Best way to run wire from panels to inverter?

I'd like to give some guidance to the installer in order to end up with as "pretty" an install as possible. My inverter will be mounted outside the house next to the main and meter, which is in the front yard on the side of the house. I've seen some houses where the wiring simply runs from the panels across the roof and loops over the side of the roof and down to the inverter. This looks sloppy to me. I'm thinking it would be pretty easy to drop the wiring down thru the shingles/roof into the attic and then bring it back out at the inverter.

Anyone have advice on this? If it is run thru the attic, would you normally drop it down thru the soffit of the roof down to the inverter? Seems like going from the attic and running it down the inside of the wall (like a normal outlet is run) and bringing it out thru the brick would be a massive tasks. If it's run thru the attic is a conduit required?

I will have 7 strings, which I imagine is going to be a fairly bulky bundle of wire coming into the inverter. Any advice is appreciated.

Comments

  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Best way to run wire from panels to inverter?

    I'm a journeyman with 12 years in the trade.

    I wouldn't run exposed wires anywhere I could avoid it. Period. (Except for small stuff like doorbells or phones and such.)

    Punching holes in the roof is always a bad idea, but one hole wouldn't be so bad.

    If you wanted to go down into the attic (I would, I don't like pipes running across a sloped roof - it looks like hell and it's a pain for the roofers), I'd probably run a short pipe up through the roof, put a flashing around it like a plumbing vent (or service entrance riser), and mount a pullbox on top of it.

    I'd use a short piece of rigid pipe for this, and lag it to a rafter in a nice strong fashion.

    You might also need to use a support bracket to keep the box stable (box to roof, or if the pipe is strong enough - i.e., rigid not EMT - box to pipe). Best would be to work it out so that the box is supported as part of the PV panel mounting rig.

    You could just lag the box down to the roof, put some flashing around the top and goop around the whole box - but that makes it a pain if you ever have to work on the roof.

    From there, you could fiddle about trying to get it down into an existing wall, but I wouldn't. It's going to be a good size flex, probably 1" at least, and the roof will almost certainly slope down to the wall you are working in. Good luck getting a big flex into that wall without breaking open the wall from the inside. (With brick on the outside forget breaking the wall open from the outside.)

    Even if it's a gable end, you'll still have a hell of a time running that big flex in the wall without breaking the wall - and if there are fire blocks, you'll end up busting it open anyway.

    AND, even if you did get the flex down the wall, you still have to get it back OUT again (and sure as shit - you'll still end up having to make a hole in the wall). If it's 1" or bigger, it's not going to bend in a tight enough radius (unless the wall is thick...like built with 2x6's or 2x8's), so you'll have to either use an LB or a pullbox, which you can't legally bury, so you'll have to leave a way in the inside wall to get to it. Best would be another pullbox mounted flush to the inside wall so you can get the cover on and off.

    Hopefully, that'd be a laundry room wall and not your living room wall since you'll see the metal cover and it would probably be too low to look good with a painting hanging to hide it.


    So...

    Get down into the attic with a short piece of pipe through the roof with a pullbox on top. Connect flex to the bottom of that pipe. Get over to the wall above the panel (or as close as possible), then get outside under the eave and run down the wall with EMT. If it's close enough to the service entrance riser, you could possibly run it next to the riser and strap it on the same unistrut that holds the riser (if there is a riser, and if unistrut was used).

    Paint the pipe to stealth it, and as my dear old mother used to say, "You'll never notice it from a galloping horse."
  • mike95490mike95490 Solar Expert Posts: 9,571 ✭✭✭✭✭
    Re: Best way to run wire from panels to inverter?

    I hear some codes require a DC disconnect BEFORE the DC power enters the house.
    (so if there is a fire, the Fire Dept can "pull the plug" before squirting water all over the 390VDC wires)
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  • foosmanfoosman Solar Expert Posts: 38
    Re: Best way to run wire from panels to inverter?

    Thanks for the comments.

    I saw another job...instead of running through the attic or coming off the roof in the front of the house, they brought the wires into a conduit that lags off the roof in the back of the house...then they ran a conduit along the side of the house from the rear of the house up to the inverter. You end up with a conduit bolted to the side of the house running down the side of the house; however, this didn't look too bad. I've seen similar conduits for gas for pools to get from the gas main to the pool...a steel pipe running down the side of the house.

    I'll talk to the installer about either this or an attic run that drops down thru the soffit. It's sounds like going thru the inside of the wall would be a nightmare. The down side to the attic run is the roof penetration. I'm not sure which is worse the roof penetration or the conduit running outside the house.
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Best way to run wire from panels to inverter?
    foosman wrote: »
    Thanks for the comments.

    I saw another job...instead of running through the attic or coming off the roof in the front of the house, they brought the wires into a conduit that lags off the roof in the back of the house...

    Lags off the roof? You've confused me - I have no idea what this means. :)
    then they ran a conduit along the side of the house from the rear of the house up to the inverter. You end up with a conduit bolted to the side of the house running down the side of the house; however, this didn't look too bad. I've seen similar conduits for gas for pools to get from the gas main to the pool...a steel pipe running down the side of the house.

    I'll talk to the installer about either this or an attic run that drops down thru the soffit. It's sounds like going thru the inside of the wall would be a nightmare. The down side to the attic run is the roof penetration. I'm not sure which is worse the roof penetration or the conduit running outside the house.


    Running in the wall wouldn't really be a nightmare, but it will almost certainly require opening and then repairing the wall. Running through the attic probably won't be a problem if there is room to work.


    As for running the conduit all externally:

    If the conduit runs across the roof at any point - then you're going to penetrate the roof anyway...since you'll have to secure the conduit somehow.

    True, the penetration might only be a few screw holes for conduit straps...but is that "better" than a single hole with a properly flashed and sealed pipe coming up through it?

    Personally, I'd go with the one big hole properly flashed. There are already some of those on every roof for the plumbing vents (and probably the electrical service entrance riser) anyway.


    If your array reaches all the way to the edge of the roof, and you can run the conduit along the array mounting hardware to the end of the array then drop it over the edge at that point, then run it back up under the overhang to the wall, then down the wall, that would work as well.


    Or, if the array is close enough, you could run the pipe up the wall and poke it through the roof at that point - one big hole again, but just exactly like a service entrance riser - and avoid going through the attic altogether.

    There's usually more than one way, and figuring out which way will be "best" is one of the fun things about being an installer. :D
  • foosmanfoosman Solar Expert Posts: 38
    Re: Best way to run wire from panels to inverter?

    I'll discuss with the installer on Tue. what they plan to do. As you point out there numerous ways to skin the cat. By lag I meant dropping the wiring over the edge of the roof, under the overhang and down the wall. I inspected the roof and there may be a good opportunity to do as you describe (where the panels come near the edge of the roof and it could be dropped over the edge) in an area that is relatively close to the main panel, but invisible to street. It would require a few yards of conduit on the exterior of the house.

    Are there electrical code issues with running the conduit along the base of the house instead of up under the eave? I've seen gas lines done like this for pools and it seems less obvious than running it under the eave and dropping it down to the panel. Although a painted conduit may be near invisible under the eave as well.
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Best way to run wire from panels to inverter?
    foosman wrote: »
    Although a painted conduit may be near invisible under the eave as well.

    Have a look at my install. That is 3/4" metal conduit. Each panel drops though the attic to a 4x4 box.

    http://home.comcast.net/~n3qik/Site/Solar_Page_6_files/hpim0666.jpg
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Best way to run wire from panels to inverter?
    foosman wrote: »
    Are there electrical code issues with running the conduit along the base of the house instead of up under the eave? I've seen gas lines done like this for pools and it seems less obvious than running it under the eave and dropping it down to the panel. Although a painted conduit may be near invisible under the eave as well.

    No real code issues. As long as you are above ground you can run EMT. You could run PVC actually, but I wouldn't - I've seen way too many broken PVC pipes.

    One issue down near the grade is moisture. EMT down at the bottom of the house which is hidden behind bushes and sprayed daily with sprinklers tends to not last but a couple of years - so in that situation I would run EMT down to within about 12" of grade then do the horizontal run in rigid.

    And, since horizontal pipe down near the ground sometimes get stepped on, or bashed with shovels or lawnmowers or whatever - I would use "way too many" straps to hold it.
  • foosmanfoosman Solar Expert Posts: 38
    Re: Best way to run wire from panels to inverter?

    Thanks for the feedback!
  • SSofAZSSofAZ Registered Users Posts: 8
    Re: Best way to run wire from panels to inverter?

    I'm not sure if your install is yet complete, but, I do punch through the roof as well. If is a shingle roof, I simply use an Oatey PV flashing for "sealant" along with BlackJack. In many cases, instead of a pull-body, I will use a service entrance "weatherhead" on top of the rigid that comes from inside the attic and place this under the module. From the roof, you won's see the penetration but it will still be serviceable. In most cases, I put my inverter in the garage opposite the SES, so the EMT will punch down through the drywall into the garage. If it is placed adjacent to the SES like you said, then it will take a little more work, but is completely doable. Good luck and congrats!
  • foosmanfoosman Solar Expert Posts: 38
    Re: Best way to run wire from panels to inverter?

    The install is not yet complete, they have mounted most of the rails, but ran out of rails today. They are using a Schuco aluminum rail system that I'm very impressed with. I discussed a roof penetration with flashing and they said they are willing to do it, but it requires an extra inspection of the conduit in the attic. I'm still undecided. There is a fun transition that has to occur from an upstairs attic to a 1st story attic. How is the attic conduit typically done? Can you just screw flexible conduit along the framing/trusses?

    Thanks.
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Best way to run wire from panels to inverter?
    foosman wrote: »
    How is the attic conduit typically done? Can you just screw flexible conduit along the framing/trusses?

    Thanks.

    Yup. For 3/4" or less you can get by with 1-hole straps, but for 1" or larger it's best to use 2-hole straps.
  • foosmanfoosman Solar Expert Posts: 38
    Re: Best way to run wire from panels to inverter?

    Just got back into town and I see a bundle of EMT on the ground and no rigid...I will ask about rigid for the portion running along the base of the house...it gets nailed by sprinklers and I like the advice of using rigid.
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Best way to run wire from panels to inverter?

    Here's a good pic of a box in a parking garage. Note the EMT into the top of the box, and the RMC (rigid) into the bottom.

    http://www.iaei.org/magazine/wp-content/uploads/2009/05/08f_weizelph7_501027899.jpg

    Whatever abuse this thing suffered, the RMC shrugged it off.


    Here's a real beaut' in what the NEC considers to be a "damp" location:

    http://richardcurrinelectrical.com/P1010001.JPG

    Box is gone, most of the EMT is gone...
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Best way to run wire from panels to inverter?
    dwh wrote: »
    Here's a good pic of a box in a parking garage. Note the EMT into the top of the box, and the RMC (rigid) into the bottom.

    http://www.iaei.org/magazine/wp-content/uploads/2009/05/08f_weizelph7_501027899.jpg

    Whatever abuse this thing suffered, the RMC shrugged it off.


    Here's a real beaut' in what the NEC considers to be a "damp" location:

    http://richardcurrinelectrical.com/P1010001.JPG

    Box is gone, most of the EMT is gone...

    Jeeze,

    How "damp" is it? Inside a pool? Filled with salt water?

    Tony
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Best way to run wire from panels to inverter?

    I think it was a barn or some other sort of agri building.
  • foosmanfoosman Solar Expert Posts: 38
    Re: Best way to run wire from panels to inverter?

    The electrician used 1" EMT and wasn't willing to entertain rigid. I have a 3/4" gray PVC in the same area for my sprinkler wiring that has been there 4 years and shows little sign of age (a little fading). It should get little water where it is at and I gotta say that the EMT looks pretty solid to me.
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Best way to run wire from panels to inverter?
    foosman wrote: »
    The electrician used 1" EMT and wasn't willing to entertain rigid. I have a 3/4" gray PVC in the same area for my sprinkler wiring that has been there 4 years and shows little sign of age (a little fading). It should get little water where it is at and I gotta say that the EMT looks pretty solid to me.

    Yea, PVC is pretty good for aging - physical damage is where it has a problem, and fixing it isn't as easy as it is with a broken water line.

    EMT is good stuff. If it makes you and your electrician both happy, then it's fine. It meets code, and if it's isn't going to be subjected to too much moisture then no worries.

    For a 1" EMT it would take a pretty good whack to damage it - but it doesn't take nearly so much to knock it out of it's straps and/or break a raintight coupling.

    As time goes on, try to take notice when you see outdoor EMT - you will certainly see a whole LOT of it which is damaged or has come unstrapped and/or has broken couplings. I see it pretty much everywhere I look.


    For the record, most of my experience dealing with broken or rotted conduit near the ground is from commercial and large residential (i.e., estates) installations - where you have lots of sprinklers AND hamhanded so-called "gardeners". If it can be broken, it will be broken - which is why I'm a firm believer in spending a few extra bucks on overkill.


    Don't forget to post some pics - we all like pics. :D
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