I've just replaced my Randall CH programmer with a Horstmann C27 (from Screwfix), With the programmer comes a conversion table and a wiring diagram.
I have wired my system as per the Honeywell C Plan.
(See
However, the diagram from Horstmann is slightly different:
Brown on zone valve to call on cyl stat instead of to common and no wire to Sat on Room stat
Although not a great deal of difference does anyone know the pro's and con's of each version, and if one is better than the other?
Tia
Kev