Setting ABV correctly

[alanm1969]

I haved some noise in rads and wanted to ensure I have the ABV set correctly.

I have read about using pump curves and min flow rates to do this.

My Worcester Bosch Greenstar 24i System boiler has an installation guide which does NOT include minimum flow rate in it and makes very little reference to the pump included in it (def no pump curve).

The ABV was set to maximum (6) for quite some time, I have since turned it down to 3 but would really like to set it optimally.

Many thanks,

Alan..

 

[Agile]

Quoting figures without units means nothing. 0.3 Bar would be more typical.

Most are set by trial and error until they just allow some flow when only 30% of the rads are on.

See the FAQ.

Tony

 

[ajrobb]

From what I've picked up in this forum, if you can measure the boiler flow and return temperatures (after the ABV) with the boiler running flat out but the ABV active (typically with the boiler cycling on the room thermostat and TRVs at their set points), you'll be aiming for a temperature rise close to 20°C but not more. You can tell if the ABV is active if the return temperature after the ABV is higher than before.

The pump should be at its lowest speed to achieve adequate flow through the boiler without the flow dropping too low through the radiators. If you turn the pump up too high, you'll need to restrict flow at the radiator lockshield valves and turn up the by-pass pressure and the radiators will be noisy.

 

[Agile]

That method is a good one to use but only if you have an accurate digital thermometer with a decimal place and a probe which gives repeatable results.

Few professionals have a good one and very few DIYers.

Its IMPOSSIBLE to use it if the boiler is cycling on/off. It needs a boiler which has modulated back to a quiescent condition.

Tony