Boiler cycling query

[Johnytuono]

If I set it at 2C from an initial obviously long burn then the 10 minute ACT is fulfilled so the boiler would wait for the 2C drop (which would be seconds, I'm guessing maybe 30?), then it would re fire, it would prob hit SP+4 within a few minutes. Say it ran for 3 minutes, then 7 minutes ACT would be left, the 2C anti hysteresis would be fulfilled (as it is only a few seconds at 2C), therefore it would use the remaining ACT of 7 minutes up. It would then reset the ACT and start over from scratch.

 

[Johntheo5]

Got it now, thanks, I think.

Just to be clear, what are your current settings of Target Flow temperature and antcycle ACT time and your set hysteresis temperature?.

 

[Johnytuono]

Target flow is 45C, ACT 12 mins and Hysteresis is 7C.
No problem at all getting to room temp of 19C although it does take a couple of hours (obviously time will tell with the colder weather to come), we find that temp comfortable for us.
It's on from 06:30 until 21:45 with a setback temp of 16C. As of 17:30 today we've used about 41 Kw of gas but that includes 3 showers and cooking. In summer we use about 11Kw for showering and cooking, so it's easy for me to work out our heating usage. Overall I'm happy with that, especially with it being over 15 hours heating ( I know it will go up and have to increase flow temp eventually)

 

[Johntheo5]

Run this past me again please.

WB say......
. If the burner is lit for a longer duration than the anti-cycle time, then this element has been satisfied when the burner shuts down and so the central heating hysteresis based on temperature will determine when the burner re-activates.

"Target flow is 45C, ACT 12 mins and Hysteresis is 7C." so if the burner on time is greater than 12 minutes, the burner relight time (after shut down) will happen once the hysteresis is 7C??.

If the burner on time is only say 5 minutes, does the burner then not relight (after shut down) for at least, 12-5, 7 minutes and then only if the hysteresis is 7C??.

 

[Johnytuono]

Yes that is correct.
f the boiler lights for only 5 minutes, then it only has 7 minutes of the ACT TOTAL time left (12-5). it will then look at wether the Hysteresis of 7C has been reached or use up the ACT time remaining if it is longer. Actually in the above scenario the remaining time(s) would be very similar i.e an off time of around 7 minutes. Usually though, even on the 2nd cycle (because room stat has obviously not been reached) the burn time is a few minutes longer therefore the hysteresis is always a longer off time.
I've watched the boiler code software change from 204, which is the Hysteresis cycle, to 202, which is the ACT. This is when I was trying out longer (20 mins) ACT settings.
Hope that helps John

 

[Johntheo5]

Yes John, many thanks for all your replies.