Dave, did you mean to put a 'not' before the 'stop working'?
The boiler will 'stop working' because of this, in fact it is STILL working but has reached the set temperature and has turned its self off until the water cools in it. This will take longer if there is less circulation through the boiler
I'm not being picky, I just want to make sure I understand. You think that I can turn off the valves in these two rads on the domestic water loop in the very hot weather? And that it will have no adverse effect on the boiler?
The boiler will 'stop working' because of this, in fact it is STILL working but has reached the set temperature and has turned its self off until the water cools in it. This will take longer if there is less circulation through the boiler
I'm not being picky, I just want to make sure I understand. You think that I can turn off the valves in these two rads on the domestic water loop in the very hot weather? And that it will have no adverse effect on the boiler?

