Connection of ATAG ONE thermostats to ATAG QR SERIES BOILER


I have an Atag QR Serie boiler and two heating zones in my house (1st floor & groundfloor) and two ATAG ONE thermostats. I know that I need a BCU module to connect ATAG ONE thermostats to my boiler. But do I need two of them, separate for every circuit or one would be sufficient enough? I would be very grateful for the technical advise.

Thank you in advance.

Best regards,

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