Thanks. That is something that I understand and can get my teeth into. Return under 55 (say 50-55) so flow has to be +20 (say 70-75) simple.
In doing a bit of reasearch I came across this on Plumbingpages.com Condensingboilers - destroying the myths:
The system does not need to be designed to condense to achieve the improved efficiency, typically a condensing boiler would have a seasonal efficiency of between 83% and 92% compared with a new non-condensing boiler at 75% and an older boiler type at 55-60.
I just don't want them to be able to come back at me and say 'no the 55 + 20 rule does not have to apply'. Is the argument to counter that 'Oh yes it does if you want the best efficiency from the boiler and reduced gas usage'?
I can understand the above and hopefully it cover the logical argument.
In doing a bit of reasearch I came across this on Plumbingpages.com Condensingboilers - destroying the myths:
The system does not need to be designed to condense to achieve the improved efficiency, typically a condensing boiler would have a seasonal efficiency of between 83% and 92% compared with a new non-condensing boiler at 75% and an older boiler type at 55-60.
I just don't want them to be able to come back at me and say 'no the 55 + 20 rule does not have to apply'. Is the argument to counter that 'Oh yes it does if you want the best efficiency from the boiler and reduced gas usage'?
I can understand the above and hopefully it cover the logical argument.