Termination/transition questions

[arcsum68]

Hi all,

Just about done with racking and about to move onto installing SolarEdge optimizers and the panels and then finally having a friend help with the electrical work.

I am sure my buddy knows this already, but I like to understand this stuff myself, plus he is not familiar with solar specific installations. I would also like to be able to pre purchase as much of the supplies as possible as to not inconvenience him.

I have 2 arrays (16 and 15 panels) that are about 6' from each other on 2 different planes.

My questions are
1. I will go from PVwire to THWN in jbox/emt to the panel. I know wire nuts are not good for this application. Can I use a terminal block for this purpose inside a sealed jbox? What is recommended?

2. What's the best way to transition from #6 bare wire to the stranded #10 ground in the jbox? Split bolt, buchanan, something else? Is there something that do the #10 and the #6?

3. Will I be able to pass emt under an array to meet up with a jbox on the other side and have enough roof clearance for the EMT?

If there's already a post with some information about this, please let me know. I dont mind reading, but was not finding anything.

Thanks!

[Sunking]

Your questions do not make much sense. The exposed wire from the PV panels must use PV rated wire that run to a Combiner Junction Box. The PV cables will have MC4 connectors that plug into one side of the combiner. On the output of the combiner box screw terminal blocks are provided to transition to less expensive THHN-2 which is ran in conduit.

[sensij]

PV wire does not necessarily have MC4 connectors at both ends, and most grid-tie installations will not require expensive combiner boxes built with MC4 jacks. Terminal blocks in a standard outdoor J-box are an ok choice for the PV wire to THWN-2 transition. You will find "Polaris connectors" occasionally recommended. For the ground, since it is a SolarEdge system it is just an EGC, so you aren't limited by the tighter splicing requirements of a GEC. Whatever you prefer should be fine.

With normal racking products, there should be room for the EMT.

[Sunking]

PV wire does not necessarily have MC4 connectors at both ends, and most grid-tie installations will not require expensive combiner boxes built with MC4 jacks..

True but they go to a combiner box with Term Blocks. My point was it was a non issue.

[arcsum68]

True but they go to a combiner box with Term Blocks. My point was it was a non issue.

Senji is correct, they will not go to a combiner box. The PV wire will run to the jbox through a gland, and then need to be transitioned to THWN.

[arcsum68]

PV wire does not necessarily have MC4 connectors at both ends, and most grid-tie installations will not require expensive combiner boxes built with MC4 jacks. Terminal blocks in a standard outdoor J-box are an ok choice for the PV wire to THWN-2 transition. You will find "Polaris connectors" occasionally recommended. For the ground, since it is a SolarEdge system it is just an EGC, so you aren't limited by the tighter splicing requirements of a GEC. Whatever you prefer should be fine.

With normal racking products, there should be room for the EMT.

Thanks

[solarix]

Mount a metal (Hubbell brand) j-box to your mounting rail under the array - preferably a panel that is easy to get at (like one on the top row) and run the EMT into it. Make sure it doesn't fall on a panel edge or panel j-box so that you have a little extra room above the j-box. Most companies use some type of terminal block to transition between PV-wire to THWN, however you can use wire nuts as they are rated and listed for 600V. You can use the type that have the goo in them to "seal" the connection but that usually gets pretty messy if and when you ever have to work on them again. Personally I don't like the European style terminal blocks as they are so plasticy and weak. American style screw terminal blocks have a lot of exposed surfaces so not my first choice when dealing with HVDC. Could use Polaris type butt splices (our dealer calls them "monkey-butt" splices) which are very reliable and sealed but are bulky. We have come around to just using regular good wire-nuts and drilling weep-holes in the j-box. I've never had a problem with wire-nuts. Even here in "dry" Arizona I've seen too many roof mounted "sealed" j-boxes with a lot of water accumulation in them. Use either a splice block or a lay-in lug for the ground. If you are running PV-wire between the two arrays, run them through EMT, but the conduit doesn't have to terminate into the j-box as the PV-wire is rated for exposure, but I still don't like having it in direct sunlight. You just need to put EMT adapters on each end to protect the wire and a bond-bushing to ground the conduit (on both ends of the GEC is run through the conduit).

[arcsum68]

Mount a metal (Hubbell brand) j-box to your mounting rail under the array - preferably a panel that is easy to get at (like one on the top row) and run the EMT into it. Make sure it doesn't fall on a panel edge or panel j-box so that you have a little extra room above the j-box. Most companies use some type of terminal block to transition between PV-wire to THWN, however you can use wire nuts as they are rated and listed for 600V. You can use the type that have the goo in them to "seal" the connection but that usually gets pretty messy if and when you ever have to work on them again. Personally I don't like the European style terminal blocks as they are so plasticy and weak. American style screw terminal blocks have a lot of exposed surfaces so not my first choice when dealing with HVDC. Could use Polaris type butt splices (our dealer calls them "monkey-butt" splices) which are very reliable and sealed but are bulky. We have come around to just using regular good wire-nuts and drilling weep-holes in the j-box. I've never had a problem with wire-nuts. Even here in "dry" Arizona I've seen too many roof mounted "sealed" j-boxes with a lot of water accumulation in them. Use either a splice block or a lay-in lug for the ground. If you are running PV-wire between the two arrays, run them through EMT, but the conduit doesn't have to terminate into the j-box as the PV-wire is rated for exposure, but I still don't like having it in direct sunlight. You just need to put EMT adapters on each end to protect the wire and a bond-bushing to ground the conduit (on both ends of the GEC is run through the conduit).

Thanks! Really good information here. Like I said, my buddy is very proficient but I like to know what's going to happen. I am doing all the rest of the install myself, so I dont want to be completely obliviously to the other work.


about this comment, as it's something ive been questioning.

"If you are running PV-wire between the two arrays, run them through EMT, but the conduit doesn't have to terminate into the j-box as the PV-wire is rated for exposure, but I still don't like having it in direct sunlight. You just need to put EMT adapters on each end to protect the wire and a bond-bushing to ground the conduit (on both ends of the GEC is run through the conduit) .

Are you saying to run the PV wire into and through conduit to where the other array meets up but use EMT adapter to keep it from being exposed to the sharp edges of the jbox?

[solarix]

Are you saying to run the PV wire into and through conduit to where the other array meets up but use EMT adapter to keep it from being exposed to the sharp edges of the jbox?

The ends of the EMT need adapters to protect the wire and should also have strain relief fittings going into the J-box as well. The PV wire is rated for exposure and can just run beneath the array (clipped up to the panels frames with S.S. wire clips (don't let me catch you using plastic wire ties) but we still use EMT between the arrays so the PV wire never sees direct sunlight.

[arcsum68]

Thanks for the clarification. I am using Wiley clips to hold the wires in place.

[arcsum68]

Mount a metal (Hubbell brand) j-box to your mounting rail under the array.

One last question solarix, how is the jbox to be mounted to the rail?

[solarix]

One last question solarix, how is the jbox to be mounted to the rail?

TEK screws - I know the mounting manufacturers have a phobia or something about using power tools on the roof and try to fasten everything with bolts in the rail slots, but forget the expensive rail systems I say. Cordless tools are the best invention since sliced bread and we use self-drilling TEK screws all over. They make a wonderful ground bond too. Get the ones with a "high serrated head" and you won't be sorry. Some inspectors claim they are a type of "sheet metal screw" and disallow their use as bonding, but they are being just rule-stupid.
WIley clips are good. There are a couple other brands that are a bit less expensive and just as good. Wiley put a lot of effort to get their stuff UL listed on the grounding clips etc, and they charge accordingly, but most building departments don't go for that unless you have a statement from the panel maker specifically approving them. We like the IronRidge grounding panel clamps instead.