Worcester 28i junior showing 4 bar

[stjon]

Hi all - I'm new here so please be gentle! I have a problem which I'd love to sort out myself but would appreciate some guidance - I'm no plumber so I'll go an expert if needed. I will try to give you all the relevant info. Our boiler was installed about 8 years ago and has worked fine until now. We still have hot water at the taps and central heating (although it's switched off until I get this sorted). If I run the central heating, pressure rises quickly to max 4 bar, at which point I panic and switch it off! When it's off, the pressure seems to stay at 4 bar. I can bleed off a pint of water at a rad and pressure drops to 2 bar, but when I run the heating it rises up again. The water refill tap on the steel braided pipe is definitely closed. The FAQs seem to suggest a faulty heat exchanger - this means little to me at present, but if it's a DIYable job I will research it and have a bash.

Any advice greatly appreciated!

Steve

 

[conbow]

Expansion vessel will require recharging or replacing.

 

[jackthom]

After it has risen hot to almost 4 bar, if you then let the boiler cool down does it eventually return to something more sensible around 1bar ?

(It wasn't clear whether you were removing water from the system each time it goes high pressure in which case there's a different problem.)

As conbow says, it's likely the expansion vessel which needs seeing to.

More info here...
//www.diynot.com/forums/plumbing/faqs.37170/[/url]

 

[stjon]

Hi guys- many thanks for the replies. To clarify, the pressure stays high even with the central heating turned off. When a hot water tap is run, the pressure dial momentarily drops slightly, then rises back to previous level. I've also now noticed that when we initially run the hot tap there is a banging in the boiler which stops if we turn up the tap ie increase the hot water flow through the tap. If the tap is left on a low flow rate, the hot water seems to 'stop and start' a little in time with the banging? I don't know if this is relevant...

 

[45yearsagasman]

Have you checked the exp vessel? If not, do it as suggested.

 

[stjon]

Will do that thnx. As far as I can tell the front panel should not be removed by an untrained person (ie me!) because it forms part of the combustion chamber. I can't get to the boiler until tomorrow, but I'm just hoping the drain cock is accessible from underneath (on the RH side I think as I look at it?).

 

[TCCHeating]

As previous poster has already said. When you drained pressure from a rad, does the pressure rise back up to 4 bar when the boiler is cold? If it does then it is an expensive repair. The old 28 junior has a dual heat exchanger. If this has gone, it probably makes more economic sense to replace the boiler.

Ps. Remove the braided hose from the filling link. Just because the valves are closed doesn't mean they are not passing. You have to physically check to be sure!

 

[stjon]

Good point re the braided hose - I'll check! Good news (if there is there is any) is that when I drain down a rad and pressure reduces, no, it doesn't rise up again if system is left cold. So I'll get onto repressuring procedure in the morning. It's gonna be a cold night! Thanks again for the support.

 

[smellmycheese]

If it's not a greenstar boiler (condenser) then the filling loop is letting by. No other explanation.

 

[stjon]

How do I identify if it's a Greenstar please? Greenstar is not mentioned anywhere on the outside. Simply Worcester 28i Junior...thanks!

 

[stjon]

I uncoupled the braided hose nearest the boiler and the on/off tap does seem to work properly. So onto draining/repressurising. I'm assuming the white plastic nipple near the pump is the drain cock..

 

[McCombi]

It sounds like standard efficiency model, there will be a blockage in the pipework between pump manifold area/pressure relief valve and pipe to expansion vessel.

It's not the easiest job to fix, you will probably find the boiler won't drain via drain point you mentioned as usually these will choke up too if above parts have also.

 

[stjon]

Update - drained boiler to zero bar - seemed to drain fine so don't know about a blockage? Did about 6 pumps with a bike pump to repressurise - the dial on the front rose to about 1.5 bar. Then the worrying stuff...disconnected the bike pump and the boiler dial slowly dropped back towards zero - should it do that? I let in water slowly to bring it back up to 1.5 bar. Then turned on central heating and the dial slowly rose back to 4 bar, at which point I switched it all off. Sounds like a bigger problem? I can't remember at what point I turned mains water back on - before or after repressurising the system - could that be significant?

 

[McCombi]

Pump the vessel again, this this leave the boiler drain point open into a bucket whilst you're doing it.
If the gauge ends up rising on boiler whilst you are pumping but no water is coming out from drain point then there is a blockage somewhere.

If so, probably best to get someone in. Might cost you but you said earlier it has been trouble free since install, pretty much unheard of in that model of boiler imho, you've been lucky.

Good luck

 

[stjon]

Final update! I did as you suggested and water pumped out of the drain plug so no blockage? I've drained / repressurised 3 times and each time the pressure rises towards 4 bar when heating is on. I did note that the schrader valve seemed to be leaking so I removed and replaced the core, which seemed to sort that, but the bigger fault seemed unaffected. It [/i]feels as though it is taking much longer than before for the pressure to rise, but it still eventually gets there. At least I've learned a bit about my combi boiler, and thanks to all who replied and supported!
Steve