WB Greenstar 29HE conventional proper setting

[PFO]

Had this boiler as a relacement for a few months now with some interesting experiences, but generally good impressions.

My question is that with the old Stelrad (20 yrs old) we always ran it at minimum heat output on a time switch/controller. It was the smallest model and still to big for our 6 rad system, but it worked faultlessly.

The 29HE looks good - is almost silent - but the instructions say to set it to 'E' setting which outputs at 75 - 80 degC, way above the pevious boiler.

OK, the rads are all hot, but are the instructions correct in recommending this high setting? Is this a feature of condensing boilers? Would I waste gas by setting back to a low output?

Thanks Phil

[Andy Hall]

Basically you turned down the previous boiler because it was producing too much output. For non-condensing boilers it is better to run them at their design temperature of 82 degrees to avoid condensation and corrosion which can occur at lower temperatures.

On condensing boilers, the lower the temperature the better - it is more efficient to run at a lower temperature. However, when the unit is installed as a replacement for a non-condensiong boiler, usually the radiators will have been sized for that and on the basis of 82 degree flow and 70 degree return.

The condensing boiler modulates its output and increases or reduces temperature as required to match the heat load. The thermostat sets the top limit. I suspect that the reason that the manufacturers suggest a high setting is so that output will be adequate when the application is a replacement and the boiler output maximum output not much more than the heating requires in cold weather.

You probably could reduce the setting, but there is no real point since the boiler output should reduce automatically anyway.

[Christian McArdle]

Run it as low as possible, whilst still being able to adequetely heat the radiators, and being no less than 5C above the setting on the hot water cylinder thermostat. (i.e. if the HWC is at 60C, run at 65C, unless this makes the radiators too cold).

If you have the built in diverter valve, you can set different temperatures for hot water and radiators. In this case, set the hot water 10C above the cylinder thermostat setting (for rapid recovery) and set the radiator temp as low as possible, provided the house still warms up in a reasonable time. In extra cold weather, you can bump it up temporarily.

Christian.

[PFO]

Thank you Andy & Christian

I think I understand what you're both saying and a new phase of experimenting begins . . . Phil