pump shuts off too quickly - new system

[type@uwm.edu]

Hi--

This is my first post, I've recently retired and have more time than money so I'm installing my own plumbing on a well for a shower house. My system is a Grundfos SQF-11 submersible pump, a Wellmate WM-14 pressure tank (precharged to 40 psi) and a 20-40 psi Shur-Dri Pressure Switch. The Grundfos is operating on AC. When I turn on the pump with the main drain valve fully open (the drain valve on the large brass "T" fixture connected to the pressure tank with outlets for the pressure meter and switch), the pump runs continuously with 9 gpm flow and about 15 psi showing on the pressure meter. When I slowly close down the drain valve, the pressure increases and shuts off at 40 PSI as expected. However, when I turn the drain valve completely off and turn on the shower valve, the pressure gauge drops, the pump turns on, water starts to come out but the pressure rises very quickly to 40 psi and the pump and water shuts off. If I leave it on like this, it keeps cycling-- jumping to the 40 psi shut-off pressure quickly after the the pump turns on. To my novice thinking, it seems like the pressure tank isn't working correctly because the water does not come out immediately when I open either valve. I'm not sure what to try next. All of the equipment is new. Rob D.

 

[Valveman]

The pump is trying to pump 8 or 9 GPM. The shower is only using about 2.5 GPM. The excess water produced by the pump quickly fills the tank to 40 and the pressure switch shuts off the pump. The shower should also very quickly drain the tank to 20 and the switch restarts the pump.

If this is a Grundfos SQE, it should have a CU controller and a pressure transducer instead of a pressure switch. This varies the sped of the pump to keep it from cycling. If you do not have a CU controller, and are applying power from the pressure switch directly to the pump/motor, then you have a Grundfos SQ. With the SQ, a Cycle Stop Valve can vary the flow to eliminate the cycling, without needing the computerized CU controller. Otherwise all your water uses would need to be at least 8 GPM to keep the pump from cycling.

 

[Sponsor]

 

[type@uwm.edu]

Thanks for your generous help! Its a Grundflos SQFlex-11 helical pump. Right, I'm using only a pressure switch, no CU controller.( Its odd that my pump system supplier knew I was using it for a shower with a large pressure tank and did not suggest a cycle stop valve.)

Is a product like this, correct? http://www.growerssolution.com/page/GS/PROD/CycleStop/csv1w

Do such valves put more strain/wear on the pump? The CSV's I found are fairly pricey,.. Might I be better off buying the CU controller? I'll also bring in my solar panels at some point.

Where's the best place to install the CSV?

Thanks again, Rob D.

The pump is trying to pump 8 or 9 GPM. The shower is only using about 2.5 GPM. The excess water produced by the pump quickly fills the tank to 40 and the pressure switch shuts off the pump. The shower should also very quickly drain the tank to 20 and the switch restarts the pump.

If this is a Grundfos SQE, it should have a CU controller and a pressure transducer instead of a pressure switch. This varies the sped of the pump to keep it from cycling. If you do not have a CU controller, and are applying power from the pressure switch directly to the pump/motor, then you have a Grundfos SQ. With the SQ, a Cycle Stop Valve can vary the flow to eliminate the cycling, without needing the computerized CU controller. Otherwise all your water uses would need to be at least 8 GPM to keep the pump from cycling.

 

[Valveman]

You won't think the CSV is pricy after you get a price on the CU controller. However, I am not sure you can even use the CU controller with the solar pump. I don't see why a CSV would not work though. The CSV1-40 would be a less expensive version than the one you marked. Do you have a battery as well, or do you only have water when the sun shines?

 

[type@uwm.edu]

Very good; I'll look into the CSV40. The SQF pump is now wired through a simple A/B switch for AC or DC (future solar) power and routed through a common pressure switch. The solar component will not have/charge batteries at this point. Investing in a controller would expand my future options if it would address the cycling too. Right, their cheapest solar controller is around $400, so, one buck at a time as I learn what the heck I'm doing. I see they suggest placing the valve immediately after the well head. I greatly appreciate your valuable suggestions. Best Regards, Rob D.

 

[Valveman]

I don't think the solar controller will double as a variable speed controller, and also deliver constant pressure. It just converts DC to AC for the pump motor. But, I don't know that much about solar, I am more from the windmill generation when it comes to off grid installations.

 

[Wondering]

You said you are running a 20/40 pressure switch.? You said your pressure tank has 40 psi in it. You need to let air out of your tank to 18psi to run the 20/40 switch. You have too much air in the tank!

 

[type@uwm.edu]

This makes sense to me. I was searching for typical pressure settings as I could not explain why tank did not seem to be filling even when the pump was on.
I ordered the CSV40 valve. I guess I'll install the valve and lower the pressure tank to 18 psi. Out of curiosity, what pressure should be in the tank for a 30/50 pressure switch? Rob D.

 

[Valveman]

Need to let air out of tank now. Will make a lot of difference. Always 2 PSI lower than the pump starts. Good catch! I missed it.

 

[type@uwm.edu]

I'll lower the tank pressure to 18 psi first. If the system works, would adding the CSV40 still benefit the system somehow? It'll be here tomorrow. The valve company made it sound like a CSV would help any system. Rob D.

 

[type@uwm.edu]

I lowered the tank pressure to 23 psi and up'd the pressure switch to 25-45 psi and it works! Next to see the Aquastar 1600H LP hot water heater on demand works. Thanks valveman and prd823! Terrific forum your efforts have created. Rob D.

 

[Valveman]

You should try the tank by itself for a few days or weeks, then add the CSV and see what you think about the difference. If you don't like the pressure better with the CSV, send it back. You should probably turn the pressure switch up to 30/50 with the CSV.

 

[type@uwm.edu]

Will do. Karen at Cycle Stop Valves computed a 25-45 psi pressure switch range with my 14 gallon draw-down pressure tank and their CSV40 so that was my cue. The Aquastar might work better with the higher pressure as you suggest.

 

[pitless]

The pump is a "Grundflos SQFlex-11 helical pump". I believe this is a positive displacement pump and should not be used with a Cycle Stop Valve or it may damage the pump or piping.

A Cycle Stop Valve is designed to work with cyntrifical pump and will work well with them.

 

[type@uwm.edu]

Thanks. I'd hate to damage or lessen the life of the brand new unit. I'll contact Grundfos and ask them first if the system seems to be cycling on and off and needs remedy. So far, setting the pressure tank pressure correctly has stopped it. Rob D.

 

[Valveman]

Thanks Pitless! That SQFlex looks like and SQ but, if it is positive displacement, don't use a CSV.

 

[Bob NH]

The Wellmate WM-14 is a 47 gallon tank with 14 gallons of drawdown with a 30-50 switch setting so it should work fine with the 11 SQF-2 pump. http://store.solar-electric.com/grsqpu.html

The 11 SQF-2 is a helical 2-stage pump and should not be used with any kind of valve between the pump and the tank. Also, the tank should be equipped with a relief valve as the pump will deliver at least 300 ft of head (about 130 psi) if the pressure switch fails closed. http://www.scsolar.com/PDF_Files/SC Solar Grundfos Pumps.pdf

 

[Valveman]

I had no idea Grundfos was using that helical design. Some of their solar pumps are centrifugal and would work fine with a control valve such as a Cycle stop Valve. The positive displacement pumps with the helical or the cork screw type shaft should not be used with a CSV. I do not even see a maximum pump pressure listed in their specs.

This type design was used back in the 60's in what we called the Peerless Wiggle tale, which was a pun on the corkscrew type shaft. I have seen a lot of pressure tanks that exploded from using this type pump. Basically there is no limit to the pressure they can build as long as the motor can turn the pump shaft. When a pressure switch sticks in the closed position, sometimes even a pressure relief valve is not good enough to keep the pressure from blowing the tank through the roof. Back in the 60's the bottom of the old galv tanks would go first, which would send the tank straight up through the roof like a rocket. I have seen the aftermath of this destruction many times. Pressure tank laying out in the pasture, 50 yards or more from the well house, with most of the plumbing still attached to the tank. Big skylight in the well house where the tank went straight up. Just lucky nobody got hurt.

I don't think Grundfos recommends this pump to be used with a pressure tank. All the examples show a reservoir or cattle water tank. These would be open ended systems which cannot blow up like a pressure tank will. I think I would at least use a vented cistern to fill from the PD solar pump. Then another pump with a pressure tank, switch, and CSV to supply pressure to the house.

 

[Bob NH]

Valveman, I think you are going overboard on the idea that the SQF helical model pump should not be used on a hydropneumatic tank. There are a lot of multistage submersibles that will blow up a tank if there is no workable relief valve.

Any time a tank is installed it is a requirement that an adequate relief valve be installed if the capability of a source of pressure exceeds the RATED capability of the tank.

There are a lot of tanks in residences that are not rated for the pressure capability of the submersible pump at shutoff conditions. If they were installed by someone who knows what they are doing they have an adequate relief valve.

There is no way that a tank can be blown up by the 11 SQF model pump if the tank has a properly installed relief valve that is designed for the rated pressure of the tank and the rated capacity of the pump.

I think the "corkscrew" type shaft that you are talking about is used in the progressive cavity pumps that are sold by, and perhaps invented by, Moyno. They are generally low-speed pumps that can operate at very high pressures. I am not aware of any submersible pumps that use that design.

 

[Valveman]

BobNH, look at the link to Grundfos you posted, page 33. That is a helical shaft on a submersible, SQF 1.2-2. Not only do these type pumps build tremendous pressure if the pressure switch sticks but, the helical shaft is hard to balance and hard to hold centered. The old Peerless pumps of that style would knock the top bushing out of the motor on a regular basis from this unbalance.

These type pumps will move water at low RPM, which is why they are good on solar and DC but, at regular RPM they will build LOTS of pressure.

We used to put pressure relief valves on the old systems as well. However, when it sits there a few years not being used, the valve will stick to the seat. So when you need them to pop open, they don't, and something is going to blow.