Boiler Replacement?

[Peter68]

Hi All,

I currently have an Ideal Combi 30 which serves my existing 57m2 (600 sqft) one bedroom flat and I'm going to be extending to a three bedroom 102m2 (1100 sqft) flat. The boiler will need to to serve the underfloor heating and two bathrooms and I'd be keen to know peoples thoughts on whether or not it's 30KW output will be enough or if needs to be replaced.

Thanks!
Nick

 

[oldbutnotdead]

The 30kw is usually the output to hot water, not the heating (that'll probably max at 24,).
That combi won't give you 2 adequate showers at the same time.
If you build to modern insulation etc standards the heat output will probably be adequate, but do your heat loss calcs anyway to make sure. If cold water pressure/flow is good, consider an unvented cylinder for hot water for the bathrooms, use the combi for kitchen hot only

 

[Peter68]

Thanks. I've just looked it up and your right the output is 24.2 and not 30. Unfortunately due to the state of my finances I desperately need to make savings to make the project happen so even getting an extra few months out of it would be well worth it. The extra bathroom has had to be put on hold so there won't be two showers running until next year

 

[oldbutnotdead]

OK. So check dynamic pressure/flow on the water supply. If its good enough then designate a space for the cylinder & get the necessary basics in (cold supply min 22mm from stoptap, primary heat, power, any control cabling, hot and balanced cold water lines to bathrooms, outlet for prv tundish).
A sensible budget for your scheme would have at least 10% contingency in it, scraping for pennies before you start increases the risk of you ending up with a half finished or badly bodged extension (from going for cheapest rather than correct, whether thats in materials or contractors)

 

[oldbutnotdead]

PS A new 30,kw combi will be just as inadequate as your existing one for 2 simultaneous showers. Boiler isn't the problem, physics is. Stored hot water will do the job more cost-effectively and better than monster combi or one electric shower.

 

[Peter68]

I know it's not how I like to do things but the mortgage market is closed at the moment if like myself you're self-employed and have just come off furlough.

The pressure from the water supply is very good and presumably if there's enough manifolds it can be made to work in the interim. I can then do the boiler when I do the second bathroom so that running two showers won't be a problem

 

[oldbutnotdead]

Don't talk to me about furlough- due to mixed income streams (all shut down by the lurgi) i've received the grand total of f*ck-all from HMG.
Your boiler will probably run the cylinder as well as ufh. It'll do one ok shower. So it isn't a priority for replacement.
If cash is tight, get the infrastructure in for what you want in the future then use placcie for temporary links to make it work now.

 

[Peter68]

Yep that's the plan. I'm doing the expensive structural work upfront and have stripped out most of the second fix carpentry and decorating. I'm fortunate in that my Dad's a kitchen fitter and can help out with most of it although he's getting on so there's a limited on what he can do.

Thanks for the advice

 

[Old Salt]

Why not use the combi with one shower and electric for the other. Then in the future if the combi plays up you will still have the leccy shower and vice versa. Yes I know about the increase in running costs but leccy showers are cheap enough in the sheds.

 

[Londoner2]

I have a 30kw combi, 3 showers ( 1 powered by combi, 2 x leccy although 1 is hardly used).

Having tanks, zones, valves just adds layers of complexity and more to trouble shoot in my opinion.

 

[Peter68]

The builder has quoted me just under £3,000 for a Worchester Bosch Greenstar 42kW Combi and I'll definitely be going for it if I have the money. I just need to do a bit of financial alchemmy in the form of personal loans in different names and a big credit card balance transfer

 

[aptsys]

I wouldn't recommend it. As mentioned, either stored water or possibly one electric shower will be better.

Don't get the builder to quote for a boiler - get someone who knows what they're doing.