How to Replace a Programmer (UK)
Swap a Horstmann, Honeywell or Drayton programmer for a 7-day 2-channel replacement. Backplate and wiring.
HoneywellDraytonHorstmann
Backplate compatibility
Honeywell ST9400C fits any 5-terminal Honeywell or Drayton backplate. Horstmann C17 uses the same universal backplate.
Fit
Isolate at consumer unit. Note wire positions BEFORE removing. Backplate stays on wall; just clip new unit on. Programme HW and CH schedules.
Frequently asked questions
- Do I need to isolate at the CU?
- Yes — programmers carry mains 230 V. Never work live.
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