On 07/10/2020 01:10, John Rumm wrote:

snip

I did find this:

http://www.worcester-bosch.co.uk/sup...ownload/TB0053

Although their note that a 24kW boiler's max gas rate is 2.6 m^3/h is
slightly surprising... it would suggest an efficiency of only 80% if its
giving a true 24kW output, and hence drawing gas at a rate of nearly 30kW

(my previous calc was assuming that the input rate is 24kW, which is
likely an underestimate, since most boiler specs now quote output power
rather than input).


I have a vague memory that the calorific value (CV) for natural gas is
permitted to vary over quite a wide range. I have absolutely no idea
what value boiler makers [have to] use when quoting gas rates and power
but do just wonder if the 24 kW is based on a low (if not the minimum) CV.

--
Robin
reply-to address is (intended to be) valid