Christian McArdle wrote:

Therefore, for it to be suggested that a room stat is mandatory
is stretching the point from the legislative, economic and the
ecological point of view.


Ah, but there is no requirement in approved doc Part L1 for a room stat,
just a boiler interlock. It suggests in a non-exhaustive list that room
stats and flow switches are appropriate for this use.

The addition of a flow switch interlock to an all TRV system would have
absolutely no bad effect (beyond the small installation cost) and much good
effect.

The pump would be running all the time, whether the flow switch was
installed or not. The flow switch just causes the primary water to cool down
if all the TRVs are hard off. If they are passing by at all, then the
modulating boiler will be allowed to fire at the low rate. The flow switch
doesn't force a modern low modulating burner to become cyclical.

The 80W from the motor can be saved by additional electronics to cause
occasional pulsing every ten minutes or so, when the flow switch shows no
flow (I see no requirement in Part L1 to do this, however). It would also be
possible to incorporate the entire lot into a combi style boiler, although I
doubt any manufacturers do.


In the case of conventional, full output on/off boilers,
possibly. The focus is demonstrably on the wrong issues.


Only if you assume that people actually turn off the system when it is warm
outside. You can't make this assumption.



So, you think people sit there dripping with sweat, with the boiler
churning away, in teh summer? I don't think so.

Even the most stupid user can work out how to s3itch the boiler ON and
OFF. FAR more than they can get the hang of adjusting 14 TRV's and a
main thermostatt.



Christian.