Vaillant Eco Tec 937 - Cycling with comfort mode off?

[Spark1964]

Hi Guys,

I've just had an Eco Tec 937 fitted as I need a high HW demand. The boiler itself is great but I am confused with a cycling problem.

Basically, I want to turn off the comfort mode setting for a few weeks (please don't ask why!!) but even with this switched off, the boiler is still firing every 15 mins or so day and night - as if it is still keeping the store at temperature.

The symbols displayed are the heating symbol (radiator) and the egg timer / double pyramid, which I assume is the fan running symbol.

I have checked the obvious like comfort mode and programmer settings but the boiler still runs this cycle.

Any advice would be much appreciated - thanks.

 

[MisterG81]

The hourglass is anti-cycling control.

If its showing it means CH is calling for the boiler to fire again shortly after shutting off.
the default setting is 20min, but i think it varys based on previous modulation and duration.

Edit to add: depending on your controls/circumstances - if using vaillant modulating controls, its possible the controls are requesting too low a flow temp.

 

[Bunnyman]

If its brand new they may have left the 24v link in many do post back when u check I bet that's it

 

[Spark1964]

Problem solved - it was the 24V link and big own goal cos I wired the boiler myself!

Cheers Bunnyman and thanks for the advice G81 - much appreciated guys and thanks again.