Thread: Ben's Garage
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Old 04-13-17, 07:29 AM   #127
stevehull
Steve Hull
 
Join Date: Dec 2012
Location: hilly, tree covered Arcadia, OK USA
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Ben,

The enphase "solution" for this string junction box is just WAY too complicated. We came up with a simple, inexpensive and quickly constructed junction box that uses plastic 6x6x4 inch electric junction boxes (Lowes, HD, Menards) with simple inexpensive weatherproof cable compression fittings to bring in the respective trunk cables and the one output 240 V line. Total cost < $20.

The boxes are easy to drill with wood paddle bits and the fittings seal really well. Actually, we now use a "punch" to knock out the holes - faster and cleaner than drilling. If there is any gap, then a bit of RTV silicone caulk seals it up. The lid screws down with a weather tight gasket.

Inside the junction box, we connect the respective leads (two trunk lines and output romex) with brass compression bolts and then thoroughly wrap each connection with high quality (3-M) plastic adhesive electric tape. The 12 G romex goes into conduit down to the combiner box where there are circuit breakers for each 20 A string. Then a larger G wire to the disconnect switch. Recall that each trunk line has four wires and a smaller box (4x4x4 inch) is just too tight in terms of space.

We always use a mid string trunk feed to prevent voltage rise on the microinverters and put the junction box under one of the mid string panels. The plastic box is attached with self tapping screws to the aluminum racking rails. In the very unlikely event that the junction box ever needs service, then you tilt up the panel for access.

The box is now protected from weather and UV rays.

I really like to have the combiner and circuit breakers inside the structure. The enclosure is cheaper (compared to outside weatherproof) and I like it right next to the structure circuit breaker box for safety and clarity.

Hope this helps.


Steve
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Last edited by stevehull; 04-13-17 at 05:07 PM.. Reason: typos
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