Vaillant Ecotec Anti cycling explanation / d2 function.

Hi

Further to a recent post on rads taking 2 hours to heat up.................

I have started to look at the internal programmable functions of the boiler. What I noticed that the boiler often switches off during the initial heating of the CH water, long before the rads are hot. I have picked up that this is due to the recycling function of the boiler that has something to do with the efficiency of the boiler.

However, even after finding some explanation online, I dont really understand it!

I have learnt that I can change the d2 setting on the boiler and this appears to allow the boiler to burn for longer, but at least this is now getting the rads hotter!

Can anyone simplify the d2 control and the recycling function for me?

Also, someone suggested the pump speed could be changed, yet when I play with the d16 option its fixed at 0 = auto.


Thanks in advance.

If u don't understand it leave it the fook alone before causing more hassle , why do people fiddle with things they don't understand

Very helpful, glad you can share your knowledge. Thanks!

Normally, anti-cycle would refer to a minimum time delay between the boiler firing for CH demand.

Imagine the boiler shutting off because the flow temp was 85 degrees, despite the furthest radiator being cold. Poor flow could cause continual on/off cycles until that final radiator was happy, perhaps happening two or three times a minute! If you set the anti-cycle period to, say, 5 minutes, then the problem is reduced.

Of course, the poor flow should be addressed!

Thanks for a helpful reply.

So, if the default setting was 20, then it could be up to 20 mins before refiring the boiler, so the rads cool. If the setting was 5, the time would be reduced so less cooling time?

I accept the poor flow needs sorting.

Thanks.

Perhaps, assuming the number is minutes. The boiler manual should explain (my Intergas one does).

If you have poor flow, and too much boiler on/off cycling, then by all means increase the time.

20 minutes sounds high, compared to mine.

Thank you!!

What's the issue with poor flow. If one of the furthest rads isn't getting hot enough, then you'd close down the outlet valve on the rads to push more heat to the furthest rad.