Author Topic: 240 v well pump...  (Read 1412 times)

RossW

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Re: 240 v well pump...
« Reply #15 on: November 03, 2018, 03:31:01 AM »
My 1/2hp 240VAC pump clocks in at roughly 1,000w (counting the lousy PF).

Something isn't right there.
1HP = 746 watts. And watts is watts!
Pumps and motors are typically rated in *INPUT* power, not output.
So your half-horse device should take close to 373 watts.
(Watts don't have a powerfactor. Volt-Amps do, and VA * powerfactor = watts)

(Mind you, if your powerfactor was 0.75, then 1HP would require about 1000 VA - perhaps this is what you meant?)

Quote
(disclaimer - it's late and I may have mucked up the math - forgive me if I did )

;)
« Last Edit: November 03, 2018, 03:34:04 AM by RossW »
3600W on 6 tracking arrays.
7200W on 2 fixed array.
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mike90045

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Re: 240 v well pump...
« Reply #16 on: November 03, 2018, 11:01:33 AM »
Something isn't right there.
1HP = 746 watts. And watts is watts!
Pumps and motors are typically rated in *INPUT* power, not output.
So your half-horse device should take close to 373 watts.

AC is actually VA not watts, and they are different.

That classic formula ignores losses and power factor.  My inverter's meter logs the pump at ~1kw consumed
for the 1/2 hp motor.  (The internal XW metering is quite accurate)
First pic "factory std" specs

Next shows the pump having come on 2x and you can read the amps @ 62V or whatever it was, and come up with the DC watts consumed by inverter & motor (I use a NiFe bank, these are not FLA voltages)

This is where theory departs from reality.   Losses and Power Factor count in the real world.

« Last Edit: November 03, 2018, 11:06:23 AM by mike90045 »
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Ron Swanson

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Re: 240 v well pump...
« Reply #17 on: November 03, 2018, 11:22:32 AM »
My 1/2hp 240VAC pump clocks in at roughly 1,000w (counting the lousy PF).
 Scaling up to 3/4hp, I'd guess at 1400w,

for 6 min (one tenth of an hour) = 140 wh   Total power wise, it's not much, but it happens in a short time, @ 24V it's going to suck about 60A out of the batteries for that 6 minutes.  Not knowing your bank Ah, I can't guess what the effect is going to be, a large 600ah bank is not going to suffer much,  a 300 ah bank, is going to start to hurt.

From his sig, he has 1105 AH @ 24 volts.

Seems like it should be fine to me.

I have seen a lot bigger pump on a lot smaller batteries and not ideal but it worked, as far as I know.

RossW

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Re: 240 v well pump...
« Reply #18 on: November 03, 2018, 06:03:57 PM »
AC is actually VA not watts, and they are different.

AC is frequently measured in VA, because it's easier.
AC, at least here in Australa, is charged in WATTS because that is actual power.
The difference between the two (caused by powerfactor) doesn't actually do any useful work. Sure, it causes additional heating in cables due to current.

Quote
That classic formula ignores losses and power factor.  My inverter's meter logs the pump at ~1kw consumed
for the 1/2 hp motor.  (The internal XW metering is quite accurate)

Now you're moving the goalposts.
Including inverter losses, cable losses etc while not incorrect for the purposes of working out actual current from the batteries, is quite different from the original assertion that the pump was 1/2 HP and therefore takes a kilowatt.

Quote
This is where theory departs from reality.   Losses and Power Factor count in the real world.

I too, live entirely off-grid.
I have a 1HP pressure pump for the house.
When the pump runs, I see the inverter load increase by about 750-760 watts, and the DC input current increase by just under 15A.
OK, my pump has an inverter drive, so powerfactor will be close to unity.
My pump is also only 20' or so from the inverter, so minimal cable losses.
Watts are still watts regardless if it's DC, AC or mechanical.
3600W on 6 tracking arrays.
7200W on 2 fixed array.
Midnite Classic 150
Outback Flexmax FM80
16 x LiFePO4 600AH cells
16 x LiFePO4 300AH cells
Selectronics SP-PRO 481 5kW inverter
Fronius 6kW AC coupled inverter
Home-brew 4-cyl propane powered 14kVa genset
2kW wind turbine

Ron Swanson

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Re: 240 v well pump...
« Reply #19 on: November 03, 2018, 06:19:36 PM »
From my measurements in the field off grid standard well pumps at 240V

1/2 HP = 5.5 A
3/4 = 9 A
1.5 HP = 12A (just from memory there)

Depends on how much head (restriction) on the pump output also.  The more head/restriction the LOWER the current/power will be.

If you read the S.F. max amps off the pump controller it will usually get you pretty close.

alyaz

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Re: 240 v well pump...
« Reply #20 on: November 05, 2018, 07:47:38 PM »
So to confirm, generally there is no advantage switching a 230v pump out for something like a grundfos 120v pump, correct?
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RossW

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Re: 240 v well pump...
« Reply #21 on: November 05, 2018, 09:52:29 PM »
So to confirm, generally there is no advantage switching a 230v pump out for something like a grundfos 120v pump, correct?

Electrically, I can't see any benefits.
A 1HP pump running on 120V will take twice the current of a 1HP pump running on 240V.
Twice the current means significantly more I^2R drop in your wires. The longer and/or the thinner the wires, the greater the losses.
As you lose more voltage in the cables on the way to the pump, the voltage for the pump to run will be less, so it'll draw even more current, compounding the situation.

On the other hand, it may be that 120V pumps are more readily available where you are, in which case there may be a benefit to that.

All other things being equal, the voltage of operation of a small pump isn't going to make much difference, certainly less difference than the power of the pump (1/2HP, 3/4HP, 1HP, etc).
3600W on 6 tracking arrays.
7200W on 2 fixed array.
Midnite Classic 150
Outback Flexmax FM80
16 x LiFePO4 600AH cells
16 x LiFePO4 300AH cells
Selectronics SP-PRO 481 5kW inverter
Fronius 6kW AC coupled inverter
Home-brew 4-cyl propane powered 14kVa genset
2kW wind turbine

alyaz

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Re: 240 v well pump...
« Reply #22 on: November 05, 2018, 10:02:32 PM »
Copy thanks.
3.3 kW solar. (1.5 kW Helios - MN Classic 150 CC; .8 kW CSun - MN Classic 150 CC; 1 kW Sharp - MN  Classic 250 CC); Magnum PAE-4024 Inverter, AGS, ARC, BMK. Whizbang Jr., Midnite Solar battery monitor, 5 Midnite SPD’s. 24V Rolls 4KS21P - 1105 a/hr FLA.  10 kW Perkins Diesel.

FNG

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Re: 240 v well pump...
« Reply #23 on: November 06, 2018, 09:11:40 AM »
So to confirm, generally there is no advantage switching a 230v pump out for something like a grundfos 120v pump, correct?

Soft start has no benefit on a system like yours in my opinion, Soft start is good for systems that have to small a generator or inverter and the surge watts get you in trouble. At the end of the day running watts will be basically the same and the same amount of energy will be removed from the battery to do the same amount of work.

Westbranch

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Re: 240 v well pump...
« Reply #24 on: November 07, 2018, 12:23:42 AM »
Al, you should get hold of the well driller and ask for a log of your well... it will tell you total depth, refresh rate in (US) gallons per minute and at least the static height of the water when the well was drilled/pounded in.
If he isn't around any more, you can try and  go to the Provincial Gov. Water management and they may have a copy of the original information.https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwjn-tmJoMHeAhXYHTQIHUE5BGQQFjAAegQIAhAB&url=https%3A%2F%2Fapps.nrs.gov.bc.ca%2Fgwells%2F&usg=AOvVaw0OZgWlYIgWLSyTgqJGovLi
good luck, I tried to locate my data and not mapped (YET?)...
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alyaz

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Re: 240 v well pump...
« Reply #25 on: November 07, 2018, 10:19:09 AM »
Thanks guys.

Westbranch, I will see what I can find, but my initial queries when I first moved here didn’t come up with anything.  I did register the well and provided as much information and mapped the location etc.  They sent me a provincial registration number that I tagged the head with and kept in my records.  :-)
3.3 kW solar. (1.5 kW Helios - MN Classic 150 CC; .8 kW CSun - MN Classic 150 CC; 1 kW Sharp - MN  Classic 250 CC); Magnum PAE-4024 Inverter, AGS, ARC, BMK. Whizbang Jr., Midnite Solar battery monitor, 5 Midnite SPD’s. 24V Rolls 4KS21P - 1105 a/hr FLA.  10 kW Perkins Diesel.