Thanks for the info, I’ll try setting the cron pattern device ping setting.
I’ve never used the “CeNT” option on the FHT80B before and I’ve just checked it in the room I’m in now and I think it was already set to On. I say that because when I selected the “CeNT” option On was the option that was immediately displayed so I assume that was the current option. I don’t have an FHZ1000 central controller, I have an FHT80B thermostat and an FHT8V radiator valve controller in each room.
In case it is useful to anyone the documentation for the “Cent” option is as follows:
9.8.Connecting to the home radio central unit (‘CEnt’)
You only require this special function, if you want the heating control to work
with a new FHZ1000 central unit or no central unit at all, in other words, you
wish to unregister the heating control from the central unit.
Radio communication between the heating control and the central unit is also
protected by the heating control’s security code. For this purpose the
respective heating control is ‘registered’ with the central unit.
To ensure that the heating control only works with your central unit and not
with your neighbor's central unit, for example, the heating control can only be
registered with one central unit.
If you want to register the heating control with another central unit, then you
must first to re- enable the heating control. 3 different settings are possible:
‘On’: Heating control is registered with the central unit
‘Off’: No radio communication with the central unit. Registration is not
possible.
‘nA’: Heating control is enabled for registration with the central unit
To set, proceed as follows:
• Press the ‘PROG’ button until ‘Sond’ appears on the LCD.
• Use the scroller to select the special ‘CEnt’ function.
• To confirm your selection, briefly press the ‘PROG’ button.
• The LCD displays the current setting (‘On’, ‘Off’, ‘nA’).
• Use the scroller to select the setting you require (‘On’, ‘Off’, ‘nA’) and
confirm your selection by pressing the ‘PROG’ button.
The heating control then returns to the normal operating mode.
Found here.
I currently use the fht (which is actually for openHAB 1.x) addon in an openHAB 2.4 system and use the remoteopenhab addon to send the values to and from the 2.4 system and the “live” 3.4 system. The fht addon can read the measured temperature and set the desired temperature. In the fht log I see a measured temperature update approximately every 1-3 minutes.
I’ll set the cron pattern and see what happens. Many thanks again 
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