Outdoor Junction Box Ventilation

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  #1  
Old 04-08-12, 08:09 AM
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Outdoor Junction Box Ventilation

Hello guys,

I have an application which requires two 175 watt MH ballast mounted in an 8x8x4 outdoor junction box. The box is sealed and runs two remote 175 watt lamps. The box is rainproof but I would like to ventilate it to help remove excess heat so that I might prolong the life of the ballast. I would like to ventilate it from the top as heat rises but would like to avoid rain from getting in. I have not been able to find a pvc type fitting for such an application - does anybody have any ideas?

Thanks
Kevin
 
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  #2  
Old 04-08-12, 09:12 AM
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You'll have to wait for a response from someone else on code compliance, but here's my idea off the top of my head:

Punch a hole in the top of the box. Use a PVC terminal adapter with silicone or a compressible rubber washer to seal it to the top of the box. Bend a piece of PVC into a J shape. Cement top of J into terminal adapter. Add another terminal adapter to the short side of the J. Cover the open end with landscape fabric or something else suitable and screw a plastic threaded bushing over the top.

Or, something similar in the side of the box, punched near the top corner for convection cooling.

For a bottom vent just use a large terminal adapter, landscape fabric etc. and a threaded bushing.

You would want to check these for problems regularly.
 
  #3  
Old 04-08-12, 09:49 AM
Tolyn Ironhand's Avatar
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Whatever you do I suggest putting some drain holes on the bottom. That way, if water got in, it could also get out.
 
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Old 04-08-12, 11:29 AM
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ArgMeMatey has a good idea but I'd go a bit simpler. 1" adapter (PVC/MPT) as suggested but then I'd just go with a short nipple, a Tee, and a 45 street ell in each arm of the Tee. A circle of screen wire silloconed to the end of each elbow.

In the bottom I'd drill a grid of " holes forming a rectangle and use silicone to glue screen wire over the holes.
 
  #5  
Old 04-08-12, 11:53 AM
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Absolutely great ideas! Code is not a huge issue as I am out in a rural county. 1) Do you guys think that the heated air will vent through and make the downward turn of the ell to escape the system. 2) Do you think this will reduce the operating temp. of the two 175 watt mercury vapor ballast which are mounted in my 8x8x4 plastic carlon junction box. I had already drilled holes in the bottom and covered with screen to prevent bugs from entering for heat ventilation. And that method worked good on a 6x6x4 box with a single ballast. The two ballast sytem however is heating up alarmingly and I think more ventilation is required. FYI This system is a homemade DIY version of an underwater HID lighting system.
 
  #6  
Old 04-08-12, 12:56 PM
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Since you already have the system in place I can see no harm in adding the top vent and seeing if that does the job. As to code in my opinion you could use plumbing fittings if they are easier to get for the vent without breaking code because the vent is not an electrical component.

They also make round siding vents you might try in the sides.
 
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Old 04-08-12, 01:38 PM
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I'd use a siding or dryer vent on the side with a small 120V cooling fan.(similar to what you use in a computer)
 
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