Ground mount: Sch 40 pipe vs. mechanical pipe?

[zzrider]

I'm working up a plan for a 6KW ground array using Iron Ridge hardware, and I see where you can use either schedule 40 pipe or mechanical tube - wondering if anyone here has an opinion on one vs. the other. Availability, cost, workability, etc.

At this point I'm leaning towards the tube because it's apparently a bit lighter than pipe; haven't priced them out yet though.

 

[Texican]

I'm working up a plan for a 6KW ground array using Iron Ridge hardware, and I see where you can use either schedule 40 pipe or mechanical tube - wondering if anyone here has an opinion on one vs. the other. Availability, cost, workability, etc.

At this point I'm leaning towards the tube because it's apparently a bit lighter than pipe; haven't priced them out yet though.

I used the ironridge system on used oil pipe 3 1/2 inch OD. I paid a guy about $500 for maybe 110 feet cut to length.
for each array. then treated it with a rust converter, then primer for rusty metal and then restoleum gray. they look great
made 3 ground mounts this way, total $1500 for pipe plus all the ironridge hardware which is not cheap

 

[Bluedog225]

I’m not familiar with mechanical tube. What is it?

 

[OffGridInTheCity]

I used 2" x 10ft galvanized Sched 40 pipe + 10ft universal strut cross members for this ground array. The vertical poles rooted in 48" deep concrete pad ballast. Used wd-40 anti-corrosion where the pipe is threaded/coupled together - and after 3 years, no rust so far.



It's been rock solid.

 

[zzrider]

I’m not familiar with mechanical tube. What is it?

Best I can tell, tubing is made to closer tolerances than pipe and is measured differently, primarily by outside diameter.

It's a bit confusing. I'm just trying to figure out what to use since Iron Ridge leaves it up to the end user to get their own material for the piers and cross pipes.

 

[zzrider]

I used the ironridge system on used oil pipe 3 1/2 inch OD. I paid a guy about $500 for maybe 110 feet cut to length.
for each array. then treated it with a rust converter, then primer for rusty metal and then restoleum gray. they look great
made 3 ground mounts this way, total $1500 for pipe plus all the ironridge hardware which is not cheap

Did you need to do any splicing to make long lengths for the cross beams? If so, what did you use to do the splice?

 

[Texican]

Did you need to do any splicing to make long lengths for the cross beams? If so, what did you use to do the splice?

my cross pipe are about 32 ft total. I used 2 pieces at 16 ft and they meet over the center post
they dont need a splice

 

[OffGridForGood]

Best I can tell, tubing is made to closer tolerances than pipe and is measured differently, primarily by outside diameter.

Pipe is primarily used for moving fluids/gases and the most important aspect is the internal diameter ID as this conveys the material. Pipe wall thickness is expressed in Schedule - schedule 40 is a common industrial pipe for example, but I have worked with steel pipes from Schedule 5 to 160.
You can have two 2" pipe sections in front of you on the bench each measuring the same outside diameter, but one could be schedule 10 and be very thin wall (this is a common sprinkler pipe schedule) and the other pipe could be schedule 40 and much thicker wall.
A 2" pipe will not be 2" outside diameter, it will be 2.375" OD and 2.067 ID
Tube on the other hand is not primarily designed for moving fluids and gases, and is typically sized from the OD outside diameter, and a wall thickness. In your application the important aspect of either is they are rigid enough to carry the loads applied to them, and enough wall thickness to prevent localized buckling or crushing, ie if you plan to use U-Bolts be sure the wall thickness is sufficient that you don't just crush the tubing.
If you plan to weld to the tube/pipe you want enough wall thickness to prevent burn through, and to be able to carry the loads without just ripping out the tube/pipe wall. I find it easier to source pipe and steel fittings to match in my area, and tend to go with pipe over tubing, but then again, pipe is part of my work, tube not so much. Tube is likely less expensive.

 

[NEpowerandlight]

home2

Create everything you can imagine, with our simple, fun and durable DIY system of steel pipes and connectors. Everything is possible with tinktube!

tinktube.com

 

[Llaves]

If Iron Ridge says you can use either and provides stamped drawings for designs, then you use whichever suits you. As to price and availability, that depends a lot on where you live. If you're in oil country like Texican apparently is, then used oil pipe can often be found at low price. But I suspect that's a rarity. If you do use pipe, make sure you get pipe that matches the size and schedule requirement of the Iron Ridge components; otherwise the clamps and such will not match the diameter of the pipe.

You might also want to look at Unirac, which has a web-base design tool that produces stamped drawings. When I looked their components seemed reasonably priced.

Don't overlook the excavation and concrete requirements. I originally looked at a Unirac system until I realized I needed to bore 12" diameter holes 8' and fill them with concrete. Finding someone with the boring capability is a major issue where I am, and the closest ready-mix plant is about 2 hours away, which means I would have been hauling in a couple of pallets of concrete sacks and mixing it on site. Even with a mixer that was just too much.

 

[Paul_R]

There's no comparison between pipe and (round) tubing as far as structural strength. It's pipe all the way. Square tubing is a different story and much cheaper than pipe if you're buying new. But as somebody else said, if you can get your hands on used oil field pipe you can save a lot of money.

 

[OffGridInTheCity]

I say a youtube where a guy got a lot of angle iron for cheap (by the pound / couple of hundred $) and welded up his own tubes for a 30 panel solar array... He also cut his own square panel fasteners for pennies.

But then, he paid hundreds of $ for some buss-bars to parallel the battery bank and actually said on camera - what's special about these? He's right, a guy like this could build his own bus-bars but he was just unsure.

 

[Llaves]

I say a youtube where a guy got a lot of angle iron for cheap (by the pound / couple of hundred $) and welded up his own tubes for a 30 panel solar array... He also cut his own square panel fasteners for pennies.

It wasn't even clean angle scrap when he bought it - he alludes to taking something apart to end up with angle. Amazing how many out there value their time at zero.
And his v-shaped array makes no sense if he has battery storage.

 

[OffGridInTheCity]

It wasn't even clean angle scrap when he bought it - he alludes to taking something apart to end up with angle. Amazing how many out there value their time at zero.
And his v-shaped array makes no sense if he has battery storage.

I was not-impressed by the V-Shape as well but did some calculations using PVWatts - and it turns out that V = Straight in overall PV production. And since it's equivalent overall power, one might justify it for various reasons such as toplogy, shading etc. And there may be some benefit to a higher floor of power early and late in the day - but I'm not sure that's a good reason alone.

 

[Llaves]

t did some calculations using PVWatts - and it turns out that V = Straight in overall PV production.

what location/assumptions did you use? For my location (NW New Mexico), fixed 45° tilt (my actual installation), the V-shaped array loses 8% compared to a flat array due south.

And there may be some benefit to a higher floor of power early and late in the day - but I'm not sure that's a good reason alone.

At first I thought this might be true, but remember that compared to a single array due south, half the array is pointing in a very wrong direction in early morning and late afternoon. I looked at the PVWatts hourly output on a clear Jan day in my location and tilt, and the combined output of the two legs of the V are always worse than the output of the due south array. For example, at 8AM, the due south array is producing 39% of rated power. The V leg pointing east is producing 39%, the leg facing west is producing 5% (!) of rated power, which averages to 21%. That's a losing proposition. Ironically, the V-array comes closest to the flat array for the hours around noon, exactly the opposite of his goal.

Time​	V-array as % of flat​
7​	1​
8​	0.590993​
9​	0.769671​
10​	0.835857​
11​	0.851795​
12​	0.862797​
13​	0.840452​
14​	0.811175​
15​	0.626941​
16​	0.625302​

 

[OffGridForGood]

There's no comparison between pipe and (round) tubing as far as structural strength.

Not accurate.
Tubing and pipe are measured and specified differently, however you can achieve the same "structural strength" with either by selecting the diameter and wall thickness you need.
Compare a 1-1/2" Schedule 40 steel Pipe to a 2" x 10ga Tube for example
A53 Std 1.5 S-40 Pipe 1.90" OD 1.62" ID 0.145 wall thickness 2.72 lbs per running foot.
A513 Steel Round Tube 2" OD 1.732" ID 0.134" wall thickness, 2.67 lbs per running foot.
Although the pipe is called 1-1/2" and the tube 2" ,
These two round sections would look nearly identical on first glance, and each would carry nearly the same loading both in axial and bending, the Tube in this case is slightly larger diameter and slightly thinner wall, a bit lighter per running foot (which typically drives price).

For any sized "Pipe" you can find a similar sized (diameter and wall thickness) "Tube"

 

[zzrider]

If Iron Ridge says you can use either and provides stamped drawings for designs, then you use whichever suits you. As to price and availability, that depends a lot on where you live. If you're in oil country like Texican apparently is, then used oil pipe can often be found at low price. But I suspect that's a rarity. If you do use pipe, make sure you get pipe that matches the size and schedule requirement of the Iron Ridge components; otherwise the clamps and such will not match the diameter of the pipe.

You might also want to look at Unirac, which has a web-base design tool that produces stamped drawings. When I looked their components seemed reasonably priced.

Don't overlook the excavation and concrete requirements. I originally looked at a Unirac system until I realized I needed to bore 12" diameter holes 8' and fill them with concrete. Finding someone with the boring capability is a major issue where I am, and the closest ready-mix plant is about 2 hours away, which means I would have been hauling in a couple of pallets of concrete sacks and mixing it on site. Even with a mixer that was just too much.

Yep the bore holes for the footings are going to be a pain in the arse. I've resigned myself to that.

I have a tractor with a PTO post hole auger for the 3 point, and I'm in south Florida where the ground is just sand, so shouldn't be too terrible. I just need to get a 16" bit for the auger. Biggest problem is the auger will only go to 4' and I need 6' holes, so I'm probably going to end up finishing by hand and/or raising the grade some and backfilling the sonotubes at the top.

Also planning on mixing & pouring it myself. It's damn near impossible to get anybody to do anything these days.

 

[pvdude]

I had a similar situation. Could not find anywhere to rent an available auger, all
out on long term, or broken, waiting on parts.
Our yard is fenced, so I could justify an auger to do the ground mount piers,
and keep up with fence post replacements.
Giant son bored the rear piers, really deep.
We already had an ancient concrete mixer, inherited
from the FIL estate.
Ground mount has survived two minor hurricanes, so far.
Schedule 40.