motor swap on jet pump

Discussion in 'Pumps and Tanks Well Forum & Blog. Water is life.' started by Wet_Boots, Nov 19, 2007.

  1. Wet_Boots

    Wet_Boots Sprinkler Guy

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    Location:
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    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. Rancher

    Rancher Guest

    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
     
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  4. Wet_Boots

    Wet_Boots Sprinkler Guy

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    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.
     
  5. Rancher

    Rancher Guest

    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
     
  6. Bob NH

    Bob NH In the Trades

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    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.
     
  7. Raucina

    Raucina New Member

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    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.
     
  8. Wet_Boots

    Wet_Boots Sprinkler Guy

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    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.
     
  9. speedbump

    speedbump Active Member

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    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...
     
  10. Wet_Boots

    Wet_Boots Sprinkler Guy

    Joined:
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    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.
     
  11. speedbump

    speedbump Active Member

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    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...
     
  12. Raucina

    Raucina New Member

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    Put in a 17.5 amp breaker and split the difference!
     
  13. Wet_Boots

    Wet_Boots Sprinkler Guy

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    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)
     
  14. speedbump

    speedbump Active Member

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    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...
     
  15. Wet_Boots

    Wet_Boots Sprinkler Guy

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    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.
     
  16. speedbump

    speedbump Active Member

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    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...
     
  17. Wet_Boots

    Wet_Boots Sprinkler Guy

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    I would think different about the service factor on the pump motors, since the jet pumps I've used all were labeled higher than 1.0 ~ 1.6 SF for the half-horse, and sliding down one tenth for each step up in horsepower Now, some customer's Flo-Tec pump on a sprinkler system I was looking at for bidding on an addition to, was probably using a 1.0 SF motor.

    Curiously enough, the 'high-efficiency' GE 1437 has a 1.65 SF, as opposed to the 1.5 SF of the other two I listed, which would suggest it has a bit more oomph, even though it draws less current (and Grainger has discontinued it, so I don't have to worry about trying the swap anytime soon)
     
  18. speedbump

    speedbump Active Member

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    I would stay far away from Flotec. Your right about the SF on them. These things are all over rated and have a life expectancy of about 1.5 years in my experience. I think you will find the one's on **** and other places are basically pumps that consumers brought back for what ever reason. They are then bought up by someone, refurbished and sold as new. You never know what that homeowner did to that pump while he had it in his possession.

    bob...
     
  19. Wet_Boots

    Wet_Boots Sprinkler Guy

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    Someone was listing a bunch of Flint & Walling 1/3 HP jet pumps, so many of them, that I thought he must have bought out F&W's inventory, since I didn't see any 1/3 HP jets on their site. (that's a pump I consider well suited for boosting low city-water pressure, without as much possibility, compared to more powerful pumps connected to a 3/4 inch home supply line, of creating negative pressures in the suction side)
     
  20. speedbump

    speedbump Active Member

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    That little jet should do a great job and not cost much to operate. Although, if it's a quality F&W (They make both) it might have a very high SF.

    It's a good thing Horse's aren't super intelligent. They wouldn't like what we have done to their reputation.

    bob...
     
  21. Wet_Boots

    Wet_Boots Sprinkler Guy

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    I can understand most mfr's dropping the 1/3 HP jet from their catalogs, since they can't cost much/any less to produce than a 1/2 HP. But that suction problem for city-water boosting (I've seen kitchen faucets sucking air when a 1/2 HP boosted sprinkler system was running) has me hoping there will always be someone offering the 1/3 HP jet.
     
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