New boiler

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Ethel | 19:17 Sun 08th Feb 2009 | How it Works
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If I replace my old, conventional gas boiler (central heating and hot water) with a new style combi boiler, what exactly is involved?

Will existing pipes have to be replaced, or just the boiler?


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as long as your exisiting ppes and rads are in sound condition then they wont need replacing unless you wanted them to be.

your system will need to be flushed before the new boiler goes in.
old boiler disconnected and removed, cylinder and tanks drained and removed, old flue hole made good.
new boiler installed after selecting a suitable position, possibly a larger gas supply will be needed to be run from the meter to the boiler. existing pipework adapted and extended to fit the new boiler.
will need a room stat, some sort of programmer (boiler may have built in one) and thermostatic rad valves fitted if you dont already have them
think carefully about the make of boiler and the power output you opt for. (id go for a vaillant or a worcester-bosch and around the 30kw mark for an average size house.)
you should be looking around �1500 to �2000 from an independant installer.
We had a man in the other day fixing our existing bolier.

We asked him about a combi boiler and he said before we could have it done we would have to replace the existing gas pipe that runs from the meter to the bolier, it needs to be wider.

Not sure who does that, the gas board or the person who fits your boiler, but it is an extra thing to consider (gucciman does mention it but you may miss it amongst his very detailed description).
Question Author
Thanks both - so not as frightening as I envisaged.
gucciman is bang on with his answer and price Ethel, regarding the flushing as rightly mentioned , a power flush can cost an extra �200 + which not all plumbers are geared up for so may not offer power flush, this can be carried out by another plumber, prior fitting of the new boiler by corgi reg plumber.
One other point Ethel there could be a fair bit of scrap copper and copper tank which is yours to sell for around �50 +
Question Author
As has already been mentioned, you might need to have a wider bore pipe fitted from your gas meter to your new boiler.

We had a new condensing combi fitted to replace our old conventional boiler a couple of years ago. It was 3 days work. British Gas quoted �3500, but we got a local trader with a very good reputation to do it for �3000.

New boilers take more gas when the fire up, hence the larger pipe.

All in all we are very pleased with it. We have instant hot water and a wireless thermostat, which makes temperature control much easier.

If you have an immersion heater and tank, all that will have to go.

Hope this helps.
Both the combi boilers I have used have had trouble delivering a decent flow of hot water to fill a bath...9 mins for 4 inches in my mother's case......The plumbers on Island say it's becuse our gas does not burn hot. If you are a bath type person it might be well to ask about the flow.( I seem to remember that Ethel takes a shower tho and they seem ok)
you mean you dont know???
the power of the boiler determines the hot water delivery, the central heating is largely irrelevant as even the lowest powered boiler will handle an average size house. basically, the more powerful the boiler the hotter and faster the hot water will be. id recommend an absolute minimum of 28kw and preferably 30kw or higher (they're up to something silly like 45kw at the moment!)
you can also buy a boiler with a pre-heat function, which will give you a much faster delivery of hot water but will cost more in gas to run.
and yes a more powerful boiler will need a bigger supply of gas and hence a larger diameter gas pipe, this can add significantly to the price of the job depending on how far from the gas meter the boiler is and what size dia pipe is needed, copper pipe is very expensive and gets more expensive as the diameter increases.

your system will need flushing to comply with the new boilers warranty but not necessarily power flushed, depends on how old and sludged up your old system is.

and theres nothing frightening about it ethel, just find 3 independant boiler installers, ask them what boiler they recommend and the power of it (let me know and i'll tell you if they're good boilers or not) and get written quotes. if you want to you can ask them to price for both their choice of boiler and one of your own. dont forget to discuss the size of the gas supply needed as you wont believe the number of installers who don't provide an adequate supply of gas to the boiler (and the boiler makers will charge you if you call them out because your boilers not working correctly and its an installation fault) finally ask them how they will flush the system as inadequate flushing is the number one excuse the boiler makers will use to get out of the warranty.
all you've got to do then is select your preferred installer and clear out of the house for the day if you can't stand the noise. inspect the work, try the hot water
If you have an airing cupboard you will lose the heat source unless you have another source fitted. This is worth remembering as I know you ladies like your airing cupboards!!
Hi Ethel,
Combi Boilers can scale up in hard water areas, but there are softening devices that can be fitted to help the problem- do a bit of Goggleing, and have a look here and here second one is a bit old, but most of the info is ok.
All the best.
i can see you now in the shower - naked

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