Combi boiler efficiency

[texasholden]

Modern condensing models are usually quoted with efficiencies above 90%.

Does that level of efficiency still apply to combi boilers ticking over to feed one or two rads?

 

[Boilerman2]

The efficiency of a boiler is dependant on it be correctly sized for the load in question on a condensing boiler you should achieve a 20'c temperature drop between the heating flow and the return, if less the efficiency will diminish slightly, but will still be in the 90's%, the question is why run a boiler of say 6 -30 kw to operate 2 rads, it may be a better option to go with electric heaters?

 

[ALEC1]

a decent combi boler can be down rated to approx 5kws. In addition the use if compensation controls ensures efficiency is maximised by never letting the radiators get hotter than necesary.

Using both these controllers efficiency is maintained high...

 

[Agile]

The efficiency is more related to the flow/return temp than the actual power output.

A return below 50 C will ensure a reasonable amount of condensing occurs which allows high efficiency.

Practically that usually means a flow temp below 65 C.

Tony