Boiler in constant anti cycle ?

[Johnytuono]

Its a look up table that Vaillant devised based on a 20 minute (default) anti cycle time (5,10,15 etc) along the top will give a actual recycle time of 20 minutes if the target flowtemp is set to a ( unlikely) 20C, if the target flowtemp is set a more likely 60C then the set 20 minute anticycle time will result in actual anticycle time of 6 minutes, but if you think this time of 6 minutes is too short you just change the set anticycle time to a higher number, setting it to 35 minutes will give a actual anticycle time of 10.5minutes, where the vertical 35C and the horizontal 60C lines, intersect, and so on.

The boiler flow&return (internal) temperatures will (have to) eventually equalize to the room temperature if the anticycle time is long enough, (a very very long time or say, if you switch off the boiler at night, all the temperatures will eventually be the same.

Thanks but when you say to watch the temp falling (when actually in an anti cycling period), how far should we want it to fall to, because, as you say, waiting for the temperature to drop to room temp isn't practical. So to give us an idea if we need to reduce or increase the anti cycle time if you see what I mean (this is what confuses me)

 

[Johntheo5]

You want to get it low enough to ensure that the boiler will get away after each recycle without multiple firings, Vaillants need a long recycle time to ensure that its low enough because they hold the firing at ~ 60% output for 1 minute before releasing the controls to modulate. You just have to determine it yourself, the modern Vaillants may not operate like this.