Replacement Synchronous Motor for motorised valves ACL Honeywell Landis Gye Satchwell Sopec Tower DIY Replacement 2-Port 3-Port Valve Failure

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A normally-open valve is open when no power is being applied to it and needs electrical power to drive it closed. When a demand comes from the programmer (via the thermostat), the motor is energised and drives the valve open to allow water to pass. When the valve is fully open, a microswitch is operated in the powerhead, connecting the grey wire to the orange wire. This is called closing the switch. It sounds a bit counter-intuitive, but when a switch is closed it is completing the circuit and allowing current to pass; when the switch is opened it is opening a break in the circuit and stops current from passing.

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. It will make it easier when re-fitting it (just remember which end the flex was connected or take a picture on your phone). The powerhead can only fit one way round onto the valve body but if space is tight that might not be obvious.The V4043B valves are uncommon and likely to be found in solid fuel systems. These valves fail-safe in the open position in the event of a power failure or valve motor failure. If, for example, the heating valve is failing in this way, you will get heat round the radiators while the cylinder hot water is being heated too. When the cylinder is up to temperature, the hot water motorised valve closes and no longer tells the boiler to fire, so the heating now stops too. V4043C1156 is a 2 port, ½” BSP Female threaded, 3-wire, normally-closed zone valve but has no end switch

If you know how to work safely with mains voltage electricity, the valve motor can be tested with a multimeter. With the mains electrical supply turned off and isolated, the resistance across the two motor wires (either both blue or both orange) can be tested. To test correctly, at least one of the two motor wires must be disconnected from the heating wiring circuit. However, if you need to replace the motor it may be easier to remove the powerhead so you can work on it in the open. Remember, on early Honeywell motorised valves (pre-1985) you can’t remove the powerhead without draining down first!

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In larger properties, 28mm valves may be used (the 5-wire 3-port V4073A1088 and the 6-wire 2-port V4043H1106). The 28mm V4043H1106 2-port zone valve has a6 th wire, coloured white. This white wire might not be used. In that case it should be made safe electrically.

Whereas the internal electrics of the 2-port valve are quite simple, the internal electrical controls of the V4073A mid-position valve are more complex. As we’ve said above, Honeywell make a large range of motorised valves. The Normal state of a valve is the de-energised state. This is the state when no electrical power is being used by the valve motor. 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 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. Replacement Honeywell SYNCHRON motors are available but are a bit more expensive. For a long time we’ve used the standard SYNCHRON motors as replacements, with very few problems.If the valve motor fails, the motorised valve will not open. The valve will not then close the end switch and so will not complete the auxiliary circuit. The boiler will not fire (with no open pipe circuit to dissipate the heat), unless another motorised valve opens another pipe circuit and calls the boiler into action. This prevents the boiler firing and the pump running when there is no water circuit open. If the powerhead (actuator) can be safely removed from the valve body (see warning above about pre-1985 Honeywell valves) you can try to turn the spindle. You may need a tool unless you have strong fingers. You must also isolate the electrical supply before removing a Honeywell motorised valve powerhead.