Optimal Boiler Settings

Pincher

Assuming your cylinder stat is set to 65 degrees, the relay will stay on until the water is at 65 degrees, which means the heat demand line to the boiler will stay on . If you turn the boiler output to say, 60 degrees, it will never get to 65 degrees.

What an intelligent controller does is to distinguish between central heating and hot water heating. When the cylinder is cold, so the return water is lukewarm, the boiler output is lower, so you get maximum condensing heat recovery. The controller see the return water temperature rising, and modulate up to compensate, until the cylinder stat relay clicks off. My boiler goes up to 84 degrees near the end.

If you have an old boiler, there is only one setting, and you are not going to adjust the boiler output every session.

rangler2

Pincher, that sounds cool - I want a new boiler!

Bengasman thanks, I read your interesting page. I read "On older boilers, the non-condensing, lowering the boilerstat does not bring any noticeable savings in the gas use, and is best left at 70 to 75 degrees Celsius" which doesn't seem to tally with my experimenting, mine is about 20 years old and definately non-condensing, but the boiler stat has a direct correlation to gas usage. Even if turning it down means it is on longer, my usage is still lower. Wierd.

System

rangler2 wrote: »

Yeah I put the timer on for 2 hours and then listened for when it turned itself off due to the tank stat.

........

You must have spent hours doing all this research and recording usage for your CH system. :cool:

You may need to get out more :rotfl:

C_Mababejive

The optimal boiler settings are in order of savings and preference...

(1) OFF
(2) Set as low as you can get away with
(3) Only on when you need it

Simples...

bengasman

rangler2 wrote: »

.. Even if turning it down means it is on longer, my usage is still lower. Wierd.

That is because you either don't have trv's, or they are set wrong.
The savings come in your case from an overall lower temperature of the house, which would not be the case with correctly set trv's.

On top of that, during the dwh on period, the boiler will cycle for as long as the timer calls for dhw, and this effectively costs more gas.
As an added bonus, the cylinder will not get hot enough to reach safe levels with low boiler temperatures and is now prone to ( dangerous ) levels of Legionella.