Need conduit advice. Any help?

[badutahboy]

Hey all, I'm in the process of installing my system, and I've bumped into a frustrating problem: Conduit.

I'm installing a 9.4KW Solaredge system. I have about a 30' run from my soladeck, through the attic, and down the back wall of my house from the eave to my main panel.

Here's what I'm up against.

1. If my math is right, I have to run 1 1/4" conduit (3 strings, so 6 10 gauge PV wires + 10 gauge ground).
2. I don't have access to a EMT bender of this size, and they're $300+ to buy one.
3. I'm not really clear on what connectors I need in order to do it right. For example, I don't see any way to keep the conduit inside my 2x4 rafters directly below the soladeck.

Since I don't have access to a bender, I'm inclined to use FMC instead of EMT.

My questions:

1. Is there an issue with coming out from the soladeck with a straight fitting and looping back up into the rafters, or do I need an elbow of some sort to keep the conduit contained within the rafter space?
2. Do I need to run watertight conduit for any/all of the run? I'm assuming inside the attic won't need to be, since it's in a sealed area and running from a watertight box on the roof, but once I get outside the eaves, do I need to make a transition to watertight conduit and fittings?
3. My inverter's instructions only have info on attaching with 3/4 or 1" conduit. Any advice on how to attach to the inverter? (Solaredge SE10000A)

Any advice you can give is welcomed. I'm a noob to running conduit, and it's ridiculous that this is the one area of the install I'm really struggling with.

Thanks!

[GRickard]

Set a junction box with a terminal strip in the attic where you can change from PV wire to THHN. Then you'll have no problem getting 6 #10s and a #6 ground in a 1" conduit. Make sure the terminal strip is rated for more than the amperage of a full string (5200 watts I think). I used a 50Aterminal on mine. Why three strings for 9.4Kw? You can do it with two.

Greg

[sensij]

Set a junction box with a terminal strip in the attic where you can change from PV wire to THHN. Then you'll have no problem getting 6 #10s and a #6 ground in a 1" conduit. Make sure the terminal strip is rated for more than the amperage of a full string (5200 watts I think). I used a 50Aterminal on mine. Why three strings for 9.4Kw? You can do it with two.

Greg

The Soladeck should already have the DIN rail built in, no additional junction box should be needed. That is one of the big reasons to use it, getting the flashed passthrough and transition in one box. Each SolarEdge string is only 15 A continuous, so 30 A terminal blocks would be fine (but even wire nuts are acceptable). Also, I agree that you should be able to do it in two strings. 1" EMT should take 16 #10 THHN, 3/4" EMT should accept 10, and should be fine.

For the attic run, you also need sufficient clearance between the roof and conduit. What was specified in your permit plans?

[badutahboy]

Set a junction box with a terminal strip in the attic where you can change from PV wire to THHN. Then you'll have no problem getting 6 #10s and a #6 ground in a 1" conduit. Make sure the terminal strip is rated for more than the amperage of a full string (5200 watts I think). I used a 50Aterminal on mine. Why three strings for 9.4Kw? You can do it with two.

Greg

I'm running PV wire all the way because I have it. I ended up relying on the design RENVU created, and I had received my shipment before I realized they spec'd PV wire the entire way. At this point, it doesn't make much sense to waste the wire or go to further expense for THHN.

As for the 3 strings, I did it for ease of expansion. 2 strings would have put me in a position where any added panels would likely cause substantial rewiring. The way it's set up now, I can add 4-9 panels ridiculously easy, simply by adding to the strings I have. I'm anticipating adding more panels in the next 2-4 years, as soon as I can convince my wife to follow my lead and get an EV. That's also why I did the 10k inverter rather than the 7600.

For the attic run, you also need sufficient clearance between the roof and conduit. What was specified in your permit plans?

It was, but I hadn't caught it until you mentioned it, so thanks for that. It totally resolved item 1. I have to stay 10" below the roof decking. Easy enough. Like I said, I have NO experience with running conduit, so I assumed it would/should/could run along the side of a rafter.

[sensij]

I'm running PV wire all the way because I have it. I ended up relying on the design RENVU created, and I had received my shipment before I realized they spec'd PV wire the entire way. At this point, it doesn't make much sense to waste the wire or go to further expense for THHN.

Relative to the expense of dealing with 1-1/4" EMT or flex, I think trying to sell your excess PV wire on Ebay and buying some THHN is an easy decision. 30 ft run * 6 current carrying conductors is only 180 ft. You should be able to get that for less than $50, for sure.

[badutahboy]

Relative to the expense of dealing with 1-1/4" EMT or flex, I think trying to sell your excess PV wire on Ebay and buying some THHN is an easy decision. 30 ft run * 6 current carrying conductors is only 180 ft. You should be able to get that for less than $50, for sure.

Unless I also switch my plan to EMT 1" conduit, I'm not sure there's really a benefit. My PV wire ran me $0.35/foot. 10 gauge THHN at Home Depot or Lowe's is available in 100 foot spools for $28 ($0.28/foot), so the cost savings is relatively negligible, and probably would be a loss by the time I sell any excess on Ebay. 1" flex conduit will save me about $15 on the conduit and maybe another $10ish on connectors.

If I switch to 1" EMT, I can buy new wire plus the full conduit cost for roughly the same price as the 1-1/4" flex conduit. But that would also require buying/renting a 1" bender, and for my own limited skill, probably running the conduit along the floor of the attic, under insulation (which is actually a better all-around solution, assuming it's acceptable for code, which I don't know). As a side benefit, I could make the entire run watertight, as opposed to just the portion that's outside.

Any feedback on the code ramifications/requirements if I want to run the conduit in the attic floor? If I can do that it means I only have 4 bends to make, with 3 being simple 90's (the only harder one is tying into the soladeck on the 4/12 roof pitch).

My plans are approved with the following language in regard to conduit: "CONSTRUCTION FOREMAN TO PLACE CONDUIT RUN PER 690.31(E) AND 2012 IFC 605.11.2. 3." From what I can tell, these sections only specify a minimum of 10" below the roof surface, but place no limitations on running it along the lower joists unless the conduit is under 3/4".

[GRickard]

You can buy factory bent 90s and use flex for the odd angle. Nothing wrong with that. If you use the 3/4", it will be a little harder wire pull, but a lot cheaper than 1 1/4" conduit.

Greg

[foo1bar]

Can you combine the strings inside the soladeck and run fewer wires back to the inverter?

With 3 strings I think you have fuses in the soladeck anyhow.

(BTW - why 3 strings? My personal install is just slightly smaller wattage and I did 2 strings.)

There are pre-bent 90s as was suggested by Greg - there are also 45's. And there's also the option of taking 2 conduit body 90's and using them to make basically any angle with some offset between the two. But that means two 90s close to each other so PITA to get wire through. So I'd probably try to do it with 45s and a "C" body to help with pulling.

[solarix]

Can't run PV wire or USE-2 wire in the attic cause those types aren't fire rated for indoor locations (lots of smoke when they burn). Change to THHN wire in the soladeck and just use 3/4" EMT or even metal flex in the attic. Sensi is right, 3/4" EMT is rated for up to ten #10 conductors.

[sensij]

PSA: The 10 AWG THHN sold by Home Depot and Lowes (Southwire Brand) is THWN rated, the THWN-2 rating is only on their 8 AWG and heavier. If it is in exterior conduit, only the 75 deg ampacity rating applies, instead of 90 deg. Should be fine for SolarEdge, though, as long as you aren't running the conduit on the roof.... for 15 A circuit in conduit with 6 conductors, I think it works out to a max allowed ambient temp with THWN of 55 deg C, while up to 65 deg C could be ok with THWN-2.

For my current install, I bought a 500 ft spool of #10 THWN-2 on Ebay for $80, and will try to sell the excess back on Ebay, or maybe to a friend who is also thinking about installing a system. The spool fits into a flat rate shipping box, so it isn't a big deal to send.

3/4" conduit bender is inexpensive too, about $40.

[badutahboy]

Can you combine the strings inside the soladeck and run fewer wires back to the inverter?

With 3 strings I think you have fuses in the soladeck anyhow.

(BTW - why 3 strings? My personal install is just slightly smaller wattage and I did 2 strings.)

There are pre-bent 90s as was suggested by Greg - there are also 45's. And there's also the option of taking 2 conduit body 90's and using them to make basically any angle with some offset between the two. But that means two 90s close to each other so PITA to get wire through. So I'd probably try to do it with 45s and a "C" body to help with pulling.

I'm doing 3 strings because I'd be close to the limits at 2 strings. I could add 1 more panel to each string before having to run a 3rd string anyway. I am anticipating adding somewhere between 4-7 panels in the next few years, either to power an EV for my wife (if Tesla announces a crossover SUV), or to power a detached garage/workshop. My layout is also designed so I can easily add on to the existing strings. With my current setup, I can add up to the 7 potential additional panels without any new electrical connection or upgrading inverter, just racking and panels.

If I added 4 panels, I'd have two 12 panel strings at 3780W and one 10 panel string at 3150W, and if I added 7 panels I'd have the two 12 panel strings and one 13 panel string at 4095W.

If I did two strings, right now I'd be at 2 15 panel strings at 4725W, so I could only add 1 315W panel to each string and remainunder the 5250W/15A limitation.

[badutahboy]

Can't run PV wire or USE-2 wire in the attic cause those types aren't fire rated for indoor locations (lots of smoke when they burn). Change to THHN wire in the soladeck and just use 3/4" EMT or even metal flex in the attic. Sensi is right, 3/4" EMT is rated for up to ten #10 conductors.

It's semi irrelevant as I'm intending to make the switch to THHN and EMT pending confirmation of my run meeting code if placed ine attic "floor" joists, but I'm curious about the restriction on PV wire inside the attic. I've read that a few places, but had no problem getting my plans approved with PV wire spec'd for the entire run. My building inspector mentioned the smoke factor, then said it could be offset by conduit, only to wrap up his thoughts with "DC wiring inside the structure has to be in metallic conduit no matter what wire you're running anyway", but he was totally okay with PV wire for the entire run, so long as it was inside conduit.

PSA: The 10 AWG THHN sold by Home Depot and Lowes (Southwire Brand) is THWN rated, the THWN-2 rating is only on their 8 AWG and heavier. If it is in exterior conduit, only the 75 deg ampacity rating applies, instead of 90 deg. Should be fine for SolarEdge, though, as long as you aren't running the conduit on the roof.... for 15 A circuit in conduit with 6 conductors, I think it works out to a max allowed ambient temp with THWN of 55 deg C, while up to 65 deg C could be ok with THWN-2.

For my current install, I bought a 500 ft spool of #10 THWN-2 on Ebay for $80, and will try to sell the excess back on Ebay, or maybe to a friend who is also thinking about installing a system. The spool fits into a flat rate shipping box, so it isn't a big deal to send.

3/4" conduit bender is inexpensive too, about $40.

Are you sure they're only THWN rated? Both HD and Lowe's show references to THWN-2 on their product page, and the applicable (I believe) data sheet from southwire specifies that Solid construction wires are THHN/THWN only, but gives no such disclaimer about stranded wire.

Here's the data sheet I found. I'm not entirely sure it's applicable as southwire doesn't cross reference to the model numbers listed by HD and Lowe's. http://www.southwire.com/ProductCata...odcatsheetOEM5

[sensij]

Quite sure. Look at the data sheet you linked, see the asterisk and footnote related to the THWN-2 rating? I've confirmed this by looking at the markings on the wire in the store.

[badutahboy]

Quite sure. Look at the data sheet you linked, see the asterisk and footnote related to the THWN-2 rating? I've confirmed this by looking at the markings on the wire in the store.

Well that was a pretty obvious oversight on my part. Thanks for the clarity.

[badutahboy]

PSA: The 10 AWG THHN sold by Home Depot and Lowes (Southwire Brand) is THWN rated, the THWN-2 rating is only on their 8 AWG and heavier. If it is in exterior conduit, only the 75 deg ampacity rating applies, instead of 90 deg. Should be fine for SolarEdge, though, as long as you aren't running the conduit on the roof.... for 15 A circuit in conduit with 6 conductors, I think it works out to a max allowed ambient temp with THWN of 55 deg C, while up to 65 deg C could be ok with THWN-2.

For my current install, I bought a 500 ft spool of #10 THWN-2 on Ebay for $80, and will try to sell the excess back on Ebay, or maybe to a friend who is also thinking about installing a system. The spool fits into a flat rate shipping box, so it isn't a big deal to send.

3/4" conduit bender is inexpensive too, about $40.

I'm responding to this quote again as it's the one that makes sense to respond to here...

I just talked to an electrician buddy of mine, and he told me that I can use the THWN dry rating for my run, as long as I'm using watertight conduit for the entire run. Makes sense to me, and the watertight fittings for 3/4 or 1" EMT are only slightly more expensive than the basic fittings, so that's my plan as of today. I can't find THWN-2 locally. Even the electrical supply stores nearby seem to only stock the Southwire Simpull wire in 10 gauge.