The Efficient Home Forum

Hi,

I live in a 3 storey, 5 bedroom new built townhouse and currently have two Hive wireless thermostats. I'm considering upgrading to EvoHome so that I can control the temperature in each room individually and was after advice to what I need and how to install it.

My current system is what Honeywell calls a Sundial+ (I think). I have 3 zone valves: One controlling the heating for the first and second floors, another for the heating on the ground floor and another for the hot water. For heating I've read that it's recommended to install an HR92 on each radiator and to disconnect the heating zone valves (leaving them in the open position) or to connect both heating zone valves together so they open and close at the same time. Unfortunately, I do not think this would be a valid option given that I have a total of 16 radiators but no need to control all of them individually. My requirements are:

1)The ground floor (living room, dining room, kitchen, cloakroom and entrance hall) is mostly open plan so I do not need separate heating zones. I'll be happy with a single thermostat controlling a single heating zone (which is already controlled by a separate zone valve).
2) On the first floor, I have radiators in 3 bedrooms, 2 bathrooms, and the hall. I would like to control the heating individually in each bedroom but I'm not bothered about the hall and bathroom radiators (don't mind if they get hot when there is heating demand from the bedrooms).
3) On the second floor I have radiators in 2 bedrooms, 1 bathroom, and the hall. Like the first floor, I would like to control the heating individually in each room but I'm not bothered about the hall and bathroom radiator. The zone valve controlling the heating on this floor is the same one as the first floor.

Based on the above requirements I think what I would need is:

1) Groud floor - Evohome controller (also working as a thermostat) connected to a BDR91 that controls the ground floor Zone valve
2) First Floor - 3 Evohome HR92 valves ( one for each bedroom) connected to a BDR91 that controls the first and second floor Zone Valve
3) Second Floor - 2 Evohome HR92 Valves (one for each bedroom) connected to the same BDR91 that controls the first and second floor Zone Valve.
4) Hot water - Evohome hot water kit with the BDR91 from this kit controlling the hot water zone valve.

This means that I would have a total of three BDR91, one controlling each zone valve individually. This way my radiators wouldn't get hot when the hot water is on and also the heating on the ground floor stays isolated from the heating in the first and second floors.

Is this a valid configuration?

Many thanks in advance for your help.

Hugo

The evohome system is not capable of 'sub-zoning'... Therefore, you can't just have a couple of HR91 or HR92 Radiator Controllers on a floor behind a motorised zone valve with all the other radiators on normal TRV's. The same reason you cannot just have one evohome Radiator Controller in a room containing more than one radiator.

When using evohome Radiator Controllers, these are what control the flow of water to the radiators and not a motorised zone valve... Hence why on a 'perfect' evohome system, the only motorised zone valve fitted is one on the hot water cylinder (unless of course you have an OpenTherm boiler and cylinder and then you have a slightly different configuration) and all the radiators in the property are controlled with evohome Radiator Controllers (Page 43 Figure 4 Honeywell evohome Installation Guide).

I hope that helps answer your questions?