OpenTherm 2+ zones

[Neilgriff63]

I have a clarification question on OT and the use of Smart thermostats for more than one heating zone.

To my knowledge, OT is a control algorithm that utilises Proportional, Integral and Derivative control actions to try and smooth out boiler action in order to track the desired temperature, unlike traditional on/off control which simply hunts around the desired temperature with the boiler fully on or off.

In current quest to select a Smart Thermostat, I have read articles promoting OpenTherm for a 2 channel installation. Unless I wasted all my academic study, these seem an almost impossible task unless the system can determine which zone it should be “controlling” at a specific time. If both zones are calling for heat, but are at different temperatures, how can the system utilise a control algorithm.

Would I be correct in thinking that OT is definitely only applicable to a single zone?

 

[vulcancontinental]

No, OT can control several zones, it aggregates to the highest demand. There are not usually huge discrepancies in required temperatures across a property either space or flow temperatures. In the case of underfloor heating at a far lower flow temperature a mixer would be involved for that zone/zones.

 

[Neilgriff63]

Ok, but an aggregated control that is implied across all zones. Thanks.