What type of boiler/ system should I use?

Good day all.

We are currently re-fitting our house part of this includes refurbishing the bathroom, adding an additional shower in a wet room, and a significant kitchen extension (6mx4m) which I'd be looking to have under floor heating powered off the central heating. Additionally I'd be looking to have 3 zones on the heating. Upstairs, Down Stairs and the kitchen.

We've currently got a 24kw combi boiler.

When we get the extension work done, we'd almost certainly be moving the boiler, as such I've been wondering if upgrading/changing to a different type would be a good idea, as I don't believe the 24kw can really cope with two showers running concurrently.

The two options i see is as follows.

1) Getting a 38kw or similar combi boiler (some thing like 15lpm but at that rate not raising the temp by only 20 or so degree's).
2) Getting a non-vented mains pressure tank, and an appropriate boiler.

I suppose my questions are...

1) What would people recommend, any general thoughts/comments.
2) If a non-vented mains pressure solutoin, then...
2a) What size tank would they recommend, for a family of 3, and frequent guests (mainly showers, though baths at times)
2b) What size boiler would be required?

On an aside, any thoughts on current manufacturer recommendations?

Thanks a lot for your input.

Doug

 

combi's are not really designed to run numerous outlets simultainiously so the option of a cylinder and heat boiler is probably the best way to go
a cylinder of 250 - 300 litres would be best
as for boiler size then i would allow 1.5kw for each rad and 3 or 4 Kw for the cylinder then take the nearest size above that figure.

as for manufacturers then i would suggest that Vaillant, Glowworm, baxi, or any of the top brands would have something suitable

would avoid the cheapo brands like Ideal, ferroli and Halstead as they are ****e.

 

Awww, fourth page, almost 5th already :\

Did I say some thing wrong?

 

Hi Kevin

Thanks for this.

I've done some looking, and the impression I seem to be getting is that system boilers (is that the right term) are no incredibly reliable. Though I thought they were meant to be more reliable than Combi's.

Am I mistaken?

We are getting an extension done which will be about 45sq m's, the kitchen which will be using under floor heating powered off the boiler will probably be about 30 sqm's, the other rooms are liable to just be radiators.

Is this likely to change anything?

 

The cheapest option would be to use your existing boiler primarily as a heat only and a 300 li unvented cylinded if the water supply is adequate.

Kevin is a bit short of work so he would like you to have a new boiler and if you can let him stay overnight he will be able to give you a good price for the installation.

Whatever you do DONT let builders anywhere near any boilers or heating.

Heat only boilers have less in them to go wrong. Most are VERY reliable but you only read on here of the problems. Unfortunately Vaillant who have a good share of the market ( about 22% ? ) have a rather fussy heat only boiler.

For reasons which escape me, their 38 kW heat only is MORE expensive than their 37 kW combi !

Tony

 

Wow, your kitchen has got significantly bigger since your first post when it was only 24m² !

 

Only by 6 sqm which isn't THAT much bigger, and we are still waiting on the drawings (what a night mare that's been!), so it's all rough estimations at the moment.

it's effectively the width of the house + garage, and about 5M's out from the wall, so around the 45sqm mark.

 

I'm some what shocked that I'd never thought of that previously, I assume there is no reason why a combi boiler could not be used to heat the water in the tank.

The pressure is good, and more importantly the flow rate is not bad, i think around 25l/m i think, and I've still to replace the lead supply pipes.

I assume going with a zoned approach to heating would still be possible, as the boiler will just be acting as a heat generator, then I'd need a separate control station to direct the heated water to specific zones.

 

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