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Discussion Starter · #1 ·
I'm looking into replacing about 250 feet of THHN wire thats been buried in PVC conduit for 20ish years. Wanting to do this in order to upsize the wire and make the circuit a higher amperage. I've done the conduit fill calcs and I'm within the limits if I upsize.

What is the best way to do this? I have 2 pull points/J-boxes in the middle of the run. Guessing I should aim to use the old wire the pull the new wire through? Should I do this one wire at a time, or all of them at once? I'd be replacing four 8awg wires (including ground) with 6awg in 3/4in PVC conduit.

What should I be anticipating as potential hiccups? Never pulled that length of wire before, let alone in an old conduit.

Would love any tips that anyone might have.

JC
 

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You should pull in all the conductors at one time. I would use an old conductor to either pull in a pull string or the conductors.

You can use a #10 for the ground.
 

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Discussion Starter · #3 ·
You should pull in all the conductors at one time. I would use an old conductor to either pull in a pull string or the conductors.
Use all the old conductors to pull in all the new ones, or pull out a few and leave one as a pulling wire? Also - what’s a good material for a pull string? Don’t want something that’d snap on the middle of the conduit from pulling too hard.

You can use a #10 for the ground.
Can I use a smaller ground for a regular circuit? Thought I could only downsize if I’m powering a subpanel

JC
 

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At what wire size does this start? I'm more familiar working with higher gauges, but to my memory, 14awg-10awg romex all have a matching size grounding conductor, right?

Good catch. It doesn't start until you get to a 40 amp circuit.
NEC table 250.122

40, 10 ga.
60, 10 ga.
100, 8 ga.
200, 6 ga.
300, 4 ga.
 

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the potential hickups..

they dont come out at all

You tie to the whole run, and pull your new wire with them, and it comes loose. Or gets stuck

You use just one wire and try to pul it, and you tie the new wire onto it, but the wire gets stuck with all that other wire inside.


You pull all of it out, using a nylon string on the end, so that is your new fish (the best thing to do)


If you can, get a fish tape. And use that.. once the wire is out, it will be gravy to pull in the new wire with it.

Im going to tell you a cheaper way to fish in wire. (this will also draw the attacks of other electricians, I know.. but the truth is, it works, and its cheaper)

A cable.
like this...https://www.summitracing.com/parts/sum-931120-34


youre really just getting it for the cable. In long runs of PVC, where something bad happens and you end up having to pull out all the wire,, and the pvc is large, then a fishtape coils up inside the pipe!
But I kid you not, that cable wont! it will just slide right in.

Once pushed to the other end, attach your wire (not using that eyelet. I use the bald end and just tape it on well)



here is another trick I saw someone do (this will also cause attacks by the other people on this site, but it worked. I saw it happen)

one guy was left on the job, and wasnt given a fish tape when the boss left. Nor did he have a wet/dry vac and a bag. . the pipe was 3 inch pvc. What he has was a string, pulled in already, weeks earlier, but someone came and pulled it out (kids in the neighborhood)

so what he DID have was Mc cable. He pushed that right in! LOL
It worked! it has 3 wires in it. so he tied the new string onto the mc, and pulled it back!



But if you have the cash, get a fishtape. and Nylon string.. incase things go bad, trying to pull the wire.

behind this post, the others will say "are you even an electrician?" or "youre no electrician because ..."
but the reality is, this is what makes me the better one.
because Im not going to say "well i dont have thios or that, so I wont do the job until I get xyz..

a tradesman thinks outside the box and gets the job done so as to get the same end results, if he has to.
 

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Hey Jon what ever method you end up using to do the pull if you end up using lube be sure you use electricians lube and nothing else. Electricians lube is specially formulated so that the materials in the lube will not eat thru the conductors insulation over time etc.
 

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Jon. 250' s a long way and its been a very long time.
Getting the old out is going to be the hardest part of this. Your conduit at 3/4" is not going to be much help.
Try pulling one wire at a time if you can. This will help loosen the others and then you may be able to pull all out. But try one wire first.

Sometimes the addition of a liquid like water can really help. Last resort, but a good option. You can always blow out the water or leave it in. I used a water hose last time I was on a job like this.
Water will be present inside conduit regardless.

You should not need a fish tape at all. With two pull points I see success in your near future.
Make sure to tie a string to the wires you remove. Use this string to pull in a bigger string or even the wires. We use jet line, but any good strong string will work just fine.

Are you going to be feeding the new wire in on wire reels?
Get reels of #6 and #10 and pull from the reels.
Below is a picture of a wire reel hack. This makes feeding the wires easy and helps keep them straight. You will need an assistant. Let the assistant pull. You feed. Feeding is the most important job!
If you get any twist while feeding in the new wire, it could jam up and you would then need to pull it back out and straighten it out.
So use the picture as an example.

Good luck and keep the forum posted.
 

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Use #8 for your ground wire.

THWN wire in conduit is allowed 65A. You get to "round up" to the next available breaker size, and use a 70A breaker.

Using #10 ground would oblige you to breaker at 60A, which is a waste of ampacity.

The ground wire can be bare if you want to save a little room.

Pullingwise, I would pull all the wires together. Trying to slide some wires against other wires creates a LOT of drag, and complicates the pull. For a DIY pull you want to stack as many things in your favor as you possibly can.
 

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"... buried in PVC conduit for 20ish years"
I would be surprised if you could still pull anything in or out at this point. That's been my experience.

How about the experiences of others?
 

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No one has mentioned one of the most important parts or maybe THE most important part of the pull..…that is the connection between the old wire and the new wire.

It needs to be secure....and I mean SECURE for a pull that long. It needs to be small in diameter so that it does not wedge in a turn or a glue joint.

Google or YouTube on how to do a satisfactory joint connection. It will be well worth your time.

Good luck.
 

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"... buried in PVC conduit for 20ish years"
I would be surprised if you could still pull anything in or out at this point. That's been my experience.

How about the experiences of others?
Certainly it is a problem. I have watered down cable lube and poured into pipe with a funnel. Then blow it in with a compressor. Make sure the far end is not in an area that will make a mess. If you can't get air to blow thru, most likely the pipe is compromised - rusted out or crushed. If it is the wires are not coming out, get a shovel. If you can get air thru, start to pull one end, then go to other, back and forth to try and break in free.

Sent from my Lenovo TB-X606F using Tapatalk
 

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Discussion Starter · #16 ·
Thanks for all the feedback everyone. Will post results when I get around to the project.

Use #8 for your ground wire.

Using #10 ground would oblige you to breaker at 60A, which is a waste of ampacity.
I might’ve considered this, but I’m upsizing the wire to get it from a 20A circuit to a 30A circuit because of how long the run is. That’s calculation I got for the length of run while staying at/under a 3% voltage drop. So it’d be a long time and some drastic rewiring before that circuit is ever used for anything above 60A. Thinking I’ll leave the #8 ground if it doesn’t create too much pulling friction.
 

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When you upsize the *conductors* for voltage drop, you must upsize the *ground wire* also - this is specified in 250.122(B).

250.122(B) Increased in Size. Where ungrounded conductors are increased in size from the minimum size that has sufficient ampacity for the intended installation, wire-type equipment grounding conductors, where installed, shall be increased in size proportionately according to the circular mil area of the ungrounded conductors.
There are 3 ways to tackle that math.
- The official way is to look up the kcmil area of each conductor and crunch the numbers.
- An unofficial but perfectly valid way is to upsize the ground *the same number of numeric sizes* as you upsized the conductors. This works because AWG wire sizes are themselves based on a mathematical curve.
- My preferred way is to figure the max breaker you could possibly use (70A), ask which ground wire is appropriate for *that* size, and then use that size ground (e.g. #8). I must admit there are technically Code issues with this approach, but I'd defend them to an AHJ.

The first method: due to 240.4(D) and 250.122, your conductors AND ground must be #10, so if you bump conductors to #6 you must bump ground in proportion (so #6 also).

The second method, +4 size bumps on conductors, +4 size bumps on ground.

I don't like either one.

My third method: You are entitled to breaker the #6 THHN at 70A, since Code does not require wire size bumps/"nanny breaker" derates for voltage drop. If you did, then 250.122(B) would be inapplicable and #8 would be fine. Now think this through. The purpose of enlarging the ground is to ensure enough current can flow to trip the supply breaker. So... I would argue to the inspector that #8 ground is legal at a 70A breaker. Downbreakering to 30A only improves the situation, so it should not require a larger ground; this is an absurd glitch of the small-branch-circuit rules, and therefore deserves a waiver.

After all, if you breakered at 40A (which you are perfectly allowed to do), that escapes the small-circuit rules, and allows #8 wire with #10 ground. One bump brings us to #6 / #8, once again my destination.



@Jim Port @Missouri Bound
 

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Thanks for all the feedback everyone. Will post results when I get around to the project.



I might’ve considered this, but I’m upsizing the wire to get it from a 20A circuit to a 30A circuit because of how long the run is. That’s calculation I got for the length of run while staying at/under a 3% voltage drop. So it’d be a long time and some drastic rewiring before that circuit is ever used for anything above 60A. Thinking I’ll leave the #8 ground if it doesn’t create too much pulling friction.
ok...you need to fact check the notion of using a larger ground "obliges" you to use a 60amp breaker by googling that to get the code answer.
Assure the word "ground" and that green GROUNDING wire arent being used interchangeably.

Its "hot, Neutral, GROUNDING wire"
Saying it that way removes any confusion talking to one tech to the next.
 

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Also, keep in mind "3%" is only a suggestion, not law since you're not in CA.

Anyway... Breakers don't cause voltage drop. Actual amps flowing do. Hence it is wrong to compute voltage drop based on breaker trip. If the load is known (e.g. post light out at the end of a 500' driveway) compute based on the known ampacity. Otherwise compute on expected loads but never more than 80% of breaker trip. The advice in this paragraph even conforms to CA code.
 
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