Boiler Refiring before Anticycle time has elapsed.

[Johntheo5]

Came across a 9 year old thread recently re the above "Boiler Cycling after fitment of new thermostat", the gist of which was that a TPI roomstat was switching very rapidly and the "Glowworm" boiler was refiring instantly but before the anticycle time had elapsed, someone ele stated that his Vaillant boiler was behaving similarly.
Any thoughts on this?, maybe @vulcancontinental ?.

 

[vulcancontinental]

I’m afraid there’s not much light I can throw on that specific subject, this has come up in the past and I’ve not paid too much attention to it because it relates to other boilers and not Vokera in particular.

The Glow-Worm could be a cast iron Space Saver or a condensing boiler similar to a Vaillant or one of their earlier designs so who knows the background or control option?

If a boiler fires when the controller apparently says not to, I immediately think of wiring issues or a fault with the programmer, either setup or internal.

Not dissimilar threads have been in the Combustion Chamber concerning what has been termed micro-firing, very rapid restarts after shutdown particularly with low temperature systems. Customer and installer in long correspondence with Vaillant threatening action. I don’t know what happened there.

There’s an ongoing thread elsewhere on social media currently concerning a Viessmann 200 with low temp heating and high temp hot water re-heat where following DHW reheat the boiler switches to modulated temp for heating. The modulation ratio is high in the Viessmann and when there is a demand for heat it fires at its ignition fan speed before dropping to it’s calculated output. The ignition power is far higher than the modulated output fan speed and injects so much heat the setpoint is immediately exceeded so the boiler shuts down then immediately refires when the system water is removed from the heat exchanger. Viessmann have told the customer this is normal but it's a 10 second cycle apparently.

I can only really speak about Vokera as it’s all I’ve known except for carrying out the odd service of a different brand over the past 22 years. We seem not to experience these problems (or I have heard of none) due to the adjustable anti-cycle delay and heating delay and hot water delay options built into the parameters of many boilers (all the current ranges)