Grundfos Pump running constantly

[mattmur]

Good morning experts!

My Grundfos pump is running constantly. I have it on the first setting, so it runs quietly, but I can hear it pumping water. I haven't used my boiler for months since it's obviously been summer. I thought the pump was on tickover and was meant to stay on 24/7.... until I seen my electric bill I thought i'd query it!

I noticed a problem over winter where if I put the hot water on only, the radiators will also get red hot - even though the heating setting was off on the boiler controller down stairs.

I have noticed the 3 port valve header/cover/housing gets really hot and the lever is floppy (I can move the lever, but it doesn't seem to have any friction - i.e swings loosely). Could the 3 port be the problem? I am unsure why the pump would always be on.. AND why my heating comes on when I just want hot water.

Thanks in advance for any replies

 

[Fluffster]

3 port valve seems like the culprit with possibilty of the internal micro switch contacts stuck closed. The lever should have resistance with no call for heat or hot water. If it is moving freely the motor has energised and is holding the valve open for heat or hot water or both.
Turn the power off and listen to hear the spring turn the motor.

Pete

 

[mattmur]

Many thanks for the reply Pete

It has no resistance when the power is on (but heating and hot water off)

Aside from the 3 port should the pump be constantly on? Or is this a result of the 3port

Thanks

 

[45yearsagasman]

Turn the power off and listen to hear the spring turn the motor

Have you done that? If so, what was the result?
Pumps should not be constantly on. They should only run during heating periods and when on a cooling pump over run.
What boiler do you have? It is important to know this as some require the pump be connected to them directly so as to be controlled by the PCB.

 

[mattmur]

It's a baxi solo 2 pf

Yes I heard it do something when I turned the power off. The lever constantly floppy though.

cheers for your time

 

[picasso]

It wont be the 3 port valve causing the pump to run constantly, the boiler would fire if this was the case, as 45years has said the pump will be connected directly to the pcb so it looks like you need to get the pcb replaced.

 

[mattmur]

Thank you

Ill have to look into a new PCB then!

Thanks both you've been a great help

 

[mattmur]

Chaps, before/whilst I purchase a new PCB - i'm trying to get my head around why it would cause the pump to run when the boiler hasn't even been used for months. When a PCB is faulty, would/could it send wrong signals, or could it be a relay stuck or something so the pump is receiving the signal to run.

Just want to learn about the problem that's all

Thanks