• Fits where a Honeywell V4073A1039 sat: 22mm compression ends, three ports marked A, B and AB, and the same Y Plan wiring centre terminals
• Y Plan heating and hot water: flow goes to the radiators, to the cylinder, or to both at once when the valve holds its mid position
• Powerhead included: supplied with the actuator head fitted and a 1m 5-core lead, ready to wire in without buying a head separately
• Wiring: brown is heating on, where a Honeywell uses white. Grey, orange, blue and green/yellow are the same as a Honeywell V4073A
• 230-240V AC, 6W: the auxiliary switch fires the boiler and pump once the valve moves off the hot water port. Power off, it returns to hot water
• Manual lever marked AUTO and MAN OPEN holds the valve open for filling and draining. Compression nuts and olives come fitted on all three ports

The LavaTherm 3 Port Mid Position Motorised Valve is a 22 mm three port valve for controlling both the heating and the hot water circuits of a domestic wet central heating system from a single valve body. It is the standard valve used in a Y Plan layout, the most common control arrangement in UK homes with a vented cylinder.

Unlike a simple diverter, a mid position valve has three working states. With a call for hot water only, the valve stays in its rest position and flow passes to the cylinder coil. With a call for heating only, the actuator drives the valve fully across so that flow passes to the radiator circuit. With a call for both, the valve holds a mid position and feeds the two circuits at the same time, which is what allows a Y Plan system to heat the house and the cylinder together rather than one after the other.

The valve is supplied complete with its 230 V AC motorised actuator head already fitted. An auxiliary switch makes once the valve has moved to the calling port, firing the boiler and pump. A manual lever holds the valve open for filling, venting or commissioning.

The actuator head is a separate assembly held on the valve body by two screws, so a failed head can be replaced on its own without draining the system or disturbing the pipework. Replacement LavaTherm actuator heads are available separately.

Suitable for installation by a competent heating engineer. All electrical work must be carried out in accordance with current wiring regulations.

This valve is a like for like replacement for a Honeywell V4073A three port mid position valve. It matches the original on body dimensions, spindle pattern and wiring, so it fits the same position in the pipework and connects to the same wiring centre terminals.

Because the valve wires terminal for terminal into a standard Y Plan wiring centre and matches the V4073A footprint, it fits straight into the space and wiring left by the old valve, keeping the repair quick and predictable.