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Small Cabin Forum / Off-Grid Living / 2 wire or 3 wire well pump
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bldginsp
Member
# Posted: 29 Sep 2015 21:32
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Curious what thoughts those of you with deep well pumps have about what type of pump to use, a 2 wire or 3 wire with control box. From reading various things on the web, it appears that it's a 50-50 choice.

Some say that a 3 wire is better because if there is a problem with the motor controls it is easily repaired because the control box is above ground. Whereas, with a 2 wire the controls are in the motor, so to fix it you have to pull the pump. Makes sense, but two wire pumps use a different control mechanism than 3 wire and are supposedly very reliable.

One perspective I read is that 3 wire is the old way, and 2 wire was introduced relatively recently. So it is still going through an acceptance curve, but is the better more advanced technology.

It appears that many pump installers believe 2 wire is the way to go for residential installations of lower horsepower (over 1-1/2hp must be three wire).

Thoughts and experience?

I will soon be buying a pump for a 400 ft deep well with static water level at 292 ft, pumping to a storage tank, not a pressure tank, with total dynamic head of 375 ft including pipe resistance etc. Not that any of that matters for the 2-3 wire controversy. Anyway I plan to use a 1hp 7gpm pump to be just right of the curve.

toyota_mdt_tech
Member
# Posted: 30 Sep 2015 00:59 - Edited by: toyota_mdt_tech
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I think the 3 wire also uses a capacitor which is mounted above in the box. I did by a 220V 3 wire pump for my well (Flo Tec) and have not installed it. Flows 10GPM. I got it new on ebay for a killer price.

I was certain a 3 wire is better.

I am using a 2 wire solar livestock well set up now.

PatrickH
Member
# Posted: 30 Sep 2015 07:14
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I use a 3 wire pump,the "control" box just houses the starting capacitor and the wire connections to the pump and from your switch source.My understanding is the cap in a 2 wire is integral to the pump and may not be serviced separately where on a 3 wire for 40 bucks there available everywhere and easily serviceable. I use a red lion 1/2 hp 90 feet deep.

bldginsp
Member
# Posted: 30 Sep 2015 08:06
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I'm still a bit unclear about whether there is a capacitor in a 2 wire pump. If there is a capacitor in it, then if it goes the only way to fix it is to pull the pump. But with a 3 wire the start capacitor is up top and easily replaced.

But apparently the 2 wire pumps produced now don't have a capacitor in the pump. Instead, they have an extra start winding that is initiated by a heat switch at startup. Then the heat switch turns off after starting. No need for a capacitor. Trouble with capacitors is that they don't last as long as the pump motor.

3 wire pumps, so I've heard, are also a bit more efficient because they have a run capacitor that is working not just at startup, but also during operation, increasing efficiency. But it is a small gain in efficiency.

All this is JWIHFSE- just what I heard from someone else.

old243
Member
# Posted: 30 Sep 2015 10:04
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My submersible pump is 3 wire. Installed first about 1980. Since then I have replaced it ,twice , both times lightning, was the cause. Also replaced the control box , I keep a spare control box on hand, so I can replace quickly if necessary.I am not familiar with the 2 wire pump. I had cattle so it pumped a pile of water.old243

bldginsp
Member
# Posted: 30 Sep 2015 11:25
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One argument I've heard is that 3 wire pumps are better if hit by lightning because if the control box is damaged it is easily replaced. But others say that lightning is an equal threat to both 2 wire and 3 wire pumps. Your expensive experience seems to bear that out. Lot of money to shell out because of a random accident of nature.

old243
Member
# Posted: 30 Sep 2015 21:57
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If your area is prone to lightning, you can install a lightning arrestor in the circuit. Probably at the distribution panel or at least ahead of the control box. Might help to protect the pump. old243

Malamute
Member
# Posted: 2 Oct 2015 01:13 - Edited by: Malamute
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I recently had the capacitor die in my 3 wire. I didnt know yet what it was, but took the control box* to an electrician and he tested it. It was bad. $13 part. I gave him more just for testing it for me and saving a lot of extra work and grief.

*Actually just pop the cover off, it has all the serviceable parts.

bldginsp
Member
# Posted: 2 Oct 2015 08:13
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Malamute- that was a quick and easy fix. 2 wire motors don't have any capacitors, they start with an extra winding instead, so the problem you had, easy as it was to fix, doesn't happen with the 2 wires. OSTTM- or so they tell me.

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