diy solar

diy solar

Pulling 17 wires through 230ft of conduit?

rhino

rhino

Solar Wizard
Joined
Jun 6, 2020
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Location
Minnesota
Wanted to do a sanity check that I wouldn't be crazy to try and pull (16) 10 AWG XHHW-2 wires plus one 4 AWG (one of the existing cables which I will reuse) through 1.5" conduit over 230ft. This is an existing underground conduit and I can't redo it. I'll be pulling out the existing wire and replacing it with the wires mentioned above. It is fairly straight shot and I might even dig down and temporarily remove one of the 90 degree elbows in the field where the solar array would be located for easier pull. I've done 500ft pulls in past but with only 3 larger cables. Just wonder about the logistics of 16 rolls of cable (plus the one larger one for ground) being pulled.

This would theoretically be for 8 separate strings of bifacial panels with 6 in series (250V Vmpp) if I decide to do that many with Isc of 13.64 under STC per string. I was going to use 12AWG but realized from discussion in another thread with @Hedges that would be too low of ampacity.
 
It is "doable", but... a couple of points:

1. 16 current carrying conductors drops the NEC ampacity to 50% of the "3 conductors in raceway values", so assuming that is OK given your Isc values from the panels, then go for it!

2. The friction will become a beast as more wire is pulled in. Use a good stout pull rope and a tractor or wench.

3. Pull in the entire group simultaneously so the pull force is as evenly distributed as possible to all conductors. Avoid pulling individual wires as stretching and insulation damage can happen as more wire is pulled in.

4. Have a couple of helpers on hand. One person is going to need to watch the feed and prevent the insulation from being damaged (scraped) by the conduit wall where the conductors are introduced into the conduit.

5. Definitely use a wire caddy and separate spools. That will make the feeding much easier.

6. Try to let the #4 take as much of the pull force as possible.

7. Use lube.

If you have any evidence that the conduit is compromised or has pulled apart like mud on the existing wire as you pull it out, stop and reassess. In that case, you'll probably have to abandon the existing conduit in place.

Good luck, hope it all goes well for you!
 
As long as its physically big enough and you have a five gallon pail of wire lube and paintbrush on one end and an appropriate tugger on the other you should be all set. BTW. there is lot to be said for pulling the old wires out and pulling in new pulling rope, then blasting the line with compressed air to clean out any water and grit that has gotten in the pipe.
 
First of all you should cut 16 pieces of #10 and 1 piece of #4 about 5 or 6" long. wrap the #16's around the # 4, you should grt 6 or seven around the #4 then try and evenly wrap the others around. You should be able to wrap up to 19 conductors into a single circle tape up the one end and make sure that you can easily slide all those conductors into a short piece of 11/2" condiut. If you can you are good to go. Secondly spread your rolls out evenly in front of the area you will feed in, and you will need long round bars to fit those rolls onto. Strip the insulation 2"off off the ends of the #10 conductors and about 6" on the #4. Then starting at the middle of the #10 rolls take one of the center #10's and wrap the other center #10 around the first close to where the insulation starts so you should end up with about 2" wrap and 4 " free to wrap around the next #10 continue until you have a long taper of all the #10's attached to each other then push the #4 into the mix and wrap the last #10 onto the #4 . Get those conductors to circle the #4 and then tightly tape down the taper. Use the old wire in the conduit to pull through a heavy draw wire make a loop onto the draw wire and attach the #4. and if those conductors will fit into the conduit with a little lubrication and no tight bends you should pull it through easily as long as you have someone conrolling the feed. also make sure that the conduit ends are de burred and that the conductors all go in without any crossovers. If the coductors are multistranded like the marine or automotive stuff you will need to solder the areas wrapped to make sure they do not come adrift. PITA I know but that is how to do it.
 
I did a little bit simillar job, of four 150 ft strings of #6
and two ground wires, but before inserting the wires,
I completely unrolled all the wires above ground.

I attached one end of each wire to a tree and stressed them one by one
to remove any rolling effects. I also use electrical tapes of different color
at each end to identify them.

When the wires started to be perfectly parallele I attached all together,
using electrical tape at about every one or two feet interval.

I hope this help. I did it by myself.

Note: What kind of MPPT and how many of them are you using at he the other end?
 
Last edited:
rhino said:
I might even dig down and temporarily remove one of the 90 degree elbows in the field where the solar array would be located for easier pull
Click to expand...
Is this a LB etc or a sweep?

Sweep is allowed to be buried but pull points need to be accessible.

And you are supposed to do the pull with fully assembled conduit instead of building the conduit around it.
 
Shouldn't be a bad pull. As long as the feeder and puller are in sync. (Like rowing a boat)
Look at the old wires to determine if the conduit is clean. (May need to swab it out)
Definitely use lube on the wire. (Not on the rope)
Take your time and communication is important between the people on both ends.
 
Okay.. I'm getting a bit more confidence this is doable :) Already have excess mule tape from other pulls I would use.

For background on why now; I currently have about 9kW situated on several top of pole mounts (some panels over 15 years old). This winter we've had many days of thick clouds resulting in only about 10% of normal production for that day. Fossil fuel generator is also not an option for reasons won't delve into here. Currently grid-connected in order to make up for the shortfall. Plan is to disconnect from the grid this summer since utility company is planning on doing work this summer that we don't want. So I am left with needing significant PV production for maintaining all loads even during these cloudy winter days.

I was looking at using either 24 or 48 of the 540W Vikram bifacial panels. Specifically looking at these since they are made in India instead of China. Would be put on a seasonally adjustable (up to 60° tilt) Sky-Rack 2.0 ground mount from Sinclair Designs. After talking with them they said those larger panels would need to use their 8 panel mount sections and since I would be using 6 panels per string I'm left with multiples of 6 and 8 hence the 24 or 48. Already in the Victron ecosystem so would use 1 or 2 of the SmartSolar 450/200 (4 independent trackers per controller). Usually hit -40 or lower in winter so have to watch that Voc and therefore the 6 panels per string only. 24 likely would be enough for now but don't want to have to expand again 5-10 years from now when everyone has EV's ;)
 
I've pulled some crazy stuff including some really long fiber pulls and I just recently pulled 36 10AWG THHN in a 2" conduit that already had 4 2AWG wire in it with a couple swept 90s. It was a pain but we got it done. Fortunately it wasn't a long pull - about 40'.

It helps a lot that you're pulling the old wire out. As someone suggested you may want to pull the old wire out and pull some new mule tape in to pull the new wire with. Obviously lube is going to be your friend. Looking at the wire size charts it looks like either 44 10AWG wire in a 1.5 inch conduit or 9 4AWG. You can get the circumferences and do the math but what you're proposing should fit.

Let us know how it goes!
 
You legally could put 29#10 XHHW wires with that #4 in an 1-1/2 PVC schedule 40 conduit. That would be 40% fill.

Your 16+1 will be no problem with 2 people, one pulling the other lubing AND pushing. You'd be surprised how much difference pulling wires becomes when the other end gives it a little push.
 
Yup
No matter which end I am on.
I can make it extremely easy for a coworker who I consider a friend.
Or extremely difficult for that idiot I was stuck with for the day. lol
 
Would it be helpful/allowable if I used 8 different cable colors (besides green) so that I can easily keep each pair of wires for a specific string matched together?
 
rhino said:
Would it be helpful/allowable if I used 8 different cable colors (besides green) so that I can easily keep each pair of wires for a specific string matched together?
Click to expand...
Wouldn't be a bad idea, being able to know which wire goes to which string will be handy. Big trick is to make sure you make lots of labels and charts so you can remember which is which.
 
Hmm. If you want to repurpose some of those as grounded conductors in the future then you will face restrictions, since relabeling is not allowed on #10 individual conductors.

That’s assuming DC- is not considered a grounded conductor.
 
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