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Thread: 2-wire vs 3-wire pumps

  1. #1
    DIY Senior Member abikerboy's Avatar
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    Default 2-wire vs 3-wire pumps

    From an ITT motor manual loaned to me by an educated professional! Im a dummy, so this is all from the manual only!!!

    3-wire prose and cons
    Pro-Capacitor start assures starts under severe circumstances, such as an excessively deep well, or excessice static head. More torque is provided at the motor for hard to start situations
    Capacitor run assures smoother running, lower current and lower running temp
    All starting components are located above ground, and though the potential for failure is greater, the components can be easily and cheaply accessed and repaired or replaced
    General electrical consumption can be lower, or greater, depending on depth of well and distance from pump to controller
    Cable requires an extra supply lead, but the cable can be lighter in guage
    Cons-capacitors can and do fail as time weakens the internal construction of these devices
    Relay is not sealed from atmospheric pressure, hence contacts can oxidize from repeated arcing
    Cable requires an extra supply lead, and though the cable can be lighter in guage, the weight is 1/4 to 1/3 more, and the added expense can be much greater
    Under residential useage and average installations, starting current consumption may actually be higher due to required setbacks and distance of control box from well

    2-wire pros and cons
    pros-Starting components are all located within the hermatically sealed stator housing of the motor
    Installation is much simpler
    No potential start relay to fail or complicate day to day operation
    No capacitors are used except in some limited designs, and where used, sealed components provide extra protection so the potential for failure of these components may be reduced greatly or may not exist alltogether
    Internal starting switch is sealed from any contact with oxygen so arcing from normal use will not cause contacts to oxidize and fail
    Internal starting switch and lack of one way capacitors can provide pulsed starting torque to prevent motor jambing due to sand mud or other restrictions
    Cable is simpler, lighter, and economical to purchase and to instal
    Motor starts softer, decreasing shock loading of pump components
    ConsIf starting components fail (highly unlikely) motor must be pulled and replaced
    Requires a better eye and closer tolerance for resistance measurements
    Lower starting torque under severe static head. this is the reason that higher horsepower pumps are currently 3 wire
    Operating temp of motor is slightly higher but this should not apply except under abusive circumstances

    *The severe conditions as stated above very rarely apply to the normal residential homeowner. The preference of 2 wire or 3 wire motors is usually a matter of taste for aplications below 1.5 hp. and a 2 wire is always recommended for these installations due to simplicity, cost advantages, and obvious maintenance reduction and extended life of starting components. Refer back to the pioneer days of the electronic semiconductor as all major devices were embrasing the new technological advances of the solid state semiconductor. Time only can prove the advantages of the new over the old.
    Last edited by abikerboy; 08-23-2007 at 03:13 PM.

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    Very good explaination! I suppose it's copyrighted or I could use it in my FAQ's.

    bob...

  3. #3
    Rancher
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    Quote Originally Posted by abikerboy
    No potential start relay to fail or complicate day to day operation
    Why would this be a con for a two wire pump?

    Rancher

  4. #4
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    Because potential relays do go bad and when they do that, the start cap is the next thing to go, then the start winding if it persists. With the two wire motor, there is no relay to go bad.

    bob...

  5. #5
    Rancher
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    So on a 2-wire pump, not having a potential start relay is a good thing.

    Why is it listed under the "con" heading.

    Rancher

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    No potential start relay to fail or complicate day to day operation
    This is what I read under the cons and I see what you mean. It should be under pros. The guy needs a proofreader.

  7. #7
    That's all folks! Gary Slusser's Avatar
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    Which proves (to me that my and Speedpump's claim) that for residential applications, 2 wire pump motors are better than 3 wire...
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

  8. #8
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    2 wire pump motors are better than 3 wire...
    Yup, every time. Three wires are just a waste of time and money for residential apps.

  9. #9
    DIY Senior Member abikerboy's Avatar
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    Quote Originally Posted by Rancher
    Why would this be a con for a two wire pump?

    Rancher
    Its there because Im very bad at details like this early in the morning. Lol! My mistake, and I'll fix it...

  10. #10
    DIY Senior Member abikerboy's Avatar
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    Quote Originally Posted by speedbump
    Very good explaination! I suppose it's copyrighted or I could use it in my FAQ's.

    bob...
    Yes, I assume it is copyrighted, but this is not worded exactly as it was in the manual...my attempt at being careful. Not sure how or if copyright would apply now, but if it's safe or legal now that it is in my words, then you're welcome to it!

  11. #11
    Master Plumber Dunbar Plumbing's Avatar
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    Everything I've either worked on or installed in my area has been 3 wire.

    I'd prefer the simpler the better on these systems but I don't exactly afford a great deal of time into the knowledge base of these since they are a dying breed in my community.

    Troubleshooting these with the customer mindset of "I only got X amount of money to get this back up and running" is not my forte of work regimen.


    Here, call this guy....
    Read what the end of this sentence means.

  12. #12

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    Having just pulled a 2 wire 1.5 hp motor from 800 feet, that would not start after having sat for several years, and then getting it to turn on the surface with just a nudge from a pair of pliers makes me a permanent 3 wire pump setter. Just a few more ounces of shock might have made this a NO PULL job.

    Better yet for our wallets and enviroment, we should be wiring with 480 volt 3 phase, then we can run 18 gauge wire down several hundred feet. This country and its 120 volts is a comedy, probably staged by the copper mills.

  13. #13
    DIY Senior Member abikerboy's Avatar
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    Quote Originally Posted by Raucina
    Having just pulled a 2 wire 1.5 hp motor from 800 feet, that would not start after having sat for several years, and then getting it to turn on the surface with just a nudge from a pair of pliers makes me a permanent 3 wire pump setter. Just a few more ounces of shock might have made this a NO PULL job.

    Better yet for our wallets and enviroment, we should be wiring with 480 volt 3 phase, then we can run 18 gauge wire down several hundred feet. This country and its 120 volts is a comedy, probably staged by the copper mills.
    Judging by what Ive seen in the short time that Ive been passing my labor off to a professional friend, if a pump sits idle in a well underwater for several years, doesnt matter if its a 2 wire or 3 wire, its going to turn into a "pull" situation anyway. You might have had more starting torque from a 3 wire, and maybe it wouldve started in the well, but my added mechanical experience of many years tells me that when any type of bearing or bushing siezes from corrosion due to non use, just write it off as a loss anyway! Even if you were able to break it free with a pair of pliers, and maybe with no effort at all, somewhere within the motor, pump, or maybe both, there is a bushing and shaft with a rough surface. Now that you have it broken free, you have a rough pitted and corroded surface crossing another rough surface at 3450rpm....cant imagine that lasting very long! At least with the pump not starting, you knew what to expect from a well that has sit idle for years...depending on your situation, you could consider yourself blessed that the pump didnt start...as if it did, my bet is that something somewhere within will disintegrate within a short time frame, and probably just when you need the water the very most. As for the 3 phase 460v, I can agree to a very short point, however beyond that, Ive seen what the average guy can do with 120v or 240v when he attemps something that he shouldnt...god forbid 460v to a homeowner! We'd have half of the country burned down by now! Plus, it wouldnt be any easier on our wallets either...heavier circuit boxes, and even though the wire guages may be smaller, you'd have more linear feet of wiring, plus the electric would cost us much more due to the extra equipment that the power company would have to install in places where as of now only single phase circuits exist.
    Last edited by abikerboy; 08-24-2007 at 03:04 AM.

  14. #14
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    if a pump sits idle in a well underwater for several years, doesnt matter if its a 2 wire or 3 wire, its going to turn into a "pull" situation anyway
    Amen.

    With the 460 thing, three phase power is not forgiving to motors that try to start on single phase power because of a dropped leg. Without the very best of protection, three phase is inferior to single phase when it comes longevity.

    bob...

  15. #15
    That's all folks! Gary Slusser's Avatar
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    Quote Originally Posted by Raucina
    Better yet for our wallets and enviroment, we should be wiring with 480 volt 3 phase, then we can run 18 gauge wire down several hundred feet. This country and its 120 volts is a comedy, probably staged by the copper mills.
    LOL It takes more wire to run heavier gauge 3 phase and more transformers to each house than single phase DA, so where would the savings be? Or do you think just buildings with wells would get 3 phase? Plus, single phase serves most rural areas where the well pumps are BUT, most electrical distribution and service drop lines are not copper.... and haven't been for like 40-60 years.
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

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