CH vs DHW

[Axel]

Scenario - start to run the bath and simoultaneously ramp up the upstairs zone room stat. Problem then is that the cold water in the rads circulates through the cylinder and cools the hot water, so the hot water runs cold before the bath is full.

What does one do? Wire the room stat via the 'satisfied' terminal on the cylinder stat? Or is there a method using a pipe stat to prevent primary water circulating through the cylinder if it's below DHW temp?

Or just get a bigger cylinder? Or a smaller bath?

 

[Boilerman2]

Just install a boiler that is big enough to cope with the load, yours sounds undersized to me!!

 

[Axel]

30kW.

I'll bet if I posted a new topic asking how powerful my new boiler should be, I would be told that 30kW was too much.

It's 80% efficient, as compared t a blue sky scenario 95%, but in practice that means it's as good as a 24kW...

I suppose that 20% would make some difference...