As some of you might have guessed I :love!: DIY work. Just gives me a new excuse to buy more tools. :tongue2:

OK, my newest project was to create a set of fans to help reduce some of the heat produced by my metal halide and it's ballast.

Parts:
1 4 inch computer fan
1 3 inch computer fan
1 12V 1500mA transformer

The fans I got from CompUSA on sale for $5.00 each (My local store was closing). The transformer I got from Radio Shack.

Extras:
Some ~16ga wire.
Various Solderless connecters.
Electrical Tape
Mounting Hardware

Step One:
Locate the positive and negative wires for each of the fan units and strip about 1 inch of insulation off. Repeat for the transformer.

Step Two: Decide how and were you are going to mount the fans. One of my fans is inside of my hood and therefore I needed spacers to allow air to flow from around the back of the unit. It would be good to go ahead and cut the 16ga wire to the lengths that you need at this time.

Step Three:
I used solderless butt connectors to attach the fans to the extra pieces of wire. I twisted the ends of the extra pieces of wire together and then attached female blade connectors to each group of wire.

Step Four:
I used Male blade connectors to make the connections to the transformer.

Step Five:
Connect the Male and Female blade connectors and plug the transformer in.

Notes: The large fan had to have small sections cut out so that I could fit the hardware in to mount it to my hood.

Here are some pics of the completed fan units.

The first three pics are of the large fan that is positioned to deflect heat away from the tank.

The fourth pic is of the smaller fan positioned to blow cool air over the ballast.

I have the transformer plugged into my light timer so that they are only running when I am burning my MH.

nice tips man.

The only thing I would recommend is that you use shrink tubing any where you make a connection unless its far from moisture. I feel it does a better job at sealing than electrical tape and it can still be removed.

The wires from the fans themselves are actually wrapped in several layers of tap to the outside of the fan housings. I did this so I had a more uniform, cleaner look. The only exposed connections are the blade connects, but they are high up under the tank itself. In there locations I am not worried about to much moisture. In my experience shrink tubing works for the most part. The best way is probably to solder the connections, then cover with shrink tubing.

Good stuff. I've done the same; both with computer fans and adaptors, and with cabinet type fans that can be fitted with a standard plug.

I've fit them into drilled holes in the left and right sides of the hood. If you place one with the air flow pulling in from the outside of the canopy (or stand for that matter, if you need to cool a sump) and one positioned as an exhaust, you have a very effective cooling system that also aids in evaporation and export of moist air.

Yours seem to be mounted without the holes in the canopy, but rather with spacers, separating them from the wood, and giving them an "intake" of sorts. Do you find that efficient too? I'd rather not have holes in my canopies if I didn't need them.

Dave

I found that the airflow was not reduced by just spacing them. If you can not find the plastic spacers you can use some 1/4" semi-rigid tubing from a RO/DI unit.

Awesome.. I'm putting a 36 bow in my family room. I am putting in a single MH over it in the DIY hood, and didn't want to have to drill holes in it and would rather keep the fan noise muted inside the hood, keeping the missus happy ;) I'll do this trick.

Thanks again dude!

Dave

I have run fans over MH before but I always made the air flow blow acroos the MH bulb. It wasnt in a housing but I am looking to build a housing and was curious is it best to have the computer fans blowing air out of the hood or over the bulbs and out of the hood through some vent holes?

It depends on the design of your hood. If you look at my tank thread "My 40 Gal" you will see my hood is free standing from the tank and has ample room under the hood. With this design I just needed to push air over the MH unit. If your hood unit is enclosed around the tank then I would actually mount one set of fans to push air in from the sides and one side to pull air out of the top. This will create a forced draft system that will also use the natural thermal movement to its advantage.

that sounds good. thanks for the info.

a question: can I run more than 1 fan off of one 12v ad/dc adaptor? The fans I have are 120mm 1600rpm

It depends on the amps that your 12V adapter puts out. Look on your fan and you will see the voltage and amp rating. Add the amp values and multiply by 1.1 in order to give you a comfort zone. If this is still below the value of amps you adapter produces then yes you can use more then one one the adapter.