understanding the potterton kingfisher boiler??

[del_bert]

I've just fitted a digital controller(Danfoss715si) to my parent's potterton kingfisher boiler, but I can't run central heating(CH) only...Hot water(HW) has to be on also. I can do the inverse & have HW only.

Is this because heating hot water when CH is on, doesn't use any more gas? so you may as well have it on?

The old Sangama M5 controller removed only ever allowed CH+HW ...or.. HW on own.

I am baffled as the boiler I have in my house is also very old but allows running of both independently. It's same hot water tank type system but I have valves fitted. Is that why? If HW is free to heat when CH is on I have to change my timer settings pronto! as I have HW on early in morning before heating comes on.
Cheers Del_bert

 

[kevplumb]

gravity hot water

you have valves = fully pumped

 

[doitall]

The more water you heat up the more it costs, so no, you don't get the hot water for free when the heatings on.