Worcester 28CDI Combi boiler - very low pressure

GrayCope1983 · 26 Apr 2011

Hi there.

We have a problem with our boiler as everyday I am having to wait at least 5 minutes if not longer (a whole sink bowl of water) before the hot water starts coming through the taps. The pressure stays at 0 and doesn't go above even when we use the shower. Also on the odd occasion when my wife has been in the shower, the boiler has made some very loud/strange noises. It is extremely annoying and I am not sure why this is happening.

My dad and I have tried adjusting the pressure valves underneath using the supplied keys but nothing has been happening. Infact one of the elements for adjusting the pressure broke while we were trying to adjust the pressure so we had to improvise with another tool and again this did nothing.

Before I have to spend money on getting someone out to look at / repair the boiler, I was wondering if anyone has any advise or would know why this is happening? And what needs to be done.

A quick response would be greatly appreciated please.

Many thanks
Graham

picasso · 26 Apr 2011

although this is the greenstar its very similair to the cdi in the way its filling loop works, although I think you have other problems with your boiler not related to the low pressure.

http://www.youtube.com/watch?v=1Ea7czrQmsY&feature=related

bengasman · 26 Apr 2011

The WB fillers are a bit special; do it right and they will never seize, do it wrong, and they break.
As you have proven you are not au fait with it, you might as well have a universal filler installed; won't be much difference price wise.

GrayCope1983 · 26 Apr 2011

So you think it might be the filler that needs relpacing? Do you have any idea how much it would cost for such a repair. I am goign to get quotes obviously but just a ballpark figure would be helpful. Many thanks Graham.

nickso · 26 Apr 2011

the filling section is not expensive and it only takes 30ish mins to fit.

two things though. are you sure it's a sealed system? a lot of 28cdi's were fitted as an open system. secondly the pressure on the guage has nothing to do with the flow at the taps.

GrayCope1983 · 26 Apr 2011

Thanks for that.
To be honest I know very little about boilers. Wouldn't know if it is a sealed system or not. I assume this makes a difference?

The pressure has stayed at 0 for a long time now. Doesn't rise at all. Heating still works and taps take 5 mins + to reach temperature.

What would you say is the most likely of problems with the combi boiler?

Just so i can describe it to a repair man.
Thanks Graham

bengasman · 26 Apr 2011

GrayCope1983 said:
So you think it might be the filler that needs relpacing? Do you have any idea how much it would cost for such a repair. I am goign to get quotes obviously but just a ballpark figure would be helpful. Many thanks Graham.

We don't do price comparison here; it is both boring and pointless, as it depends largely on the local situation.

gayzar · 26 Apr 2011

By the sound of things if your hot water takes that long to heat up and the boiler is making noises when you run the hot water I would say your heat exchanger is getting clogged up.

MrGassafe2011 · 28 Apr 2011

Open Vented System = You will have a Feed and expansion tank in loft
Sealed System = No Tank

As for the filling loop - As suggested these can cause problems - Sounds like a Div Valve problem if water takes ages to come through - Does CHB Fire when tap opened ? And is CH Working ok on it's own ?

GrayCope1983 · 5 May 2011

Hi regarding the same problem, can you please help?!

Following the posts on here I have had a gas man come out yesterday who add a new filler system to the bottom of the combi boiler. This one has two black mini levrs that you turn to let flow theruogh.

The pressure is now up when you turn these. The heating is working fine, however we still have the same issue with the hot water taking ages to heat up. For some reason it seems to come out quicker if i turn the heating on, which is silly.

Also, there is no LED showing on the tap section of the boiler either.

The gas man did mention that the large red cyclinder had water at the back (which was dripping at times), but said he would be reluctant to touch this unless it gets worse as due to the pressure being low for a long time i might have an effect on it.

Any advice on why I am still not gettnig hot water as quickly as thought would be appreciated. From your posts it sounds like it could be Diverter Valve, but I am by no means familiar with heating/plumbing.

nickso · 5 May 2011

sounds like it needs a bit of an overhaul.

if you turn a tap on and the red light with the tap symbol does not come on then either the diaphragm or the microswitch are at fault. i would be inclined to change the whole diverter in this case though, you can bet you would change just the diaphragm to find the diverter part is sticking.

if the expansion vessel is dripping water then it likely needs replacing. i usually just cap them off and fit a remote vessel as they are a cow to get out and it usually ends up with plastic manifolds breaking and all other kinds of mayhem.

GrayCope1983 · 5 May 2011

Thanks Nickso,

Weirdly, I can get hot water to my taps when the heating is on (the water demand indicator light remains off however) but when I turn the heating off, I just get cold water.

You think it might be the diaphragm then? When you say possibly changing the whole diverter what sort of price are we talking for these jobs as ball-park figure? Spent around £50 yesterday just getting the pressure gauge to work with the new pipe the boilerman fitted?

MrGassafe2011 · 5 May 2011

Think you need a new Div Valve section and if Exp Vessel gone 90% of the time it is the Core Shraeder and NOT The Vessel itself !!

Either way an RGI is Required

nickso · 5 May 2011

if the shraeder is leaking lots of water the vessel is goosed anyway whether or not the shraeder is, replace as my original post. sometimes they have a little condensation in them which is fine.

your man reckons it's leaking from the back? then the seam has burst, replace as above.

prices for a new diverter could vary a lot as some RGi's wont touch it with yours and others will charge the earth or a reasonable price depending on how often they have done it before.

GrayCope1983 · 5 May 2011

So from your expert experience would you recommend I contact an RGI or local engineer and mention what you have posted or see what they suggest? I don't want them to fob me off with other issues I have no idea about?

Sorry guys, I really appreiciate all your help. Thought it would be quite a straight forward job initally but sounds more complexed now.

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Worcester 28CDI Combi boiler - very low pressure

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