Knocking/banging noise from Airing Cupboard

[flipsix3]

Hi, I'm hoping that you good folks may be able to give me some pointers for initial ideas on an issue that's developed today - before I go down the route of calling in the plumber, only to find out it was something I could've sorted myself. I'll openly admit to not being overly technically minded, although I can follow straight-forward instructions

This morning, when our Central Heating and HW timer switched on, we got a knocking/banging noise from a unit within the airing cupboard - never happened before today (house is 15 years old or so, and we've lived here for 5). If I switch the CH to 'off' it stops, but I can leave the HW on.

The noise is coming from a unit that appears to sit on a pipe junction just before/after the pump - see photos. On the underside of the box there's a lever with an 'Main Open' setting, which the lever appears to be able to notch into, and an Auto setting.

The lever is situated somewhere in the middle at present and if I apply pressure toward the Main Open setting (without 'notching' it) I can feel it pushing against my thumb in time with the knocking - when I take my thumb away it 'pops' back toward the middle area and it feels as if there's been a release of some little amount of pressure in the system. If I notch it, it pops straight back out.

From initial searches I'm thinking an air-lock in the system and maybe I should be looking to bleed the pump? However the layout is not making it easy for me to apply pressure on a screwdriver and the adjustment 'screw' is tight to say the least.

Any thoughts?

General Layout:

Pump:

Unit making noise:

Switch panel:

 

[plumbplumb]

If it's coming from the 3-port (silver box) and your getting a knock every couple of seconds when there is a call for central heating it sounds like the valve is faulty.

I.e motor moves over to heating and it drops back out of position and continues to move over and keep dropping back out of position

 

[D_Hailsham]

The noise is coming from a unit that appears to sit on a pipe junction just before/after the pump

That is a motorized valve, which looks fairly new. Has it been replaced recently?

 

[flipsix3]

The noise is coming from a unit that appears to sit on a pipe junction just before/after the pump

That is a motorized valve, which looks fairly new. Has it been replaced recently?

Nope, certainly not since we've been here - and as far as I know not prior to that. House was a new build some 15-6 years back and if I was a betting man I'd say it was original.

 

[biscuit77]

Flipsix it sounds to me like the synchron motor inside the mid position valve is loose, turn the power off to your central heating at the main isolator and remove the silv cover there will be a motor in there with one or two screws securing it. Check if they are tight. If they're loose when you switch the heating on the motor will slip making the noise you described. REMEMBER to isolate the electrics first. If you dont feel comfortable doing this any decent heating eng should only charge a call out fee if its this fault. 15 mins max.

 

[D_Hailsham]

The noise is coming from a unit that appears to sit on a pipe junction just before/after the pump

That is a motorized valve, which looks fairly new. Has it been replaced recently?

Nope, certainly not since we've been here - and as far as I know not prior to that. House was a new build some 15-6 years back and if I was a betting man I'd say it was original.

That eliminates the possibility of the valve being part of a recent bad batch which exhibited similar problems.

 

[flipsix3]

Thanks guys, got a local plumber out to take a look who confirmed the problem being with the motorized valve - unfortunately there was some wear/damage in the unit - fortunately replaced at a modest charge and all up and running again.