Optimal boiler / shower configuration?

[pete1980]

Hi, we're currently having an extension built, and looking for some suggestions on the best options around boilers and showers please.

The house is currently a 3 bed semi with one family bathroom (bath and shower), heated by a 30kW combi boiler. Our current combo boiler works fine but is around 10 years old so probably nearer to the end of its life than the beginning.

After the extension is complete it will be 4 bed with 3 bathrooms all with showers. Two of the showers will be used regularly and potentially at the same time. The third shower is downstairs and will have occasional use only (e.g. after gardening etc). We are also adding a decent sized downstairs extension which will have underfloor heating (central heating powered, not electric).

We are wondering what the best option for us will be please?

Our original working assumption:

• Replace the boiler - cost included in the builder's quote for another Worcester Bosch Combi boiler of an appropriate size, probably 40kW
• Both upstairs showers powered off the boiler
• Downstairs shower to be an electric shower, so we have a backup e.g. if the boiler broke down.

However we had a comment from the plumber that Combi boilers aren't great for multiple showers running simultaneously, though going for a larger 40kW model might be OK? What's the best option for us please?

• I wondered if a better option might be to put an electric shower in the new upstairs bathroom instead, as it is then unlikely that the two boiler fed showers would then be used together.
• Would a 40kW combo boiler be passable with two showers running together, or would a different boiler type be more appropriate (System boiler etc)
• If we don't need the boiler to be able to support running two showers together, then is 40kW still about right or is this an overkill?
• The builders have factored in the cost of replacing the boiler with another Worcester Bosch model, is this a reasonable choice? The plumber suggested 'Baxi would be better value and has a longer warranty, but my gut tells me to stick with Bosch.

Any advice gratefully appreciated.

Thanks,
Pete

 

[Dan Robinson]

my gut tells me to stick with Bosch.

Why?

A 40kw combi is mahooooosively over sized for the heating and undersized for the hot water . Yes , two flow restricted showers will function , but they won't be very luxurious .

Stored water is the best solution .

Builders are the last people to be advising you . Let alone doing the work . As demonstrated by the automatic solution of slinging the biggest combi they can think of (their imaginations being limited ) at the wall and hoping for the best .

 

[Dan Robinson]

If you're adamant that you want to stick with a big combi boiler as the solution , perhaps changing the thread title to "least schit boiler - shower configuration "

 

[pete1980]

Hi,

To clarify - yes it is the plumber advising us, who the builder subcontracted to - the working assumption was just what was in the original tender pack, we're not adamant on any solution hence the post to see what's best.

What are the pros and cons between a stored water solution and a combi boiler running one shower with the other as a a (decent) electric shower, both cost and performance wise please? (I am ignoring the 3rd shower in this as it will only be used very occasionally).

How much extra space does a stored water system need vs a combi boiler, and what would be an appropriate size of boiler? The house will have 10 radiators and one open plan area (around 50m2) with under floor heating running off the boiler.

The 'gut feel' comment around sticking with Worcester Bosch was because our current boiler has been very reliable and they have a good reputation. I don't know much about Baxi but they seem to be a more mid-range brand, and not seen as many positive comments etc. Is a 10 year warranty really worth it or would it be full of small print / exclusion clauses etc?

Thanks
Pete

 

[pete1980]

Sorry one more question - how about the Worcester High Flow combi boilers (or similar) - would they be worth considering?

Thanks,
Pete

 

[oilboffin]

Go for an unvented cylinder and a smaller boiler I would think you'll save a bit of cash in the long run.Bob.