed, then has to turn to go in the hood, then turned again to go out. Unless it gets built differently than the picture?

Firstly, he doesn't need a 12" fan. His 8" fans will work fine.

Second, in a way, it is a 90 degree turn, but there isn't any pinch's that would normally happen with flexible ducting. Its kind of hard for me to explain, which (if you read my quote from Einstein) must mean I don't understand it well enough. The most I can say, is this is the most efficient design for cooling, period. I've seen it work.

Stealthy · Jan 30, 2008

Mr Celsius said:
Not a dumb question at all.

With a fan pushing from the intake it will cause the first to get more airflow then the second and so on until the 4th. However, you have a fan also pulling from the opposite side, therefor the "4th" hood will actually be the first hood having air pulled from it. Do you see how the fans balance each other out?

BTW to create pressure, the long duct that the pairs of hoods connect too should be 8" and the actual ducting to the hoods and in between hoods should be 6", as to create pressure. Basically, on the long duct, just have the fan attached to a 10" T

and then on the T part that goes to the hood, put an 8" to 6" reducer

.

Also, seal all your hoods cracks with metal tape, this wont allow any heat from the hoods to escape back into the room.

You aren't going to get away with cooling the entire room with just this. You will need additional ventilation; whether that be AC or another fan, this will depend on the size of the room.

Hope this helps, you can PM me anytime. Growing ain't cheap!

Mr Celsius,
Thanks for explaining but I have a few more Q's for you.
So you don't think I'll need to go with 12" fans?
When you said ...
"the long duct that the pairs of hoods connect too should be 8"
your taking about the main manifolds, right?

I do plan on using a window unit or split unit, Dehumidifier, etc. I've also got lots of extras...Green Air Atmospheric Controller, CD-6 Co2 Gen, Co2 digital sequencer / controller.
I know growing aint cheap but I'm trying to keep spending under control...you know how it is and since I already have two 8" Cans I was hoping to utilize them rather than purchase larger fans.
I've been growing for over 10 years but I've never done 8KW so I wasn't really sure how I should configure my venting.

Here's my plan for the rest of the room
Like I said, this will be a sealed room -KINDA- but I will have a 10" or 12" exhaust duct connected to a CanFan w/ Can 100 Filter. This will be connected to the Atmospheric controller and only kick on if temps or humidity get way way out of control. I will have "always closed" dampers connected to this exhaust and intake. They will only open when the exhaust kicks on. I also will have a UVonair 3000 that is placed inside the duct so not only does the air get scrubbed but it gets a jolt of ozone to mix with later on down the duct line before getting exhausted outside.
Just waiting on my beans...hope they don't suffer the same fate as my last batch.
Thank again guys!!

Edited to ask another question...
Just gave my fans a closer look and one 8" CanFan is a high output, the other is a standard 8" Can Fan. Which one should be pulling and which should be pushing? The HO fan moves a couple hundred CFM more than the standard.

Mr Celsius · Jan 30, 2008

Stealthy said:
Mr Celsius,
Thanks for explaining but I have a few more Q's for you.
So you don't think I'll need to go with 12" fans?
When you said ...
"the long duct that the pairs of hoods connect too should be 8"
your taking about the main manifolds, right?

I do plan on using a window unit or split unit, Dehumidifier, etc. I've also got lots of extras...Green Air Atmospheric Controller, CD-6 Co2 Gen, Co2 digital sequencer / controller.
I know growing aint cheap but I'm trying to keep spending under control...you know how it is and since I already have two 8" Cans I was hoping to utilize them rather than purchase larger fans.
I've been growing for over 10 years but I've never done 8KW so I wasn't really sure how I should configure my venting.

Here's my plan for the rest of the room
Like I said, this will be a sealed room -KINDA- but I will have a 10" or 12" exhaust duct connected to a CanFan w/ Can 100 Filter. This will be connected to the Atmospheric controller and only kick on if temps or humidity get way way out of control. I will have "always closed" dampers connected to this exhaust and intake. They will only open when the exhaust kicks on. I also will have a UVonair 3000 that is placed inside the duct so not only does the air get scrubbed but it gets a jolt of ozone to mix with later on down the duct line before getting exhausted outside.
Just waiting on my beans...hope they don't suffer the same fate as my last batch.
Thank again guys!!

Edited to ask another question...
Just gave my fans a closer look and one 8" CanFan is a high output, the other is a standard 8" Can Fan. Which one should be pulling and which should be pushing? The HO fan moves a couple hundred CFM more than the standard.

I don't really know how big your room is or the ambient air temps of the air that you'll be pulling through the hoods or any of the other variables, but I would like to say that the 8" fans will be enough. Try to pull air from the coldest source (usually under the house, but use a good air filter).

Your kinda throw in a funky thing there with the different fan speeds of the two.... If you had to use both (both with ideally be the same cfm) you would want the strongest pulling and the weakest pushing. I'd really just try and exchange the weaker one for an equal sized one.

Bigger is almost always better in the growing world, so as Chosen said, a 10" or 12" would be even better, but the 8" will work.

By the long ducting, I do mean the manifolds.

I personally would go with a 16000 btu mini-split AC unit. There's no air exchange and they are pretty compact. Probably run you about $900< for a good one. eBay is always a good place to find one. Maybe you'll be lucky and one of the sellers will be in your area.

Depending on your can 10" or 12" you'll probably want a can 125. I don't feel that the ozone generator is necessary if your using a good carbon filter; unless you mean its in your hood ducting. I personally love my Can fan Max 10" (1024 btu, hooked up to Can 125 cooling 6kw with the same type of ducting; also have a Can 100 w/ Can RS8L on a computer if temps get to high).

Sealed rooms are very difficult because your dealing with air exchanges of heat, you have a pretty solid plan, just make sure you're dealing a competent AC unit. The standard rule is 4000btu per 1000w light, but since you'll be venting them so efficiently, I brought it down to 2000btu (I'm 92% sure that'll work), if you wanna be 100% sure, make it 3000btu per 1000w.

BlindDate · Jan 31, 2008

Blind, I dont understand. Its still a 90 degree turn that the air has to make. The air is being pushed, then has to turn to go in the hood, then turned again to go out. Unless it gets built differently than the picture?

Yes, but since the volume of the manifold is (should be) so much larger than the 6" hood duct it acts as a straight pull when evacuated by a large (12") fan. Don't think of it as a duct, but rather a large suction chamber. Now if he goes with the 8" manifold then yes, the air is making all kinds of 90 deg turns.

I would still seriously recommend the 12" manifold and fan. The extra cost in parts is nothing compared to the time and effort of the assembly. You can never be to big, yet if it's too small you're fucked. But then I have no idea where you are growing. If you're sucking sub-zero air into that thing then 8" might be fine.

Consider that the area of 4 each 6" ducts is exactly the same as the area of a single 12" duct.

An 8" manifold is equal to the area of only 2 each 6" ducts. Installing 4 of them would be major blockage.

Stealthy · Feb 7, 2008

Mr Celsius said:
Most efficient cooling method.

Lets say I use this setup but instead of 12" fans I use the 8" fans. Would I be better off entering the room with my 8" duct (w/ fan pushing air), then attach the 8" duct to the larger 12" manifold which then supplies the lights with cool air (via the 6" outlets built onto the manifold) to be exhausted out the opposing manifold and ducting on the other side. Should the "exit" manifold also be 12" then reduced back down to 8" duct (with 8" fan pulling at exit end of 8" duct).
Or will 10" manifolds work? Benefits of a larger manifold (larger than incoming and exiting duct)?
Hope this makes sense...I'm pretty baked! :rasta:

Thanks guys

Mr Celsius · Feb 7, 2008

No no, you want the manifold ducting to be 8". You want high air pressure and the 8" fans would not create that pressure.

Whatever size your fans are is what size your manifold should be.

Albert Hofmann · Feb 7, 2008

I'm currently building the setup that Mr. Celcius is talking about...8 lights (2 x 1000, 6 x 600) 4 runs of 2 with 1 10" vortex pulling through a rigid duct system consisting of 10" intake and exhaust connected to 14" x 8" manifolds with 4 6" feed and exhaust lines, everything is siliconed and taped to be airtight...this sytem pulls like a sonofabitch and I am firmly confident that it will be up to the task of cooling my system...oh yea, intake air will be 70 summer and 50 winter, which is an important factor

sorry, my room is such that I cant get pics with the whole system in one shot

Stealthy · Feb 7, 2008

Mr Celsius said:
No no, you want the manifold ducting to be 8". You want high air pressure and the 8" fans would not create that pressure.

Whatever size your fans are is what size your manifold should be.

Got it!! Mucho thanks Mr.C

Albert Hofmann,
No need to apologize about the pics, they're great!! Do you have one 10" pulling or do you have two (one for pulling - one for pushing)?
My plans are to enter the room with standard 8" insulated duct then connect that to a "metal" type manifold. I assumed that the manifold should be larger but after reading the Mr.C reply I realize that I need pressure (which I loose by going larger with the manifold).
Did you make that manifold yourself or did you have it made? I'm not very handy with things like that...anyone have any DIY tutorials or links on this issue (tools needed etc.)? It shouldn't be to difficult, right?

Mr Celsius · Feb 8, 2008

Albert, very professional, I must say. I have no doubts that you'll be extremely happy!

Guest · Feb 8, 2008

Albert...........f*#@ing outstanding and a professional job, absolutely BEAUTIFUL and well laid out. Hope you didn't cut your fingers on the sheet metal.

If you find that more air is being pulled from the 6" elbows/ducts/hoods closest to the fan pulling the air you can install dampers in them and balance the system.

Gotta say it again, Beautiful!!!!!!!!!!!!!. Can't wait to see it when you finish.

Hoooah,

TyStik

Stealthy · Feb 9, 2008

Great idea on those dampers Ty-Stik!!

Most efficient way to cool 8KW?

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