Switching From CM900 to hive hot water and heating

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Please can anybody help. I'm looking to switch my current honey cm921 programmer to the hive system hotwater and heating. We are on oil boiler Grant vortex Pro boiler and have separate immersion heater for water. I have taken off the current Cm900 honeywell wireless unit and found what you can see in picture. N and L I understand but there is then a connection from the live to port A with Port b having two wires in it brown and red. I am not stubed as to how this translates to the hive back box with is N L 1 2 3 4 I know that 2 and 4 is heating off and on that is it. Can anybody help. FYI I should point out the wireing you see is how we found it when we brought the house.
 
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The link is to apply mains voltage to the A-B-C side. The 2 wires don’t make much sense, unless you have a combi boiler?
 
and have separate immersion heater for water
So I would assume for central heating so single channel Hive terminal 3 is B and terminal 1 is A, if using duel channel then terminal 4 is B.

However you say in title "to hive hot water and heating" so it seems you want more. So now looking on how plumbed, we tend to use the Honeywell plans, so S plan uses two x two port motorised valves, the Y plan uses a single three port valve, where is also a W plan which also uses a three port but rare, and we have three versions of the C Plan two which don't use any valves and one has a single two port valve.

Not quite that simple I have a C plan with two x two port valves as the heating is zoned so can heat main house or flat, but at least number and type of motorised valves gives us a good idea of the system, next is the hot water cylinder, other than the immersion heater has it got a thermostat, and is there a hot coil to heat the domestic hot water?

The Hive thermostat has a special function with the duel channel designed for C Plan as I have detailed in your screwfix post. But not now sure if your system was designed to heat DHW from the central heating boiler?
 

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