I finally had this installed. I did everything but the HC60NG myself; pretty easy. The HC60NG is not hard either, if you know what you are doing. Because it does not have a battery, my friendly electrician put the neutral back into action (the CM907 that I had does not use neutral). The bridge for the Live was pretty easy, really. I exercised caution and hope others do the same too as required; this is 240V.
Early thoughts: it works. The room temp overshoots the TRV temp by 2 degrees. I think I may be able to get the system to compensate for that, but I need to investigate this further if I can be bothered.
I needed to order an adapter for my ancient Danfoss RAV valve. Honeywell advised on that but could not supply; I ordered from
My current consideration is that the HC60NG calls for heating for short periods of time; does this mean that the dino-boiler short-cycles?
In terms of comfort, it does what it says on the tin. I doubt I will recoup the cost from the gas savings, but I now have a much needed second zone. Could I have done it by moving the central stat in that coldest room and relying on TRVs? Possibly; however, I now no longer heat that romm much in the morning and that "feels" better.
Oh, and Honeywell said that a new system is about to launch (evo-home) with a better controller. The CM67z is a step backwards from the CM907, with no party mode and no back-light.
I hope this helps,
Kostas