Wiring for Nest thermos with Central heating and Underfloor heating

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DaveS79

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Can someone clarify for me please if from looking at photo if this is likely to be an S plan or Y plan system as wiring up for 2 x Nest thermostats 1 for wet underfloor heating and 1 for central heating. Both the underfloor and the Central heating are only on 1 zone each. The valve on the left is under floor and to the right of this is central heating. Previous plumber has done one and just trying to decide on how to connect up wiring centre etc.

Thanks
 

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I would say that the valve on left (vertical) is going to central heating? The one on the right (horizontal) is UFH and probably goes with the pump. You should have a separate controller box to connect for UFH the valve and pump should I believe wire into this.
The central heating would be wired individually. I may be wrong it’s been a while since I did this sort of set up.
 
As Andy said.. your photo only shows 2-port valves.. so NOT Y-plan..

Should be just a simple Thermostat operates valve.. Then valve operates boiler arrangement?
 
Probably too late now but I agree absolutly with Sharpend. The demand from the Central Heating Nest goes to the demand on the Honeywell (left) controller (Brown) NB on these valves Grey is permanent live. The dedicated controll box will have a demand input which is connected to the other Nest demand output, connections for the pump, valve and and the three UFH zone valves, and finally a demand output. A micro switch in the Honeywell and a relay in the dedicated controller provide isolation of their outputs so that they may be joined together to go back to the boiler demand and will not interfear with each other.

So very like an S Plan where the dedicated controller replaces one of the valves.

 

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