As some of you know, I just upgraded my lighting to dual 250w HQI's this week. I ended up mounting my minipendants to a 2x4 that I mounted inside the hood


Now, I didn't realize how hot these mini pendants get, and I'm really concerned that the heat might ignite the 2x4 that the pendants are mounted too.

What do you guys think? I could get some spacers at Sears, but they're plastic and would probbaly melt.

I would sandwich a piece of fireproof board between the light and the 2x4. You should be able to pick some up at Home Depot. I believe it is used around woodstoves and gas fireplaces.

Good luck.

Marty

I posted this reply in the DIY section. I hope it helps.

I have found wood to not be a good material of choice for aquarium reef hoods. When a combustible material such as wood is exposed to heat for extended periods of time, the wood fibers break down and the kindling temperature is significantly reduced. This phenomena is called Pyrophoric Action which is the chemical decomposition of wood due to the continuous or intermittent application of heat. At about a year, I noticed my painted homemade wood hood beginning to crack. The wood was drying out!

Exposed to high temperatures, wood burns at a temperature of about 400c or about 750f. Furthermore, wood also ignites easily because of the production of flammable gasses brought on by the high temps. The heating value of one kilogram of dry wood is 4000-5000 kilocalories. There are differences among species derived form differences in density and the presence of extractives like resins in pines.

After building my new light hood out of a 1/8’’ sheet of aluminum, I sleep much better when I am away from home. You might want to read this: http://www.housedetective.com/columns/archives/hd9.htm

I mounted my MH reflectors in such a way that there is about a 2" clearance between them and the surface of the wood. I have a radio shack fan ventilating the hood, but I'm thinking of adding 2 fans, mounted on the top of the hood, - either blowing on the reflectors or ventilating the exhaust. This should keep the wood at safe temperatures given the clearance of the reflectors.



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Why not take them out of those pendant boxes that glass on them is limiting the light fromt hem I have 2x250 mh's and 2x96 watt p.c.'s with 2 4" fans no probs.......You should definately not have your ballasts on back of the hood thoguh move them away from the hood and tank as far away as possible..Dan

Hi,

Glass shields are a must with a HQI lights. They emit too much UV radiation. They are not like normal mogul based MH lights. Mogul based lights have shielding built into the outer envelope. Double ended HQI lights have none and would seriously burn the corals.

Later
Drew

[This message has been edited by Drew (edited 02-12-2001).]

Have you thought of puting some kind of ceramic tile underneath? Then you could use fire-rated silicone to adhere the tile to the wood, the only problem I can see is finding a way to mount the pendants onto the ceramic. [img]/ubb/frown.gif[/img]

Ryan

thanks for the reply everyone. I'm leaning towards the fireproof board between the light and 2x4.

Why not take them out of those pendant boxes that glass on them is limiting the light fromt hem I have 2x250 mh's and 2x96 watt p.c.'s with 2 4" fans no probs

Bamm Bamm,
HQI's require a UV sheild...there is really no way around that.

You should definately not have your ballasts on back of the hood thoguh move them away from the hood and tank as far away as possible

Why is that? They are above the waterline in the tank and have no chance of ever getting wet.

You can put a reflector expensive alum sheet or cheap alum. flashing just clean the oil off with degreaser first. (slight oil) You can also use washers as spacers to lessen the heat but the alum will act as a shiel=heat shiels no sweat. IMO no canopy should have exposed wood above the light not only for heat but over the years it dry rotts or whatever it gets ruined and starts to fall apart IME

Take the reflecters off and put a few washers between the top of the reflecter and the wood. this will give you an air gap and will help keep the wood cool. I agree that mounting the ballasts on the hood isnt a good idea also....Mike

From IceCap:
1. glass shield is a must with double ended bulbs!
2. spacer between metal hood and wood is a must with double ended bulbs. Metal washers will do fine. You don't need a lot of space. The space between the reflector and the top of the hood gives some protection from the intense heat.
3. Unpainted wood is a problem over time. I used high gloss white pool paint which water-proofed it also. So far it's working well.

Andy