Need help with submersible pump/motor selection

[riverside67]

Hello all,

I am building a home and am hoping to utilize an old well that is on our property. This well will need to supply the domestic, irrigation and fire sprinkler demands for our home. The fire sprinkler demands are 45 gpm for 20minutes.

Conditions of our well.
Drilled in 1973.
160' deep
12" steel casing, 1/4" wall.
Top of well elevation = 4270
Standing water level elevation = 4240 feet.
Can sustain a constant flow of 100 gpm for 4 hours before breaking suction.
Well located approx 450 feet from home.

Conditions of our home.
Pad elevation = 4322
Single story, 3600 sq ft
3 bathrooms, 2 with multi show head configs.
Fire sprinklers throughout.
Very large slope areas to landscape/irrigate.
4370 is elevation of highest point to irrigate.

Conditions for our pump/motor
3 phase power already present at well.
Needs to be able to supply 30 psi at elev 4370.
Needs to supply 50-60 psi at elev 4322.

We have been given an estimate from a local well company for $15,000 that includes a 10 hp submersible motor set at 147' depth with a VFD drive, a 6" -55GS100 water end pump, transducers, piping electrical, an 85 gal pressure tank, etc. They were suggesting a VFD to avoid the use of a CSV so the pump wasn't deadheading. (I'm still torn between VFD vs CSV setups)

This seems awefully high to me and we really need help configuring a pump/motor/tank system that will cost less and work best for our home's domestic, irrigation and fire demands.

Any suggestions? Please help us setup a great system.

Thank you

[speedbump]

Without me having to do all the math. What is the highest distance from the top of water in the well to the highest place you will need water and at what max pressure. Like maybe 40 psi for sprinklers or maybe a shower if it's higher. What is the max flow needed for the fire sprinklers? What is the max flow needed for your irrigation and house needs.

You may be ahead of the game to put in two pumps. One for the home, the other for the sprinklers and irrigation. That would keep the fire sprinkler pump exercised and you could put in an irrigation system that could make full use of the fire pumps capability.

I am not a fan of VFD's and do like CSV's. I would recommend one for each pump and bladder tanks to go with them. Get me the specs above and I'll size a couple of pumps.

By the way, do you have the level in the well that the pump broke vacuum at? Is that maybe the pumping level or how did they arrive at this figure?

[riverside67]

What is the highest distance from the top of water in the well to the highest place you will need water and at what max pressure.

82 feet above water level we will need 50-60 psi for the home.
130 feet above water level we will need 30 psi for irrigation.

What is the max flow needed for the fire sprinklers?

45 gpm for 20 minutes

What is the max flow needed for your irrigation and house needs.

I would assume that the pump will need to be sized to meet the 45 gpm for fire flow and this flow will be more than adequate to provide both domestic and irrigation needs.

I am not a fan of VFD's and do like CSV's. I would recommend one for each pump and bladder tanks to go with them. Get me the specs above and I'll size a couple of pumps.

I would prefer to go with whatever pump system would be most efficient, last the longest, meet our needs and of course cost the least.

By the way, do you have the level in the well that the pump broke vacuum at? Is that maybe the pumping level or how did they arrive at this figure?

They were tracking the pumping level during the test. It broke suction around 145 feet after about 4 hours of pumping at 100+ gpm. The water level dropped approx 30 feet every hour at 100 gpm.

I ran the test pump myself for 9 straight hours at 50 gpm and it never broke suction.

[speedbump]

You missed one question. What is the max gallonage needed for the house alone? I know you said you had a shower with multiple heads.

[riverside67]

Doesn't the pump need to be sized to supply demand to the fire sprinklers (45 gpm for 20 minutes)?

I can't see the home requiring more than that at any one time, even if the irrigation was running or a washing machine or dishwasher was running and a shower or two were both on.

I think a pump that delivers between 50-60 gpm would be fine for our purposes.

Thanks!

[valveman]

We have been given an estimate from a local well company for $15,000 that includes a 10 hp submersible motor set at 147' depth with a VFD drive, a 6" -55GS100 water end pump, transducers, piping electrical, an 85 gal pressure tank, etc. They were suggesting a VFD to avoid the use of a CSV so the pump wasn't deadheading.

I think I would look around for a pump man with a little more education. First there is no way a CSV can "deadhead" a pump. Anybody who thinks that, and also thinks a VFD is better than a CSV, still has a lot to learn about pump systems. Also the 55GS100 is not a 6" pump, it is a 4" pump which is designed to run at about 550' of head and you only need 225' of head. So the pump is not sized correctly. A 60GS50 or a 55GS50 is only a 5 HP and will give you 55 or 60 GPM at 225' of head. A 75GS75 is only a 7.5 HP and will deliver 85 GPM at 225' of head. A 10 HP should be a 90L which would give you 100 GPM at 225' of head, which is way overkill for your well and system. No way I would use a 55GS100 for your application.

There is only two reasons a legitimate pump company would sell you a VFD. Either they are not educated on how pump systems really work, or they know exactly how they work and are only out to get as much of your money as they can.

I think he priced you a 55GS100 because of the VFD. You loose about 10% of the pumps capability when it is controlled by a VFD. You also need a very steep pump curve like the 55GS100 so that a VFD can actually slow the pump down when needed, and still produce enough pressure to work properly. With a VFD, head is lost by the square of the pump speed, so you can't slow a pump down very much, unless it is extremely oversized to start with like the 55GS100. And if they are claiming the VFD will give you energy savings, they know even less than they think they do. No matter how you control a 10 HP pump, it can never use less energy than a properly sized 5 HP.

But hey, everybody needs to try a VFD once in their life. That is where we get our best CSV customers. CSV's were designed to replace VFD systems, and we have been doing so since 1993. If you want something expensive and short lived, get a VFD. Then it won't be long before you will want something long lasting and dependable, and you will be back for the CSV. A CSV and the 5 HP 55GS50 pump should cost half what you were quoted for the 10 HP and VFD. And I know it will work much better and last longer.

I also like the two pump idea since you have 12" casing. Two pump systems are easy to set up with CSV's and then you have a backup system, and do not have to run a big pump when only one shower is being used.

[riverside67]

Thank you Valveman! I am going to ask them to re-configure to a CSV type system. I totally agree with you. Would I still need bladder tanks with a CSV type system you speak of valveman? If so, how many and what size?

Speebump, I can't wait to see what you dual system design will cost in parts.

How do you seal off two pumps in one well? Is there a special seal for such applications?

Thanks guys!

[speedbump]

I still need the max gallonage for the house.

I'm sure we can find a well seal for a 12" well that will allow two pumps.

[valveman]

I would still use an 80 gallon size bladder tank, it only holds about 25 gallons of water. This size tank will work with either a large single pump or with two smaller pumps, you would just need two pressure switches for the two pump system.

[riverside67]

I still need the max gallonage for the house.

I can't imagine the home needing any more than 30 gpm

[riverside67]

I would still use an 80 gallon size bladder tank, it only holds about 25 gallons of water. This size tank will work with either a large single pump or with two smaller pumps, you would just need two pressure switches for the two pump system.

Would this tank need to be at the pump or at the home elevation?

[valveman]

It could be at either location but, it would probably be better if you can put it at the well. What is elevation difference?

[riverside67]

What is elevation difference?

60 feet from top of well to top point of use in house.
90 feet from standing water level in well and top point of use in house.
(Desire is 60 psi at this point)

100 feet from top of well to highest irrigation point.
130 feet from standing water level in well to highest irrigation point
(Must be min 30 psi at this point)

Cary, would there be any harm in running a single 60GS50 pump and 5hp motor with a 2" CSV?

[valveman]

would there be any harm in running a single 60GS50 pump and 5hp motor with a 2" CSV?

That would be the best choice for this application. You will have to set the pressure switch for 75/95 and the CSV at 85 PSI to get 60 PSI up 60' to the house. At this pressure an 80 gallon tank only holds 15 gallons of water but, it will still be OK.

[riverside67]

Would the 60 psi at the home be the high or low end of the range?
Would I still have the min 30 psi at the highest irrigation point?
Could I use a larger bladder tank and/or two tanks in series?
Would the single pump scenario be cheaper overall as compared to the dual setup speedbump sugested?

Thank you