This will cause the valve to take a mid position and allow water to flow through both ports A and B, supplying heat to both hot water and heating circuits.
Why is heating coming on with hot water? A frequent and likely cause is a faulty or jammed three port valve. In a typical central heating and hot water boiler system, the valve sends water to either the radiators, the hot water cylinder, or both. In the list of possible repair costs for a heating system, your problem is a fairly economical one to rectify. Why do my radiators come on when the heating is turned off? When a diverter fails or gets blocked with debris, hot water intended for the hot water circuit can get into the radiator circuit.
Then the radiators will be hot even though the heat is turned off. You do not have to live with constantly hot radiators. If you are experiencing this specific issue with your radiators. Why does central heating only come on with hot water? The motorised valve contains a microswitch that controls the boiler when central heating only is selected. If this fails, the valve moves to the heating only position but doesn't operate the boiler, when hot water is required the boiler comes on because in this mode the boiler is operated by the cylinder thermostat.
How do I drain my heating system? How to Drain a Radiator Turn off all power to the boiler. The power switch will be located on the boiler. You must feel for this; it does not turn full circle like some valves! We changed the failing zone valve with a new 22mm Honeywell VH zone valve and tested the operation. Everything worked normally with the hot water now operating correctly on its own again. Since the boiler worked OK for hot water we looked at the programmer to check that it was set to call for heating and checked that the room thermostat was set high enough to be calling for heat.
The manual lever of the 3 port valve was only slack for about one third of the length of the slot which is the normal position for hot water only. The valve spindle did not feel unusual tight when we pushed the lever against the spring and the valve returned normally. Using a multimeter set to V AC we checked for V between the valve white wire and valve blue wire in the local junction box and found V present so we suspected the valve motor.
After isolating the electrical power we disconnected one lead from the motor within the valve actuator and checked the resistance through the motor across the two motor leads. This figure is normally about ohms but in this case the leads were open circuit, with a resistance reading millions of ohms, indicating a break in the motor windings. We changed the motor for a new genuine "Synchron" motor our experience of cheaper, generic motors is that they can fail very quickly and the system worked fine, with the mid-position valve opening to heating correctly on demand.
Original Synchron motor removed from the Honeywell VA valve. The Synchron motors fitted to Honeywell motorised valves have blue wires. Most Synchron motors have orange wires. The manufacturing date code is written on the side of this motor, , week 23 in Unwanted hot radiators can be caused by bad pipework design but this system had had no pipework changes and had worked normally before. The Honeywell VA motorised valve rests in the hot water only position the heating port, A, is closed when the valve is de-energised.
However, if hot water was satisfied and heating was the last thing calling, the valve can remain partially energised with the heating port open. We switched off the power and the valve rested in the hot water only position. Typically, in this position, the lever is loose in the slot for about one-third of its travel, with the remaining two-thirds of the travel pushing against a heavy spring. With the boiler running, the pipe from the motorised valve port A to the radiators immediately became hot, indicating a fault in the valve.
The rubber ball in the Honeywell valves can become dented if left in the hot water only position for a long period. This often happens during the Summer when no heating is called for. The dent prevents the ball from seating correctly for a while, allowing a small amount of let-by into the radiator system but this will often resolve itself after a few days.
Honeywell designed the valve so that the ball turns slightly on its spindle each time it sits down. Clever engineering! With this design the ball tends to round itself up and avoid permanent dents. When we buy new Honeywell valves to put on stock we check that they are in the locked open "manual" position for storage. That way the ball doesn't sit down and doesn't dent. If the white wire is not used, the 28mm zone valve is wired in the same way as the 5-wire 22mm zone valve, and operates in the same way.
It is now relatively unusual for the white wire 6 th wire of a Honeywell 2-port zone valve to be used. It is used to allow independent temperature control of both the heating and the hot water circuit where the installation has pumped heating but gravity hot water. The Honeywell mid-position motorised valve has three ports in a T configuration. Water enters via port AB. Water leaves by either port A or port B or by both at the same time. Port A is normally connected to the radiator circuit and Port B to the cylinder coil to heat hot water.
The circulating pump is usually connected to feed water from the boiler into port AB. The Honeywell VA 3-port valve has five wires. Note that the grey and orange wires are used differently from the grey and orange wires of the 2-port valve! The blue wire is the Neutral, N. The white wire is connected to the wire from the room thermostat which calls for heating radiators or underfloor.
The grey wire is used to drive the valve to the Water Off position, in which only the heating port A is open; it closes port B. The orange wire provides a Switched Live Switched Line feed to run the boiler and pump.
Whereas the internal electrics of the 2-port valve are quite simple, the internal electrical controls of the VA mid-position valve are more complex. The Honeywell VA is a spring-return valve. Port A or port B can be closed by a rubber ball, though never both at the same time. The rubber ball is moved between ports A and B by an actuator shaft or spindle which is driven by the powerhead.
The inlet port AB can never be closed; the ball only moves between port A and port B. The VA 3-port valve never closes water flow through the valve completely. The rubber ball sits against the circular port right side in photo , closing it off.
This regular slight rotation evens out distortions in the ball. A little piece of elegant design work by Honeywell! 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. When a VA 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. When Heating is also called for, the white wire is energised and the valve will motor to, and stop in, a mid-position. Power for the boiler is still supplied directly from the cylinder thermostat.
The orange valve wire may have a potential of V but this is coming from the cylinder stat to which the orange wire is also connected and not from the circuitry of the valve. 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 V supply onto the orange wire, to power the boiler. Only when both white and grey wires are energised and the valve goes to the Heating Only position can the orange wire get its V supply via the valve itself. Remember, the orange wire can also get V from the cylinder stat if it is calling and a hot water program is on.
When Heating Only is on, and then is switched off or the room stat demand is satisfied, a lower voltage of between 50V and V will remain on the orange wire. The motor will continue to be energised though on lower power and will remain warm. The valve will remain in the Heating Only position port A open; port B closed.
If Hot Water is turned on again, or all the mains power is turned off, the motor will be de-energised and the spring will pull the valve back to the Hot Water Only position port A closed; port B open.
Honeywell say that the manual lever located on the end of the powerhead is not a position indicator and should be used used for filling the system and for draining down only. You set the valve into the manually open position by turning the power off, then pushing the lever towards the Man Open end of the slot. You will be pushing against the return spring. You can then lift the lever slightly and release the pressure so that the spring pushes the lever back, leaving it caught behind the hook at the top of the slot.
The lever pushes the valve open against the return spring. The valve does not pull the lever over towards the open end as the valve opens. With the 3-port valve, port A is closed and port B is open when the valve is de-energised. This is the state either when all the power is off or when Hot Water Only is selected. In this valve position, the lever is only slack in the slot for about a quarter of the slot travel starting at the Auto end.
If the lever is moved further to the right you can feel the strong resistance of the return spring as you force the valve open. After forcing it open, if you release the lever it will be pushed back towards the Auto end. When Heating and Hot Water are both selected, the valve drives open to the mid-position and stays there. The lever then becomes slack for almost the entire travel of the slot.
You should be able to feel a bit of spring resistance, right at the far end Man Open end of the slot. 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. So, if you set the system for Heating Only Hot Water must be off or satisfied on the cylinder stat the valve motor drives the valve to close port B while it leaves the heating port A open.
The lever will be slack across the whole length of the slot with no end resistance at all. This is because the lever can only drive the valve just a little past the mid-position but the motor drives it much further.
Starting with the controls set for Heating Only, hold the lever tight against the right side of the slot. You may need to turn the cylinder stat up to make it call. That noise and that bump are diagnostic.
They tell us that the valve has moved into the mid-position where both Heating and Hot Water ports are open. If you can make a Honeywell 3-port mid-position valve move into all three of those positions, the valve and controls appear to be wired correctly and the valve appears to be working normally. The manual lever on the 2-port valve tells us less. When the valve is open, the lever should be free across the whole of the slot.
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. 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 the powerhead actuator can be safely removed from the valve body see warning above about pre Honeywell valves you can try to turn the spindle. Not great those Honeywell valves I think and looks like you will need a new Honeywell actuator, or have someone replace the entire valve with another brand if you wanted. Centre Brand motorised valves are a lot cheaper. Danfoss - avoid!
Drayton break inside after a few years. I actually think Myson, which are a cheap valve, seem reasonable. Billy Bob Bob. Thank you everyone for your suggestions and prompt advise. So, just to check I am on the right track: I have this valve VH and it seems that the power head replacement for it, Honeywell brand, is Status Not open for further replies.
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