(206) 949-5683, Top Rated Plumber, Seattle
Page 1 of 2 12 LastLast
Results 1 to 15 of 24

Thread: motor swap on jet pump

  1. #1
    Sprinkler Guy Wet_Boots's Avatar
    Join Date
    Mar 2007
    Location
    Metro NYC
    Posts
    798

    Default motor swap on jet pump

    I was wondering about the feasibility of something I once considered, as a workaround for lack of sufficient amperage for a 3/4 HP Goulds jet pump. What I noticed in a Grainger catalog was a high-efficiency 3/4 HP motor with the same current draw as a standard 1/2 HP, so it looked liked it would work on a 15 amp branch circuit without much risk of popping a breaker. I think it was a GE motor, and had the same service factor as a standard 3/4. Little possibility of upgrading the power to 20 or 30 amps.

    The idea was to make a jet pump supply the same amount of water as the city-water supply did, which pointed to a 3/4 pump. I never did try the motor swap, since it turned out the city-water supply line was galvanized steel, which loses so much pressure at higher flows, that a 1/2 HP pump was the better match.

    So I wonder, would the swap have worked, one 3/4 HP 56J 1.5 SF motor for another, even with the new one drawing current more in line with a standard 1/2 HP jet pump motor?

  2. #2
    Rancher
    Guest

    Default

    Motors are matched to the pump head they are supposed to work with. A 1/2 hp motor spins at the same RPM as the 3/4 hp motor, so I don't see an advantage to doing this.

    If you want more water (higher pressure) use a "booster pump" which is really a multistage centrifugal pump layed on it's side.

    Check the pump performance curves in that high priced Grainger catalog.

    Rancher

  3. #3
    Sprinkler Guy Wet_Boots's Avatar
    Join Date
    Mar 2007
    Location
    Metro NYC
    Posts
    798

    Default

    The initial idea was to get a water supply pumped from a pond that could match the home supply, which was a 3/4 inch supply line with over 100 psi street pressure, so it looked like it would take a 3/4 HP jet pump to match. The power was a problem, and the customers were looking for 'one-stop-shopping' on this project. Since I've seen 3/4 HP motors trip 15 amp breakers, I wasn't wanting to take chances on installing the Goulds J7S pump. I noticed this 'special' motor in a Grainger catalog, and toyed with the idea of using it to reduce the current draw on the J7S, if it would otherwise be identical. The 3/4 HP high-efficiency model had a current draw that was actually a wee bit less than a standard 1/2 HP motor, which made me think the swap might work (all this swapping being done on a J7S pump)

    The actual (reduced) city-water supply flow making this whole line of inquiry unnecessary, I shelved the swap idea. The thread that touched upon Grainger and motors made me think of it again.

  4. #4
    Rancher
    Guest

    Default

    OK, understand now the swap of the motors idea.

    The 3/4 hp motor tripping the 15 amp breaker is dependent on the length of the 14 AWG wire to the motor, the shorter the better, I've never actually tried a 3/4 hp on a 15 amp circuit so I can't say it would or wouldn't work.

    Really depends on the start-up current.

    Again a jet pump is very inefficient, a centrifugal with multi stages is the way to go.

    Rancher

  5. #5
    In the Trades Bob NH's Avatar
    Join Date
    Oct 2005
    Location
    New Hampshire
    Posts
    3,307

    Default

    A 3/4 HP motor with 1.5 Service Factor is capable of delivering 1.375 HP. The smaller motor probably would not have operated the pump and it probably would have overloaded the motor.

    You could have gotten the pressure you needed wih a submersible, or a multi-stage centrifugal if you don't need the lift.

  6. #6

    Default

    I don't get the amperage problem. The 3/4 hp 56c motors I have draw about 10/5 amps, 120/240 V

    If the feed is 14-2 Romex with ground, use 240V with the bare as the ground, dont need a neutral anyway. Or run it on 120 volts if you insist, as long as its a cap start. I have a few 1 hp motors running on 120 volts, 20 amp breakers and 14 gauge wire. no issue with overheating of motor or wire. Not a very good idea, but possible.

  7. #7
    Sprinkler Guy Wet_Boots's Avatar
    Join Date
    Mar 2007
    Location
    Metro NYC
    Posts
    798

    Default

    Quote Originally Posted by Rancher View Post
    Again a jet pump is very inefficient, a centrifugal with multi stages is the way to go.

    Rancher
    Perhaps I should have also stated that this work was to supply a lawn sprinkler system with polyethylene tubing. Jet pumps are perfect for this, because they don't develop pressures high enough to cause any damage in the event of any stuck control valves. Goulds jet pumps are especially good at holding prime, as well, due to their construction with the inner diaphragm. As for any thoughts of sticking a deep-well submersible in the pond, not an option in a number of states, as it is forbidden by codes and/or law.

    As for running the standard 3/4 pump on the 15 amp branch circuit, it might have been okay, but once I witness a breaker trip on a 3/4 HP motor, I figure it can happen again, and this was a circuit that also powered some outlets and lights around a pond-side deck (so no 240 available)

    The Grainger catalog pages point out the necessity of matching horsepower as well as service factor, which this swap would have done. A lot of work to save a few amps, and I was happy not to have needed to try it. But I still wonder.

  8. #8
    Previous member
    Join Date
    Jul 2005
    Location
    Riverview, Fl.
    Posts
    4,540

    Default

    I'm still not sure what you were trying to accomplish.

    BobNH, how did you come up with the actual horsepower on that .75 hp motor with a 1.5 SF?

    bob...

  9. #9
    Sprinkler Guy Wet_Boots's Avatar
    Join Date
    Mar 2007
    Location
    Metro NYC
    Posts
    798

    Default

    Quote Originally Posted by speedbump View Post
    I'm still not sure what you were trying to accomplish.

    BobNH, how did you come up with the actual horsepower on that .75 hp motor with a 1.5 SF?

    bob...
    Just trying to reduce the current draw of the J7S pump, that's all. Insurance against tripping a 15 amp breaker. The new motor would have given a current that's less than their J5S pump. No real energy savings, per se, since I figure that only the phase angle of the current is really changing, when you have a 'high-efficiency' motor.

  10. #10
    Previous member
    Join Date
    Jul 2005
    Location
    Riverview, Fl.
    Posts
    4,540

    Default

    I'm not sure what you mean about a high efficiency motor Boots. Sta-Rite started this Service Factor thing way back when. You could buy a 1hp pump with a 1.65 SF motor and you really had a 1.5hp pump. They actually put the 1.5hp impeller in the pump. I never could understand why they did this, as most people false advertise in the reverse. Their 1hp submersible blew everyone else's away because it really was a 1.5hp. This was true of their sub's and their jets. Since then, everybody seems to be doing it.

    The pool pump motors are termed Uprated or Max Rated and Full Rated. The Max rated on a 1hp for instance would have the 1.65 service factor making it a 1.5 horse motor with a small service factor. The 1hp with the 1.24 SF would be the standard 1hp motor. Actual horse power is obtained by multiplying the name plate horse power by it's service factor.

    The big thing to keep in mind it that any given impeller will require a given horse power motor turning the usual 3450 rpm's. Anything smaller will simply pull higher amps than rated and nuisance trip.

    bob...

  11. #11

    Default

    Put in a 17.5 amp breaker and split the difference!

  12. #12
    Sprinkler Guy Wet_Boots's Avatar
    Join Date
    Mar 2007
    Location
    Metro NYC
    Posts
    798

    Default

    Quote Originally Posted by speedbump View Post
    I'm not sure what you mean about a high efficiency motor Boots. Sta-Rite started this Service Factor thing way back when. You could buy a 1hp pump with a 1.65 SF motor and you really had a 1.5hp pump. They actually put the 1.5hp impeller in the pump. I never could understand why they did this, as most people false advertise in the reverse. Their 1hp submersible blew everyone else's away because it really was a 1.5hp. This was true of their sub's and their jets. Since then, everybody seems to be doing it.

    The pool pump motors are termed Uprated or Max Rated and Full Rated. The Max rated on a 1hp for instance would have the 1.65 service factor making it a 1.5 horse motor with a small service factor. The 1hp with the 1.24 SF would be the standard 1hp motor. Actual horse power is obtained by multiplying the name plate horse power by it's service factor.

    The big thing to keep in mind it that any given impeller will require a given horse power motor turning the usual 3450 rpm's. Anything smaller will simply pull higher amps than rated and nuisance trip.

    bob...
    This is an example of what you miss by not having a Grainger catalog ~ a GE C1437 motor is 3/4 HP, and draws 7.5 amps on 115. a GE C1089 is 3/4 HP and draws 12.2 amps on 115. a Dayton (6K706) 3/4 HP HP motor draws 10.5 amps. And so on, and so on.

    All of them are 3/4 HP 56J motors, but the first one is marked as a 'capacitor-start capacitor run' model, which is what probably makes it draw less current (the run capacitor alters the usual phase angle between voltage and current)

  13. #13
    Previous member
    Join Date
    Jul 2005
    Location
    Riverview, Fl.
    Posts
    4,540

    Default

    Your right about the Run Capacitor making the motor pull less amps, but not that many. I think you will find that either these motors have far ranging Service Factors or the horse power ratings are as bogus as they are on Above Ground Pool Pump Motors.

    I don't know what Government Agency is in charge of false advertising, but the Motor Companies have been pushing the envelope pretty hard lately.

    bob...

  14. #14
    Sprinkler Guy Wet_Boots's Avatar
    Join Date
    Mar 2007
    Location
    Metro NYC
    Posts
    798

    Default

    I remember the numbers 'bloat' back in the day of stereo systems. One company's amplifiers were suddunly 20 percent more powerful. In the fine print was the statement that the numbers were subject to EIA tolerances, which just so happen to be 20 percent. I may still have a Jacuzzi catalog with some 1 HP pumps with a performance curve like a 3/4 HP. Of course the service factor on these new bargain pumps is 1.0 - the thing was essentially just a relabeled 3/4 HP pump.

    I'm still not quite sure why some Home Dungeon air compressor will be labeled as 5 HP, when it doesn't even consume 5 HP of electrical power, let alone deliver 5 HP.

  15. #15
    Previous member
    Join Date
    Jul 2005
    Location
    Riverview, Fl.
    Posts
    4,540

    Default

    I'm with you. The label is certainly not what it seems.

    Above ground pump motors are all 1.0 SF. They make a 5 hp motor that weighs a little more than a 3/4hp motor. Go figure. They even claim to have a 4 hp pump. Never heard of 4 hp until this came out.

    As for generators, people ask me how big a generator they need to run a certain hp sub or jet motor and my first question is: "Where are you going to buy the Generator?"

    bob...

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •