Grundfos Constant Pressure System - Constantly Pumping, won't turn off automatically

[Jim Scott]

Hi.

I have a Grundfos Constant Pressure System with SQE pump installed in 2006. About a year ago we experienced problems with the pump/system when the pump wouldn't stop running. We lived with it until about a month ago when I saw my electricity bill!! I got in touch with the contractor who drilled our borehole and installed the pump. Gave the symptoms and he suggested a leak in the system. I was sure we didn't have one but did not excavate pipework underground. I told him we ruled out a leak and he suggested we replace the pressure sensor which was the cheapest option. This didn't sort it so he came out. He lifted the pump and saw that when disconnected at the top the water didn't drop back down the rising main so the non return valve was working. We then replaced the CU301 control panel, and today the pump. It's still happening and won't turn off. I haven't excavated the underground pipework yet. Does anyone have any ideas please.

Thanks.

 

[Valveman]

Make sure you don’t have another check valve up top. Then while no one is using water shut the pump off manually. If the pressure stays exactly the same for an hour, you don’t have a leak.

Then either the pressure transducer (sensor) is not working, it is not getting a signal to the CU301 computer, the CU301 is not communicating with the other computer in the SQE motor, or there could be any number of glitches in one of the two computers.

The only good thing about the SQE is that it will run off a standard pressure switch in place of the CU301. So as long as the pump itself will run, you can replace the pressure transducer with a standard 40/60 pressure switch. Then you can be sure it will turn off when the pressure gets to 60 PSI. Install a Cycle Stop Valve set at 50 PSI before the pressure tank and new switch. This will give you the 50 PSI constant that you want, and allow you to keep the small pressure tank you have. Or you can do without the CSV if you install a very large tank, and get use to the pressure fluctuating between 40 and 60 anytime you are using water.

This way you will already be set to use a more heavy duty, standard 4”, 3450 RPM pump when the little 10,600 RPM toy pump you have leaves you standing in the shower with soap in you eyes.

 

[Sponsor]

 

[Ballvalve]

All agreed, but so what with the 10,000 rpm's if the bearings are correctly designed to survive that?

And the control sys may be fatally flawed, but I do not think the pump itself Qualifies as a toy by any standard.

 

[Valveman]

From Grundfos’ own engineering manual, it says doubling the RPM of a pump, will quadruple the wear rate. 10,600 RPM is triple the RPM of a standard 3450 RPM pump, so it should wear out 450% sooner than a 3450 RPM pump. Which I believe is kind of the goal of the manufacturer for the SQ/SQE.

The SQE weighs 11#, compared to about 35# for a standard pump/motor. The SQE spins 3 little impellers really fast to produce the same water as about 10 impellers in a normal speed pump.

It is like the difference between a heavy-duty 3450 RPM bench grinder, and a light weight 10,000 RPM Dremel tool. They will both grind or cut metal, but which one will last the longest? If I were cutting metal all day, I would consider the Dremel a toy compared to a bench grinder. For pumping water, I would consider the SQ/SQE a toy compared to a standard pump/motor.

 

[Masterpumpman]

I'd install a Square "D" pressure switch and a Cycle Stop Valve and forget the complicated troublesome computer. Then when replacing the pump I'd go back to a regular 4" pump.

 

[Ballvalve]

I dont know much about the SQE and wouldnt buy one, but grunfos seems to have created some pretty amazing products from their own engineering.

Doesnt that pump run at variable speeds, often lower than 10,000? And I think we both know that you can make a bearing of a quality to survive high speeds. Water or oil lubed bearings dont have any contact at all, except perhaps a nano second at start up.

Why dont they have an issue with cavitation at the impellers at such a speed?

 

[Texas Wellman]

Wait, lemme get my popcorn.
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Proceed.

 

[Valveman]

Your probably gonna need a soda pop with that while your at it.

Grundfos makes very good standard RPM pumps. I started using them in 1973, and still have several in my own wells. From what I understand, the SQE is R and D for their futuristic stuff. It proves they are the smartest pump company in the world, so when you need a real pump, like a 50 HP, a 10 HP, or even a 1 HP standard 3450 RPM pump, you will think of Grundfos.

Personally I think it is a bad decision. I know of people who said they would never use another Grundfos, because of the problems they had with the SQE.

If the technology of the SQE is so great, why do they continue to make all sizes of standard 3450 RPM pumps? Because probably 95% of all the pumps they sell, especially through contractors whose reputations are at stake, are the standard 3450 RPM pumps. Go into any pump supply house, and you will see a few SQ/SQE pumps on a shelf, right beside hundreds of standard 3450 RPM pumps filling all the other shelves.

The SQ stays at 10,600 RPM. The SQE version varies the speed. But because you lose head by the square of the speed, it can only be slowed to about 8,000 RPM and still lift water and deliver 50 PSI.

Yes most bearings are basically frictionless, but they don’t last forever. You can get bearings by their hours of service, like 20,000 or 50,000 hours. 24/7 for 5 years would be 43,000 hours. I doubt they are rated for that. And remember the SQ/SQE has about a 5 second soft start. So those bearings are not just in contact for a nano second as they would be in a normal pump. Plus varying the speed goes through resonance frequencies, which is not good for bearings either.

I am sure cavitation is a problem at that RPM. So the impellers are made of a composite material, which should be more resistant to cavitation and flying apart from the high RPMs.

Some contractors like that they can make a lot of money with the SQE. Which unfortunately for the consumer was a higher priority in their design than dependably pumping water.

Sorry to sugar coat it so much. Just trying to keep it PG.

 

[Ballvalve]

Yes, I believe its more of a profit maker for the "car salesman" at the supply houses.

Go take a look at the water heater forum - some Taiwan heater called the "eternal" - I would call it the infernal. Cost 5 times or more than the tank heater, and unproven complicated insides. But our boss here sells them so I better not say much more. They should call it the SQE Eternal heater.

Why sell a $199 40 gallon electric heater or a 300$ gas rig and make 20 bucks when you can sell a $2000 rig full of taiwan parts and make $700?

A well guy here lives like a Microsoft boss because he has fleeced half the county on these constant pressure systems and treatment systems so complicated that you need to call NASA to figure them out [dont work anyway].

I dont have any CSV's yet, but at least its US made and a honest little piece of SIMPLE [understandable] engineering.

 

[Valveman]

A well guy here lives like a Microsoft boss because he has fleeced half the county on these constant pressure systems and treatment systems so complicated that you need to call NASA to figure them out [dont work anyway].

Now that’s a shame! But it is happening all over the country. There was a time when honesty meant something. Now there are many who just want to make that extra 700 bucks, instead of doing what is right.

It’s the same with a CSV. Why would an installer want to sell a 100 dollar tank with a 90 dollar CSV that would actually make the pump system last longer? When they could make an extra grand on a variable speed system that will need to be replaced before their kids’ need a new pair of tennis shoes.

There was a time when you got what you paid for, so paying extra was a good thing. Now paying extra means you get what you deserve, for not doing a little research on your own.

They use to say, “a sucker is born every minute”. Now they say, “give me a minute and I’ll make a sucker”.

 

[Ballvalve]

I have a 2000 dodge caravan base model - the Sunday special - one for 13,995$ maybe it was 12 - had to fight for hours with a series of "closers" - phych majors that worked me and the wife to get the $28,000 model that had the bigger engine [big failure rate] and the better transmission [all replaced twice now] Finally, they decided it would take 2 hours to get it out of the back lot where they put the junk, so I went for lunch. Never even drove it, just wrote a check.

Best damn vehicle ever made. Not a breakdown on the road yet. Still gets 24MPG +/- and now hauls tools.

The new breed of ethically bankrupt salesman have put America in a deep dark hole - pumps, cars, you name it.