[OpenTRV-interest] Weather compensation

[Tim Small]

On 23/12/16 01:48, John wrote:
> However with lower flow and return temperatures it can extract quite a
> bit more heat by condensing (more) steam from its flue gases to liquid
> water.

FWIW, roughly 10% more heat can be captured by this condensation.

i.e.

heat from: (gas + O2 -> CO2 + Water liquid)

... is about 10% more than

heat from: (gas + O2 -> CO2 + Water gas)

The figures for oil are similar.

For historical reasons, the efficiency figures quoted ONLY express
recovered % of "heat from: (gas + O2 -> CO2 + Water liquid)".

This is not what most people expect, and makes all the boiler on the
market look better than they actually are.  It also explains the
occasional >100% "efficiency" figure you see quoted.

For the boiler I've just bought, it means that the nice sounding "97.7%
efficiency at 30°C return, 30% of rated output power" is really a so-so
88.8% efficiency.

... and the "88.4% efficiency at 60°C return, 100% of rated output
power", is really 80.4%.

Tim.