Boiler size

[magico]

Hi all.
After a bit of advice or reassurance.
I have a 3 bed semi at moment with 6 average rads 2 small rads and 1 bathroom towel rail. I' doing a 1st floor side extension so gonna need another ensue towel rail and a radiator for bedroom.
I have a year old worcester 25i combi boiler. Would that be OK size to run the 2 extra rads?
Many thanks

 

[flameport]

Extra radiators - yes.
Extra bathroom - certainly not.

 

[magico]

Thanks for reply.
Im guessing you mean for hot water feed.
So running a bath in main bathroom and having a shower at same time in ensuit ect...
Is a no no

 

[flameport]

So running a bath in main bathroom and having a shower at same time in ensuit ect...
Is a no no

Exactly.
Or two showers.
Or two of anything that uses hot water, including the kitchen.

That boiler can do 10 litres / minute at absolute best - just about good enough for one shower, or a bath if you don't mind waiting for 10 minutes.
If you have 2 outlets, then it's 5 litres per minute for each at most.

 

[magico]

Hence why the shower dips in temp when washer or kitchen tap is turned on. I thought so from what I'd already googled . .but for the time being as only 1 bathroom will be used at once it'l have to do. Should of had a bigger kw boiler put in last year.i did tell him I was planning an extension before he picked a boiler. From what I've read....not sure it would aka much difference anyway.
Atleast it'll do the rads ok then yeah?

 

[Phill Peck]

All dependant on your incoming flow rate.

Any space for a hot water cylinder.
No need to replace the boiler.

 

[Phill Peck]

Other than the fact it’s a Worcester

 

[flameport]

Combination boilers are generally only suitable for a single outlet at a time, regardless of what rating they are.
For multiple outlets, a hot water cylinder is the usual solution.
However it's totally possible to have a hot water cylinder with a combi boiler, so you don't need to replace the boiler.

Radiators will be fine - the boiler is a 25kW model, your radiators will be far less than that.
If you don't know the output of the existing radiators, look here: http://www.wickes.co.uk/radiators and find those which are similar in size and type, and just add up the total watts for all of them. Note that those are in watts, and 25kW = 25000W.

 

[ABC Gas Care]

Flameport sumed it up heating fine 25Kw run big house heat only its taps hot water your down fall 25Kw not best size but I wouldn't buy new boiler if your happy wth your hot water tap temp now . but if you were buying new buy min 28 to 30Kw . norm small price more .
But then again never buy Bosch with Aluminium heat exchanger and loads plastic in it but some plumbers love them and public think there good as they market them well but its good for ten more years if you get plumber to put loads inhibitor in after work .