Air-cooling a bunch of lights

[grow nerd]

I'd like to see some input on how you'd go about air-cooling 35 lights in a rectangular room.

Right now in my mind I have the room at about 30' x 33', with 5 "rows", each row consisting of (3) 4x8 tables and (1) 4x4 table with (7) 1000w lights over them. About 16" spacing between rows. Can you picture it?

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I'm open to suggestions on what type of equipment you'd use and how you'd use / place it, how you'd lay out the ducting, etc.

Me? I don't really like the idea of running more than 3 lights in-line for 6" ducted hoods. So simply installing one fan pulling at one end for each horizontal row of 5 lights doesn't really fly. Maybe a plenum box / splitter in the middle with a fan attached, and two large (14"-16") passive fresh air plenums running down the sides of the room feeding each row of hoods. Thing is although the equipment list is flexible, I'd like to keep it simple yet efficient.

So what comes to mind is:

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[] = table
x = fan
# = rigid metal duct
~ = flexi duct

...or use some 4-way plenum and cut the number of fans in half.

This room will be inside of an existing building (box in box), where it will likely be drawing air from (I could duct the cold air intake plenum to outside of the building, but probably not necessary). The exhaust would be ducted outside of the building, likely through multiple roof vent cap type devices.

Another thought, but one that would use lots of rigid ducting, would be to run long cold/hot plenums down the length of the row (some shared by 2 rows), and have 1 fan at the end of each hot plenum pipe. The concern about this is how even the distribution of air will be through 7 outlets across a ~30' length...

Any input from the real HVAC pros much appreciated on how best to cool these things.

What are your thoughts on using standard inline centrifugal vs mix-use (CanMax, S&P) fans for plenums?

 

[grow nerd]

Planning on cooling the room using a 5-ton split A/C with the air handler mounted in the ceiling for sideflow, and a diffuser sock attached to the output. I think it would pretty wise to build for 10' height rather than 8'? I could put the AHU on the ceiling and have ducted return & cold air, but would it give me any advantages at all really?

Also in the plans is a smaller (2 ton? non-mini if I can help it, for the reason of bigger AHU) unit that will ensure that the A/C won't short cycle or the room temperatures won't fluctuate too much... and just as a backup for just a real hot day.

 

[Lazyman]

Hey I like it man, here's what I would do:

8" fans and insulated ducting to 8" magnum xxxl hoods, one 8" per 5 lights (running your ducts sideways. I think 7 is too many even with the fans on max speed, and it would be noisy!)
12" sheetmetal manifolds on each end and 12" tees, with 12-10-8 reducers. Kinda expensive but it would be sturdy, flow well and it would be quieter than a ton of flex ducting. Home depot sells 12" stuff.

If possible I suppose having a separate intake and exhaust port for each chain would be ideal though, I think you'd exceed a manifolds airflow capacity with that much volume. Look up the flow rates for various duct sizes and subtract 50% for each 90*elbow or tee.

For your fan question, once you know the volume of air you can move through a given system, compare the flow charts for each fan and see what kind of pressure it can do it against. Higher numbers are better!

Let me know if you want an Excel Air XL 5 ton, I can get you a killer deal. DIY install once you have your 40A 240v circuit in.

 

[Lazyman]

Oh forgot your last question, I love emergency cooling plans.

instead of a spare ac, what about splitting the lights onto two timers, and stagger them both evenly so each one can sorta illuminate the whole room. Put both systems on a high temp shutdown, but set them at different temps. That way half of the room will shut down first, but all plants will get some light. If it still gets hotter the rest of the lights turn off. Put in a couple 12" max fans on a temp sensor, so if it exceeds 90* CO2 turns off, and the exhaust fans go nuts. Cheaper to do all of this than a second ac, and would probably work better if needed.

 

[DIGITALHIPPY]

why not use 8" reflectors? and do one 8" for each row of 5?
or alternatively, you can duckt all the ref's to one big trunk line and have a 18" max or 20" max fan pull the air through them all.??

S&P fans are great, but only for short throws, not sure if all that ducting will allow proper flow. maxfans are better for large runs/lots of drag.

or more S&P's like 1 6" for each 3 ref.s
ive used the 6" s&p on 4 hoods, with no issues.

 

[grow nerd]

Staggered lights-on is already planned. 9 x 40A contactors, each driving 4 lights. In 4 separate banks with on-delay timers so they turn on in series.

Almost out of battery. More later. Thanks for now.

 

[grow nerd]

I very much dislike 8" reflectors, I don't think you gain much cooling at all compared to a better overall cooling design. The extra light lost isn't worth it IMHO.

I've done plenty of watts of cooling with 8" and 10" (not much diff than 8" besides mouth size really) fans, so I'm not real afraid of 'em. But bigger would probably be better all around for initial reasons mentioned, I don't know. Argh low battery shutoff warning.

More later.

 

[BlindDate]

Get a 20 ft high ceiling and 1 big industrial blower. forget the air cooling. Heat travels UP.

 

[Lazyman]

Get a 20 ft high ceiling and 1 big industrial blower. forget the air cooling. Heat travels UP.

Air-cooled grow = no ability to run CO2.

Air cooling hoods with outside air = ability to run CO2, and run hoods closer to canopy.

Makes bulb changes a bitch though, but whatever.

Hey GN, got any links to studies on the size of the duct in correlation to loss of lumens? I'd love to see the data on that.

Thanks buddy

 

[grow nerd]

Lazyman, bulb changes are fine if you have hinged hoods. On duct size (or existence) / light loss, pico has a pretty good thread that shows that type of data.

BlindDate, 20ft isn't possible but I could certainly pitch the roof and have something like 10-12' (edge) - 18' (center), if it'd help. But still would prefer air-cooled lighting to remove extra heat from the dense room. Your further thoughts / arguments on this appreciated.

Happy Thanksgiving, everyone. Have so much to be thankful for, and am very happy with where things are going.

 

[grow nerd]

Haven't had much time to spend thinking about this project lately, but now that it's about to start I'm back to the drawing board... and I can't think of too many other designs.

I'm going with BD's advice and going with as high a ceiling as possible w/o going into complicated construction. This means minimum 10', possibly 12', but likely no higher than that. I've dealt only with 8' drywall, but I imagine 10' and 12' pieces are going to be quite a pain to deal with overall. But probably easier than dealing with the extra seams, which is probably why they make 10' and 12'. I don't know, I'm new to all this construction stuff.

 

[BlindDate]

35,000 Watts in a 30 x 35 x 12 room is going to be tough. I think that your only option is up. Build a floor baffle box with grates in it and put several big ass blowers on the roof sucking air up and out. You will need massive intake vents all around the floor. Heat travels up so that helps. It would also help if you lived in a cool climate. If this grow is in SoCal then forget it, you need a bigger building or scale back on your ambitions.

 

[grow nerd]

You think 35kw in a 35x35x12 room with air-cooled hoods and 7 tons of A/C power will be difficult?

I've never done a 35kw single room, or anything close to it. Closest I've come to in a single room is a 12kw sealed with 8' ceilings, which was a breeze using a 1.5ton mini split and air-cooled hoods. Also done a few non-air-cooled setups in low (6kw in 7') and higher-than-average (8kw in 10') setups and have a little bit of feel on how things work.

But I know, probably better than most, that not many things in life scale linearly. Hope this is one of the few that scales a bit better, though.

I thought once about the floor grates and fans sucking air up and out. In fact I still dream about a setup like this (similar to computer server rooms, raised floors, cable trays etc all underneath... although in grow rooms cable trays should be above).

It seems your domain is mainly larger plants indoors, in non-sealed, fresh-air rooms. I'm not sure that some of the concepts would apply very well in closed/sealed rooms with environmental control equipment... or do you believe it does? I've done fresh-air rooms a few times, and also have a little bit of feel for how things work, and can see your thought process. Or am I mistaken / confused?

Either way, planning on breaking ground before the end of the year, so we'll see...

 

[muttley]

With the 5 rows of 6 lights, a custom lighting controller should be used. You can control all the lights to be on at certain time, then have a certain number of lights rotate off as the same number be turned on. Since it takes several minutes for a bulb to reach full brightness, wait until the light is on full, say 15 minutes, then power off a closer light. 30 ballasts all on at once for say half the light cycle, then program the lighting panel to repeat every two hours, lights going off and on. With temp control, turn off lights to help bring temps down. Program a sequence to turn off certain light(s) when room gets to warm. Seen some nice controllers to handle this.

 

[grow nerd]

Hi muttley, I think I have that covered already.

Staggered lights-on is already planned. 9 x 40A contactors, each driving 4 lights. In 4 separate banks with on-delay timers so they turn on in series.

 

[250wscrogger]

holy shit man 35kw? I'd just make 2 rooms with 16k in each and run it on a flip flop...probably much easier to cool that way, but wtf do I know?