Swap Ravenheat Condensing Combi for Worcester Combi- Flue?

20 Jun 2011
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United Kingdom

I'm looking for some advice on if I need to buy an all new Flue or not for a replacement condensing combi boiler?

I currently have a Ravenheat condensing combi which has a vertical flue already fitted (100mm dia - 2x1m extensions with an exit through the roof). The Worcester 25Si I have bought which will be replacing it looks to take an identical 100mm dia flue (if I buy a horizontal to vertical flue adapter) but could somebody please advise if I need to buy a whole new flue or can I use the existing one? as far as I can tell they are both the same construction - looks like stainless steel inner tube with a plastic outer.

I want to get all the equipment necessary ahead of getting a gas fitter in to install it all.

Thanks in advance,
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I want to get all the equipment necessary ahead of getting a gas fitter in to install it all.

Thanks in advance,

Why, this is part of our job, he won't charge you extra to get the bits, get the RGI to sort all the parts himself as you have no idea what you're doing ( no offence ) and you won't get gas advise off this site, especially regarding the flue, read the site rules
Every few weeks we read about advice wanted "before calling the registered installer".

In many cases there really is no registered installer planned and its just a DIYers attempt to get the information to do it himself.

As stated we dont give DIY gas advice on this forum. If you really intend to have a registered installer then obviously ask him!

As far as I know those two flues are not compatible.

Also be aware that some installers will not fit boilers bought by the property owner. Those who do will rarely get involved in any warranty claims. If the installer supplies the boiler then he has some legal responsibilities as the supplier to you!

One wonders why you want to replace an existing condensing boiler! Have you failed to manage some DIY repairs?

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Ok Guys - you called my bluff.... I was just trying to get away with writing a short version of the story - here goes....

I have already spoken to 2 gas safe fitters - the first one said he couldn't come around to quote for a while so I offered to source the boiler if it made it easier for him to quote - he said it's just a straight swap 1 condensing boiler for another then quoted me over the phone £140 for fitting - I ordered a boiler online, thinking I just needed that and the controller. But then started thinking that it was very cheap, and I was worried there were going to be hidden costs.....
So I phoned another one to get a second quote - he came around and had a look and reckoned there was a couple of days work... Clearly a contrast in the amount of work required - but he said the flue might be interchangable....

So now knowing a bit more about it (emphasis on bit - i.e. the flue is more complicated than just plumbing the old one in) I phoned back the £140 bloke to find out what the quote included - flushing of sys etc and fitting of boiler - when I asked about flue he said I'd need to get one but he could fit. So that's where I'm at now and why I started looking for information on flues.....
I can assure you I have absolutely NO intention of fitting it myself! My DIY skills most definately do not stretch to this! My Ravenheat packed up a little while ago and I got a guy around to fix it but it's 7 years old and the bloke said it was a temporary fix and that I should look to replace the boiler. My wife is now pregnant so I suddenly find myself ...... encouraged..... to get all the jobs sorted, and really can't afford to be messing about with not having hot water/heating when it comes to winter!

Sorry for breaking the rules - I read the stickys but was only looking for somebody asking the same question. apologies. Thanks anyway.

Most people on this forum would be very suspicious of anyone fitting a boiler for £140 !

Did you tell him its a vertical flue? It may not even be in the same position on the new boiler!

Lets say he does not power flush as recommended and just uses chemicals, X800 sludge remover and X100 inhibitor. They cost about £32 !

That then leaves him £108 for fitting and commissioning the boiler. It also has to include sealoing the flue that might need a new roof plate and some sealing goo all at further cost.

He must be very desperate for some work!

What exactly went wrong with your Ravenheap? It's not a great make but even so fixing it should be cheaper than a new boiler!
The Ravenheat wouldn't fire up. The fan would start but then the light came on to signify that there was no flame. The bloke who fixed it at the time took the fan assembly off and lubricated up the bearings - apparently the fan wasn't spinning fast enough. He phoned for the cost of a replacement fan and it was something like 300-400quid so I just decided was best to get a replacement as he said it was a crap boiler anyway and was getting to end of useful life...

Thanks for advice guys - think I'm going to go for a 3rd quote as think 2 days work is excessive and £140 (2 hrs?) is too short (worried there will be hidden costs that appear half way through job that I haven't budgeted for). And get them to have a proper look at the current flue installation.
No, £840 and that isn't too cheap!

Just reasonable when the job is done properly using the right chemicals.

But that would not include any accessories for fitting the correct vertical flue. If they are done properly they dont leak.


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