I read a bunch of threads here but didn’t see anything specific to my questions so thought I would ask...
As many others may have found, the 240 v well pump is our largest draw. With the old set of batteries I just set the delay on the Magnum remote / inverter for 9 minutes and the generator never came on. However, with new batteries, Steve at Rolls didn’t think it would be the best thing to let the pump pull that long on the batteries, so I have the generator starting up now when the pump comes on.
Question(s): Is there a timer or something that a person could install to maybe trigger the pump to come on for just two minutes at a time (with maybe an hour or so in between the two minute runs) and then not come on once it senses that our three pressure tanks are full?
Just thinking of a way to make this whole well pump draw a little less severe.
And... are the 120 v Grundfos SQ pumps really that much better? Any experiences switching from a 240 v pump to the Grundfos SQ?
Thanks...
Describe the water system a little better. What horsepower is the pump and why? Why is it 240 now? Do you have 240 inverters or a transformer off 120?
The best system is one where you can install 1000+ gallons of storage on a hill with enough gravity to run your faucets and pump only when the sun shines, provided the inverter is up to the task.
For just changing pumps you have a few options:
1. Regular old 1/2 horse pumps, 120 or 240 to match your existing system voltage. They are cheap and common. This is my favorite option for those who can support it. Might even add a soft starter control if possible.
2. SQ AC pumps have a nice soft start. But the price is higher than above and I always want to avoid fancy electronics where possible.
3. SQ flex which is the AC/DC pump, very expensive and seem to fail sooner than they should. Not a fan of these where they are not needed.
Thanks Ron.
When we purchased the home it already had the 240 v well pump, 3/4 hp. One well driller on Island and that’s all he ever installed. Probably for no real good reason.
We now have a Magnum MS4024PAE inverter 120/240v.
Well head is about 150 feet away from our gen shed, where there is the pump control and three pressure tanks. Then the house is about another 75 feet further away from the shed. House is about 15’ higher in elevation than the gen shed, and the gen shed sits about 10’ higher in elevation than the well head.
The well head is located in an area that is fully forested and solar would be a huge challenge. For various reasons we would not do a water storage tank, although we get why that is an efficient option.
Will your pressure tanks last you from LOS (Loss Of Sun) till your panels reacquire the Sun ? If so, I just use a timer along with the float switch on my elevated tanks, and only allow the pump to run 11am - 4pm
But if you have a house of kids, and do laundry, showers and dishes at night, I guess not.
We do fine when we have sun and yes we can make it through the evening and night without having to refill the pressure tanks.
What is aggravating is that we could run the generator and after turning it off, the next time we turn the tap on, the pressure switch could refill the pressure tanks. Hope that makes sense. We do not have a way to know how much water is in the tanks nor do we have a way to refill the tanks (not sure you could anyway) even if we did know they were almost empty.
Up here in the Pacific Northwest, now thru winter, we don’t have much sun if any for many days. We end up running our gen once a day and it would be nice if we could at least ensure the pressure tanks are filled when the gen runs...
Here are some things you could do in no particular arrangement
1. Replace pump with 1/2 HP. Stick with conventional 240V pump, no reason to go all fancy.
2. Install more pressure storage tanks
3. Install additional pressure switch at lower set point and run off this during night time, (to prevent total loss of water pressure), use higher set point switch to pump tanks to higher pressure when solar or generator is available
4. Lower air pressure in tank bladders so you have a longer cushion before running out of water completely (this is contrary to typical bladder tank advice)
Quote from: Ron Swanson on November 01, 2018, 09:02:18 PM
3. Install additional pressure switch at lower set point and run off this during night time, (to prevent total loss of water pressure), use higher set point switch to pump tanks to higher pressure when solar or generator is available
This, I think can be a good idea. We had a similar-ish problem with an effluent treatment tank. It had a 2HP submersible pump that would run when the final tank level got high. The tank would easily handle typical overnight use, but we had no idea and no way to know where it was, so it could be that one toilet flush would push it over the threshold and it would then have to run for 15 minutes to empty.
Simple fix was a second, lower-level float switch that was powered when we had surplus power (daytime, or generator already running). It isn't perfect, because it means the pump cycle is shorter, but it works.
One question is how deep is your well? Or at least the water level in the well case. If not to deep, a dc piston pump can be very efficient. Pump into a storage tank and use a booster pump to draw from your storage tank into your pressurized house system. My experience with a older piston pump is that they can draw 20 feet and push for miles! Just a thought.
The wife has a thing about ‘holding tanks’ ... so ain’t going to happen. I know that is the most efficient way to pump water in this situation but need to find the next best solution.
We received nuttin about our well info when moving here. It is apparently 100 feet deep but I have no idea where the water level sits. We have never had an issue with having enough water even if we are watering the gardens etc...
Are there any pumps similar to the Grundfos SQ ones that people have had better luck with, or is Grundfos one of the ‘biggest’ players in well pumps?
If it comes down to installing a second - lower pressure, pressure switch I will have more questions...
If you can't add any water storage then your storage needs to be in your batteries (i.e. bigger batteries)
Anything else will be extremely small potatoes.
Copy Ron.
Is it that the pump draws the voltage way to low or is Steve worried about the instantaneous current draw? With 1100 AH you should be able to draw around 160 amps continuous so that is about 4000 watts, I doubt the pump draws that much. I wouldn't think it would be that big a deal to let the pump run on that size of a battery?
Thanks FNG...
Today I made a few calls and learned that the pump is actually a 3/4 hp pump that draws about 7 amps.
I think Steve was just concerned that if the battery bank was, say at 24.4 v or 24.2 v (worst case scenario) and the pump came on, it would pull the batteries down to 23.4 v or 23.2 v (there abouts) and if I had the delay set for 9 minutes to circumvent the auto gen start, that the battery voltage could draw down even further until the pump finishes. He did say once in a while it should be okay but not to make it a habit. He’s probably talking best practice, and after spending 7K+ on the new batteries, I would prefer to not push it :) or go against what Steve suggests.
I know lots of people running pumps way harder than that little 3/4 off batteries.
I don't understand what Steve is concerned about, it may pull the voltage down when running only but it is the state of charge we really care about and that is not going to change fast one way or the other.
I would just run it as-is, nothing to be gained here.
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.
Scale it up to your 9 minutes, and you can see how bad it is. If the inverter is able to reliably start the pump motor in the early morning, your batteries are "ok for now" but some morning is going to come, and the batteries are going to be low & tired and won't be able to supply the surge amps to the inverter.
Then you have to decide to scale up the bank ah or step up to 48V, new inverter and only a 30A draw for the pump
(disclaimer - it's late and I may have mucked up the math - forgive me if I did )
Quote from: mike90045 on November 03, 2018, 02:33:26 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 )
;)
Quote from: RossW on November 03, 2018, 03:31:01 AMSomething 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.
Quote from: mike90045 on November 03, 2018, 02:33:26 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.
Quote from: mike90045 on November 03, 2018, 11:01:33 AM
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.
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.
So to confirm, generally there is no advantage switching a 230v pump out for something like a grundfos 120v pump, correct?
Quote from: alyaz 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?
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).
Copy thanks.
Quote from: alyaz 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?
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.
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?)...
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. :-)