Originally Posted by
DBMandrake
From this and comments in other posts of yours it really doesn't sound like opentherm is modulating properly for you.
If the current room temperature is 19.5 degrees and you turn it up to 22 degrees that is a 2.5 degree change - which should result in "full" boiler demand. On a BDR91 relay this would be 100% duty cycle (continuously on) and on an OpenTherm system I would have thought it should raise the flow temperature to the maximum (user set) flow temperature, and remain there until the room temperature got to at least 20.5 degrees before it started to back off the flow temperature. If its just staying at 37 degrees that is just not right.
I use a relay instead of opentherm but if I was to make the same adjustment in my bathroom I know for a fact the radiator would come on full blast and be piping hot very quickly.
As I don't use OpenTherm I don't have any suggestion for how to find what the problem is though, hopefully an OpenTherm user with a similar boiler to you can help out, or perhaps you need to contact Honeywell support directly.
Does it still remain at a flow temperature of 37 if you turn your bathroom up to a really high setting like 25 or even 30 ? If it does, something is definitely wrong.