Grundfos pump switch

Sam Russell

I have a Grunfos circulation pump that drives my underfloor heating which does not appear to be working.

On the side of the pump there is a three position switch the is marked with | || |||. What are these for?

The heating has not been used since it was serviced - could this have been 'adjusted' by the technician and be the reason it does not appear to be working?

The other reason could be the pump is jammed.

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The numbers are the pump speed.

Is the pump powered on? If it is turn it to three and give the pump a light tap with a hammer to see if it gets going again.

Sam Russell

Thanks

I will try hat. How big a hammer? :)

John.G

If its a older type of Grundfos (usually red) then there may be a brass bleeding screw in the centre of the pump, remove this and you should be able to turn the pump shaft very easily with a screwdriver, if the newer type then there should be LEDs which should illuminate when the pump is powered up on UFH request.

Sam Russell

It has a screw slot in the centre. I intend to open it and see if it turns.

I will let you know the outcome.

Sam Russell

I tried the centre screw and it has a square hole that I do not have anything remotely like it and I tried a small screwdriver in it, but it would not budge.

Those pumps can be disassembled in situ but need the water drained (obviously).

Now this drives an underfloor heating setup. There is a white box that has the electrical connection passing through it, and there is a connection to the plumbing to that same white box - not sure what that is for - any ideas?

Wearb

https://www.boards.ie/discussion/comment/119801113#Comment_119801113

Pic of the nut you tried opening and one of the complete pump.

Sam Russell

Well, I checked the pump and it appears to be pumping.

However, the underfloor is not getting a hot return, just extremely feeble warm after an hour. So I now think pump is OK but the underfloor pipe needs flushing.

In my research, I see that there is a new generation of Grundfos pumps that are more efficient, and self righting for some problems and indicate working or not. They can also be changed as just the head part - so I will investigate that. Current pump is about 14 years old.

Thank you for your replies.

Sam Russell

Well, I removed the head of the Grunfos pump to check if it was turning and it was seized solid. Grundfos recommended a new pump (Alpha1 L) for Ireland, but a different one for the UK - not sure why.

I had already purchased the new one, so fitted that (after the occasional four letter word) and all is now working. It is very quiet and runs cool.

The new pump has LED lights to show it is working, which is great.

Also new pump can be set for 'radiator' or 'underfloor'. What is the difference?

Thank you for your help and advice.

Sam Russell

@Wearb

Well, I took the old Grunfos pump apart and took out the cartridge, and removed the impellor. I tried to drift out the rotor with a big hammer but to my surprise, it started turning freely.

So hitting it with a hammer is probably the best first step.

I will not be using the old one - I just tried to find out why it failed.

Thanks for your suggestion.