Thanks, I am interpreting this (1) that the boiler is maintaining the SP temperature when in cycling mode so not a problem really apart from loss of boiler efficiency?
(2) that the 35 min run time is from cold rads but both zones on (all rads in service) and then cuts out, this is puzzling as it will take ~ 25/30 minutes to heat the water contents from cold to 75C, but once the BF reaches 75C then it should modulate down to maintain this temperature and shouldn't cut out (at 80C) because the total radiator output (~12/15kw) is way above the minimum modulating output of the boiler which is around 5kw.
I can only think of one or two reasons for this and that is that the boiler is not modulating or is too slow to modulate down before it reaches its cut out temp of 80C. The only reason that I can think of re no modulation is that someone has set the low limit output to the same as the hi limit output but this would be very very unusual, the boiler hi limit output is often adjusted (range rating) but the low limit is normally always set to its lowest limit.
I presume that the boiler then cuts back in again after this 35 mins? and does it then run in continuous modulating mode or does it start cycling again.
What does HW60 refer to?.
(2) that the 35 min run time is from cold rads but both zones on (all rads in service) and then cuts out, this is puzzling as it will take ~ 25/30 minutes to heat the water contents from cold to 75C, but once the BF reaches 75C then it should modulate down to maintain this temperature and shouldn't cut out (at 80C) because the total radiator output (~12/15kw) is way above the minimum modulating output of the boiler which is around 5kw.
I can only think of one or two reasons for this and that is that the boiler is not modulating or is too slow to modulate down before it reaches its cut out temp of 80C. The only reason that I can think of re no modulation is that someone has set the low limit output to the same as the hi limit output but this would be very very unusual, the boiler hi limit output is often adjusted (range rating) but the low limit is normally always set to its lowest limit.
I presume that the boiler then cuts back in again after this 35 mins? and does it then run in continuous modulating mode or does it start cycling again.
What does HW60 refer to?.