Add HR92 to existing Valve Zone?

[golfcaddy]

I appreciate my requirement may well be somewhat unique, but here goes....

I have upgraded most of my heating conrol system to the Honeywell Evohome kit. I previously had three zones in the house with three thermostats (upstairs, downstairs and another zone in a downstairs extension area).
Both the upper and lower stats controlled a V4043 2-port valve and were wired to create boiler demand. The third zone (extension) was only controlling a V4043 and didn't demand heat.
I now have BDR91 controllers wired to all three of those valves and the upstairs one is set as the boiler control.
The downstairs and extension BDR91s are bound as separate zones and they correctly operate and will fire up the boiler when necessary. This is much better than the older system as I can now have heat just in the extension since I have also fitted HR92s to all the upstairs bedrooms, so even though the upstairs valve is open when the boiler has demand, it doesn't heat the bedrooms unless they need it (it does heat the towel rails in the bathrooms as I want it to work that way).
The Evohome controller is in the hall and is the stat for the downstairs zone, I have HR92s on all the rooms upstairs and I have a T87RF wireless stat bound to the third zone (extension).

So my issue/question is this....

I have a small room (study) which is on the downstairs circuit. The downstairs radiators (with the exception of the extension area) are all on one zone with the controller as the stat (ordinary TRVs on those rads)

All good so far. However, I'd like to provide individual control on the study since my wife works from home and be able to just heat that room without the rest of the downstairs being heated.
I bought an HR92 for this purpose but can't figure out how to get it to work on its own. Via the Evohome controller it can demand heat from the boiler, but this only opens the upstairs valve and not the downstairs valve.
Is there any way of being able to say that room is effectively a "sub-zone" of the Downstairs zone so that the downstairs valve opens when that room's HR92 demands heat in the Evohome configuration, or maybe have two valves designated as boiler control (upstairs and downstairs), or do I have to explore other options such as HR92s on all rads downstairs and remove the downstairs valve?

Thanks!

[Richard]

Hi,

OK, firstly you should have implemented an evohome 'figure 4' system from the outset. The 'boiler control' relay is exactly that and is not designed to control the boiler through a zone valve as part of a 'multi zone' system.

So to clarify, each zone valve should have had its own BDR91 relay and a 4th relay should have then acted as the 'boiler control relay'.

Sub zones are not possible - it is all or nothing at all. Therefore the downstairs would have to have the motorised zone valve removed or bypassed and HR92's then put on each of the radiators downstairs. Obviously the boiler control relay also needs to be implemented at this point correctly.

I hope that helps.