using CSV, how long should it take to reach cut-out pressure

[Greenmountain]

I just installed a new well pump and csv. I have a 4" 16gpm 1hp grundfos in a 5" stainless flow sleeve in an open water well.

I don't have an accurate size for my pressure tank, so I am fussing with the pressure switch and csv to try to obtain optimal pressure but am not sure how long it should take to go from CSV-constant-run-pressure to cut-out pressure. I'm currently running the csv around 55psi and cut-out pressure is about 62; time from water shut-off to cut-out is about 75 seconds.

I believe I've seen the recommended time at 2-3 minutes, but I'm concerned that the pump running that long with such minimal flow, even in a flow sleeve, may not cool the motor enough. I have been checking amperage draw and it doesn't seem to fluctuate much at all... still pulls about the same amperage when all valves are closed and the pt is filling as when it is flowing 5-6gpm (difference is less than 1 amp)

please advise
thanks

 

[Reach4]

I don't have an accurate size for my pressure tank,

75 seconds sounds good, but http://www.cyclestopvalves.com/runtime_app.php recommends 2 minutes or more.

Here are some ways to measure tank size, though you may not need that info now:

1. Check the tank for a label.
2. Measure the tank with a tape measure.
3. Run until the pump turns off. Turn off power to the pump. Measure how much water you can draw before you run out of water.

 

[Sponsor]

 

[Greenmountain]

It's approx 16 x 48. Can't find any model #'s for specs, but judging by comparison I'd say it's a little over 30g. Draw down is a little under 10g I believe. air pressure is about 37psi with 40psi cut-in.

My main concern though is that with a 5" flow sleeve over a 4" pump, the 1 gpm flow allowed by the csv as the p.t. refills may not do much to cool the motor... esp if it's still drawing full amperage at the reduced flow.

 

[Valveman]

At 5 GPM the pump is already running at reduced amperage. Those 16S Grundfos pumps are really good at dropping about 50% in amperage. But a 1HP is a 9 amp motor. So to see the 9 amps you would need to open enough faucets to use 16+ GPM. Then you would see that the 6 amps it is probably pulling at 5 GPM is already reduced from 9 amps, then it drops 1 more amp to about 5 when filling the pressure tank at 1 GPM. That is the way most pump systems work when using a CSV. The pump rarely goes to full amps, because you rarely use full flow. So a 9 amp pump just lopes along at about 6 amps most of the time. This is one reason the pump/motor runs so much cooler when using a CSV.

But even if the amps only drop from 9 to 8 as with some other brands of pumps, that is still a reduction of about 12%. Even this small drop in amps will de-rate the motor enough that it doesn't need as much flow to stay cool. A 4" shroud would be better, but the motor will still stay plenty cool in a 5" shroud. Motor companies claim that their 2HP and smaller motors no longer need a shroud, even in a top feeding well. This is because they have shortened up the motor so much that the bottom end is only 12-14" away from the pump intake, and there will be enough flow circulating to keep the motor cool. It is not like in the old days when one of those motors was 30" long, and you needed a shroud to cause some flow 30" away from the pump intake. Of course those old motors where better and much more heavy duty. So it is especially important to use a CSV on the new shorter motors to reduce the amps, which makes it run cooler, and to eliminate cycling, which greatly shortens the life of the motor.

Then as far as tank run time goes, as long as the amps are reduced as I have said, the motor only needs to run for about 30 seconds filling the tank, to have plenty of time to cool off before it stops. But even if the pump runs at 1 GPM 24 hours a day, it is not going to hurt the pump. So it is fine if it takes 30+ minutes to fill the tank, it is not going to hurt anything, except to use a little more electricity than is needed.

 

[akcooper9]

So it is fine if it takes 30+ minutes to fill the tank, it is not going to hurt anything, except to use a little more electricity than is needed.

+1...I think once you have hit the minimum run time for the motor once it has started, it doesn't matter how long it takes to fill after all water has been shut off.

On my well with a CSV, once all water is off, its takes 3 minutes to fill the pressure tank and kick the well off.

 

[Valveman]

+1...I think once you have hit the minimum run time for the motor once it has started, it doesn't matter how long it takes to fill after all water has been shut off.

This is true, but if the pump is not drawing maximum amps, you don't even need the normal "minimum run time".

 

[akcooper9]

This is true, but if the pump is not drawing maximum amps, you don't even need the normal "minimum run time".

Makes sense to me. Ill let you do all the technical thinking and Ill enjoy the benefit of the CSV

 

[Greenmountain]

ok, sounds like I'm in a safe range then. I didn't go with a 4" sleeve because the total area of draw for the pump would have been less than that of a 1" pipe, and my pump feeds into a 1" pipe. I know it would have been better at cooling the motor, but just seemed real tight.

At cut-in, it kicks on at about 9amps, then drops to about 7.5A while running a little over 3gpm at 55psi.
(Haven't checked amps yet at higher flow rates.)
With all valves closed, it take a little over a minute to hit cut-out at 62psi. This is where amps don't really drop off... it drops from around 7.5 to maybe 7.3 during the minute+ to cut-off. I suppose when it goes from running higher volumes to tank refill the drop will be bigger since it will be pulling more amps, but the amperage during refill seems like it will always be in that 7.3-7.5 range.
So no need to change anything then?

many thanks!

 

[Valveman]

You are good. No need to change anything. And I know a 4" shroud is a tight fit on a 3.5" pump, but that is why it cools better. And I have tested it to know that even though it is a tight fit, it doesn't restrict much until you are pumping more than 60 GPM.

But that still doesn't seem like the amps are going as low as they should for a 16S Grundfos. Are you checking amps on the incoming L1 or L2 lines? I have a 1.5HP, 16S here at my shop and it ranges from 11.9 amps to 5.

 

[Greenmountain]

I don't actually know which line is which... I thought that with 220V both lines should show equal amperage?
What could cause it to maintain higher amps like that?

 

[Valveman]

I don't actually know which line is which... I thought that with 220V both lines should show equal amperage?
What could cause it to maintain higher amps like that?

Yes both lines should read the same amperage. I thought maybe you had a 3 wire motor and was reading after the control box. Unless there is something wring with the pump or motor, low voltage is the only thing I can think of that would make a new pump draw more amperage.

 

[Greenmountain]

huh... I'm stumped. I have 8 gauge copper running to the pump, and it's only a couple hundred feet, so I don't know how that could be happening. Guess I'd better check my splices...

Only other thing I can think of is I used a hose clamp to seal off the top of my flow sleeve. I only tightened it just enough to hold everything together. That couldn't be restricting the movement in the pump could it?

 

[Valveman]

huh... I'm stumped. I have 8 gauge copper running to the pump, and it's only a couple hundred feet, so I don't know how that could be happening. Guess I'd better check my splices...

Only other thing I can think of is I used a hose clamp to seal off the top of my flow sleeve. I only tightened it just enough to hold everything together. That couldn't be restricting the movement in the pump could it?

No if the shroud slips down over the intake it may burn up the motor or shut off the flow of water, but it shouldn't make any difference on the amps. And I don't think it is the wire or the splice. Just check your voltage at the source. You may have 208 volts instead of 240V, then the higher amps would make sense.

 

[Greenmountain]

I've got 240 at the panel... will check in the well.
Also, can the CSV be installed under water?

 

[Valveman]

Yes under water is fine. And the amps are not important, just trying to understand why it is an amp or two higher than I would have thought.