On 2007-06-27 19:49:10 +0100, Lurch said:


You can get mini valves that can be fitted to each rad. Not exactly
sure where you would source the as I've never looked tbh.


Sauter make them.


There are two basic types, both intended to sit on a TRV valve base in
place of the normal manual head.

- Thermal drive e.g. AXT 111. This is basically a commercial
version of John Stumbles' idea. They work reasonably well if one is
happy with on and off control - fully open or fully closed. I tried
to make one do proportional control and partly open the valve, but it
wasn't all that successful - very non linear and variation between two
units, so would have to be individually calibrated. However, they are
about the same size as a TRV head

- Motor drive e.g. AXM 117S. These have a positioner and can be
controlled by a DC voltage of 0-10v. They seem to be consistent as
well. The motor body isw a bit larger but not obtrusive if the
overhanging piece is pointed back towards the wall.