Range rating, modulation and manually setting the CH temperature question.

[vulcancontinental]

This idea of driving additional zones sounds perfect as I'm considering replacing my downstairs rads with a retrofit UFH e.g Wunda,Polypipe etc next year.
The Vision Plus manual describes how I can add a BE16 accessory board to manage an additional zone and enable it by setting parameter P4.23.
The manual entry for this parameter states:
"P.4.23
This parameter allows you to activate the management of an additional heating zone (the use of the BE16 accessory board is required, not supplied as standard).
The default value is 0, set to 1 to activate the function.
Note: this parameter cannot be changed when an OTBus chronothermostat is connected."

Does the last line mean that if I use EPH Opentherm controls (which I assume is an OTBus chronothermostat) then I can't activate an additional heating zone via a BE16 accessory board?

I will find out but it's not a configuration I've come up against before. EPH can be either switched or OpenTherm.

If you use a mechanical blending valve that's the cheapest way but if you did want to use OpenTherm and an electronic blending valve (up to three) then there is a different accessory box you can use