HRT4-ZW and Indigo

Hi,
I would like to control my heating and hot water via Indigo so I purchased a HRT4-ZW thermostat and 7 day timer (scp 317) from Vesternet http://www.vesternet.com/z-wave-secu...oom-thermostat

The timer looked identical to the centaurplus c27 timer that I already have (complete with a wired room thermostat) , I was hoping that I could just swap the Z-wave timer with the c27 and all seemed to work (in terms of display and communication with the HRT4) except that the boiler wouldn't fire manually or with the HRT4.

Does it just need some rewiring or have I bought the wrong thing? would it need to control the hot water and the heating as my non Z-Wave timer does?

Thanks for any help.