Rattling noise on Puma 80e after HW/CH turned off

Hi all,

The Low Pressure light on my Potterton Puma 80 combi boiler recently came on and the boiler stopped firing up for both HW and CH. I checked the pressure and sure enough it was around 0.5 bar. I topped it up to around 2 bar (where my red pointer is) using the filling loop, but the Low Pressure light stayed on and the boiler failed to fire. I topped it up till it was at 3 bar but still no joy.

After searching this forum for hints it sounded like the Pressure Switch may be stuck or broken. I disconnected this on the PCB, turned a hot tap on and hooray, the boiler fired up! However whilst reading around I realised I'd been foolish in letting the pressure get so high, so I bled the radiators till the pressure was 1.5 bar.

HW and CH are working, but the problem is that the boiler makes a loud rattling noise when the taps are turned OFF. While they're on it's making the "normal" amount of noise it always has. I turned the CH on for 30-45 mins and again it made a normal amount of noise, but after a while it started rattling, getting progressively more unsettling and louder until I turned it off. The radiators do get hot and there's hot water coming from the taps, so it's just the noise and the stuck/broken Pressure Switch that are worrying me.

Any help would be much appreciated!

Yours shivering,

Ciaran

EDIT: Just to add - the HW & CH were working fine until a couple of days ago, before the Low Pressure light came on.

I also turned off the mains water recently to fix a leak with the dishwasher. A few days before the Low Pressure light came on I had to loosen the mains stop cock as the cold water pressure was too low.

The pressure switch can be cleaned internally,

to do so,
drain system, remove switch, there will probably be a black 'dot' in the middle of the brass base, use a small sharp instrument to remove this 'dot' it's actually a hole about 10mm deep, finally flush under clean cold water and refit etc

A new fan will quieten a Puma considerably (its never been so quiet)

but your noise is more than this!

Is it a water/boiling/air noise? or metallic/grinding noise?

Hi baxpoti, thanks for the advice, I'll take a look at the pressure switch tonight.

I had a proper listen to the noise last night and it sounds like a rotor blade (as on a fan or pump) that's blocked. It doesn't sound like "kettling" as it's not a banging, explosive noise or popping noise, more a rhythmic rattle with a bit of a whine! God noises are hard to describe!

So the fact it was rhythmic made me think it might be the pump, so I had a listen to it and it certainly seems to be coming from that direction. It gets damn hot too, but since I know little of how boilers work, I presumed that could be because it's pumping hot water! Does the pump operate when ONLY the HW is on and does it continue to do so for a minute or so after the HW is turned off? Or is this the fan I'm hearing?

With a cold boiler check the pump spindle (big black nut on the front of pump) is free (have a rag ready) it should spin easily and continue to spin freely when you let it go for a few seconds.

If its a permanent pilot the fan runs continuosly (albeit at low speed when no demand)

I would go for the pump first as this is a much cheaper option

It's just possible your pressure relief valve started letting out water when you got it to 3 bar, and is therefore still doing it (cos they do ), making a noise. Check the pipe outside. You would also be losing a bit of pressure, but sometimes not a lot.