Solved: Which Wiring Plan is this Honeywell 42002116-002 connected to a st9400c & R6660D->hcw80 -

[WindyWard]

Hi

Before I install a Tado extension kit I'm trying to work out if the wiring I currently have confirms to any of the Honeywell Sundial Plans: i.e W or S etc. I just can't match the physical wires to the layout in the HoneyWell wiring guide in that the R6660D seems to go into the wrong connectors as does the boiler.

If this can be done then I would like to decommission the R6660D and replace the st9400c with the Tado extension kit.

Any help identifying the layout appreciated and then the best way to decom the R6660D.

thank you

 

[stem]

S-Plan two, 2-port motorised valves are controlled by a room thermostat and hot water cylinder thermostat

S-Plan+ motorised valves are controlled by more than one room thermostat to create multiple heating zones. May or may not have a hot water cylinder attached. [Only recently become common]

Y-Plan a single 3-Port motorised valve is controlled by a room thermostat and hot water cylinder thermostat. The valve can direct water to the heating, hot water, or heating and hot water

W-Plan a single 3-Port motorised valve is controlled by a room thermostat and hot water cylinder thermostat. The valve can direct water to the heating or hot water [not both simultaneously. Very uncommon system]

C-Plan Natural gravity circulation of hot water around the hot water cylinder, pumped central heating [Old design not installed for 40 years]

Once you have determined which system you have someone will be able to assist you. As you have figured, the ST9400c, which is a dual channel programmer with heating and hot water control, so the Tado extension box usually replaces that, and the old thermostat / receiver R6660D is removed and a small wiring modification is made to complete the circuit.

 

[WindyWard]

H. thanks Stem - really helpful - I have the S-Plan two.

I proceeded with disconnecting the R6660D by looping the terminals into which the grey and black had been connected - photo included to show the wiring.

Connected the Tado Extension box, 1 thermostat and 12 radiator values.

All is working 'to my amazement'. The tado system now controls the HW and CH.

thanks