Gundfos SQE overload. Converted to CSV and still problems. Replacement pump?

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TimCL

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I have had the Grundfos CU301 and 10SQE05-160 (10gpm 1/2hp 160' of head) in a 24" 40' bored well with 12gpm flow for 5 years with no issues until a month ago.

Issues started one night where the CU301 indicated overload, I believe this happens in pumps built in electronics/VFD when the pump pulls more then 4.7Amps. Waiting 5 minuets or turning off power to the system restores water every time. So after some simple trouble shooting I realized my pressure tank was holding no air and the air valve appeared to be broken, I replaced the valve and filled the take with air and the bladder held air and appears to be good. Once the tank was fixed the water pressure is perfect when it is working, but still cuts out.

According to Grundfos the overload error is most likely a problem with the pump being blocked or worn out, so I pulled the pump. I opened and cleaned the pump components. Nothing seemed worn or even dirty, just a bit of iron that rubbed of easily.

After doing some more reading I have seen all kinds of people complain about the wireline communications creating errors and overload warnings. Based on this I deiced to install a pressure switch with a CSV1A. I have to say I was doubtful about the CSV but after installing it, it's a pretty cool little valve. It is easy to use and install. That being said IMO a VFD in the house with a 3 phase pump is they way to go on a new install. Even with the pressure switch and CSV my pump still cuts out and goes into the overload mode. I now see only two options the motor on the pump is worn out and needs to be replaced or the conductors from the house to the pump are damaged. I can run a temporary wire above ground and connect the pump to see if this makes a difference.

Now finally, my question. If it is the pump what should I do. I am not a huge fan of buying another Grundfos SQE pump due to the VFD being in the well and I feel like this is what failed. I could replace the whole system with a VFD in the house and install a 3 phase pump in the well (I have 4 conductors going to the well from the house) I am not a huge fan of the cost of replacing the whole system due to it being around 3k CAN. Last option, I could buy a 2 phase standard pump and throw it in the well with the current pressure switch and CSV, this is the cheapest easiest option. What pump would you recommend for my application, I need a 10GPM pump with a minimum of 150' of head.

Cheers,
 

Reach4

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Did you try bypassing the CU301 and feeding the supply voltage right to the power lines of the pump? You can use an SQE as an SQ.

Now finally, my question. If it is the pump what should I do. I am not a huge fan of buying another Grundfos SQE pump due to the VFD being in the well and I feel like this is what failed. I could replace the whole system with a VFD in the house and install a 3 phase pump in the well (I have 4 conductors going to the well from the house) I am not a huge fan of the cost of replacing the whole system due to it being around 3k CAN. Last option, I could buy a 2 phase standard pump and throw it in the well with the current pressure switch and CSV, this is the cheapest easiest option.
If you have a 5 inch or larger casing or fully cased 4 inch pvc casing, then you could go to a "4 inch" pump. If 4 inch steel, you still might be able to go to a slimline/trimline/streamlined 4 inch pump.
 
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Valveman

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Even with the pressure switch and CSV my pump still cuts out and goes into the overload mode.

If you removed the CU301 you should not be able to see that it went into "overload mode". You need to remove the CU301 and use only the regular pressure switch when using a CSV. The motor could be overloading because of a bad thrust bearing. Swapping to a CSV isn't going to magically make the thrust bearing work again. If the pump is bad, you will need to replace it before you really see how the CSV is suppose to work. If you have 4" or larger casing the regular 10S05-9 would be a less expensive and better pump to work with the CSV.
 

TimCL

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Did you try bypassing the CU301 and feeding the supply voltage right to the power lines of the pump? You can use an SQE as an SQ.


If you have a 5 inch or larger casing or fully cased 4 inch pvc casing, then you could go to a "4 inch" pump. If 4 inch steel, you still might be able to go to a slimline/trimline/streamlined 4 inch pump.

Yes, I have bypassed the cu301 and wired the pump directly. It does run sometimes other times it will not run until 5 minutes passes or the beaker is flipped.

The well is 24" with over 20' of water so size of the pump is not an issue.
 

TimCL

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If you removed the CU301 you should not be able to see that it went into "overload mode". You need to remove the CU301 and use only the regular pressure switch when using a CSV. The motor could be overloading because of a bad thrust bearing. Swapping to a CSV isn't going to magically make the thrust bearing work again. If the pump is bad, you will need to replace it before you really see how the CSV is suppose to work. If you have 4" or larger casing the regular 10S05-9 would be a less expensive and better pump to work with the CSV.

The CU301 is completely disconnected. You are right I can not see that the pump is overloading with the CU301 disconnected. That being said, with the pump having a built in timer to try and restart after 5 minutes on a overload and the fact it exhibiting the exact same behavior with the CU301 showing overload, I am confident that is what is happening.

Have you replaced a thrust bearing on one of these pumps? Can you measure tolerance or feel play in the bearing? Do you need the Grundfos motor liquid? (this was the reason I never inspected the motor when I pulled the pump.)

The Grundfos 10S05-9 is a much cheaper option, from what I see this pump can be operated with a standard pressure switch and has no controller or electronics in the pump?

Thanks for the suggestions.
 

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That does sound like the auto reset overload in the motor is tripping. They normally just have to cool down before they will reset, not working on a timer as far as I know. The SQE has ball bearings where the standard 4" motors have a Kingsbury type beaing. The Kingsbury bearing has a film of water between the shoes and plate, so it is completely friction-less when spinning more than 50% of full speed. Ball bearing are only friction-less in a specific load range. Either type bearing is right on the bottom end of the motor, which is the furthest part from the pump intake. Which means your 24" casing and 20' of water standing above the pump is most likely the reason for a thrust bearing failure. The larger the diameter of the casing and the more water is fed to the pump from above, the hotter the thrust bearing gets. Especially when running at 1 GPM or less as the CU301 will let it do.

Motors get more cooling when the casing is barely larger than the pump diameter, and all the water comes in from below. A simple flow inducer or shroud is an easy way to make that happen. A shroud draws all the water past the motor before it enters the pump intake, keeping the motor cool.

And yes the 10S05-9 is a really good pump that doesn't have any electronics in the motor, and is controlled by a simple pressure switch. Adding a simple mechanical CSV1A valve to the system makes it deliver constant pressure just like when those CU301 variable speed controllers are working properly.

shroud 3 pics.jpg
 

TimCL

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What is interesting about the pump failure is that it only occurs 1/3 of the time when the pump starts. Once the pump is running it and I leave a tap open it can run for hours with no issue.

Appreciate the information. Do you have a supplier you would recommend for purchase of the 10S05-9?
 
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