When using two 2-port valves, the control system may be known as a Sundial S Plan system or a Honeywell S Plan system. In smaller properties there is usually one programmer which has two channels. One programmer channel controls the heating (radiators or underfloor) and the other programmer channel controls hot water. Where additional zone valves are used there will usually be another programmer or timer. Honeywell motorised valve construction

The Y Plan and S Plan names are more commonly used when other Honeywell controls are also used (programmer, room thermostat, cylinder thermostat and wiring centre). Honeywell make a large range of motorised valves used in domestic central heating systems. The most common by far are the 22mm 3-port, 5-wire, mid-position valve and the 22mm 2-port, 5-wire, zone valve. These 22mm valves (3-port V4073A1039 and 2-port V4043H1056) are used in smaller and medium sized properties. Honeywell V4073A1039 22mm 3-port mid-position diverter valve. These are 5-wire valves. When used with other Honeywell controls the setup is know as Y Plan

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The Honeywell V4043H1106 28mm 2-port zone valve has 6 wires. Five of these wires are the same as 22mm 2-port valve.Green/yellow is Earth, blue is Neutral, brown is Live (or Line) to the motor, grey and orange are connected to the end switch and form part of a separate circuit. These valves have compression pipe connections, though Honeywell make motorised valves with threaded connections too. How motorised valves are used

The Honeywell valves have a D-shaped top to the spindle but you can also use a spanner on this. If you do this, you must use very little force as it is very easy to shear a spindle or damage the valve internally. It may be easier to have the valve set in the manually open position using the manual lever. (See Honeywell Motorised Valve Manual Lever, below.) The Honeywell 22mm Midposition Diverter Valve V4073A1039 has been designed to control the flow of water in domestic central heating systems, where both radiator and hot water cylinder circuits are pumped. It is typically suited for small to medium sized installations. The Honeywell motorised valve faults detailed above are likely to apply to most domestic Honeywell valves.The auxiliary circuit (grey and orange wires) is commonly used to operate the boiler and/or the circulating pump. The auxiliary circuit could be set to work at a lower voltage than mains but it is normally carrying mains voltage. It works like this: One of the two wires, typically the grey, is connected to a permanent mains Live supply (about 230V AC in the UK). The other wire, usually the orange, is connected to the Switched Live feed to the boiler. The wires to disconnect are the two wires which run from the motor. On earlier motorised valves, these were both joined to other wires using metal crimps encased in plastic. On more recent valves, one wire is joined with a crimp and the other is wired directly to the electrical components of the valve. When a V4073A mid-position valve is set up in a Y-Plan configuration and Hot Water is called for, power to the boiler is provided directly from the cylinder thermostat. The valve is not energised.