Honeywell Sundial Plans Wiring Centre (42005748-001) help needed

[apr719]

Hi all
In our current home the heating/hot water system works fine except that when you select either Heating or Hot Water on the programmer BOTH motorised valves come on. The room and cylinder stats work correctly in that the relevant motorized valve correctly turns off when the room or water is at temperature, and the boiler turns off when both values are off.
Looking at the Honeywell wiring centre, the links L2, L3 and L4 only have been cut. I’m wondering if L1 should also have been cut? In the lid, it says: “If using Programmer (not basic Time Clock) Cut link 1.” I know that the wiring centre was replaced relatively recently so I’m wondering if that could be the problem. Thanks.
Components:
Baxi Solo 3 PF boiler
Honeywell ST9400C programmer
Honeywell Sundial plan wiring centre 42005748-001
S-Plan setup, 2x 2port Honeywell motorized valves
Honeywell room stat
Honeywell cylinder stat

 

[D_Hailsham]

Remove link L1 (make a note of which terminals it connects) and see what happens. Then, if you still have problems, you can easily replace it.

Woops ! I'm thinking of the Drayton wiring centre, which has removable links. The Honeywell one has soldered links.

You have a programmer, not a basic timer, so I would follow Honeywell's instructions and cut the link.

 

[apr719]

Hi D_Hailsham Thanks for your reply - yes I agree, I'm thinking of cutting L1, but as they are soldered, I'd ideally like someone to tell me if the symptoms are exactly what you would see if you had forgotten to cut L1 before I do so.

 

[D_Hailsham]

I don't know how the Sundial wiring centre is wired behind the circuit board; but I can understand why the link need to be cut.

Time clocks are one-channel devices; programmers two-channel. If a time clock is controlling both heating and hot water there needs to be a switched supply (presumably from the CH ON terminal of the wiring centre) to both CH and HW thermostats. But if a programmer is used there will be separate supplies (from CH ON and HW ON) to the relevant thermostats. Link L1 appears to be providing the required connection between CH ON and HW stat C terminal when a time switch is used. Breaking this link, when a programmer is used, is therefore logical.

Leaving the link in place would give the symptoms you describe.

 

[apr719]

Hi D_Hailsham, that makes sense to me. I shall go ahead and cut the link. Thank you again for your help. Kind regards

 

[ianmcd]

just snip the link , if it causes problems just solder it back up again

 

[apr719]

Cutting Link 1 has worked. The programmer now controls HW and CH independently. Excellent. Thanks.