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I have pumped hot water and CH on a three port valve, a Y plan I believe The wiring seems standard to many Y plan diagrams, where there is no wire to terminal 2 (Heating off) on the controller

My guess is I need this wired up for the hive to function fully, but where should it be wired to?

The existing controller is a Centaurplus C27 and N, L, 1, 3 & 4 connections all correspond to the hive layout. The boiler is a Halstead Best 60 (set to pumped Hot water). I have removed the existing room thermostat and connected the live to the switching live.
If I connect the hive and turn on both HW & CH the boiler fires, but not just one or the other. Attached is a digram that reflects my wiring
 

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The signals required are not really anything to do with the Hive. All Hive does is turn the heating and hot water 'on' and 'off'. That's it.

What it depends upon is what signals the type of heating system you have requires to do that. Central Heating 'off 'is not needed by the vast majority of UK heating systems, perhaps with extremely rare exceptions, probably much less than one in one thousand that have a MOMO type valve controlling them, and yours is not one of them.

Heating 'on' and hot water 'on' is used with 2-port motorised valves (heating off and hot water off isn't used)

Heating 'on', and hot water 'on' and hot water 'off' is used with 3-port motorised valves, aka Y Plan (heating off isn't required which is as per your diagram, no connection made to Hive dual channel version terminal 2)

Heating 'on' and hot water 'on' is used with older systems, pre 1980 that have pumped heating and gravity circulation of hot water (heating off and hot water off isn't used)

Most systems know that when it's not 'on' it's 'off' without having to be specifically told it's 'off'. Hence why heating off isn't used. No functions of the Hive are are lost. remember Hive is simply two on and off switches, one for heating and one for hot water. So, you don't need a connection to Hive Central Heating off, the Y- Plan system can work it out for itself. There isn't anywhere you can connect it to.

If you just removed the room thermostat, the central heating wiring would be open circuit and the heating won't operate. The live switching wires [L and SL in your diagram] that went to the old thermostat need to be electrically joined together to complete the circuit. From your post it would appear that you have done this.
 
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Thanks for that, I spent hours googling diagrams, before stopping to think, what would be able to tell if the room was hot enough, only the thermostat or the hive, the thermostat didn't have a heating off wire and you've just confirmed that the hive doesn't. So I'll look elsewhere, my first thought is user incompetence!
 
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With the standard Y Plan for domestic hot water the motorised valve has no power on it, the boiler is switches on directly from the tank thermostat, default valve position is DHW.

When the grey wire has power, it makes the valve move all the way across so only central heating is active, without the grey wire you can have DHW or CH + DHW you can't have just CH.

The grey wire is normally connected to both the N/C on the tank thermostat and the N/C on the programmer on the DHW contacts.

So this diagram Y-Plan.jpg is little change when fitting Hive would expect this
Y-Plan-hive.jpg
note DHW off still used.
 

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