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Thread: Generators and well pumps

  1. #31
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by Texas Wellman View Post
    Yes, the Grundfos SQ have a soft-start.

    I'm guessing that PWM = pulse width modulation? I have no idea if they are PWM. You plug them in, they work LOL.

    Yes that is what I was meaning, pulse width modulation.

    Inverters use the same technology.

    Sometimes they do not play well together, It depends on their switching Frequency.
    Theory only works perfect in a vacuum.

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  2. #32
    DIY Senior Member Reach4's Avatar
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    Quote Originally Posted by Texas Wellman View Post
    Yes, the Grundfos SQ have a soft-start.

    I'm guessing that PWM = pulse width modulation? I have no idea if they are PWM. You plug them in, they work LOL.
    I expect they are the same technology used in the brushless DC motors, except the power comes in as AC, and is probably converted to DC on a capacitor. An inverter produces 2 or (more likely) 3-phase AC power to drive the synchronous motor. The aspects of the AC produced control the motor speed and torque. http://en.wikipedia.org/wiki/Brushle...electric_motor

    Grundfos has similar pumps (SQFlex) that can run on 30-300 VDC and 90-240 VAC I don't know much about them, but the off-grid people like them. They can hook solar cell banks to these pumps without having a regulator or battery.

    Those high RPMs seem scary.

  3. #33
    DIY Member Arky217's Avatar
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    Thanks again for all the replies.

    I've narrowed my choice of pumps down to 2 choices.

    Sorry for the long post, but I thought if I give all of my well specs., that someone might point me to the right choice.

    My well is 6 diameter and 115' deep; it's rated output is 5gpm.
    It was drilled on 4/30/13 and at that time the static water level was 50'.
    As of Jan 4 this year, the static water level was 57'.

    With the pump at 100' deep, the amount of water available from the static level to the pump (43')
    is approx. 60 gal. (1.4gal/ft).

    If I set the pump on/off at 30-50psi, the total head at the 30psi start is:
    57' (ground to static level) + 4' (house sets 4' off ground) + 69' (30psi) + 8' (approx. friction loss, 100' of 1 pipe + 62' of 3/4 pipe @ approx. 5gpm) + 10' (approx. loss for (2) 90 deg. Elbows @ 5gpm) for a total head of 148'.

    And the total head at the 50psi cutoff (after pumping 15 gals to fill the pressure tank) is:
    68' (ground to static level after pumping down 11') + 4' (ground to house) +115' (50psi) + 3 (approx. friction loss, 100' of 1 pipe + 62' of 3/4 pipe @ approx. 2gpm) + 3' (approx. loss for (2) 90 deg. Elbows @ 2gpm) for a total head of 193'.

    A total head worst case scenario would be if I were to pump down to the 100' level, at which point the total head at cutoff would be 193' + another 32' for a total of 225'.

    My pressure tank will be a 44 gal. Model with a fill capacity of approx. 15 gals.
    My water usage will be such that when the pump comes on, it will only pump the 15 gals to fill the tank. (Unless some flushes the toilet while the pump is running, then the pump would probably pump another 3 to 5 gals.)

    Now, for the 2 pumps that I'm considering.

    (Pump #1 will be marginal, and may not work on the worst total head scenario.)
    It is a Grundfos Model 10SQ05-160-115v, a 10gpm rated pump, 2 wire, 1/2hp, 115v.
    It's pump curve goes from 14gpm @ 80' total head to 1gpm @ 220' total head.
    (The 5 & 7 gpm Grundfos pumps in 1/2hp, 115v seem to be special order items at a significantly higher price and 1 or more month lead time.)

    Pump #2 is a Goulds Model 7GS05411C, a 7gpm rated pump, 3 wire, 1/2hp, 115v.
    It's pump curve goes from 10gpm @ 120' total head to 1.5gpm @ 290' total head.

    On pricing, the Goulds pump with control box is $28 more than the Grundfos pump.

    One advantage of the Goulds model is that I could increase the pressure from 30-50 to 40-60.

    Base on the test that VAWellDriller did with the 2 wire pump, from what I have been able to learn, the
    3 wire pump should require even less start current from the Honda generator.

    So, which pump of these two would you choose and why ?

    Again, thank you so much for your replies,

    Arky

  4. #34
    DIY Senior Member VAWellDriller's Avatar
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    For those watching and waiting, I don't have a Franklin 1/2 hp 115 to try out....sorry. I don't do much that small and even less that's 115, so I doubt I'll come across one to try any time soon.

    Arky, given the 2 choices you gave, I'd get the Goulds.... why? The Grundfos 1/2 10 isn't quite enough pump for your conditions. Not sure why the 1/2 5 or 7 Grundfos is that hard to find, but it may be a regional thing. As to the Goulds, I prefer 2 wire pumps, but that's another debate for everyone. The 3 wire should be easier to start, so go for it.

  5. #35
    DIY Member Arky217's Avatar
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    Quote Originally Posted by VAWellDriller View Post
    Really bored today and I guess you sparked my interest; so I re-tested with pressure gauge and 1" water meter.
    I'm not at all following you with the statement about 50% power loss or more??? And also not at all following you on the inverter throwing off the amp readings.

    Here's what I got:

    9.8 amp, wide open, 16 gpm
    9.2 amp, 60 psi on pump, 10 gpm
    6.6 amp, 103 psi deadhead pressure.

    Repeated this test with shop power and got results within +/- 0.1 amps.

    As I see it, the motor was right on for the manufacturers nameplate amp draw, and the wet end was pretty close on the pump curve (actually high on the deadhead) and a little low on flow at 60 psi. This pump is about 5 years old and was pulled out to install higher flow pump for the customer.
    One last question:

    If the flow of the pump that you tested was limited to 5 gpm with a Dole flow control valve, what is your guess as to what the amp draw would be ?

    Sorry, one more question.

    The Goulds 2 wire Centripro motor (unlike the Franklin motor) has a combination start/run capacitor in the motor, whereas the 3 wire Centripro motor has no capacitors in the motor; it instead has a start capacitor in the control box.

    If the increased cost of the wire and the control box were not factors in the 3 wire pump, what then would be the pros/cons of the 2 wire vs 3 wire on a Goulds pump ?

    Thanks,
    Arky
    Last edited by Arky217; 02-04-2014 at 11:27 AM. Reason: Another question

  6. #36
    Jack of all trades DonL's Avatar
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    I am good at guessing.

    8.6 amps ? Calculated using the numbers given above. Just a best guess.

    You should look at the power curve for the pump.

    Or maybe VAWellDriller could measure it. He be the Man.


    Good Luck.
    Last edited by DonL; 02-04-2014 at 11:40 AM.
    Theory only works perfect in a vacuum.

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  7. #37
    Moderator valveman's Avatar
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    I would think the amperage at 5 GPM would be half way between 6.6 and 9.2, which would be 7.9 amps.

    Capacitor start should be capacitor start, no matter if the capacitor is in the motor or the control box. And capacitor start requires less inrush current on startup than a 2 wire without a capacitor. However, I thought they made them quit putting capacitors in submersibles because of the possibility of a bad capacitor contaminating the water as oil leaked out? Maybe it was just capacitors with PCB’s?

  8. #38
    DIY Senior Member VAWellDriller's Avatar
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    Quote Originally Posted by DonL View Post
    I am good at guessing.

    8.6 amps ? Calculated using the numbers given above. Just a best guess.

    You should look at the power curve for the pump.

    Or maybe VAWellDriller could measure it. He be the Man.


    Good Luck.
    The wet end design is what will dictate how the amp draw and flow curve relate....I don't have the model laying around to test.

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