Originally Posted by
mpkaye
New self-install Evohome user here. Our system is a Honeywell S-Plan with HTG and DHW 2-way zone valves, oil boiler and (obviously) pump. I have wired exactly as per S-Plan diagram (Figure 9) in the installation guide. However, I am finding short cycling a problem so I would like to switch to a boiler relay system.
We have 14 radiators in total, 10 zones comprised of 12 HR92s, 1 manual TRV set to off, and a towel radiator with manual valves (partially open). The boiler is a 17 year old oil fired Camray 3, doesn't require pump overrun. No bypass valve.
I would like to validate my wiring plan. As I understand it, to switch to boiler relay I need to do the following:
1. Electrically disconnect the HTG zone valve completely and latch open on the lever.
2. Remove the DHW zone valve end switch connection (orange wire).
3. Wire current HTG BDR91 terminal B to pump and boiler live (terminal 10).
4. Hard reset and unbind all system components and setup from scratch with boiler relay.
5. Pay attention to Cycle Rate and Minimum On Time parameters.
Am I right in thinking these are the actions necessary to move from S-Plan to boiler relay and so gain some control over boiler firing?