Honeywell V4073A Mid-Position Zone valve

White
(input)		 Grey
(input)		 Valve Position Orange
(output)
O O B (idle)
Hot Water		 O
Live O A + B
CH and HW		 O
O Live Hold in last position  O
Live Live A
Radiators		 Live
In the absence of any signals on the white or grey wires to the valve, the valve will remain in its idle position which is port B (Hot water). The pump will receive a supply from the boiler where a 'pump overrun' is fitted. Where this is not the case, the pump will be fed from terminal 8 (same as the boiler).

When the cylinder thermostat is satisfied, the contact will change over from cold to hot and the system will shut down. The live now presented on '7' will be used in the situation that both CH and HW are on and the cylinder thermostat is satisfied. The live from '7' feeds into the valve via the grey wire and causes it to take up position A when a signal is also present on the white.

Please note that all information on this web site is provided 'as is' . Whilst every effort has been made to ensure its accuracy, no responsibility can be accepted for any damage, loss or other misadventure as a result of its use.