Worcester boiler very noisey & cutting out - is it the p

[Snowy]

I have been hunting through old questions but can't seem to find the answer to this - apologies if I've missed it somewhere.

I have a Worcester 24SBi on a sealed system which serves the central heating and hot water (in pressurised tank). Boiler is about 2 years old and up until 2 days ago has been working everyday with no problems at all.

Now when the boiler switches on it heats up the rads but after about 10 mins it starts banging and clattering, the pressure gauge goes crazy and it cuts out. If you leave it for half an hour or so - and do not reset the system - it will fire up again and go through the same process again.

I had an engineer out yesterday. He took the front screw off the pump and twiddled inside. It then worked fine all the time he was here and he said the pump had probably got stuck and should be OK now. Inevitably it only broke again after he left.

I have rung them back and they tell me the system needs inhibitor and then flushing a week later. Some of the messages I have been reading on here that mention similar symptoms speak of problems with the boiler stat. Can you tell from my description if it is sludge in the system or the stat? (by the way, boiler was new 2 years ago, but was fitted to old system).

thanks in anticipation.

 

[taydo]

is the pump working, if it had jammed it has quite likely burnt out. or turn the stat down to the min and see if it still does it.

let us know what happens

best regards

Brian

 

[Snowy]

Hello Brian,

I have a worrying new symptom - went downstairs to try out your suggestion of turning the stat down and there was water dripping from the boiler. This is coming from a small black valve on the top and is frothing slightly and looks rusty in colour.

I have turned everything off...

By the way, I do believe the pump was working earlier - could feel vibration

Help!

 

[Snowy]

maybe it looked rusty because of dirt on top of the boiler?! The water is now clear, but still seeping out...

 

[taydo]

ok this black knob on top of the boiler does it turn if it does turn it off turn the stat down and start the boiler moniter it carfully see what happens

the knob on top sounds like an auto bleed valve this has blown its seals due to the pressure build up in the boiler.

if it isnt the stat you will need to flush the system through and you will probably have to replace the abv as well.

 

[Snowy]

Thanks for all your help.

The 'black knob' is on a screw thread, so have closed it down and run the boiler on min.

It appears to be ok on this setting. It has heated up and cut out normally when up to temperature. Have watched it do this a couple of times.

OK, so I will sort out some inhibitor and flush the system - am I right in thinking we should run it with inhibitor for a few days/a week before flushing?

Is it safe to run on min for this time with that abv closed down? or do we need to get that fixed first?

Thanks again.

 

[taydo]

ok run it for a little while and then try opening the auto bleed valve a little if it still leaks you should really get it fixed but as long as you open it once a day to release any air in the system you should be ok. play with the stat a little try turning it up a little until you get a happy medium. buy some central heating cleaner follow directions then drain flush through and re-fill with inhibitor

Good luck

 

[Snowy]

The bleed valve leaks water constantly when open, steam when boiler is going crazy. So have kept it shut when running and released steam after cutting out, but it obviously needs fixing!

We added inhibitor last night but still the longest it has run without going bang is only 20 mins - and that is when trying from cold - when system is warm it goes for max 10 mins. (and the only time it has cut out 'normally' was when watching it before my last posting yesterday - sod's law)

This morning have tried again, but while in it's 'cooling down' phase there was a bang and the fuse went on the main switch on the wall and it tripped the mains. Have replaced fuse but no light at all on boiler so something has blown inside.

So now clearly need a professional on site. Have put a call in to the engineers. They are talking probable new pump and new circuit board (though will try to free old pump before fitting new and will try fuses on board before fitting new).

Anyway - thanks again for all your help and advise.

Cheers

 

[COG]

first off your auto air vent is blowing beacaus you keep overheating the boiler ,the pump may be going but is it going but is the water ? ,in other words your syptoms are describeing a stuck moterised valve the pump may be spinning but the valve may be blocking its path.The SBI can have an internal moterised valve or external ones fitted, dop the front panel down and look if its internal you will see a black plastic body with three ports and a white box on top.