Manual modulation?

[meow2222]

Gas boiler efficiency rises when power output is modulated down. With old cast iron exchanger boilers, modulation can also reduce cycling, bringing a 2nd improvement in efficiency.

How workable is the idea of manually modulating an old cast iron boiler to improve energy efficiency? The idea would be to turn the gas valve down a little in milder weather so it runs at lower power and higher efficiency.

The experiment worked well, with high efficiency resulting, so I wonder how appliable this is for people with old boilers.

NT

[John Stumbles]

2 problems: one practical and one legal. There's a risk that running at higher efficiency may promote condensing resulting in corrosion and demise of the boiler (which may be A Good Thing on energy efficiency grounds but probably not what the owner wanted!). Legally, it's running the boiler outside the manufacturer's specifications and almost certainly falls foul of the GSIUR.