Solar Ground mount install Conduit run...

[gpiggaz]

I am about to install a ground mounted solar array and the conduit run from the array to the inverter will be about 75 ft outside of my house and another 70 ft inside ( through the basement) of my house I know in the basement I'll be using EMT for that part of the run, but outside the digging is miserable, it's all rocks and caliche- However, I have a concrete block fence. that roughly follows the route the conduit has to take to get from the array to the house- The array is about 3 ft from the fence. My two choices are:

1. Dig a 75 ft long 18" deep trench and use 3/4 PVC (Sch 80 at least where exposed) to get from the array to the house then transition to EMT at an LB where the conduit enters the basement through the rim board.

2. Using Unistrut ( or superstruct) Mount 3/4" IMC conduit on the fence, and only take it underground ( using wrapped IMC) where the conduit crosses the sidewalk. I'd even keep the conduit above ground from the array to the fence, as it's only a few feet and the area won't have any foot traffic so tripping isn't a concern. Using wrapped IMC I think I only have to go down 6" at the sidewalk.

The cost difference is minimal using IMC for the whole exterior routing even though I think I could use EMT for all but the underground part.

Doing it on the fence saves a lot of back breaking labor- are there any downsides to that method? I know the only drawback I see is additional pull points needed for the run vs the PVC and underground- I think it's 3 additional LBs needed as pull points if I do it on the fence, vs 270 degrees of bends between pull points if buried.



FWIW- the conduit will have 2 # 10AWG and 1 #6 AWG EGC conductors in it.

Thoughts? and Thanks in advance.

 

[vavet]

Can you rent a trencher? Or mini-ex? Is the rocky soil a problem with one of those?
How visible will the EMT be on the block fence? It doesn't seem like a pleasant aesthetic. How much longer will the conductors be if you mount it on the fence? Will that require the conductors to be upsized?

 

[gpiggaz]

I can rent a trencher- but the last time I did that when adding my shop, the trencher broke due to the rocks- mini exe might work, but would make a much bigger hole- and cost more to rent than the trencher.

Distance wise it's a wash- maybe 2 -3 ft different. The aestheics are not too much of a concern, it's going to be on the "inside" of my back yard, and while it would be visible it won't be to obnoxious ( I think) FWIW_ the fence is actually a low block wall with pillars every 8 ft and iron fencing between the pillars on top of the low blocks. So I'd be mounting the conduit maybe 6-9" above the ground. Of course it will have to be marked to show it has PV conductors in it. But that is ok too. I think the marking has to be every 10 ft and at each pull point

 

[Noltz]

The marking scheme sounds right. I'd mount it as low as possible so it can be hidden with vegetation later. Bury it between the array and the fence too though. Additional pull points are what, $50? How much was that mini-ex?

 

[gpiggaz]

Mini Ex rents for about $300/day I think it would take me the better part of a day to dig the trench with it. I'm also not sure I can pull it to the house from the rental place, so there could be delivery charges too. The more my back thinks about the whole underground trenching thing, the more I like the fence mounted conduit. While I still have to somehow get the 10 holes for the piers dug ( which will be a struggle in our "soil" conditions)- My plan is to try to use a skid steer mounted auger for the holes, but that may fail too. I think digging up the landscaping such as it is and making that big mess is less attractive than just putting the conduit on the fence.

 

[gpiggaz]

Another question- Are there any specific rules on Superstrut/Unistrut concerning the fasteners holding it to the masonry fence? ie fastener size or finish etc... I haven't started buying the strut yet- and want to make sure I pass inspection

 

[gpiggaz]

Anybody know of any rules on the Superstrut or Unistrut usage - outdoors on a block wall. I I received my building permit today and I'm about ready to start- I'm currently planning to use redheads to hold the strut to the wall probably every 8' of so- I think IMC is 10' max but the wall has pillars every 8' so it will be simpler to do that spacing. Probably 2 red heads per strut piece and make each strut piece about 6-8" long center the conduit and use a Strut conduit/pipe clamp. This will hold the conduit off the wall a decent amount and should make the installation pretty clean. Any advice is appreciated.

 

[gayler]

I have nothing to add about the strut mounting but would like to see pictures of your install and info on who you bought the equipment from. Thanks!

 

[gpiggaz]

I bought the equipment for Unboundsolar.com- (what used to be called Wholesalesolar.com)

MissionSolar panels and SolarEdge Inverter and optimizers mounted on IronRidge ground mount racking. I'll take pictures when I am doing the work. Next step- Dig 10 holes for the piers. Probably start that this weekend.

 

[gpiggaz]

I talked to the county plan inspector today- he told me -yes, it's ok to mount the conduit on the fence, and even said it would be ok to use EMT- He said the only catch is that the actual building inspector may require a resubmittal of the plans with an update to show the conduit on the fence. That will be much easier than digging in this area. I'll still have to dig a small piece where it passes under the sidewalk, and to minimize the depth, I'll switch to IMC over that distance, Not too hard - and will save my many hours of back breaking labor (I hope)

Edit to add- I'll be wrapping the IMC in the protective tape to slow the rust down. That is required I believe too

 

[dcg9381]

A mini-excavator would help digging the posts for the array and a few other things.

> I can rent a trencher- but the last time I did that when adding my shop, the trencher broke due to the rocks- mini exe might work, but would make a much bigger hole- and cost more to rent than the trencher.

We have a ton of rock here. I rented a 24" deep rock saw. $500/day through.

 

[gpiggaz]

I gave up after spending $800 to rent a skid steer with an auger. Didn't even hardly dent the ground and the bit wandered when it did dig in. I've resorted to a demolition hammer and a vacuum cleaner, slow going but it's working, I can dig almost 1 hole per day. I've gotten sore hands, but it is what it is. This "soil" is impossible I'm not going to spend anymore money, just time on the excavation.

 

[dcg9381]

There is a skid steer auger that is made for rock... And it needs a "larger" skid steer, but with the right auger, it's night and day.

Like you, I tried the "regular auger" in limestone with a skid steer - waste of time. Find the right rock auger.. It's slow, but you'll make progress, especially when you blow through layers of rock.

I own a jack hammer too - about the same progress as you, but the right skid steer and rock auger can drill limestone.. If you're on stuff harder than that, maybe I've got it wrong.

 

[walrus]

I'm trying to scrounge enough 2" galv pipe to make a ground mount. I have about 160 ft so far, all for free. Need a few hundred more feet to do it according to the plans. My soil is bony(lots of rocks) clay. The problem is getting the supports in straight , plum and parallels to each other so the racking will go together correctly

 

[gpiggaz]

I'm trying to scrounge enough 2" galv pipe to make a ground mount. I have about 160 ft so far, all for free. Need a few hundred more feet to do it according to the plans. My soil is bony(lots of rocks) clay. The problem is getting the supports in straight , plum and parallels to each other so the racking will go together correctly

How big of an array are you putting in? I have 20 panels and only needed about 135' of pipe.

BTW- not just any pipe will do- it needed to be SCH 40 Galvanized pipe Class B or Allied tubing 12GA. Otherwise it's not strong enough for the wind loads.

 

[gpiggaz]

Following up- Passed the foundation inspection today- my hands are still sore from the jackhammering, but we've got 10 holes ready for concrete In the end, 6 holes were dug to 4' and 1' in diameter but with some of the boulders that were under the surface 4 holes were dug only to 3' but 20" in diameter to meet the engineering requirements. Spent a total of 40 hours jackhammering the caliche. The larger holes just require 2X the concrete in those holes as the 1' diameter ones. Hopefully, the rest of the installation will go smoothly.