diy solar

diy solar

New to Residential Solar (have questions)

bighammer

New Member
Joined
Sep 21, 2020
Messages
35
I'm underway with a 5kW ground mount grid tied system. I have posts in concrete and racking set. (all but one piece damaged by trucking company) While I wait one the one rail, I thought I'd tackle some of the wiring.

The package includes a 2 pole disconnect in a box. The wiring diagram shows it as an AC disconnect between the breaker panel and the string inverter. (Sunnyboy 5.0) I plan to mount the inverter in my basement on the wall near the panel. My question: Does this disconnect need to be outside, (as in accessible to utility personnel) or is it OK, just on the basement wall between breakers and inverter?

When I get to installing the panels, they each have a TS-4-R-F Rapid Shutdown module. THe outputs of the panels get plugged into the module inputs, then the modules are connected to form each of the 2 strings. The panel instructions say they should be covered with opaque material while installing. Even though this is a ground mount, it sounds like PITA. (can't imagine messing with it up on a roof) I'm guessing the module outputs would be dead until they are all connected to each other and the inverter. If I make the panel-module connection while the panel is still face-down, I'm thinking I should be OK, right?

Burying the lines between the array and house: I'm guessing 18" is the standard depth. It's just under 100' and I'm thinking I might trench it by hand to avoid the $200 machine rental. PVC sounds easier to me than EMT, but where it sticks up out of the ground to the transition (combiner?) box, does it need to be sch 80 or somehow protected? I thought PVC couldn't be left exposed. I might use EMT for the whole thing. Can I just go thru the basement wall at trench depth and seal with hydraulic cement, or do I have to come up, go thru wood or exposed block, then drop down again in the basement? I am close to my limit. Kit included 4 PV lines at 100' and my wall is at 93' from the array.

I guess that's it for now. Thanks in advance.
 
119657803_10158049021252144_5039744500764445911_o.jpg

Why are there only 7 of 8 rails up?

Thank you XPO Logistics. Looks like one of your forklift drivers tried to drive over a bundle of racking.

IMG_20200909_142717044_HDR (1).jpg
 

Attachments

  • IMG_20200909_143654667_HDR (2).jpg
    IMG_20200909_143654667_HDR (2).jpg
    141.1 KB · Views: 3
NEC code says an emergency disconnect should be accessible in the event of natural disaster or fire so be it outside. Solar panel becomes alive with the sunlight. Even if you keep them face down, there is always indirect sunlight hitting the solar panel so you have to be very cautious. Cutting a hole in the wall at trench depth and seal with hydraulic cement doesn't sound good. I would rather keep it above the ground as much as possible.
 
Last edited:
Thanks for the reply. I just got an email that the replacement rail should be here on Mon, but not holding my breath. ? (same trucking company)

I went ahead and started laying panels, because I'm not sure what I need for the wiring part of it. The inspector said I need a fused DC disconnect (and since it's 2 strings, I'll need 2) near the array as well as the AC disconnect for inverter.

Maybe it was my misinterpretation, but it sounded like it would be a complete kit except for the steel pipe and concrete. :(

DSC_4200crop.jpg
 
Your ground mount looks awesome. You may keep 2 DC fuse in one DC disconnect box. Keep it posted with the progress in your solar system!
 
Rapid Shutdown boxes shouldn't be needed for ground mounts, just for rooftop.
They do make all voltages low when not activated.
Never mind the opaque material. Even without rapid shutdown and connecting up to 600V strings, MC4 connectors are touch-safe. So long as circuit is open, they can be mated and unmated safely. I check with DMM before paralleling or connecting to a home run, make sure there isn't voltage between the terminals I'm about to connect.

Your utility company may require an AC disconnect they can access. 15 years ago I had to put in a visible-blade disconnect. Now they have the option of yanking the meter instead.

Your newer Sunny Boy may include AC disconnect for servicing inverter. Some of my older ones have DC only, not AC.

Thin-wall EMT isn't for underground, use threaded rigid or IMC for that.
PVC - just use the heavier schedule 80 everywhere. Deburr and deeply chamfer even lengths you don't cut - the right angle corner will snag wire jacket, especially where joined to bends.
You may be allowed to use direct burial like UF. It would be backfilled with sand and a red ribbon on top as warning if someone starts to trench through it.

Metal conduit is buried 12" underground, PVC 18". That's one of the reasons I used rigid, even though much more expensive.

Basement have a concrete floor, or not? Can you run conduit under the foundation wall?

Don't see any diagonal braces in your mounts. That would make it much stronger against wind/earthquake. Your upright pipes are fairly large, though.

Are the two strings paralleled at the array? If so, maybe only one disconnect required. I wouldn't expect fuses required for single strings or only two in parallel.
 
I didn't know that about the rapid shutdown modules, the kit just included them. (maybe rooftop is just more common?) Seems to me like the inverter output would go off when the grid shut down all on its own. Is it more of a fire prevention device?

I would guess pulling the meter would be the preferred shut off for a fireman. Seems odd to me to require a shut off for solar, but not one for the rest of the house.

I was out running other errands and bought a 100' coil of direct bury flexible conduit. Might be a little more cost, but no joints to make. (and I could bring it home in the car rather than returning with my truck)

Basement floor is concrete, walls are block.

It's a 3" sch 40 (3 1/2" OD) structure. No earthquakes here and our trees are dampening winds.

The wiring diagram showed 2 separate strings using 2 of the 3 inputs on the inverter.
 
Rapid shutdown isolates panels (or shorts their output), so a fireman can put an ax through one without getting electrocuted. It may or may not have a feature to help with shade. With no shade, you might leave them out.

What brand inverter? Some (SMA Sunny Boy) have an AC connection that works even when grid is down, but only if Rapid Shutdown isn't installed.

Visible blade switch was so my backfeed into the grid could be shut off for lineman safety. Pulling meter accomplishes the same thing, but leaves customer without power until put back in.

OK, so separate runs back to the inverter, each with its own switch.
It'll be easier to snake a pulling line through the conduit before you bury it and it has bends.
I've also seen vacuum cleaner to suck a pom-pom on a string, rather than trying to push a rope.

3" sounds strong. My original tilt mounts were supposed to be one, 6" pole sunk in concrete. I bolted a 4" pipe to existing concrete and braced it. The rest of my stuff is 2", and we do get an earthquake once in a while. Also occasional strong wind off the bay.
 
No shade except for a tree to one side that was looking more sick last year. It's still not healthy and now that this is finally happening, I might take it down any day that mood to destroy something hits. (although splitting wood is also good therapy for those days) We have planted trees all over our property, but our old garden plot seemed to be most logical spot for solar. It's in the front yard near the driveway, so keeping snow cleared off should be easier.

The kit included the SMA Sunny Boy 5.0-US-41 inverter and 16 of the SMA TS4-R-F rapid shutdowns. The rest of the package is 16 Astronergy 320 watt Mono PERC panels, IronRidge XR1000 racking, and related hardware for ground mount, AC disconnect, and 4 coils of 100' of 10 AWG, clips, labels, etc. Interestingly, no directions, so I'm wading thru it and figuring it out. I've built 2 houses, so I was very comfortable with boring the holes (rented a big toy) and setting and bracing pipes, and pouring concrete. I've done a bunch of electrical, so adding the backfeed breaker to the panel won't be a problem, it's just all the stuff in between.

The toughest part of renting something like this is wanting to own one. I dug a big hole for a compost pit in an area that had a lot of roots. I realized I could buzz around the property and mangle the roots around some stumps (sometimes the stumps themselves) to make their removal easier. So far, the project has been just one crazy old man, me. (and my tractor)IMG_20200915_144519985_HDR (1).jpg

DSC_3839small.jpg
 
I thought my idea for using the IronRidge hardware to support the posts was pretty slick. I plumbed and braced the 2 ends, then set the cross piece, and hung the center off it. I couldn't picture how just one guy could get the height with a big X like they suggested. A 2x4 over the hole and setting the bracket at the desired height made leveling a LOT easier. The bracket also kept it close to plumb in the one direction while I got a brace on the other way.

IMG_20200915_144338019_HDR (1).jpg
 
We recently had a fiber optic line bored from the road to our house last year. (beats the heck out of our old cable speeds) The guys put in what looked like an orange pex conduit that had a very strong ribbon for pulling the actual fiber thru. I asked what they do with it and they said they normally just pitch it. Before they wadded/tangled it up, I wound it onto an old spool, so I have almost 350' of high strength pulling ribbon.

Is it allowed to have the PV disconnect just be a DC rated breaker? And would that only break the + side, or is a double pole switch required for higher voltage DC circuits? I looked at the specs for the panels and 31.39V and 7.6A each make each string a potentially a 251V and 60A circuit; need quite a switch for that.
 
All looks very good.
The pole top clamps with U-bolts are just like some of my Unirac. Others are aluminum with bolts to clamp the top pipe.

I got a D6 with backhoe for my 10 acre mountain property. Bought a separate straight blade and cylinders and fabricated mounts. But I never kept it working long enough to cut a driveway. I did replace 3 out of 4 clutches getting it going.

Now I have a trencher, with electric start Onan. (The Cat had a rope start pony motor.)

By not using the rapid shutdown, you should have available the Secure Power feature, 2000W when the sun shines during grid failures. That should run refrigerator and other things.

If you get one Sunny Island (about $2200 on eBay), 120/240V transformer, battery, and a 48V relay for load shedding you could have a backup system. SMA's list says these inverters are only compatible with off-grid not grid backup, but they emailed me otherwise.

Sunny Boy Storage and Automatic Backup Unit is the officially supported configuration, but that isn't the bargain you can get on SI 6048.
 
Last edited:
Not exactly sure on the codes. Switch at Sunny Boy probably opens both. Once I've done that I unplug both ends of MC connector at the panels.
My earlier systems were at a time code thought we should not break negative, so only positive. Square-D 30A 600V heavy duty disconnect has 3 unfused poles. Outback/Midnight DC breakers daisy chain several ganged breakers to achieve 600V.

Why do you say 60A? Two strings, each 7.6A so each switch or pole only breaks 7.6A (or 10A short circuit from the data sheet). Series string only adds volts and watts, not amps.

Open circuit voltage is 40.42, 8 in series is 320V, a bit more on cold days (-0.2722 %/degree C) so that is what a switch should be good for, not 251V.

Home Depo rents a mini tractor with auger, bucket, other accessories on a trailer that would be nice, but I don't see them at all cheap.
 
OK, I was off on my calculations and what figures to use... I thought with a series circuit you total the volts as well as the amps. :rolleyes:
 
Back
Top