Suggestions for a 2 well system with pump motor problems.

[BowlesGarden]

Here is the set up. Two separate well and pump systems both feeding pressure to one large underground network of 2†PVC pipe with 15+ yard hydrants and a 60 zone computer controlled irrigation system. We are experiencing the problem of going through pumps on well # 1 rather quickly in my opinion. The 33GS50 in the well now is shot I think. It is the 4th pump since 2003. I am not interested in diagnosing the broken pump in the well but more interested in coming up with a better solution to our setup. I believe the pump is killing itself cycling on and off during the medium usage. I would appreciate any suggestions anyone may have.

Our water usage is medium to high. It is not uncommon for 1-4 hydrants to be on all day in the summer. One hydrant can be 5-7gpm. 4 or 5 hydrants is usually the tipping point of pressure loss The irrigation runs in the evening for a couple hours with water usage in the 2-25 gpm range.

The pump in well #1 is set as primary. The pressure readings below are what I observed on the guage during cycling.

Well # 1 (Primary Pump)

Submersible Goulds 33GS50 5 HP Installed July 2012
230v Single Phase (3 wire and a ground)
300’ of 8 awg from control box to pump
725 feet deep well
depth of water 50’
depth of pump 280’
50 gpm recovery rate
well casing 6â€
Well drilled between 15 and 20 years ago
Diaphram Tank 119 gallon
Pressure switch setting on 52psi off 75psi
Dual VU-Flow filters
1 ¼ “ out of the well then T, half to filters and underground, half to pressure tank

Well # 2

Submersible Goulds 18GS30 3HP Installed Dec 2007
230v Single Phase (3 wire and a ground)
1000’ 8†well
depth of water 20’
depth of pump 360’
20 gpm recovery rate
Well drilled Dec 2007
Diaphram Tank Champion CH10050
Pressure switch setting on 55psi off 72psi
Dual Vu-Flow filters
1 ¼†out of the well, then filters, then T to pressure tank and underround to 2â€

 

[LLigetfa]

Have a look at www.cyclestopvalves.com
They have experience with multi-pump systems.

 

[Sponsor]

 

[Valveman]

Here is a link to a graphic of how a two pump system works with Cycle Stop Valves. http://www.cyclestopvalves.com/simple/home.php?anim=2well

 

[BowlesGarden]

I have read over the cycle stop valve website. The cycle stop valve looks really promising. Our well guy suggested a VFD pump. I asked him about the cycle stop valve and he said he was familiar with them but by no means an expert. I still cant get over the fact that throttling a pump motor does not make it work harder. Has anyone had any experience with the Cycle Stop Valves not working with specific brands or models of motors. I ask now because I have the opportunity to build the system from the pump up.

 

[Valveman]

I still cant get over the fact that throttling a pump motor does not make it work harder.

Everybody gets it wrong. That is why it is so easy to be conned into a VFD. Throttling is good for a pump and a VFD is hard on a pump. It is counter intuitive, which is why it is so easy to misunderstand how it works.

Ask you pump man how he is going to make those two VFD pumps talk to each other and still maintain the minimum cooling flow required for each pump.

After being in business for 20 years with hundreds of thousands of successful installations, you would think you could find something negative about the CSV. You can certainly find a lot of negative stuff about VFD’s, but not CSV’s. That alone should tell you something.

 

[BowlesGarden]

I also have a question as to placement of CSV in Well #1. Because the pipe Tee's out of the well , left goes to the pressure tank and dead ends..... right goes to the filters and end usage. My guess is because the water flow on the left side is bidirectional the CSV can not go there. And now that I am thinking about it the water may be bidirectional through the right side from time to time when Well pump # 1 is offline and pump 2 pushes water into diaphram tank 1. And based on the system what size CSV would be the best to use? Would the best pressure settings on the 2 CSV's be similar to the CSV's on the two well pump animation on the CycleStopValve website?

 

[Valveman]

After looking at pictures and checking the pump curves, this is what I think. It would be very helpful to know the pumping level of each well. With such high static water levels and such good recovery rates for each well, I doubt that the water level is drawing down very much even when pumping full flow. No matter how deep the pumps are set, they only lift from the actual water level. So if the water level in the well doesn’t pull down very much, both of those pumps are way oversized. This makes the pumps run in an up-thrust condition, which could be part of the problem.

I would test the pumping level in the well that still has a good pump, then consider the other well to have about the same pumping level. If the pumping level doesn’t pull down more than I think it will, you can probably reduce the size of those pumps by 50%. The smaller pumps would be less expensive to replace when needed, save a lot of energy, and still pump the same amount of water.

Also the check valves on each wellhead need to be removed. The pumps must have check valves on them at the bottom of the well, and those are the only check valves you need in the system. The check valves at the top of each well can cause water hammer, which could also be big part of your problem, as this water hammer can go down and shatter the down thrust bearings in the motors. The best place to install a CSV is where the check valves are, so remove the checks and install CSV’s in these locations.

Without changing the size of pumps, the high static levels and deep set pumps mean you will respectively have 251 PSI and 264 PSI back pressure before the CSV’s. You will need to use a CSV2W1.25T 50/120 Cycle Stop Valves on each well. The CSV’s will need to be fitted with what we call a “red seat” to be able to handle the high differential pressures. I would run the 5HP as pump #2, set the CSV to 65 PSI with a 50/70 pressure switch. Then I would run the 3HP as pump #1, and set the CSV at 70 PSI with a 55/75 pressure switch.

These CSV2W valves will have a minimum flow of 5 GPM each. So it would be best to always use more than 5 GPM when irrigating. But with a large tank or two, flow rates of less than 5 GPM will still not cycle the pump very fast and will work fine. If you could change the 3HP pump to a 2HP, we could do a minimum flow of 1 GPM, so neither pump will cycle as long as you use more than 1 GPM.

If you test the pumping levels and change out the pumps accordingly, we could use different CSV’s, have less differential pressure, and work at lower flow rates without cycling the pumps. If you stay with the same pumps, the special made CSV2W’s are the best for that application. These CSV’s will eliminate the pumps being destroyed by cycling. The additional backpressure from the CSV’s will keep the pumps form being destroyed by up-thrust. Removing the above ground check valves that are not needed will eliminate the water hammer, which could be destroying the down-thrust bearings.

Adding the CSV’s will give your pumps a good long life. Checking the pumping levels and sizing the pumps accordingly could greatly reduce your electric bill.