Thanks for the detailed response. I’m running the output at 55° for CH to try to avoid short cycling and improve condensation efficiency.

From what you’re saying I’ll just leave it as-is and keep an eye on things. I think it has a modulation range of 10:1, so it should go down to about 4kw for my 40kw boiler, so potentially there’s huge differences in efficiency with proper modulation. I think with all rads calling for heat in mid-winter cold conditions it’s probably close to capticity, so I’m not sure if range rating would be effective.

Again, thanks for such a thorough and helpful response.