"Set Square" wrote in message
...
In an earlier contribution to this discussion,
logized wrote:

I am looking at replacing my Danfoss 3 way motorised valve as part of
a central heating re-fit.
I have changed the actuator a few times over the years, so I am now
looking to find a type that is known to be very reliable.
So far, I cannot find much independent info to help me decide on a
make. Drayton seem to make good TRVs, so are their motorised valves
as good? or maybe Myson or Honeywell, their specifications look good
also. Any ideas.

Dave

3-port mid-position valves have an inherent weakness in that they rely on
microswitches in the actuator to control both the valve and external parts
of the overall system - inluding switching boiler and pump on in CH-only
mode. It only needs a bit of wear on the cams which operate the
microswitches for the whole system to fail. Some makes may be marginally
better than others - but there ain't a lot in it.

The only satisfactory cure is to convert from a Y-Plan to an S-Plan by
throwing away the 3-port valve and replacing it with two 2-port valves.

The best way is to fit a 3-port "diverter" valve to give a priority system.
A diverter is similar to a 2-port valve with just another port. The boiler
will need to be on full temperature. A simple clamp-on pipe stat on the flow
can be fitted to keep the CH flow temperature down if that is a problem.
Better still, if the cylinder is old replace it with a quick recovery
cylinder to reduce time heating the cylinder. Travis Perkins do the Telford
Typhoon very reasonably. Doing this will transform the system for little
outlay.