Somewhat OT: Well Wiring

From what I understand of wire insulation codes, ANY TW or THWN wire (or other wire with a W in the type code) is waterproof, period. Conduits
are assumed to be full of water if they run outside, so wet location wire is supposed to work fine in water.
I'm wiring a submersible well pump. 12-2 w/g "well wire" is thus far so much more costly than 3 rolls of 12-gauge wire and I "twist it myself" (the product I'm comparing is just 3 wires twisted, no jacket) that I'm rather tempted to do exactly that, since I can't see that there's anything "special" about "submersible well pump wire" other than its "special bend-over price." At least, if I understand wire insulation codes correctly. There's no "special insulation code just for wells" - the stuff is typically TW (60C - no problem in a hole in the ground that stays near 10-15C most of the time.)
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On 3/26/2010 9:15 PM, Ecnerwal wrote:

I think pump cable is annealed due to the movement it is subject to when the pump cuts in/out.
MikeB
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The torque arrestor (rubber football-like thing clamped to the pipe just above the pump) is supposed to keep the rest of the system from moving, much. Likewise, a series of standoffs/spacers is supposed to keep the pipe, wire and rope from tangling up or hitting the sidewalls. Still, worth a thought. Thanks.
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Ecnerwal wrote:

Consider using stranded conductors.
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I was planning to - and looking into it further most well wire does, as MikeB suggests, specifically state annealed, while most regular stranded wire does not. Probably there is some movement despite the football.
A related ugly thought occurred to me last night. The well casing (100 feet of steel) is the end-point of my grounding system (100 feet of 2/0 copper, with 4 8 foot rods driven in from the bottom of a 3-4 foot deep trench, and then connected to the well casing.) The (PVC) conduit for the well pump power runs mostly parallel to, but as much as 2 feet away from the ground wire. If I run a ground with the pump power from house to well-head, that creates a ground loop if I (as I gather I should) park a surge arrester at the top of the well casing and tie the piddly ground wire into the well casing as well. I'm thinking I should just run power wires in the conduit, and tie the down-hole ground wire (and surge arrestor) into the well casing, which is tied to the main ground system (by wire far larger than the well power wires), and thus not create a ground loop. It does create some loop area between the ground and power, but at least does not create a full on ground loop.
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On Mar 26, 6:15pm, Ecnerwal

We live in the desert and have a well about 600 ft deep. The pump is a 3hp.
Last summer we had to replace the pump. The 1 1/2 pipe is 540 ft, as I remember. The wire was three individual conductors, Twisted, as you suggest. The pipe had one of those "football" things on it and the well maintenance guys took it off and threw it away. Said it doesn't stop twisting of the pipe, only dampens the vibration and with that much pipe, didn't really do anything.
We reused the old wire and tried our best to examine it and tape any abraded places. The wire was taped in many places as it went down the well.
About a month later, the pump quit with a short to ground. Apparently we had missed an abraded place and it had worn more and shorted to the pipe. So, another session of pipe removal. They got a spool and a half of new wire. This wire was flat and the three conductors are molded together in some type of poly insulation. Yes, it did cost a lot, but the scrap price for the old wire covered almost 1/2 the cost of the new stuff. The new flat wire will probably not have the abrasion problem the old wire had.
I would submit that you are foolish to not use the more expensive wire specifically designed for well usage. The cost of replacement in a few years will more than exceed the cost difference.
Just my experience.
Paul
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On Sat, 27 Mar 2010 09:10:26 -0700 (PDT), " snipped-for-privacy@coinet.com"

I've seen a fair bit of both types of wire. Yes, the twisted stuff is more easily damaged, especially if the hole is crooked, has offset joints, or is uncased. But generally, it works well. It's an easy way to save quite a few bux on deep wells if there aren't any special problems. Even if there are issues on a particular hole, one could probably still save over the double-jacketed type by putting a torque arrestor say, every 100'. http://www.deanbennett.com/misc-well-accessories.htm Or make centering devices out of strips of pvc and hose clamps.
Reasonable wire prices here. http://www.deanbennett.com/submersible-pump-wire.htm
Wayne
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snipped-for-privacy@citlink.net wrote:

I'm simply buying plastic centering devices (aka cable guides) and sticking them on the pipe every 10-25 feet (recommendations vary - the things are only a couple bucks each, with holes to isolate pipe, wire, and safety rope.) Could certainly add a couple more footballs, I guess. The things pump guys do (ie, throwing that away) are sometimes based on future pump guy business...I suspect.
Best price thus far on the well cable is 62 cents a foot delivered, which is bearable, but I find occasional surprises, like the 100 bucks less that one local lumberyard is charging me for 200PSI poly pipe .vs. best price I could find on the internet, (while local lumberyard #2 could not get 200PSI pipe, and wants $1.57/foot plus tax for pump cable.)
I have shifted to mostly shopping for 300 feet of pump cable and putting a junction (and arrestor) at the top of the well, rather than buying a reel at 500 feet (should cost less per foot, so far does not) and running pump cable out to the wellhead from the power source, since "non-pump-wire" costs considerably less, and that part is just sitting still in conduit.
It's easy to se where this can get horribly expensive the second time - right now time is not of the essence and I have the latitude to shop around. Once dependent on the well working, local lumberyard #2's extortionate price on pump wire might look better than a week's delay. Avoiding a second time as much as possible is certainly part of the plan.
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That's starting to add up to a bunch of length you're shopping for. The original post stated 12 ga, have you allowed for voltage drop at that distance? One job I hooked up we had to go huge (#2) for a few hundred feet of the underground portion and splice to #10 for the pump wire at the well head. That kept the pump wire to a reasonable size and voltage drop under 5%. Total circuit was 600' IIRC.
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The total wire run is just under 400 feet. 3/4 hp, 2-wire, 230 V - the pump specs on the particular pump I'm shopping claim 12 Ga is good (for up to 525 feet) though I might run 10 Ga for the ~100 feet out to the well-head and switch to 12 for the 300 feet down the hole. The price of copper has made massive overkill somewhat less appealing, so I'm sticking with mere overkill, though I had pencilled in 10 Ga as well as 12 Ga on the prospective shopping list, just to see what it added. In shopping for the 500 foot reel I was planning to use the extra 100+ feet for some other exterior wiring.
The alternate pump I'm considering claims 545 feet for 12 Ga, so if I switch units, I'd still be well inside the suggested range.
I could use a 1/2 hp pump but I'd like to both be able to actually use some of the storage (drawdown) in the well, and not be screwed if the static water level measured when drilled is not the static water level at all times of year.
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