Fan Orientation in DIY Hood

[shadowbearwv]

I'm in the process of building a hood.

The hood will house 2 175 MH , 1 2 bulb T5 Actinic Retrofit and some fans.

The hood I'm planning will be sealed Plywood with some trim just to hide the lights. I'm planning on using wood L brackets to mount it to the wall behind the tank with cabling to raise and lower the lights.

I want to get the best air flow for the the lamps what would be the correct orientation of the fans? I was thinking of getting computer case fans with LEDS and use those for cooling and moonlighting, but was worried about evaporation causing problems with the fans.

I plan to suspend the light about 14 inches above the top of the tank.

Any help is appreciated.

SB

[kaylo]

I can't answer all of your questions, but I will toss this out.

As far as the LED lights in your fans, you will probably not be running the fans at night or when the lights are off. This would make the LED lights only on during the day and pretty much useless.

I believe the best way to run your fans is over the water to help with heat from the halides and your water temp. So mabey air intake on one side and exhaust on the other. If you are using them to cool the fixture, mabey same setup but higher up in the hood.

I'll tag along and ask another question that may help us both as I will also be building a hood soon.

Is there any type of computer case fan that should NOT be used for a hood for any readon?

[swearint]

Orient the fans so that they blow into the hood. That will extend the life of the fans and improve performance slightly since the fan will be moving cooler, drier air from the room. As fan as whether to blow long-wise or cross-wise, probably won't make that much difference. It's more a matter of the hood layout, nearby obstructions, and aesthetics. For comparison, I am using four fans for a total of approx. 200 cfm in a hood with two 175W MHs and four 96W PCs. They are on a thermostat set at 85F and the cooling is more than adequate, they cycle about every five minutes.

Todd

[lizardarm]

Two fans both blowing in from the ends or the back with vents in the top of the canopy directly above the halides to help push the already rising hot air out.

[shadowbearwv]

<a href=showthread.php?s=&postid=14439832#post14439832 target=_blank>Originally posted</a> by lizardarm
Two fans both blowing in from the ends or the back with vents in the top of the canopy directly above the halides to help push the already rising hot air out.

Perfect!

Thanks for the help.

SB

[leezer]

Yes, only position the fans to be pulling cool air into the hood. Do not have one pulling in and one pushing out. A engineer friend of mine explained the reasoning behind this to me once. If you do, you'll basically be running two fans to move the same amount of air as one fan would do by itself. Instead, having two fans pulling in cool air from outside the hood will move twice the air volume as the previous set up would move.