Best heating and hot water system for a full reno terraced 3 bed house?

Mr.B said:
I'll be honest and say I only understand half of the above :

Yes, I get the bit about 25mm blue MDPE being the best for an unvented set up due to the higher volume it can pass (although I also understood that both a decent flow AND a decent pressure is needed, and there's no mention of the latter).

BUT, if I've got this right, you've said if there's only a 15mm incoming main, then stick to a combi --- however I thought it was well accepted that a respectable incoming pressure and flow was required for a combi to produce a decent hot water supply (ie it can't supply more than it's receiving). And if there's only a 15mm incoming main then how is that going to be any better for a combi than it is for an unvented?
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Usually with an unvented you also plumb in the cold from the pressure reducing valve so you have a balanced hot and cold supply. A 25mm water supply will give you plenty of volume for a good shower. There is no hard and fast rule on this, I fitted a 40kw combi on a 25mm mdpe supply to a two or three bathrooms house a big place I can't remember now.......the customers opinion the hot water performance was outstanding. Shouldn't have worked that good really but it did.
Go for a combi, cheaper, easier to install and an unlimited hot water supply unlike an unvented !
 
durhamplumber said:
Combi boilers have moved on a great deal in HW output.
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Too true, what is the latest rating , 45kW for hot water supply ? Good hot water supply.

But what about central heating demand....

Even if the boiler can modulate down to 1/10 for central heating then 4.5kW is still a lot of heat for a modern well insulated house.

Can the boiler maintain it's claimed efficiency over the entire 10:1 range of output ?
 
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