Very Strange Priming Problem

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Danielpeaster

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I got a pump from a customer who had replaced it a while ago because of it “not working”. I put in a new capacitor and tested it with a short hose to a water tank and it worked fine.

I installed the pump with a new foot valve for a different customer.

The pump is a Grundfos X which has a small built in pressure tank but I also hooked it up to an exterior larger pressure tank.

Here in Hawaii that water is on catchment so instead of a well there’s a big full tank of water that the suction line is going into (where I put the new foot valve).

The pump just absolutely won’t prime the way it is.
I put a tee with a cap going up about 6’ outside so I could fill all the lines from the catchment to the pump. I have a clear canister sediment filter right before the pump so I can confirm the suction line is completely full and I’ve of course filled the pump through it’s prime port.

It’ll discharge the water from the pump and seems to empty out the suction line but then it just runs dry and shuts itself off.

Any advice would be greatly appreciated
 

Valveman

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Been selling Grundfos since 1973 and never heard of a Grundfos X pump? Google brings me to Scala and CMB, so which type pump do you have? Most likely it is the "smart" part of a "smart type" pump that is giving the problem. A regular jet or muti-stage booster pump won't shut down on low amps when trying to get a prime, which is what I think is happening to you. Picture is worth a thousand words.
 

Danielpeaster

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Been selling Grundfos since 1973 and never heard of a Grundfos X pump? Google brings me to Scala and CMB, so which type pump do you have? Most likely it is the "smart" part of a "smart type" pump that is giving the problem. A regular jet or muti-stage booster pump won't shut down on low amps when trying to get a prime, which is what I think is happening to you. Picture is worth a thousand words.
Aloha thanks for your response, the alarm light is turning on when it shuts off which I imagine is a feature to keep it from running while dry. It definitely is sucking in air not water.
 

Danielpeaster

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Aloha thanks for your response, the alarm light is turning on when it shuts off which I imagine is a feature to keep it from running while dry. It definitely is sucking in air not water.
When I hooked it up to a short hose going into the catchment it would build up pressure and shut off then once opening the hose nozzle it would kick on again just like it’s supposed to. The issue is only when it’s plumbed in.
 
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