Boiler rating confusion and flow rate

Combi boilers are often over rated for heating radiators quite a large heat output is needed to provide instant hot water. 28Kw is not uncommon and more that you would probably need to heat a 4 bedroom house.

You need to know how much heat your radiators can handle. Increasing the boiler size beyond the capacity of the radiators won't keep you any warmer. What may help you is ensuring that the central heating output temperature is set to its maximum value.

Thanks for the replies...

What would be regarded as a good flow rate these days?

Steve........

Pointless question unless you know what temperature uplift it can achieve at said flow rate.

MBQ

A kilowatt corresponds to about 3400 BTU per hour.

Surely that temperature uplift is given by the boiler's power rating. I.e. a 28kW boiler at full blast will be able to give an uplift of 4 degrees C to about 100 litres of water per minute, or of 16 degrees to 25 l/min.

I would suggest reading the DIY combi FAQ:

Good? 14 litres/minute. You can go up to 25 litres/min using an ATAG instant combi. Many other combis have stored water and can also deliver around 15 litres/min.

How many showers, baths, etc do you have?

Pointless question unless you know what temperature uplift it can achieve at said flow rate.

The defacto standard is a 35C uplift. Only in kitchen taps do you need temperatures over 45C. So, 45C at the taps (ideal for a shower) will give

Washing machine is cold fill only.

It's a 4 bed, 3 storey old Victorian house with large rooms and high ceilings.

Steve...

Steve, Get the Avantaplus 35c at 14 litres/min or the 39C at 16. If you do mainly showers get the 35C. Also get the weather compenstion package. You will not reget it. Avantaplus are made by Remeha who bought out Potterton and Baxi.