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what am I doing wrong with my Grundfos pump?


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I bought a new Grundfos 15-50 pump on Ebay for my hot water circulating loop. Plumbed it in, got water in the system, turned it on. Didn't start. Tried all 3 speed settings, wouldn't start.

I removed it, and checked that the voltage is getting to the pump. It is. So I took the impeller cover off, and (this is done with the impeller wet) with the cover off, it spins beautifully, and if power is applied (just for a second), it starts and turns perfectly.

But when I put the cover on, it binds up and won't turn.

All I did was remove the cover. I didn't touch the gasket. Spins without the cover on, won't spin with the cover on.

I can't take it back because it came from a private seller on Ebay, bought it months ago.

And yes, I'm installing it with the shaft horizontal.

Any suggestions would be much appreciated.


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No, it doesn't sound like that. I have already checked the connections: they are fine.

Well then, I guess I misinterpreted your statement that included "just for a second". I understood that that the pump ran for "just a second" but I guess you meant that you applied power "just for a second".

I'm serious here:

Using a small hammer deliver a series of sharp blows to the beefiest part of the pump casting from a few different angles. It will relieve the stress in the bearings and budge things into alignment.

You probably tweaked things by not tightening the flange mounting bolts evenly.

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I agree with Chad regarding the stress angle and flange bolts. I would leave the bolts a little loose and see if it runs. Likely the actual driver is weak, for what ever reason and not worth fooling with.

Has this pump been modified to run clockwise in the Southern Hemisphere? joke

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thanks for the suggestions guys. Here's what it's doing: if I apply power with the shaft vertical and the end inspection port pointing DOWN, it starts and runs fine. The moment I move the pump so the shaft is horizontal, the impeller/shaft assembly is able to move about 1mm up and out of the motor housing and it then locks solid. I can duplicate this behavior by running it with the impeller cover off.

It's a mechanical, not an electrical problem.

I'm told that the water goes down the drain in the opposite direction in the southern hemisphere.

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I don't know about water going down the toilet bowl but hurricane winds turn counterclockwise in the northern hemisphere, clockwise in the southern and this is no joke.


PS: Just checked my toilet. It went CCW! Can I collect a PhD for this?

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