Air-cooled hoods, push or pull bulb heat?

murtymaker

Well-Known Member
Do you pull the heat away from your hood? <<<<<<(LIGHT)


Or do you push air through your hood over your light? >>>>(LIGHT)>>>>
 

UserFriendly

New Member
The more heat you've got, the more you should be pushing. You don't want all those watts running through your fan, but essentially pushing and pulling perform similarly. The only time it would really matter is if there is a leak in the ducting somewhere, which would affect pressure differently on both sides of the fan.
 

FullMetalJacket

Well-Known Member
depends on situation and fan...doesnt really matter

But if they had the same cfm SP push and push would be better because you would have more air molecules around the light as the pressure is higher here as pulling you create somewhat of a vacuum affect. More molecules take longer to heat up. I chose to pull as the difference is minute and my fans pull better.

 

Hotwired

Well-Known Member
When you "push" the air thru all the duct and hoods the air is more prone to getting "stuck" in pockets. This will cause backups and can be a pain in the ass.

When you "pull" thru all the duct and hoods you basically get straight line winds which surround the bulb and "grabs" all the heat it could hold and exhausts it.

Think of it like this:

Push Method:
You are in front of a giant fan and it is "pushing" air at you. It's blowing you backwards but not just in one place, but all over your body. Above, below and on the sides of you too. This is the air "spreading" out and losing cohesiveness. You lose air volume and speed like this and eventually it gets too weak to do anything.

Pull Method:
Now think of a giant tornado. It starts by "pulling" up air from the ground. It looks like a giant vacuum as it spins towards the ground and almost comes to a point. The air is now super streamlined to shoot straight into the cloud by being "pulled" into it. It can even bend by 90 degrees and NOT lose it's potency.
Now think of the intake part of your fan. It "pulls" the air toward and then thru it. It has the ability to go around bends and maintain it's strength (to a point, that is what static pressure does), speed and volume. The air will be streamlined around the bulb and "grab" all the heat it can hold while going by. The cooler the air the more heat it will be able to hold.

99% of inline fans can handle heat up to 140 degrees. Trust me, even if they could only handle 100 degrees you still wont hurt the fan.

The real things that effect bulb temperature are:

1. The temperature you are using in the duct to cool the light(s)
2. The speed of the air flowing over the bulb
3. The volume of air flowing over the bulb

The cooler the air temp cooling the bulbs the less speed and volume of air is needed to cool it. IMO, the best way to cool those lights is to pull the air over them. Keep the air as streamlined as possible so it escapes holding as much heat as it can.

The same can be said with clearing air from a room. Pull it out, don't push it out :shock: :joint:
 

Little Tommy

Well-Known Member
I also pull my air through the ducting system. I have an intake outside the room at floor level. It goes through the light, past the bulb and then through the fan which is 6" away from the exhaust which is at eye level outside the room. I tried to keep the duct runs short and pull with a 250 cfm 6" duct booster fan. The exhaust coming out doesn't even feel very warm to me. Dropped the temps in my room by 15 F.
 

BigBudBalls

Well-Known Member
I like to push. Gives more air molecules to absorb more heat. Also keeps the fan cooler (if thats an issue) I rather not stave, but feed a heat exchanger medium/area.

As far as the eddys, if you have an eddy friendly system its not a problem. But with a system with eddys, changing to pulling, air is still flowing past hic-up, just a little less volume of it resulting in a smaller eddy current (due to lack of volume of air).
 

Apalchen

Well-Known Member
I've done both. It really depends on your setup. If your fan is large enough than I recommend pushing. There are always gonna b small leaks in reflectors, at least any of them I've used. If your pushing the smelly air is pushed back into your room, if your pulling those same leaks suck unfiltered air into the duct and the smell will come out the exhaust.

So if smell isn't a worry for you than either way will work but if your not in a friendly state I'd push the air for peace of mind about the smell.
 

Homie Da Clown

Well-Known Member
I run 4 hoods (1000 watt each)
I use 2 fans that our identical.
both of them are fastened to the wall where they exit/enter the grow room, and they are hooked to a register upstairs. And that’s how I heat my house all winter.

However if I only had one hood, I would push the air through the hood. And I have ran it this way myself. It has nothing to do with the fans efficiency, but more to do with smell. I’ve had several hoods and 75% don’t completely seal. If your pulling air you can pull smell thru the hood, and that can be an issue. If it isn’t an issue, then I would try both ways, and data log each one. And then you tell us (community) what your findings are. Hell if you do a killer job it might even get a sticky from a mod or something
 

oill

Well-Known Member
I run 4 hoods (1000 watt each)
I use 2 fans that our identical.
both of them are fastened to the wall where they exit/enter the grow room, and they are hooked to a register upstairs. And that’s how I heat my house all winter.

However if I only had one hood, I would push the air through the hood. And I have ran it this way myself. It has nothing to do with the fans efficiency, but more to do with smell. I’ve had several hoods and 75% don’t completely seal. If your pulling air you can pull smell thru the hood, and that can be an issue. If it isn’t an issue, then I would try both ways, and data log each one. And then you tell us (community) what your findings are. Hell if you do a killer job it might even get a sticky from a mod or something
Always liked the idea of heating the house in winter with hps.
 

Homie Da Clown

Well-Known Member
Always liked the idea of heating the house in winter with hps.
Yes! It is a game changer. My electric bill is about 300 a month from October to May. But June, July, Aug, Sept, it’s been to hot to grow. Just picked up a mini-split, so I’m gonna grow thru the summer, but I’m slightly scared what my electric bill may look like.
 
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