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. This can cause the valve spindle to seize. It often becomes stiff to turn at first and the valve may give intermittent problems. Eventually, the spindle may become so stiff that the valve motor cannot turn it at all. If Hot Water is then satisfied (either by the programmer or cylinder stat), the grey wire is energised. As there is still a demand for Heating, the valve will motor to the Heating Only position (port A open; port B closed) and switch a 230V supply onto the orange wire, to power the boiler.

System boilers may also have a diverter valve or zone valve built into them and might not have any external zone valves. The Honeywell V4073A 3-port valve has five wires. These are blue, green/yellow, white, grey and orange. Note that the grey and orange wires are used differently from the grey and orange wires of the 2-port 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. 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. 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.) In normal operation, with a heat-only boiler, central heating water is heated in the boiler and then pumped round the system by a circulating pump. Motorised valves are used to split or divert the flow. The heated water can either be sent to the radiators (or underfloor heating) or to the cylinder coil to heat the domestic hot tap water. The cooled circulating water is then returned to the boiler to be heated again. You should be able to feel a bit of spring resistance, right at the far end (Man Open end) of the slot.

Slide the blunt end of the motor sideways until the flange comes out from the tab holding it down. This can be a bit of a fiddle. The motor then comes free of the valve, held only by the two wires which connect it electrically. These two wires may be blue (in a Honeywell original Synchron motor) or orange (most replacement Synchron motors). The auxiliary circuit allows several 2-port motorised valves to be used to control separate zones without interacting electrically. Otherwise, if several zone valves were used without auxiliary circuits, and all were connected to the same pump so that the Live wire that opened each valve also fed the pump Live, there would be problems. The Chancellor Jeremy Hunt has today (Wednesday 22 November) announced a range of tax, benefits and savings measures. We round up the key announcements and what they mean for you. When all electrical power to the heating controls is switched off, the spring pulls the ball across to close port A, leaving port B open. This is the relaxed state or de-energised state of the valve. It is also sometimes called the Normal state.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. 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.) This can be difficult to feel for at first. It is most obvious when the valve has been in the Heating Only position and reverts to the mid-position.

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Typically, a small or medium sized property will have either one 3-port valve (which splits the central heating water flow between cylinder and radiators) or two 2-port valves (one governing flow to the cylinder and one governing flow to the radiators). The Honeywell V4043H1106 28mm 2 Port Zone Valve 240V series of two port motorised valves has a wide range of flow control applications in domestic central heating systems. The V4043H normally closed models have end switches for electrical control of boiler and pump. The normally open model is particularly applicable to the control of solid fuel systems since it will always fail-safe in the event of a power failure. Key Features The rubber ball sits against the circular port (right side in photo), closing it off. We’re told that the ball touches one edge of the circular port first, causing the ball to rotate slightly on its spindle. This regular slight rotation evens out distortions in the ball. A little piece of elegant design work by Honeywell! Both of these genuine SYNCHRON motors work in Honeywell motorised valves. The motors SYNCHRON make specifically for Honeywell come with two blue wires A failed motor will prevent the motorised valve from opening but it is not the only cause of a valve failing to open correctly. After years of use, the O rings sealing the valve spindle (or actuator shaft) can fail. When this happens, central heating water will seep past and will corrode the metals.

Where two 2-port motorised valves are fitted (one for the heating circuit and one for the hot water cylinder circuit) the fault may be disguised. Even though one valve only partly opens itself and is unable to fire the boiler, the valve on the other circuit can open fully and fire the boiler. The pump then pushes heated boiler water through both the open valve and the partially open valve. The Honeywell motorised valve faults detailed above are likely to apply to most domestic Honeywell valves.

Honeywell 2-port motorised zone valves (V4043H) are electrically quite simple. The powerhead contains the motor, which is used to drive the valve open, and an auxiliary switch or end switch. Honeywell 22mm zone valve operation (V4043H1056) Thanks for your reply. I don't know much about heating / plumbing so I'm a bti concerned about taking the cover off the unit and messing around with it whilst power is live to it. 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.