This is the Horstmann CentaurPlus C27, a two channel programmer which gives independent control over hot water and heating with up to 3 ON/OFF settings for each day of the week. It also has a 1 hour manual boost button for the hot water and an advance button for the central heating. The honeywell system should then take care of the thermostat, however, there is a room thermostat that needs to be removed, and that part Im not sure of. I suppose I could set it on full and let the evohome do the job, but Id rather remove. Any tips? or anything I havent got right? note it says Centaur Plus is volt free, so it seems the centaur plus is same as Hive single channel and standard one is same as Hive duel channel, so I would be hunting on the actual device to see if there is a diagram. Your picture clearly shows a brown sleeve on the blue wire going to 3 so clearly a line not neutral.

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And this is what we have remaining for our horstman C27 which is controlling only the hot water now. -so the neutral and live on the left will come out will go straight into the new nest heatlink. Just wondering if somone could advise where the grey and white cable currently in number 1 and the brown one in number 3 will go within the hot water part of the heat link.Look at the wiring diagram for your make/mode of thermostat that you are removing. If you don't have the instructions for it, a diagram is usually printed inside the lid. This will show which are the two live switching wires, and which is the neutral wire. (If there is a neutral present. Not all thermostats need or have one fitted) Im pretty sure its as simple as connecting the live and earth from the C27 to both BDR91s, then C27 1&2 go to the BDR91 for heat conections B&C, C27 3&4 to the BDR91 for hot water B&C and a link L to A on both BDRs Hi.. Thanks for the reply. The C27 thats in place at the minute is working to the extent where I can turn the heating and HW on and off, Just not set timers, (screen is dead) You can now disconnect all of the wires going to the old thermostat and remove the cable and thermostat. Having a few issues wireing in the Nest Heatlink - mainly trying to work otu what the current Common and Call-For-Heat connections are - have been looking at http://www.horstmann.co.uk/files/86..._guide_CentaurPlus_C21-C27_installer_web1.pdf but havent managed to work it out my self , we also have one thermostat on the system which will be replaced if that helps.

Centaurplus C27 with Nest Gen 3 | DIYnot Forums Replacing Centaurplus C27 with Nest Gen 3 | DIYnot Forums

Probably no one has answered you because you have added your post to the bottom of someone else's where it is hidden away and not visible as a new post. For future reference, this is also against the forum rules. Just done that and its all up and running - Thank you so much - Saved me alot of money there getting it installed. The Boiler is a Grant Vortex Pro External Combi21e, as the name suggests the boiler is outside in a casing so it's a bit more difficult to trace the wiring. The Nest Heatlink will need the usual Live and Neutral, from the same supply as the programmer etc, for it's power. lt;li>Operating periods per day: 3 per day for Central Heating and 3 per day for Hot Water</li>Now im after some help getting the hot water element up and running with the new nest to completely replace the Horstman C27. There is a separate immersion switch I can use to heat the water, but this can become expensive I I forget to turn it off. The red cable from terminal 4 of the programmer will no longer be required and should be removed from the programmer and made safe (unless for some reason you want the programmer to still have some control over the heating which the following does not allow for). CentaurPlus. 7 day control with 3 on/offs per day, advance, over-ride and boost settings and a 6 terminal wall plate.