In article , Richard Perkin
writes

The name confused me when I was speccing the system, and I spoke to
the Keston Technical Department who confirmed that it was not a
Honeywell product. Unsurprisingly, they did not offer any more info
on where I could get a lower cost alternative but did confirm that
any OpenTherm (OT) device would do.


I have the Keston C36. I confess that I was hoping for more from the
OT controller, but perhaps I was over optimistic. Given that OT is a
two-way protocol, it offers:
- display of boiler and pump info, including burner and pump status,
flow temp etc
- display of outside temp
- reasonably comprehensive time programming
- optimised temp control (rather than directly programmed room temp)
via the external temp sensor and return flow temp [but this is poorly
explained in the manual]

However, whether this is much better than an external temp sensor +
normal switched live controller I'm not sure, since with just the
external temp sensor the boiler implements weather compensation
directly...

Thanks for the information Richard which was mostly new to me.
--
fred
Plusnet - I hope you like vanilla