The V4073A 3-port valve never closes water flow through the valve completely. There is always an open pathway from port AB to port A or from port AB to port B or from port AB to both ports A and B at the same time. If the property uses a combi boiler (rather than a heat-only boiler) the boiler will usually contain a diverter valve. In small properties there may be no other motorised valves.

Autumn Statement: State pension confirmed to rise by 8.5% from April 2024 – while some benefits will go up by 6.7% A programmer and cylinder thermostat (stat) are used to control the times when the hot water is heated and to control the maximum temperature of the stored hot water. Only when both white and grey wires are energised (and the valve goes to the Heating Only position) can the orange wire get its 230V supply via the valve itself. (Remember, the orange wire can also get 230V from the cylinder stat if it is calling and a hot water program is on.) Honeywell V4043H1056 22mm 2-port zone valves have five wires: 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.On older style valves pre-1985, which do not have the replaceable head feature, the adaptor plate assembly can be used to upgrade the valves, to allow the replaceable powerhead to be used.”

Inside a Honeywell V4073A 3-port motorised valve showing the rubber ball which closes one or other port, never both. Synchron valve motors can remain energised and hot for many hours a day, all through the winter. They may eventually fail. A failed Synchron valve motor will prevent a 2-port motorised valve from working. The valve won’t be driven open and the end switch will not be made (connected) so power will not be sent on to the boiler or pump. If it’s the other way round, and the 2-port valve controlling the hot water circuit is failing, it may be less obvious. The heating circuit valve may be open for long periods telling the boiler to fire. If the hot water valve is partially open, you may not run out of hot water.

The electronics in Honeywell motorised valves tend to be quite stable and show relatively few faults but the motor may fail after years of operation. Honeywell use Synchron motors and these are freely available but there are lots of cheap cloned motors out there. These look identical but, instead of the name SYNCHRON, they use the word Synchronous.