Grundfos 6 SQF-2 capabilities

OffGridiot · August 2014

Hello all,
I have a situation that needs addressing soon. About 5 years ago, I had a well drilled close to my house. Both the quality and the quantity of the water leave something to be desired. Now that we're into the dog days of summer, it's basically gone dry again and I'm in the position of having to haul water up to my property to get by until we start to get some rain. I installed a Grundfos 6 SQF-2 helical rotor pump 260 feet down that disappointing hole and it has done a very nice job getting water to my holding tank, when there was anything to pump.
One of the reasons I chose the pump that I did was the fact that it was, a)positive displacement and, b) very versatile in the spectrum of electricity it will accept...anywhere between 30 and 300 volts....AC or DC.

So, my questions for you have to do with another option that I'm considering, using the same pump but in a different water source that is located around 3000 feet away, and about 100 feet lower in elevation than my holding tank (it's a shallow well with awesome quality and quantity). I know that I need to consider more than the elevation and static psi in this scenario (which I think would be in the neighbourhood of 45 pounds).

Some of the issues I'm having a harder time figuring out are regarding line friction in a 1 inch line of that length with anywhere up to 7 fittings inserted along the way and how that affects the workload of the pump.

And the other consideration is the electrical supply for the pump. I've been pumping out of the deep drilled well (into the aforementioned holding tank, as opposed to into a pressurized system) from as much as 260 feet down but with a much shorter distance (total pipe length of maybe 400 feet) with 110 volts AC, and having checked the wattage with a KillaWatt meter, remember it drawing around 460 watts when the well was about to run dry. I have an extra generator that I could set up by the new well to power the pump, and in one regard, that seems like a good option because it would supply more than enough juice for the pump motor. On the other hand, I could rearrange some of the solar panel situations I have going on here to set up a dedicated array for the pump, at say 48 volts nominal (which hypothetically falls within voltage specs) but might be short on the overall wattage that it's been used to....say 200 watts? If the pump were to move even a tenth of the amount of water, but over a much longer period of time (sunlight provided), it could potentially really work for me, but would this be possible without destroying the pump motor? Would it just be a matter of placing a controller that would shut things down if certain electrical parameters weren't met? Or would having less power available than the pump would like to see be a problem, from a pump-life point of view?

So.....am I crazy to think this might work? It wouldn't be the first time I'd been called that...or worse

Thanks in advance!
Cheers,
Bruce

vtmaps · August 2014

Re: Grundfos 6 SQF-2 capabilities

OffGridiot wrote: »

Some of the issues I'm having a harder time figuring out are regarding line friction in a 1 inch line of that length with anywhere up to 7 fittings inserted along the way and how that affects the workload of the pump.

Welcome to the forum,

I don't know the answers to all your questions about the grundfos power requirements. Whether it will work through 3000 ft of 1" pipe is entirely a matter of how many gallons per minute you will be pumping. What are your needs?

The fact that you are pumping to a holding tank and have all day to do it works in your favor.

--vtMaps

Edit: Here's a fairly simple calculator: http://www.calculatoredge.com/mech/pipe%20friction.htm

example: 2 gpm through 3000 ft of 1" HDPE pipe will result in a loss of 10.6 feet of head. Not a problem... instead of pushing the water 100 ft uphill, the pump will have to push the water 110.6 ft uphill.

If you try to pump 10 gpm through the same pipe, the resistance of the pipe will add 209 ft to the uphill rise.

Aguarancher · August 2014

Re: Grundfos 6 SQF-2 capabilities

If you do plan on having such a long run, it may be to your advantage to install a check valve after the pump and a few more along the run. Cheap insurance and it will help take the load off of your pump.

BB. · August 2014

Re: Grundfos 6 SQF-2 capabilities

The pump should not burn out with lower input voltage--It will just run slower (assuming it has enough power to run). I forgot the exact numbers--But the pump needs something like >60 to 90 volts DC for optimum operation.

Will the pipe be buried below the frost line (guessing it gets cold where you are at)? Otherwise, you may need to have the pipe drain back anyway to prevent freezing/damage.

-Bill

Dave Angelini · August 2014

Re: Grundfos 6 SQF-2 capabilities

Have you considered just removing the well casing and drilling deeper?

Texas Wellman · August 2014

Re: Grundfos 6 SQF-2 capabilities

The grundfos likes voltages above 90VDC. It will run at lower voltages but as has been said it will run lower and give less water. You need to look at the curve to see if it will still meet your demand for water at a lower voltage.

If it were mine I would set up a 3 panel rack (24V panels) that would give the pump a nominal voltage of about 90-110VDC. Panels should be the 200W variety. That gives you ~600 watts and you're above the 90V mark. Since the pump has built-in dry run protection you won't have to worry about that problem. The grundfos has a max input of about 1400 watts IIRC.

How are you going to get the water from the new well to your normal water system? If there is an elevation change (going downhill) you can simply let it gravity flow. If not you can go directly into a pressure tank from the pump and then from there pressurize it to your home. Every 1 ft in elevation takes about .4 psi to overcome. Horizontal distance doesn't really matter as much as elevation. If going 3,000 feet you should look at the friction loss charts to size your pipe according to the flow you expect to get.

OffGridiot · August 2014

Re: Grundfos 6 SQF-2 capabilities

Aguarancher wrote: »

If you do plan on having such a long run, it may be to your advantage to install a check valve after the pump and a few more along the run. Cheap insurance and it will help take the load off of your pump.

I'm pretty sure that there is a check valve down at the pump already. If I do end up moving it to the other well so far away, would another check valve or two (further up the line) help that much? I'm not disagreeing with you. There's plenty of plumbing related issues I don't feel qualified to opine on with much confidence, and this may be one of those many issues that I'm not understanding completely. It seems somewhat redundant but, like you say, cheap. As far as taking a load off my pump, I assume that you're referring to after the power has been shut off, the pressure in the pump chamber will relax. And, of course, the water that's in the pipe won't flow back to the well, necessitating the re-pumping of that (wow. just googled the volume of water in that 3000 feet of pipe and was surprised that it's) 145 gallons.
Wouldn't the extra check valves just hold back some of the pressure on the bottom one?

Actually, as I'm writing this out, I think I'm beginning to see the wisdom of your advice...one check valve at the bottom, taking all the pressure is probably usually going to be fine but ...if a bit of grit were to get in the way of it doing its job, then a few others along the way would at least keep the whole line from draining and at best save even that lower section from draining, due to no air being able to get past the upper check valves into the top of the line.

The down hill neighbour, whose property the awesome spring well is on, actually grew up in Czechoslovakia (true). Maybe I should ask him if he knows any plumbing shops over there that could send over half a dozen or so 'Czech Valves'. :cool:

Thanks again. Great tip!
Cheers,
Bruce

BB. · August 2014

Re: Grundfos 6 SQF-2 capabilities

If you get grit that damages a check valve--It will probably also damage the pump too.

To fine of screen/filter/clogged filters on the inlet creates a pressure drop--And if the pump is "lifting" water, that will dramatically decrease lift capabilities (if 20' at sea level is maximum, if you have a 1 lb drop on the filter, that is approximately 2' of 'lost lift").

Also, if you pull vacuum at the pump inlet, that can cause cavitation--Really bad for pumps too.

Cavitation - Wikipedia

-Bill

Texas Wellman · August 2014

Re: Grundfos 6 SQF-2 capabilities

You need the built-in check valve at the pump .
For good measure if you're pumping into a cistern at the end of the line I would put one there also. That's all. That way if your pump check valve leaks you're protected there, if the line between the cistern and pump leaks you're protected there.

OffGridiot · August 2014

Re: Grundfos 6 SQF-2 capabilities

BB. wrote: »

The pump should not burn out with lower input voltage--It will just run slower (assuming it has enough power to run). I forgot the exact numbers--But the pump needs something like >60 to 90 volts DC for optimum operation.

Will the pipe be buried below the frost line (guessing it gets cold where you are at)? Otherwise, you may need to have the pipe drain back anyway to prevent freezing/damage.

-Bill

Good to be reassured about electrical concerns. Thanks. The specs for voltage are supposed to be 30 to 300 volts DC or AC. Was more concerned about inadequate amps.

At this point, we're considering swapping back and forth, seasonally. Have it in the drilled well for the winter, where it is freeze protected. Then move it to the other spot for the warmer part of the year, when the days are longer and the solar panels can earn their keep. I've had the pump out of the deep well a few times, and it's not that big a deal to pull.

Cheers,
Bruce

westbranch · August 2014

Re: Grundfos 6 SQF-2 capabilities

Another thing to consider is how will you dismantle for repairs, modifications, add ons if you ever have to pull the pump, etc... not any specific recommendations just have it so you can do it easily and not down a 4 foot diam 8 foot deep well hole.... don't ask...

hth

OffGridiot · August 2014

Re: Grundfos 6 SQF-2 capabilities

Dave Angelini wrote: »

Have you considered just removing the well casing and drilling deeper?

Indeed I have.
I think that if the quality of the water that's there were better, I might opt for that. The other water is far superior in quality as well as quantity.

Thanks

Bruce

OffGridiot · August 2014

Re: Grundfos 6 SQF-2 capabilities

Texas Wellman wrote: »

The grundfos likes voltages above 90VDC. It will run at lower voltages but as has been said it will run lower and give less water. You need to look at the curve to see if it will still meet your demand for water at a lower voltage.

If it were mine I would set up a 3 panel rack (24V panels) that would give the pump a nominal voltage of about 90-110VDC. Panels should be the 200W variety. That gives you ~600 watts and you're above the 90V mark. Since the pump has built-in dry run protection you won't have to worry about that problem. The grundfos has a max input of about 1400 watts IIRC.

How are you going to get the water from the new well to your normal water system? If there is an elevation change (going downhill) you can simply let it gravity flow. If not you can go directly into a pressure tank from the pump and then from there pressurize it to your home. Every 1 ft in elevation takes about .4 psi to overcome. Horizontal distance doesn't really matter as much as elevation. If going 3,000 feet you should look at the friction loss charts to size your pipe according to the flow you expect to get.

I'd like to treat this pump as well as it had treated me some I bought it. If it prefers the higher voltage, that's what I'd rather give it.
The pump curve chart I saw suggested is get close to the amount I need with as little as 200 watts. I'm thinking that's at least a little optimistic. Thought I'd start in the 300 watt range and add more if appropriate. There are other people using the distant well, as well... also, I mean. I'd hate to over draw from it and leave anybody else dry. Also, if I end up with a full cistern, I'd have to either go down to the well to shut off the system, or figure out a way to have that done automatically (a remote control system that is likely a bit beyond the scope of the project I've been envisioning thus far).

So with those things in mind, I'm now thinking that (if I can find them at a reasonable cost... or at all, for that matter) 4 X 75 watt 24V panels would get me started with the 300 watts I was thinking about, and the 96 volt range you were thinking about, and again, add another panel or two of necessary.

The pump at the new well will push water 3,000 feet horizontally and 100 feet up hill to the same cistern I've been pumping to from the old well, and then gravity feeding my house and barn.

Cheers,

Bruce

OffGridiot · August 2014

Re: Grundfos 6 SQF-2 capabilities

BB. wrote: »

If you get grit that damages a check valve--It will probably also damage the pump too.

To fine of screen/filter/clogged filters on the inlet creates a pressure drop--And if the pump is "lifting" water, that will dramatically decrease lift capabilities (if 20' at sea level is maximum, if you have a 1 lb drop on the filter, that is approximately 2' of 'lost lift").

Also, if you pull vacuum at the pump inlet, that can cause cavitation--Really bad for pumps too.

Cavitation - Wikipedia

-Bill

Apparently this pump can handle a bit of grit. Hopefully it doesn't have to deal with anything that'll cause me trouble, either with the pump (yikes) or making the check valve not close properly (the latter scenario hopefully being taken care of with the installation of more than one).

The pump SHOULD always be submerged so cavitation shouldn't be an issue as long as the well's recovery keeps up with my added demand AND the low water shut off sensor works like it's supposed to.

-Bruce

OffGridiot · August 2014

Re: Grundfos 6 SQF-2 capabilities

Texas Wellman wrote: »

You need the built-in check valve at the pump .
For good measure if you're pumping into a cistern at the end of the line I would put one there also. That's all. That way if your pump check valve leaks you're protected there, if the line between the cistern and pump leaks you're protected there.

I like your way of thinking, Panda!

Bruce

OffGridiot · August 2014

Re: Grundfos 6 SQF-2 capabilities

westbranch wrote: »

Another thing to consider is how will you dismantle for repairs, modifications, add ons if you ever have to pull the pump, etc... not any specific recommendations just have it so you can do it easily and mot down a 4 foot diam 8 foot deep well hole.... don't ask...

hth

OK, now THAT sounds like the voice of experience. Don't worry. I won't ask.
Another great tip, though.

Thanks,
Bruce

BB. · August 2014

Re: Grundfos 6 SQF-2 capabilities

I have seen a couple in well pumps with "sand socks" around them... don't know how common or if really useful (or more problems than it is worth).

I do like submerged pumps (and pumps mounted below the water level)--Positive pressure does make air leaks, cavitation, and filter restrictions much less of a problem.

The check valve at that tank--A good way to prevent your water from "disappearing" over night (failed pump, broken pipe). Of course, you can just have the pipe enter the top of the tank with a air-break and do the same thing.

Drain back systems--Needed for freezing weather.

Not sure how big of an issue--But over sizing the diameter of a pipe can lead to slow flow rates and silting in the pipe (silt settles to bottom of pipe, eventually reducing flow/plugging pipe). I saw a water/well manual once that had recommended pipe diameter vs minimum flow rates towards that end.

And look at panels... The "small" panels (130 watts or less) are frequently 2x or more the costs of the "big" > 160 watt panels ($$$/Watt). Shipping panels >140 watt can be more expensive too...

Look at the total price of panels at your front door. You may find that 4x 100-140 Watt 17.6 volt panels may cost almost the same as 4x 250 watt 30 volt panels.

-Bill

vtmaps · August 2014

Re: Grundfos 6 SQF-2 capabilities

OffGridiot wrote: »

Also, if I end up with a full cistern, I'd have to either go down to the well to shut off the system, or figure out a way to have that done automatically (a remote control system that is likely a bit beyond the scope of the project I've been envisioning thus far).

I would not like to run any sort of control wires in the trench with the pipe... you set yourself up for too many lightning and grounding issues.

How about a pressure switch and small pressure tank at the pump end of the trench and a mechanical float valve at the cistern. When the cistern is full, the pump will shut off at a pressure you set.

I guess that you set the pressure to be about 20 psi above the 100 ft head. That 20 psi number is important to understand and is just a guess...

The more power you give the pump the faster it will pump. As I explained earlier in this thread, the faster you pump, the more head you lose due to pipe friction. Therefore you can get into a situation where the pump turns on and pumps too fast and the back pressure exceeds the pressure switch setting. Then the pump shuts off, the pressure immediately falls and the pump turns on. That will kill the pump.

Three solutions that can be used individually or together:

1) put a pressure tank at the pump end of the line

2) raise the pressure at the pressure switch

3) limit flow rate of pump... if it can't pump more than 2 gmp then it can't create enough friction back pressure to exceed your pressure switch setting (I guess something like 20 psi above the 100 ft head. That assumes 2 gpm through 3000 ft of 1 inch HDPE pipe). There are many ways to limit pump flow... mechanical and electrical. Electrical includes (but not limited to) limiting solar array size.

--vtMaps

Grundfos 6 SQF-2 capabilities

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