Dont MH lights need a cooling fan???

[reefobsessed]

I cant seem to find a MH fixture that has a cooling fan if it does not also house florescents. Dont I need a fan to keep the temp down and prolong the life of the bulb??

[Electrobes]

Argh! I wrote out an entire thing and it just got blipped out because I hit another key and it changed web pages!!!!! Oh well... anyway cooling fans from what I gather aren't really meant for the bulbs but for the tank's water. 1) The evaporation rate goes wayyyy up without a fan... which means more money spent on RO water from the LFS. 2) Again without the fans... also means way higher tank temp which is crucial to keep stable in a reef tank, or in most tanks for that matter. I don;t own a reef tank myself, but have a friend who has two MH and 4 VHO's and lemme tell you the things he scaremed about when a friend of his brother's broke a fan and didn;t tell anyone about it. Thats when I learned what I am telling you now :P HTH

[Bearfan]

MH build up a lot of heat. Running them without fans would be foolish. More than one instance of MH causing a fire have been reported, even on this website.

whoops hit submit instead of preview...

Some fixtures do not need fans because of the way they are designed. If they have a lot of air surrounding them, then no, they prolly don't need fans.. If they are in an enclosed canopy, you may need fans.


Make sure that when or if you have fans in your canopy or fixture, that you draw the hot air out, and not cool air in....This will greatly improve the life of the bulbs and the heat that is generated from them...

[Bearfan]

Running cool air across a hot bulb is always a bad idea, just to elaborate.

[Biggen]

I don't run fans for my MH. I have a pendant style MH system. The pendent itself gets real hot but since it is in the open air, the surrounding area stays cool. Except for underneath the bulb of course.

I think fans are more needed in canopy style systems like Timbo2 suggested. Especially when running multiple bulbs. This is why I opted for the pendant. Keeps heat down and it looks like a really clean install. Plus, I don't have to worry with fans.

[dustybrannum]

kind of a side question but when i get my mh's set up and ready to go i have a window unit that has a thermostat on it. should i set it slightly lower than the temp i want my tank at or equal to it?

[Biggen]

kind of a side question but when i get my mh's set up and ready to go i have a window unit that has a thermostat on it. should i set it slightly lower than the temp i want my tank at or equal to it?

It is a "wait and see approach". If you have adequate evaporation, you may not even see a temperature increase in the MH. Let them run for a day and that will tell you if you need to adjust your heaters, fans, A/C, etc...

Speaking of Fans where would be a good place to get some good cheap fans for cooling my canopy??? I was thinking a couple of the 4" from RadioShack but wanted to know if others had any opinions.

James

[vega]

For canopy type, used a DC fan instead of AC type as AC fan actually had the transformer buildin the fan and it will add extra heat within canopy's air.

DC fan's normally need to connect to a power converter (eg.115V -> 12V) but since the converter is locate outside the tank's canopy, not extra heat is added to the tank.

Also DC fan is much lighter (without the buildin transformer) so its easier to mount to the canopy. i simply use hot glue to mount DC fan in my tank.