Thanks mickyg.
The HW Cylinder currently reheats in around 4-minutes, and I often use that feature to top-up the bath (since one fill leaves it too shallow for a luxury soak
I follow your logic re tweaking down the rating of the boiler, but, it seems me that no matter how low I tweak it, it will still quickly heat up a small slug of water and cut out at max temp until it resets and tries again - as it does now. The only difference would be that the slug of water would be slightly larger as it would take longer to heat up with less power.
What seems to be wrong, from your explanation, is the initial firing of the boiler at 70%. On start-up it would be much better to begin at low power and slowly modulate as the water temperature increases. If I am right, I am surprised it does not work in that way.
With systems like mine, the demand will only ever approach maximum in very cold weather, when all the rad-stats are open on initial firing-up. At all other times the demand will be lower, and can be anything right down to a single small rad or even just DHW, and the boiler has to cope with that range of conditions doesn't it?
The HW Cylinder currently reheats in around 4-minutes, and I often use that feature to top-up the bath (since one fill leaves it too shallow for a luxury soak
I follow your logic re tweaking down the rating of the boiler, but, it seems me that no matter how low I tweak it, it will still quickly heat up a small slug of water and cut out at max temp until it resets and tries again - as it does now. The only difference would be that the slug of water would be slightly larger as it would take longer to heat up with less power.
What seems to be wrong, from your explanation, is the initial firing of the boiler at 70%. On start-up it would be much better to begin at low power and slowly modulate as the water temperature increases. If I am right, I am surprised it does not work in that way.
With systems like mine, the demand will only ever approach maximum in very cold weather, when all the rad-stats are open on initial firing-up. At all other times the demand will be lower, and can be anything right down to a single small rad or even just DHW, and the boiler has to cope with that range of conditions doesn't it?