Many thanks simond.
I contacted the company who supplied the DT20 today and they said the same and apoligised that the salesman gave me bum info, they have refunded me so will get a Honeywell to replace the faultly Horstman.
Are you able to say what should have been fitted instead of a...
Hi,
I want to add a DT20 programmer to a greenstar 30CDI regular boiler previously contolled by an external Horstman programmer through a 10 contact wiring centre. I can not find on WB literature site any instruction of how the wired 3 port valve, room stat and Tank stat should be wired so as...