Generators and well pumps

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VAWellDriller

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Still bored, going home after this....looked at Centri-pro book harder....This motor is listed as having full load amps of 7.9 and efficiency of 42%, and service factor amps of 9.8 with efficiency of 54%; maybe Don is smart enough to know that a 1/2 hp isn't very efficient if it draws 9.8 amps; I don't know that much about motor efficiency buy apparently he's right that it's losing about 50%; important point here is that it is performing as designed by Centripro, and operating within their ratings.

I think that you have absolutely nothing to worry about running this motor on your Honda....it performed exactly the same for me with mine and on shop power. As far as overloads, the motor has a thermal overload built in, and you have the overload on the generator, so I don't think you need anything else.
 

DonL

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DonL, Are you saying that the motor is not developing the full 1/2 hp at the 9.8 amps ?

From the Goulds Electrical Data, the FLA of that motor is 7.9

Does that mean that running the pump from the generator will be detrimental to the motor ?

Also, about overload protection for the motor on submersible pumps; is it built into the motor somehow, like a thermal switch, or should overload protection be added to the circuit ?

Thanks,
Arky


No, The Motor may even be producing more than 1/2 hp. Best to under rate than over rate.

1/2 HP is equal to about 372 watts, That is at 100 percent efficiency, and could only happen in a vacuum, then maybe not. You will never see 100% efficiency.

9.8 amps at 120V is about 1.5 HP, of power being used to run a 1/2 HP pump. So 1 HP is wasted, or 745 watts. 6.2 amps wasted, making heat. That is why pumps get Hot.

The Generator losses have to be in the equation also. As far as I can tell the motor on your generator is a about 4 HP, running on good fuel.

Most inverters generators operate at around 80% efficiency, or less. That is why a 4HP motor can only make 2000 Watts of Output power, If even that much in the real world. That is why you use more than 2980 watts of power to make 2000.

Are you confused yet ?. I hope I got my math correct, in all of that mess.

I am not a very good explainer,(Yes New word that I invented) But I hope you understand.

Sounds like VAWellDriller made some nice test today. Big thanks to him.

A good Extra protection for your pump, would be a 10 amp breaker, or a 10 amp Ceramic fuse, like used in Microwave Ovens.


VAWellDriller has been Playing and proving data for real world test, And I hope getting paid for it. Very nice work.


Have Fun.
 
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Texas Wellman

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What Don is saying I think is that the 1/2 HP refers to the output power of the shaft, not the input power to the motor in the form of electricity.

Another reason I like the Grundfos SQ is because it uses permanent magnets in the motor. A regular induction run motor uses some of the electricity to generate it's magnetic field, causing the efficiency that Don is talking about to be lower. The grundfos may be 1/2 HP but it will use less electricity to generate 1/2 HP at the shaft.
 

VAWellDriller

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This thread has been very informative. I always wanted to know if the EU2000i would run the 1/2 HP 115V motors.

FWIW I am told that the Franklin 2-wire and the Centri-pro 2-wire are not similar. Supposedly the Centi-pro has a start-cap built into the motor whereas the Franklin has the biac-switch. The franklin manual clearly states that the 2-wire uses 2x the power to start via a generator.

PM sent on where to get a grundfos for a great price.

HA -- I guess now you'll want me to try it with a Franklin?
 

DonL

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What Don is saying I think is that the 1/2 HP refers to the output power of the shaft, not the input power to the motor in the form of electricity.

Another reason I like the Grundfos SQ is because it uses permanent magnets in the motor. A regular induction run motor uses some of the electricity to generate it's magnetic field, causing the efficiency that Don is talking about to be lower. The grundfos may be 1/2 HP but it will use less electricity to generate 1/2 HP at the shaft.


The only problem with permanent magnet motors is that they will normally have Brushes, and run on DC. More parts to go bad.

AC is converted to dc in the pump , But they can run at higher, and variable RPM.
 

Valveman

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The franklin manual clearly states that the 2-wire uses 2x the power to start via a generator.

Yeah I don’t understand the locked rotor amps being twice as much for a 3 wire with a control box, because I know it takes twice as much to start a 2 wire motor.

Still bored, going home after this....looked at Centri-pro book harder....This motor is listed as having full load amps of 7.9 and efficiency of 42%, and service factor amps of 9.8 with efficiency of 54%; maybe Don is smart enough to know that a 1/2 hp isn't very efficient if it draws 9.8 amps; I don't know that much about motor efficiency buy apparently he's right that it's losing about 50 %.

Don is right, 4” submersibles do good to get up in the high 50% for efficiency. I think that is way they don’t publish efficiency charts for 4” pumps. I believe it is the small diameter of the impellers that lessens the efficiency.

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.

Good to know that the Goulds 10 GPM impeller will reduce the amp draw by 33% when the pump is restricted to low flow. Pentair 10 GPM pumps don’t drop in amps at all, but Grundfos 10 GPM drops almost 50%.

Harmonics off of a inverter, can throw off the reading of a amp meter.

An inverter actually pulses out a 60 hertz radio frequency instead of a smooth sinusoidal wave as from a regular generator. You really need an RMS meter to get an accurate reading from an inverter, but it is probably close enough.

The harmonic content of the power from an inverter actually increases the motor heat as opposed to a sinusoidal wave. The voltage spikes from an inverter can be 4 times the line voltage. But when you start at 115V, the spikes will usually be less than 500 volts, and the motor is probably made to withstand 600 volt spikes. A low voltage motor doesn’t suffer from inverter voltage spikes nearly as bad as a 480 volt system. But inverters do shorten the life of motor windings.

The only problem with permanent magnet motors is that they will normally have Brushes, and run on DC. More parts to go bad.

AC is converted to dc in the pump , But they can run at higher, and variable RPM.

I think most permanent magnet motors now use a Hall sensor instead of brushes. This has been a big advance in motor technology, but there are still problem with permanent magnets. I don’t think the magnetism is really permanent?

This thread has been very informative.

I agree! Thanks to everyone for the info!
 

DonL

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The motors I use do not have brushes, they are brushless.


That is good. I can see where Not having a Field winding could save power.

I would guess them motors would have a Soft Start to bring them up to speed slow.

Less surge current can let you use smaller wire.

Some of the PWM motors can cause RFI, I take it that they use PWM, but not really sure on the models you use.


Are the pumps that you use high RPM models, that use PWM ?
 

Texas Wellman

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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.

That is good. I can see where Not having a Field winding could save power.

I would guess them motors would have a Soft Start to bring them up to speed slow.

Less surge current can let you use smaller wire.

Some of the PWM motors can cause RFI, I take it that they use PWM, but not really sure on the models you use.


Are the pumps that you use high RPM models, that use PWM ?
 

DonL

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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.
 

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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/Brushless_DC_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.
 

Arky217

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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
 

VAWellDriller

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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.
 

Arky217

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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
 
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DonL

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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.
 
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Valveman

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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?
 

VAWellDriller

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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.

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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