When the valve is powered and reaches the fully open position, the grey and orange wires are connected together. This is normally used to activate the boiler and pump. Overview Video Unlke the Y-plan system, operation of hot water and heating are totally separate, and this layout can easily be extended to support additional heating zones simply by adding an extra valve and thermostat for each zone. It can also be adapted for use with underfloor heating. Operation - Hot water It can still be fitted today, however is not suitable for systems with more than one heating zone. 3 Port Valve Operation

The live and nuetral in the honeywell wiring centre are connected to the room stat connectors 1 and 3. E for the earth, terminal 2 is empty. The room thermostat is shown with a neutral connection. However a 2 wire thermostat can be used which does not require a neutral. Operation - Hot water only This causes the valve motor to move to the mid position, and water from the boiler flows to both the hot water cylinder and the radiators.If your O or B terminal shares a label with another wire — typically W —identify whether you have a heat pump system or not. A heat pump runs your compressor for both heating and cooling. If you don’t know your system type, place this wire in the W terminal. If you have a heat pump system, put it in the O/B terminal. Here the motor will move to position A (heating only). When it gets there, an internal switch connects white and orange together, and this output is used to activate the boiler. I have bought a Honeywell sundial wiring centre to help me out which is pretty self explanatory as far as the connections are concerned. This video covers the wiring and electrical operation of a Y plan system. Wiring diagrams and further information continues below. View on Youtube. System Wiring Here, power is also applied to programmer terminal 4, which connects via wiring centre terminal 4 to the room thermostat. If heat is required, power continues to terminal 5 in the wiring centre, and therefore to the white valve wire.

Locate any unconnected wire labeled W or W1. If you identified an O, B, or O/B wire connecting to the O/B terminal in the previous step and it has a separate W wire, place it into the W2 terminal. Connect the W wire to the W terminal if you don’t have a wire connected to the O/B terminal.This scheme uses a 3 port mid position valve. In the past this was by far the most common setup, as it only requires one valve. At the moment I have a wired stat (Servowarm) which has a 3 core and earth cable connecting to it from a Honeywell Wiring Centre. Only two of the cores and the earth are being used at both ends. (Yellow, Red and Earth) There is no standard for which color wire controls each function. When wiring, each wire should be identified by what terminal(s) it connects to — never by color. If you don’t know to which terminal each wire connects, it may be necessary to go to the HVAC system and look at the designations on the control board. Consult your owners/install guide for wiring examples and systems compatible with your thermostat*. Once the valve is fully open, a switch inside connects the grey and orange wires together. Since grey is permanently connected to power, the orange wire provides power to terminal 10 in the wiring centre, and from there to the boiler and pump. Operation - Heating