J-box PV conductor splice issue

We failed inspection yesterday on a 5.2kW interactive PV system. The inspector noted that the j-box wiring splices must be performed with PV crimped connectors. We are using Schott panels, with Tyco Solarlok connectors for all exposed locations. In the j-boxes we have two strings wired through. We used 600v UL listed set-screw butt splices with heavy shrink tubing (max system voltage 517 vdc per NEC calculation). Each j-box has a a maximum of four splices, each terminating either 10awg to 10awg, 10awg to 6awg, or 6awg to 6awg. There are no "double cabled" screw connections.

I could not find any info suggesting that our work was contrary to code. The j-boxes are being used simply for integration of the array wiring into the conduit at different points along the way to the DC disconnect.

Does anyone have any ideas on this? Is this wiring considered bad practice? Or maybe better alternatives without having to install the PV connectors in an enclosed box (seems like overkill)?

We believe the inspector is in error, but do want to complete the job properly. As always, safety first.

Thanks in advance!


  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: J-box PV conductor splice issue

    approach the inspector and ask him specifically what he means by crimped connectors. he may be looking for the mc4 connectors common to many current pvs, which lock together, but i don't see the problem with hardwiring pvs either. my guess here is if the wire has spade connections or something similar then he could be worried the the connector could pull off of the wire and soldering isn't a good alternative as these must be crimped. if this is what he's referring to then buy some more connectors (or the installer needs to get and do this) and cut off the old ones so the news ones can be crimped onto the wire. this tool may be used if the lug connections are heavy duty, but i'm sure there are probably hand crimpers suitable for small gauge wires too.
  • lightmindlightmind Registered Users Posts: 5
    Re: J-box PV conductor splice issue

    Actually, he was uncomfortable with the set-screw barrel splice connectors we used. The connectors are rated for 600v and had heavy heat shrink as insulation. We believe they are OK for this application but wanted to get corroboration.
  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: J-box PV conductor splice issue

    Why did you have to use them in the first place? I don't see a difference in those versus polaris connectors....polaris are used all the time. I used them in my install.
    The jbox is weathertight correct?
  • BB.BB. Super Moderators, Administrators Posts: 30,633 admin
    Re: J-box PV conductor splice issue

    If these are non-accessible splices (i.e., not connections to a breaker / bus bar in a service panel)--I would tend to prefer UL Listed crimp type connections. Screw type connections tend to be a bit less reliable (not really gas tight, if subjected to temperature extremes may tend to loosen).

    My installer (~5+ years ago) just used simple copper crimp rings in our Jbox (small/simple GT system) and electrical tape (as I recall). I am sure there are better out there--but it has worked fine so far.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lightmindlightmind Registered Users Posts: 5
    Re: J-box PV conductor splice issue

    From what I can tell, the difference between these basic set-screw butt splice and the polaris connectors is the polaris are insulated, UV rated- and more than twice as expensive. Electrically, I believe they are similar. The j-boxes where the set-screw butt splices are installed are weatherproof and accessible only if a tool is used. So the UV rating is unnecessary. The splices are insulated with heavy shrink tubing. We prefer these over crimp types because a crimp type must be cut for servicing, shortening the working length of wire in the box, vs simply removing the shrink tubing and releasing the set-screw (after safely disconnecting panel circuits of course).
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: J-box PV conductor splice issue

    Dumb question, so here goes.

    Are they rated for stranded wire ???

    Ok, time to craw back under the rock :D
  • WindsunWindsun Solar Expert Posts: 1,164 ✭✭
    Re: J-box PV conductor splice issue

    I have heard of inspectors failing Polaris connectors also, simply because they are not that commonly used or known (and expensive). They do have the advantage in theory of being UV/watertight, but otherwise I could see little real difference in the quality of the actual connections with Polaris vs standard electrical off the shelf set-screw connectors. The main advantage of them is time savings, you don't have to mess with heat shrink.

    But aside from that, I think you will have to get more information from the inspector as to exactly what they mean.

    A good crimped connector is usually more reliable, but far too many crimps are not good, and as noted by someone, you have to cut the wire for access.
  • lightmindlightmind Registered Users Posts: 5
    Re: J-box PV conductor splice issue

    Thanks for all of your help. We decided to go ahead and install the Tyco Solarlok connectors inside the j-boxes to move the project along. We don't want to make waves, as we depend on these local code inspectors to certify our installations.

    We do plan to challenge the inspector to document exactly why the set-screw butt splices and shrink tubing were not accepted- maybe we can all learn something new.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: J-box PV conductor splice issue

    keep us informed as to what the inspector says.
  • rhino 660rhino 660 Registered Users Posts: 4
    Re: J-box PV conductor splice issue

    for our jobs 10kw or less we make all strings home runs.
    on bigger jobs we use a combiner with fuses. we only used the Polaris lugs on our first 3 jobs
    allmost every job we do is in a different city and most of the inspectors are baffled to begin with 8)
    Off grid.
     Temporary system while i build house 
    8.5 kw pv, 70kwh's tesla model S batteries, 4548 xantrex 
    2 60A xw cc 1 80A outback cc. 25kw diesel gen 
    Looking at skybox for 20kw ac 18.5kw dc pv when done

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