Honeywell ST9400C to Hive

[Smarty64]

My Honeywell ST9400C boiler controller has failed after less than 10-years (from the widely reported flashing display fault) and I am considering replacing it with a Hive Mini Dual Controller (CH+HW). The receiver wiring looks to be configured exactly as per the old ST9400C back-plate (N, L, 2, 3, 4).

I have a multi-zone wet underfloor heating system with 5 x hard-wired Honeywell thermostats through 2 x Heatmiser controllers (UH4 upstairs) and UH8 downstairs) plus DHW cylinder. My question is can I simply use the Hive hub and receiver (ex thermostat) to control my heating via the app and keep the existing hard-wired thermostats?

 

[Stuckinarut]

It seems as though the ufh is separate, so I would say yes

 

[ericmark]

Other than to turn on DHW, what does the thermostat do? In theroy with Drayton Wiser even with radiators and TRV's there is no need for a wall thermostat connected to the hub, and the UH4 and UH8 are in essence hubs, the idea is to allow one heat source to heat all rooms, so you could have with the UH4 and UH8 12 rooms independently controlled, and 12 wall thermostats connected to the UH4 and UH8.

I would suggest that 12 x Hive thermostats is a little expensive. So why do you want Hive? Would a Sonoff relay do the same thing, I can't work out why you want a Hive thermostat, fitting should be easy, but why?

 

[RandomGrinch]

Just to clarify, are all the heating needs met by the Honeywell thermostats and what model are they?

The problem I see, if the ST9400C controls all the heating, then as the Hive isn't just a timer, it incorporates the thermostat; for the Hive receiver to call for heat, the programmed timing has to be active, as well as the thermostat calling for heat.
The Hive thermostat could be set to a high temperature, but it would have to remain connected to the system.

 

[Smarty64]

Thank you for all for your input, however after much searching the SONOFF 4CHPROR3 4-Gang Wi-Fi Smart Switch with RF 433MHz RF Control (appr £30) is a fully configurable substitute for a conventional timer and will do exactly what I need for a fraction of the cost of a Hive. No additional hub required, and no subscription for the bells and whistles. Like Hive, he SONOFF is configured and controlled via a phone app (eWeLink), which in my application will give me remote controlled CH and HW timing programs and on/off control.