Roof top J-boxes [RE-wrenches]

[Glenn Burt]

We have been using a 4x4x2" PVC jbox mounted directly to the roof 
decking with SS screws. Through the back of it we run a 1.25" galvanized 
pipe nipple, ending in a 6x6x4" steel jbox that we screw to a rafter.

>From this box we run our FMC to the DC disco.

Outside we use Arlington water-tite couplers on the PVC jbox to allow 
our conductors access to the inside (one coupler per conductor 
normally). In the steel jbox in the attic we transition to THWN-2 for 
the run to the DC disco (no wire nuts please!).

We are liberal with the use of a roofing compound made by Henry (flows 
much easier in the cold months up here than others we tried (note that 
SikaFlex is NOT recommended by its manufacturer for use on asphalt 
shingles)), and bend up a custom flashing from Al coil stock to fit over 
the upper edge of the PVC jbox, slipping & adhering this under the row 
of shingles above.

All this we place under one of the last modules to be laid down in the 
array for additional protection.

Over 100 installs and no troubles yet (knock on wood...).



Steve Johnson wrote:
> 
> there was a thread some time back about junction boxes where you take 
> the wiring through the roof.  we are using a WP aluminum die cast bell 
> box (regular outdoor box)mounted to a rail side under the array and 
> going through the roof with sealtite through a 3/4" neoprene roofing 
> boot about 18" away.
> 
> Occasionally we come out of the bell box with EMT, right out the back.  
> I like this better but doesn't work well lots of times since the roof 
> boot causes the box to be higher than the rail or difficulty in 
> alignment.
> 
> I don't like this solution.  I remember someone was just mounting the 
> bell box directly to the roof.  The would be neater and simpler.
> 
> Any suggestions?
> 
> Steve Johnson
> LightWave Solar Electric
> Nashville, Tennessee



-Glenn  -KA2DTH
Technical Specialist
Renewable Power Systems
Averill Park, NY


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