Worcester 240 Boiler - Water pressure suddenly increases

[Jen_needs_help!]

I have a Worcester 240 boiler - I have recently had problems where hot waters does not come on. An expert has been out & told me to increase the pressure so it is between 1 & 2 when it happens which has fixed the problem in the past. Same thing has happened tonight, when I have increased the pressure & turned the hot tap on, the boiler fires up for about 30 seconds then the water pressure valve suddenly increases past 3 then 4 and makes a noise like it's about to blow up! So I turn the water off. Has anyone any idea what might be wrong. I scared to keep trying it in case it does blow up! As i'm sure you can imagine it's freezing tonight and I have no hot water or heating! I would be extremely grateful for any advise. Thank you.

 

[gas4you]

Sounds like the expansion vessel needs re-pressurising or replacing.

Are you actually getting hot water out of the taps when this happens?

 

[Rob]

Sounds like the pump has failed. This model may have two pumps in which case you may still have htg which in turn will provide some HW untill it is repaired.

If it only has one then this needs replacing although a new boiler should be given some thought as these are getting on a bit.

 

[Jen_needs_help!]

Thank you. Yes hot water comes through then the gurgling noise starts. What do you think would happen if I left it on whilst the noise and pressure increases? It it not advised to try?

 

[gas4you]

No don't try it. Put yer thermal knickers on for tonight

Do the radiators get hot at all?

rob could be on a better track than me with the pump stuck at present

 

[Jen_needs_help!]

I've just dug the thermals out!! :

I haven't tried the radiators - just got home from work & wanted a shower! The radiators did work fine last night though.

Thanks for your advice - I'll call the expert out AGAIN!!.

 

[Jen_needs_help!]

Thanks for your advice Rob - I was dreading somebody saying a new boiler might be needed!!

 

[Agile]

Although they are getting a little long in the tooth they are still quite maintainable.

However, you do need a competent engineer. As Rob suggests it sounds like an EXV problem.

I have never seen a 240 with a spare pump inside though.

Tony

 

[gas4you]

Tony you really have had a bottle or 2 tonight

Rob said pump, I said exp vessel

 

[Agile]

Sorry Dave, I was distracted by heavy thinking searching for memories of a two pump 240 !!!

Dave first said EXV and I second that!

Not so sure about the second pump though! Thought that was the Viessmann, 280 or that old one.

Tony

 

[Rob]

Ive never know an expansion vessel to make a boiler bang at 3 bar!

With regards to the two pumps i must be thinking of the 350!

 

[Agile]

Customers think a PRV sounds as if its about to blow up! One who called me had called the Fire Brigade !

I think its one of the 35 CDIs with two pumps screwed into the backplate which contains all the water ways. They never repeated that so it must have been unsucessful.

Similar arrangement on an older Viessmann to where the two pumps are DIFFERENT !!!

Tony