CH Pump Problem

[yartin]

Hi
My CH system has an issue. The HWC is taking long time to heat over 2 hours, used to take an hour before. Same applies to the heating. There were grinding noises in the airing cupboard one day last week. I started looking last night, the two divertors valves are working fine, I bled the 2 AAVs and rads. The boiler is firing but only stays on for 20 sec or so then a long while 30mins or so to fire again, there was quiet grinding noise in the airing cupboard; assume from the Grundfos pump which was extremely hot to touch. I tapped the pump but no change.
I think the pump is at fault??
Any tests to do?
Photos attached, Is turning the big slotted screw would help?
Thanks

 

[denso13]

You need to remove that screw and turn the inside shaft with a screwdriver. You may here the grinding noise then.

It's ok to do it with the water on, you might get some water coming out, but it's ok to check it like that.

 

[yartin]

You need to remove that screw and turn the inside shaft with a screwdriver. You may here the grinding noise then.

It's ok to do it with the water on, you might get some water coming out, but it's ok to check it like that.

I tried twice, screw inside turning freely and in both directions. Turn heating on, same boiler fires 20 sec stops and pump v hot to touch. Verdict?

 

[denso13]

Verdict?

Doesn't sound correct, especially if the heating performance is worse. Can you alter the speed of the pump and see if it makes any difference?

 

[Deluks]

I'd go back to the valves.
In the past I've taken a valve head off to see if was working ok and assumed it was, only to find that the spindle was stiff and only moving when it felt like it.
If the valve bodies are as old as the pump, they might not be as smooth as they should be.

 

[yartin]

I'd go back to the valves.
In the past I've taken a valve head off to see if was working ok and assumed it was, only to find that the spindle was stiff and only moving when it felt like it.
If the valve bodies are as old as the pump, they might not be as smooth as they should be.

Which valves? AAVs?

 

[yartin]

Doesn't sound correct, especially if the heating performance is worse. Can you alter the speed of the pump and see if it makes any difference?

I tried with different settings; same.
I have 2 AAVs in the airing cupboard, the heating one seems fine as water comes out when loosen. However, I unscrewed the whole of the red cup on the hot water AAV and nothing there, see photo attached, is this normal?

 

[yartin]

I put magnet touching the pump and started vibrating if means anything, I made a video but don't how to put it on here?!

 

[yorksbuilder]

Which valves? AAVs?

However, I unscrewed the whole of the red cup on the hot water AAV and nothing there, see photo attached, is this normal?

He means the 2 port valves, you called them divertor valves.
Your second comment also points you even more to check those valves, looks like you are onto it, one of them is probably faulty

 

[yartin]

He means the 2 port valves, you called them divertor valves.
Your second comment also points you even more to check those valves, looks like you are onto it, one of them is probably faulty

Both ports valves are making the noises when turned on and off from the timer; suggests they are fine I thought. System is behaving the same when hot water or heating turned on; boiler fires then shuts off after 20 sec. The heating port valve is new Hanwell 1 year old. It would be odd for both die same time.

 

[oilhead]

Change your pump. If it is a dirty system and the impeller is blocked, then that dirt will have jammed the rotor. If dirty, then clean flush it.

 

[yartin]

It's definitely NOT the port valves because boiler fires when timer set to HW or Heat stops after 20 sec and fires again after 20mins, why would boiler re start if it was/were port valves issue/s?!

 

[yartin]

Change your pump. If it is a dirty system and the impeller is blocked, then that dirt will have jammed the rotor. If dirty, then clean flush it.

Give the information; my retired plumber said exactly the same. It's been there since moved to the house in 2002. I just ordered the part. Cheers

 

[oilhead]

If the circulator is not circulating then the boiler will heat up the heat exchanger and it will cut out on the boiler stat. After 20 mins the boiler will cool down and switch back on.

 

[ChrisJP]

Change your pump. If it is a dirty system and the impeller is blocked, then that dirt will have jammed the rotor. If dirty, then clean flush it.

But the OP said in an earlier post that he was able to turn the pump rotor freely in both directions.