Need help with submersible pump/motor selection

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Nofears67

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How much electricity would I expect to save between a 5 hp and 7.5 hp pump/motor under the same operating/demand conditions?

Would I expect to see BIG savings each month with a 5 hp motor vs a 7.5 hp motor?
 

Valveman

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Running full out for irrigation, the gallons per kilowatt would be the same. You would just get through 33% faster with the 7.5 HP. The 7.5 HP would cost more up front and later on when a replacement is needed but, would deliver 33% more water or get across 33% faster.

Using a CSV when needed just for the house, the 7.5 HP would be pulling about a 4 HP load, or the 5 HP pump would be pulling about 3 HP load. The house doesn’t use much water so this would probably only be about 5 dollars a month difference.
 

Nofears67

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Thank you.

So I'm ready to run conduits from my electric subpanel to the well in preparation for the slab and I have a couple questions.

1) I'll be getting a 3 phase Franklin pump panel with ESP. Does this panel sit at the discharge of the well or can I mount it to the wall of the well building?
2) If to the wall of the building, what size conduit should I install for the 3 phase wiring from the panel to the well? {distance about 10'}
3) Does the pressure switch get wired into the pump panel? I assume I should install a conduit for that wiring too before I pour the slab, correct?
4) Any other conduits I should run that I'm not thinking of?

Thanks!
 

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Thank you.

So I'm ready to run conduits from my electric subpanel to the well in preparation for the slab and I have a couple questions.

1) I'll be getting a 3 phase Franklin pump panel with ESP. Does this panel sit at the discharge of the well or can I mount it to the wall of the well building? It can be inside or outside of the building and hanging on a wall is good. You just need at least 3' of clearance in front of it to be code.

2) If to the wall of the building, what size conduit should I install for the 3 phase wiring from the panel to the well? {distance about 10'} Depends on the size of wire but, usually 3/4 will work.

3) Does the pressure switch get wired into the pump panel? I assume I should install a conduit for that wiring too before I pour the slab, correct? Two wires and a ground to the pressure switch, again 3/4 conduit.

4) Any other conduits I should run that I'm not thinking of? Power to the panel, power from panel to well head, and control wires to the pressure switch should be all.


Thanks!


I like the flex tight conduit and connectors.
 

Nofears67

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Running full out for irrigation, the gallons per kilowatt would be the same. You would just get through 33% faster with the 7.5 HP. The 7.5 HP would cost more up front and later on when a replacement is needed but, would deliver 33% more water or get across 33% faster.

Using a CSV when needed just for the house, the 7.5 HP would be pulling about a 4 HP load, or the 5 HP pump would be pulling about 3 HP load. The house doesn’t use much water so this would probably only be about 5 dollars a month difference.

This pump will only serve our home. It will of course serve the irrigation around our home but not large scale orchard irrigation. I believe you are thinking of some of our previous discussions regarding orchard irrigation.

I only need this pump to produce 38 gpm @ 310 feet of head to satisfy the
fire dept and fire sprinkler req'ts. The irrigation system will be designed to pull no more than 24gpm from any one station.

It appears that the 55 and 40 GS50 series pumps would both meet this criteria, the 60GS75 woulod just give me a lot more head and ability to expand the system if I ever wanted to, correct?
 

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It appears that the 55 and 40 GS50 series pumps would both meet this criteria, the 60GS75 woulod just give me a lot more head and ability to expand the system if I ever wanted to, correct?

Sort of! The 60GS75 will not give more head, just more volume. And it will use more energy per gallon when using a low flow rate. At high flow rate, cost per gallon would be the same. But if it is never used for anything more than 24 GPM, the 5 HP will use less energy than a 7.5 HP.
 

Nofears67

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One of the main factors I am considering is the pumping level in the well. When I had it flow tested is only dropped 30 feet after pumping for 1 hour @ 100 gpm. I will never reach flows like that under normal use and probably not even if multiple fire sprinklers were activated at one time.

If for some reason the static well level dropped from where it is now, let's say 20 feet lower, then I would need to have a pump able to compensate to make up for that loss in head.

I have not accounted for this scenario in any of my total head calulations. If the well level did drop 20 then I would definitly need the 60GS75 as the 5 hp pumps would not provide the flows I would need after adding in that additional 46.2 feet of head.

Is this a good way to think/plan head?
 

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The 40GS50, 55GS50, and the 60GS75 will all give the an additional 46' of head if needed. They will just pump less volume.

40GS50 at 225' delivers 54 GPM.
275' 46 GPM

55GS50 at 225' delivers 60 GPM
275' 52 GPM

60GS75 at 225' delivers 75 GPM
275' 70 GPM

I still think the 55GS50 would work best.
 

Nofears67

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The minimum head I need is 310 feet and preferrably 340. Adding the additional 46 ft of head brings me to 356 min and 386 max. I see the 60GS75 being the only one that could provide the min 38gpm fireflow at these heads.

Am I missing something?
 

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With 140' of drop pipe the draw down can’t be more than that. 60' elevation to the house. Need 60 PSI which is 138' pressure at the house. Even adding in another 10 PSI which is 23' for friction loss, that all adds up to 361' total. At 361' the 60GS75 will give you about 55 GPM.

The 40GS50 will only give you 32 GPM at 361'. But it would give you 50 GPM at 20 PSI in the house for fire flow, even if the water level in the well was all the way down to 140'. I don’t think you ever said what pressure the fire sprinklers needed?

The 60GS75 won’t hurt anything except maybe adding 5 bucks a month to the electric bill, and cost more up front. The CSV will let you use the pump anyway you want. So since you have a CSV, it would be better to have a bigger pump and not need it, than to need a bigger pump and not have it.
 

Nofears67

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Then I guess the last thing to consider would be the speed at which either of those pumps would refill the two (2) 85 gallon bladder tanks.

Any deal breaking difference between the two?

I can deal with an additional $5-$10/mo.
 

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The CSV is what determines the tank fill rate but, only after all faucets have been closed. The CSV will let the tanks fill at 5 GPM above the set pressure of the CSV. At 75/95 pressure switch setting, an 86 gallon tank holds about 15 gallons of water, and two tanks would make 30 gallons of draw down. With the CSV set at 90 PSI, the tanks are 3/4 full before the CSV starts topping them off at 5 GPM. At 90 PSI the tanks would already have 22.5 gallons in them, so when you close off the faucets, the last 7.5 gallons goes into the tanks from the CSV at 5 GPM. This will give you another 1.5 minutes of run time, on top of how long the pump has already been running to supply the demand required.

Without a CSV, the 60 GPM pump would fill the tanks in 30 seconds and shut off. Your demand would then drain the 30 gallons from the tanks, and the pump would again refill them in 30 seconds. So you can see that to get the same 2 minutes of run time without a CSV, you would need 120 gallons of draw down, which is 8 pressure tanks. Even then the 8 tanks would not stop pump cycling, just slow it down a little bit. A constant demand of 30 GPM means 8 tanks would be filled in 4 minutes, and drained in 4 minutes, which is a cycle every 8 minutes, or 180 cycles per day.

The same continuous demand of 30 GPM using the CSV and 2 tanks would only let the pump cycle once per day. Eliminating 179 cycles per day will increase the life of the pump, motor, tanks, switches, starters, etc., many times over. Intermittent uses of water for the house would mean that the pump would cycle a few times per day but, nothing like it would without the CSV.

So it doesn’t matter which pump you use, the CSV will determine the tank fill rate, and reduce the number of times per day the pump cycles.
 

Nofears67

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A couple other things...

1. Will the 2nd pressure tank need anything special on its plumbing if it is located at the house pad or can it just simply be tee'd into the 2" line coming from the well and 1st tank located at the well?

2. What pressure setting should the 2nd tank be set at?

3. What amperage 3 pole circuit breaker should I install in the subpanel to feed the 60GS75 pump/motor? The voltage is 230V.

Thanks!
 

Valveman

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A couple other things...

1. Will the 2nd pressure tank need anything special on its plumbing if it is located at the house pad or can it just simply be tee'd into the 2" line coming from the well and 1st tank located at the well?

Just tee it in. A pressure gauge would be nice but, you can just use a tire gauge on the top of tank to test the pressure.

2. What pressure setting should the 2nd tank be set at?

After the system is up and running, note the lowest pressure you see at this tank while using maximum flow. Then adjust the air pressure to about 5 PSI below this lowest observed pressure.

3. What amperage 3 pole circuit breaker should I install in the subpanel to feed the 60GS75 pump/motor? The voltage is 230V.

12 amp motor, book says 30 amp breaker.

Thanks!

Pump Panel should already have proper fuse or breaker and overload.
 

Nofears67

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Pump Panel should already have proper fuse or breaker and overload.

I figured that but I was asking for the circuit that will feed the pump panel. I have the main 100 amp meter panel/ main breaker, then a 100 amp subpanel and this subpanel will have individual circuits that will feed various items:
- pump (30 amp)
- 110 circuit (15 amp)
- ext lighting, etc (15 or 20 amp)

Thanks again Cary!
 

lukejenson

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BTW, even a home owner can go to Driveswarehouse.com and pay only 153 bucks for a VFD that is much better than any of the ones put out by the pump and motor companies. Installers who are educating themselves about VFD's are now using these because they have so many more adjustable parameters, and they cost much less. That is until they realize that the CSV is far superior to any VFD.

I agree that it's better to buy a vfd manufactured by a specialist company rather than from pump & motor companies. I believe companies like driveswarehouse.com are resellers. They probably buy large quantity of a particular drive & try to sell it on price. You can get a cheaper price, but if you need tech support they may not be any help. I suggest that when you buy a vfd that you should go thru a factory authorized rep/distributor.

http://www.ctiautomation.net/Products.htm
 
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Nofears67

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4) Any other conduits I should run that I'm not thinking of? Power to the panel, power from panel to well head, and control wires to the pressure switch should be all.

I like the flex tight conduit and connectors.

Do you happen to have a picture of a typical wiring setup that shows a wall mounted pump panel and the wires/conduits that run from that panel to the well head and pressure switch?

I'm installing the conduits today and I don't want to miss anything.

Thanks!
 

Nofears67

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Here is a sketch of how I planned to run my conduits. Please let me know if I am missing anything.
 

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Nofears67

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I'll be ready to install the pump in about two weeks and now I need to decide if I will be making a mistake by using sch 80 pcv drop pipe as well as a safety rope/cable. I am seriously confused as a couple of you have highly recommended against this and others say it will be fine.

I see you want to set the pump on pvc.

DO NOT DO THAT! It will break off.
That motor will fatigue the pipe quick ,and the pipe will break and the pump WILL fall.

Anything over a 2hp should be set on steel and not set on pvc.
Travis

Ditto Ditto Ditto!
I didn't do up a quote because it sounded like you had gone for the one pump fit's all scenario. And you never told me what your max usage for the home would be.

I prefer 2" galv pipe also but, I have installed many pumps larger than this on PVC pipe without any problems. I just use a CSV so there is not enough cycling to unscrew or destroy the pump. The CSV makes a big difference, because when running low flow for 24 hours, the pump will only cycle once instead of 720 times..

I don't know what to do now...Any final words from you guys regarding the pvc drop pipe? I will be using a CSV BTW.

And what's the deal with saftey ropes/cables? Are they a good idea?

Thanks
 
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