Behaviour of Zoned vs Independent TRVs . . .

hugbilly

I wonder whether anyone else feels that the tadoº TRVs behave differently with regard to opening and closing when they are set to independent in contrast to when they are assigned to a zone controller and able to call for heat.

For this year’s heating season I have made several of the TRVs in the “communal” areas of the house, hall, landing, etc, independent because I’ve previously found (as others have noted) that when all the TRVs in the system are able to call for heat the result is that the boiler runs almost continuously. I’m hoping to make some cost savings because, aside from the convenience of scheduling, I haven’t really noticed any particular economical benefits since replacing the conventional TRVs the system had before; which is disappointing.

So far the new arrangement has worked well with the independent areas heating up quite satisfactorily when the call for heat rooms are active (the scheduled start and end times are the same.)

What I have noticed however (or at least think I have) is that with regard to the “wavy lines” the independent and zone controller TRVs behave differently. 

It’s always bothered me that when the TRVs which are able to call for heat get to the single wavy line stage they very nearly shut and yet continue to fire the boiler. In contrast, it seems to me, when the independent TRVs reach single wavy line status they are open to a greater extent than the zoned ones, and their attached radiators are warmer as a consequence.

I shall continue to try and measure this and I may, of course, be mistaken but it would be very interesting to know what others think.

I do wonder also, whether the way the zoned TRVs behave might really be better suited to OpenTherm, or other modulated systems, rather than the simple boiler on or off arrangement which many British tadoº installations use.

wateroakley

@hugbilly That's a number of interesting observations.

• Pleased to hear your 'independent' configuration is working well for you.
  
• I've not noticed any particular difference between the rads in rooms where the TRV calls the 'zone controller' for heat and those rads with TRVs that are 'independent'.
  
• We micro-manage the schedule and use geofencing. Our use of gas for heating and hot water has reduced substantially. I've posted usage charts below for comparison:
  a) Annual kWh gas consumption versus the "2024 National Energy Efficiency Data-Framework (NEED) Publication" for comparable homes in our Local Authority; and
  b) Monthly percentage consumption at the same outside temperature (mean CET).
  No promises that similar savings are achievable for everyone.
  
• Whilst not Opentherm, our 13 year-old system boiler does modulate. The 2024 service engineer demonstrated this when the Tado TRVs were shut down - the boiler behaved nicely and throttled back. Therefore, I tend to agree with your last paragaph when multiple zones (Rooms) can call for heat at different times, that modulation contributes to the efficiency of the heating system.