Which boiler for my house??

Liam999uk

I have a 4 bed detatched house with one bathroom and a downstairs WC. I'm wanting to replace the old boiler but which system should i get, a combi boiler or keep the system boiler and tank? The shower in the bathroom is electric and i am happy with that so it would not be getting changed. Would a good combi boiler be sufficent? It would power 5 double rads and 5 single rads and the rest of the DHW requirement. Flow rate into the property is 20L/min which i believe is a good rate.

Many thanks

EnglishMohican

You are probably in a state where it is more a question of judgement and taste rather than mathematical fact.

I have a similar house and faced a similar problem. My decision was helped by the fact that my water supply was not so good and would have been a possible problem. Therefore I ended up with a 12kw boiler and a hot water cylinder and loft tanks which works well so far (its quite new still so time will tell).

If you have a combi boiler it will probably have to be 30kw or more to give you a reasonable rate of fill for the bath. I understand that 30kw will heat between 10 and 15L/min depending on the temperature of the cold water and how hot you want the hot to be. But 30kw will be a huge overkill for the house heating. That probably means that the boiler will modulate down as far as it can go - maybe 10 to 15kW - which is still far to high for a reasonable house - so it will turn off and a while later turn on again and so on. Turning on and off may not be good but it depends on the circumstances. My 12kw boiler will modulate down to about 6kW which is still more than my house needs but it is a much closer match

So the combi has advantages in that you can get rid of the hot water cylinder and the loft tanks, get instant hot water (in limited quantities) but the disadvantage that it will be much more powerful than the central heating needs and almost certainly less efficient than a smaller boiler better suited to the central heating needs.

That takes us back to my starting point of you takes your choice based on your judgement of what matter most to you.

Best of Luck

Cardew

Above post sums up the situation well.


On MSE there are literally hundreds of posts on the Combi v 'Conventional' boiler debate and it largely comes down to personal preference.


There are also no grounds for concluding either system is more economical than the other. It depends on boiler siting, usage, pipe runs etc.


Having considerable experience of both boilers, my personal preference is the conventional system with a HW tank - and my wife would be most upset to lose her airing cupboard!