Worcester 280 Problem

[sprooser]

Hi

I've got a Worcester 280 that has an overpressure problem. It used to happily loiter around the 1-1.5 bar pressure but just recently the pressure has been much higher. I bled a radiator yesterday to get the pressure down to an acceptable level and then tried to diagnose.

On the FAQ Wiki it suggests that a constantly climbing pressure may be due to a seepage from the flexihose on the filling loop or a perforated heat exchanger. Well, my pressure isn't constantly rising...I've discovered it only rises when I turn the hot tap on - by about 0.1 bar each time. Turn the hot tap on ten times throughout the day and guess what? The pressure gauge reads 2.2 bar not 1.2 bar.

Additionally there's a small patch of water beneath the boiler - presumably from the overpressure - and every now and again (at pretty irregular intervals) I hear a very, very quiet groaning sound that sounds like it's from the boiler area - or it might be the patron saint of heating engineers rolling his eyes.

I put the heating on this morning just to see what would happen and the pressure gradually climbed up above 3.0 bar until I heard what I think is the pressure relief valve releasing a bit outside.

Does it sound like I've got a valve that needs to be changed or is the perforated heat exchanger the most likely diagnosis? The only reason I ask...I'm thinking of replacing the whole thing. Spending a small amount on getting a valve changed would be ok but spending £200+ on getting a new heat exchanger put in, well, Boiler Scrappage Scheme there I'd go.

Cheers.

 

[Agile]

First thing is to check the EXV. See FAQ.

Your words imply a diverter valve fault but this would be rare on your model.

Tony

 

[sprooser]

Thanks Tony,

By EXV, do you mean Expansion Vessel (ie Pressure Vessel?) I've seen the guidance for refilling it which is very clear. Strangely, mine appears to have the air refill valve on the underside...

I must admit I was wondering whether the Divertor Valve might be at fault. I'm in two minds here. Heating Engineer or Boiler Scrappage Scheme? I might be able to get £700 in total off a new condensing combi. What's that, about half price for a c.24kW output boiler?

 

[sprooser]

Well,

After discovering that even with the mains switched off for a few hours the pressure was still rising slowly (suggesting it's not a perforated secondary heat exchanger - right?), I've bitten the bullet and decided it must be my pressure vessel and followed the very clear guidance in FAQs gone at it with my bicycle pump.

I could only get the pressure down to 0.4 bar by bleeding radiators - I couldn't find an obvious drain cock to get it down to zero and I wasn't going to take a lucky guess. Nonetheless, the pump went onto the schraeder valve without a leak and I followed the guidance. Pump, pump, drain, drain, pump pump etc until it was just air which I left at 10psi.

However, when I released the bicycle pump from the pressure vessel a bit of water squirted out this time. I'm guessing that's a bad thing...

Filled the system back up to 1.0 bar and then put the heating on. Within 15 minutes it was at 2.0 bar and showing no sign of stabilising.

Is the diaphragm in my pressure vessel u/s? That's my best guess.