Fire prevention:

[lachrimae]

Hello group. I've been reading posts here for a while but never dove in. Now's the time!

I’ve got a question for those of you who DIY’d your own canopy with metal halides (especially for those of you with HQI pendants).

I recently bought 2 400W HQI PFO pendants driven by PFO ballasts (10,000k FYI) and am amazed at how hot the pendants get (as well as the ballasts). I know that this has something to do with it being a magnetic ballast… I could fry an egg on both the ballast & pendants I’d bet.

Anyway, I plan on retro fitting the lights into my old canopy and have a question about the fire danger of doing so. I could mount the screw holes of the pendants right up against the wooden roof of my canopy but I don’t know if this will create a fire hazard due to the heat (I will be running at least two 120cfm fans in the canopy, bringing air IN).

Would you recommend using some kind of heat resistant padding between the pendant and the canopy? Please expound on this if you have insight!


Here is an idea of how my canopy will probably be organized:

On a side note: The pendants I am using are supposed to be mounted perpendicular as seen above but I’ve noticed that light seems to spread further out from the ends than the sides. If I turn the pendants parallel I think it throws light futher in each direction of the tank (length-wise) which is a good thing due to my center brace that keeps me from putting a strong MH light over it. Thoughts on mounting parallel instead? The benefit for me on a parallel mount is that I could run longer PC bulbs & could probably get 4 x 65W actinic instead…

Thanks!

Mark

 

[Len]

Hey Mark!
:welcome:

These lights will get hot enough to char soft wood if it's directly mounted to it. The easiest solution is to get metal spacers between your pendant and the wood. Even 1/2" will suffice. This will give breathing room above the pendant to dispose to extreme temperatures. It's a nice, simple solution

Most reflectors are designed for perpindicular distribution. If you find you get more coverage mounting parallel, there's no harm mounting it this way

 

[Anonymous]

My pendents have eye-bolts on the tops, and I just hang them on hooks.

 

[Anonymous]

Might want to space those actinic bulbs out too, I had a 55w actinic bulb crack and that was just from a SE 175w halide.

 

[Anonymous]

I had to space the metal halide's I used on my tank away from the plywood I built the canopy because they were burning the wood.

Used some pieces of copper pipe about 3/4" long and just stuck it over the bolt that I used to bolt the reflector on with.

Seemed to work great. Don't drop one in your tank though, that would be bad.....


I did have a lot of charring when I took the thing down, but that was at the bottom where the light shined directly on the wood and my fan broke.

 

[lachrimae]

Thanks for your informative responses.

I'm not saavy in heat conductivity, but it appears that each of you recommend placing a heat conductor (metal) in between the pendant & wood instead of an insulator (glass, fiberglass, or maybe part of a cloth oven heat pad etc...).

Knucklehead, does that copper pipe conduct less than other metals?

What about a baking mat like this http://www.amazon.com/gp/product/B0002V3ZXG/?tag=reefs04-20
Or a cloth baking mitt to block the heat from reaching the wood? (covered by tinfoil to prevent scorching)

DanConnor, I like the idea of hanging them down slightly but I only have 10" to work with inside the canopy and am concerned about losing another inch of that. I will do that if need be.

sfsuphysics, thanks for the tip on spacing the PC further out.

Thanks,

Mark

 

[Len]

You can use nylon spacers if you'd like (or go nuts with carbon fiber ) but the heat spacers conduct isn't a big issue. What they're mainly designed to do is to allow ventilation above and around the reflector (which is a huge heat sink). So long as you space it from the wood and preferably provide some air flow in the canopy, the conducting issue is a non-issue

You can also install a sheet of aluminum across the entire top of the canopy lid. It'll act as an even bigger heatsink and spread the heat around. Charring only occurs directly over the halides (if you don't use spacers or a larger heat sink).

 

[Anonymous]

What Len sayed.....