# Worcester Bosch Boiler Problem



## Chris_Foci (Feb 21, 2006)

Hi

I know there a lot of knowledgeable people on here, just wondering if anyone can help with an issue with my Worcester Bosch 28CDI RSF Combi?

The boiler is around 12 years old and had a new expansion vessel and diverter valve in the last 18 months. 

Recently it has started gaining pressure on its own getting up to 3bar before i manually drained down a rad to lower the pressure. Ive now got to keep draining down a rad about once a week to keep the pressure down. 

The filling loop is closed so no water getting in that way. A quick google search has suggested an internal leak on the heat exchanger could be to blame?

Any ideas?


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## davies20 (Feb 22, 2009)

Our old vaillent started doing this after we had a new expansion tank + prv fitted. We thought it might be a filling loop issue but never found out as we moved!

Side note, it's 12 years old, get a new'en whacked in like I've just done in the new house!


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## Deathstar (Jan 13, 2013)

I would suspect the expansion vessel.
Check and see if there is any air in it, as it may need re-pressurised. 

Sent from my SM-G930F using Tapatalk


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## Chris_Foci (Feb 21, 2006)

There is air in it. I checked the schrader valve and it gave a good hiss. No water came out of it thankfully.

Any ideas how to rule out the expansion vessel?


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## 182_Blue (Oct 25, 2005)

Are you just getting water out of the radiators or or you getting air out ?


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## funkydunk (Aug 16, 2016)

Does the pressure go up with the boiler turned off. Or when the heating is on.if it goes up with the boiler off it could be the plate to plate heat exchanger (although i can't remember if that boiler has one). Or you will need to properly check the filling loop first ( take it apart if you can). If it goes up only when the heating is on then its definitely the expansion vessel which because you only get air coming out the schrader valve can be repressurised, but you will need to drain the heating to do this properly.


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## Chris_Foci (Feb 21, 2006)

I am only getting water out of the rads, there is no air in them at all.

I will turn the boiler off overnight and see if the pressure rises, problem is it does it over about a week and need the heating as we have a baby so will need it back on in the morning. 

What pressure should the expansion vessel be pressurised to? I can drain it down tomorrow and check it and re pressurise it if its too low.


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## funkydunk (Aug 16, 2016)

Think its about 0.9 bar. It should say on the side of the vessel


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## Chris_Foci (Feb 21, 2006)

Just an update to this. I drained down the system and checked the expansion vessel pressure, it was at 0.25 Bar. It should be at 0.5 Bar. Is this enough of a pressure drop to cause problems? 

I've 're pressurised it up to 0.5 Bar regardless.


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## Chris_Foci (Feb 21, 2006)

Anyone have anymore ideas on this? I topped up the pressure in the expansion vessel and I am still having the same problems.


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## donnyboy (Oct 27, 2005)

Try changing the filling loop. Its cheap to do. They can start 'letting by' and its enough to build the pressure up with the boiler off.

I had a pressure problem when the wee black tap broke off. I was topping it up using pliers. I hadn't turned it off properly and the pressure rose up within an hour or so.

If the loop is faulty it could take longer to rise at a slower rate.


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## wanner69 (Mar 14, 2010)

Chris_Foci said:


> Anyone have anymore ideas on this? I topped up the pressure in the expansion vessel and I am still having the same problems.


I have a thread running on here too but having the complete opposite pressure going to zero after heating has finished everyone tells me it's the expansion vessel so getting that changed out soon


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## donnyboy (Oct 27, 2005)

wanner69 said:


> I have a thread running on here too but having the complete opposite pressure going to zero after heating has finished everyone tells me it's the expansion vessel so getting that changed out soon


When expansion vessel on mine went, the pressure would rise up to 3 when the heating was on. This would trigger the PRV and I would get a drip from the pipe and lose some pressure.

Sometimes you can re-pressure the expansion vessel with the heating drained. If the diaphragm is burst it will just keep doing the same.

You could have a leak in your system, and if its under a floor you might never find it.

Ive used this type of stuff in the past - https://www.screwfix.com/p/fernox-f...od-LsJFA#product_additional_details_container


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## Chris_Foci (Feb 21, 2006)

Thanks for the replies. Having done some research it appears as I have an integral filling loop with a key to lock and unlock before you start to fill the system a passing loop is near on impossible. 

Anyone with knowledge of this boiler confirm? If this is the case I will buy a new plate to plate heat exchanger and replace that. Id rather not keep throwing parts at it due ti its age incase I do need to bite the bullet and get a new boiler fitted.


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## GP Punto (May 29, 2007)

I feel like I am in the stone age, the house was built in 1983 and the boiler is the one that was fitted at the time, it has had one service in 20 years, I asked the servicer does it need a service, he said no because the gas is now so clean. Had a new Worcester boiler fitted at another house and it was nothing but trouble, got a mate who put a £2000 boiler in his house, the tank went at 2 years old and out of warranty, told that he might as well buy a new boiler. Another mate spent £6000 on a German system with sensors everywhere dealing with rooms that were being used and outside temperature, nothing but trouble.

I will keep going with this boiler until it must be changed, I know its the boiler equivalent of the Morris 1000 but it always works and never goes wrong, it even heats my garage!


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## streaky (Dec 2, 2006)

I've got a Worcester oil Boiler. Routinely breaks down every year despite servicing. Biggest pile of c r a p going.


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## funkydunk (Aug 16, 2016)

You are right about the filling loop. Did you check whether the pressure rise is all the time or only when the heating is on.


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## Chris_Foci (Feb 21, 2006)

funkydunk said:


> You are right about the filling loop. Did you check whether the pressure rise is all the time or only when the heating is on.


Very difficult to check as I can't leave the heating off for more than overnight as we have a young baby. The pressure rises over a few days. I've bought a new plate to plate heat exchanger for it today which should arrive in the next week so will see what happens when I put that into it.


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## Karl woods (Mar 15, 2012)

I feel your pain, I have a two year old grant combi and when it’s running the pressure slowly rises to 2.5 - 3 bar and dribbles water out from the pressure relief valve until the system is empty (usually when I’m at work and the wife’s at home on her own),it’s had a new pressure vessel as when I checked it had water in it, then it blew the top off a sensor so I’ve replaced it to.
The boiler before this one was only 5 year old and it was nothing but trouble and had to be replaced, feels like this one is going down the same road, a right pain in the butt.


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## sshooie (May 15, 2007)

GP Punto said:


> I feel like I am in the stone age, the house was built in 1983 and the boiler is the one that was fitted at the time, it has had one service in 20 years, I asked the servicer does it need a service, he said no because the gas is now so clean. Had a new Worcester boiler fitted at another house and it was nothing but trouble, got a mate who put a £2000 boiler in his house, the tank went at 2 years old and out of warranty, told that he might as well buy a new boiler. Another mate spent £6000 on a German system with sensors everywhere dealing with rooms that were being used and outside temperature, nothing but trouble.
> 
> I will keep going with this boiler until it must be changed, I know its the boiler equivalent of the Morris 1000 but it always works and never goes wrong, it even heats my garage!


Ditto, I'm sitting in the garage now with my 20 year old Ideal classic chugging away in the background. I've lived here for 10 years and never had it serviced, we bought the house from friends who moved in when it was new and it's never been touched.

I have CO detectors in the garage (not used for a car) hallway and landing linked to the intruder alarm so I'm comfortable wit the sealed boiler in any case.

I rent a couple of houses out, one with a Worcester Bosch Jr that I had fitted new around 10 years ago, that's had a couple of call outs, one from Bosch as they were the cheapest to replace a plastic manifold that had split.

Another house I had a Vokera that faulted every 12-18 months, fans and diaphragms iirc, it's now a Baxi that's had 2 faults in 9 years, and another with some cheap Italian piece of **** in it that's been faultless. All are serviced annually obviously by the same guy and the Italian one amuses him as it's the most reliable one.

Keep it simple imo.


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## GP Punto (May 29, 2007)

sshooie said:


> Ditto, I'm sitting in the garage now with my 20 year old Ideal classic chugging away in the background. I've lived here for 10 years and never had it serviced, we bought the house from friends who moved in when it was new and it's never been touched.
> 
> I have CO detectors in the garage (not used for a car) hallway and landing linked to the intruder alarm so I'm comfortable wit the sealed boiler in any case.
> 
> ...


Thats the advice I have been given, dont make changes unless you have to.

I was talking to an architect who is very into heat sinks and reccyling waste hot water and Scandinavian kit houses that are hugely efficient. He does house conversions, people spend £10,000 to save £300 a year on gas bills. I asked him what he did with the old boilers - throw them away? - Not a bit of it, he keeps them all and puts them in his houses and those of friends, they are less efficient but never go wrong.


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## GP Punto (May 29, 2007)

Just had a central heating engineer in today to put some inhibitor and cleaner through the radiators. I asked him about Worcester boilers and he was very critical saying that there was some very cheaply made aluminium parts inside them, lots of problems and expect to replace the boiler within 10 years. The only boiler that he would recommend is Eastman.

I asked him about replacing my 35 year old boiler and his view was to keep it as long as you can, very simple boiler, cast iron with few sensors to go wrong, all it does is heat water.


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## P4ULT (Apr 6, 2007)

I have been in the gas industry for over 20 years and fitted many different brands. For me Worcester are my go to boiler, I get very little problems with them and if I do then their warranty s second to none. If you buy wisely you can also get a ten year parts and labour warranty. I have fitted a couple for parents and in laws up to ten years old and none have had any faults.


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## Chris_Foci (Feb 21, 2006)

Just to update this, I fitted a new heat exchanger last week and it's been holding its pressure perfectly since. 

Thanks for everyones help!!


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## Itchy finger (Feb 8, 2018)

While reading through the thread I was think it's going to be the plate to plate heat ex. Sounds like you have sorted it. 

Worcester boilers are better then most brands in my experience, i fit 20-40 of them a year. Every boiler has its problems, the biggest reasons for any modern boiler breaking down before you would expect is poor installation and maintence. Normally if it's fitted to a dirty system and under gased it's going to break down and perform poorly.


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