Need expert advice asap about diy 150 watt hps

My friend made a homemade remote ballast and he is concerned if the transformer from an older outdoor security light (150 watt hps) melt plastic or start a fire. The ballast, ignightor and capacitor were placed in a project box purchased from radio shack. It is made out of plastic. Does anyone know that has made one before?
Here is a link to the exact project box.
http://www.radioshack.com/product/index.jsp?productId=2062285

I didnt check the link, but if it all works you should light it up and monitor it closely for several hours, maybe more than once. Some plastic is great w heat, some not so much... Some ballasts get super hot, some not so much. a fan on it would help, as would lining the plastic w aluminum foil (afew layers w air spaces/pockets between.) Hope it helps.

as would lining the plastic w aluminum foil (afew layers w air spaces/pockets between.) Hope it helps.

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I don't think lining the plastic with aluminium foil and LEAVING AIR POCKETS will help. Air tend to act as an isolator, trapping the heat inside the contraption, also aluminium foil is a shiny metal which cannot radiate infrared radiation(aka heat) as efficient as a black body will.
http://en.wikipedia.org/wiki/Black_body
look here for explanation.
just my 2 cents

Take the lid off, add a computer fan and a couple of vent holes, it will be fine.

schtrudel said:

I don't think lining the plastic with aluminium foil and LEAVING AIR POCKETS will help. Air tend to act as an isolator, trapping the heat inside the contraption, also aluminium foil is a shiny metal which cannot radiate infrared radiation(aka heat) as efficient as a black body will.
http://en.wikipedia.org/wiki/Black_body
look here for explanation.
just my 2 cents

Click to expand...

aluminum does not retain heat, take a piece out of a 400deg oven and you can handle it bare handed in a matter of seconds, it will act as barrier also. If the ballast gets to the point it would cause the plastic to ignite, the aluminum will diffuse the heat and spread it out more than straight ballast on plastic. Air gaps would help to diffuse it even more (the whole idea behind insulation is pockets of air that prohibit a fast transfer of temperature up or down. The point he's wondering/worried about is the ballast getting too hot for the plastic. I've made a reflector for a 400w hps bulb (which gets plenty hot) out of cardboard lined w aluminum, worked fine without a worry for the cardboard getting too hot. They use thin mylar sheeting as insulation in the space program to protect heat sensitive instruments, all mylar is is aluminized plastic. Try it out, monitor it closely and see if it works.

We don't need to get technical w black body radiators for this one lol.... Shit bolt it all to a 2x4, a ballast won't get hot enough to light that on fire, but it can melt plastic, soooooo.

You can place aluminum foil over a flame, w a cotton ball right on the other side, the cotton won't ignite cuz the aluminum is able to dissipate heat so efficiently. . . . .

And a black body radiator uses tungsten which holds heat very well, opposite for aluminum. We use it in the oven because it dissipates heat quickly. 2 totslly different ideas going on here.

Thanks everyone for your help! He's been monitering it amd using it only when he was home since it was built and we think everything will be ok. He drilled some vent holes when he built it and it seems to be fine. We'll be adding some aluminum foil on the bottom of the ballest to help it from melting the plastic but we cant add it to the top since thats where the quad tap terminals are ) thanks everyone for your help!! I love this site!

Yeah don't wrap it w aluminum, just use it as a heat shield/barrier against the plastic... And put a fan blowing on it ...(and in another room if possible) Good luck