Why does the Honeywell mid position valve VA valve stay in its last held position? If the controls are calling for hot water only there is no electrical supply to the valve. The valve will be fully open to port B allowing water to flow through port B only, supplying heat to the hot water circuit. If a call for heating is then given by the controls then an electrical supply of volts is applied to the white wire of the valve. 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.
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Honeywell 3-port mid-position valve operation VA and VA Common Honeywell motorised valve types 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 VA and 2-port VH are used in smaller and medium sized properties. In larger properties, 28mm valves may be used the 5-wire 3-port VA and the 6-wire 2-port VH This white wire might not be used. In that case it should be made safe electrically. These valves have compression pipe connections, though Honeywell make motorised valves with threaded connections too.
How motorised valves are used Honeywell VA 22mm 3-port mid-position diverter valve. These are 5-wire valves. When used with other Honeywell controls the setup is know as Y Plan. 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.
When using two 2-port valves, the control system may be known as a Sundial S Plan system or a Honeywell S Plan system. The Y Plan and S Plan names are more commonly used when other Honeywell controls are also used programmer, room thermostat, cylinder thermostat and wiring centre.
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. In medium sized or larger properties there may be an additional zone valve, external to the boiler, which allows the heating to be split into two zones. System boilers may also have a diverter valve or zone valve built into them and might not have any external zone valves. Under Part L of the Building Regulations, many new properties must have the heating radiators or underfloor heating split into two zones.
This creates a living zone and a sleeping zone which both have separate time and temperature controls to improve energy efficiency. Where there are two heating zones there will usually be an additional zone valve.
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. A programmer and room thermostat stat are used to control heating times and room air temperatures. The programmer and room stat may be combined into a single programmable room stat. 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.
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 Raised pip on the metal cover of a Honeywell motorised valve powerhead Nearly all Honeywell valves have a powerhead also called an actuator which can be separated from the valve body. The valve body is the brass casting which is bolted into the pipework. The powerhead or actuator is the electrical section.
These are contained within a silver coloured metal box which is connected to the brass body. The powerhead drives a spindle or actuator shaft which is part of the valve body. On modern Honeywell valves, if the powerhead fails it can be removed from the valve body without draining down.
With very old Honeywell motorised valves the powerhead could not be removed without draining the water first. Removing a Honeywell motorised valve powerhead Non-contact voltage tester made by Fluke Check that the valve is not so old that the system needs to be drained before removing it. As far a we know, Honeywell motorised valves which were made from , and which carry the raised pip small bump on the top of the metal cover, allow the powerhead to be removed without draining down see above.
Isolate all electrical power to the central heating system and test to ensure that it is electrically safe. We use a non-contact volt stick to confirm that it is safe. Non-contact voltage testers are much safer to use than traditional neon testers.
The ones we use are made by Fluke. With the power off, release the powerhead cover screw and lift away the metal cover. Recent valves have an internal earth wire which connects the cover to the powerhead. Once the cover has been lifted clear it can be hung to one side.
With earlier valves, the cover was completely free. One of two screws which hold the powerhead to the valve body. They are diagonally opposite each other. With the cover removed you have access to the two screws which secure the powerhead.
These screws are diagonally opposite each other and pass through the steel base plate of the powerhead actuator into the brass flanged top of the valve body. Unscrew both of these screws. Motorised valves are often fitted in tight spaces with limited visibility so note the orientation of the powerhead. 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. With the powerhead cover removed you also have access to the screw which retains the motor.
The motor can, if necessary, be removed without disconnecting the powerhead from the valve body. 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. The commonest fault with Honeywell motorised valves is motor failure.
Honeywell valve motor fault? The motors SYNCHRON make specifically for Honeywell come with two blue wires 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 are all synchronous motors synchronous is a generic term for a type of electric motor.
We never use cloned motors. We tried in the past and, in our experience, they fail really quickly. 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. 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. We find it is normally about 2. I think that a reading anywhere between 2. If the reading is many times higher than that, or it is open circuit, the motor has failed. Having come this far, if you suspect the motor may be faulty, it would be worth changing the motor. Remember, there are lots of poor quality synchronous motors out there.
Changing a Honeywell valve motor Synchron motor securing screw in a Honeywell 3-port motorised valve Synchron valve motor flange secured below metal tab Replacing a failed Synchron motor in a Honeywell motorised valve is quite straightforward, assuming you know how to work with mains electricity safely. Make sure you read the whole process through before starting! First, isolate all electrical power from the central heating system controls. Then, using a non-contact voltage tester like the Fluke volt stick above, check that the system is safely isolated.
It may be easier to have the valve set in the manually open position using the manual lever. Remove the metal cover of the powerhead by removing the cover securing screw, then lift the cover clear. Remove the motor securing screw which is located at the side of the Synchron motor.
On the other side of the motor there is another flange which is located below a metal tab. There is no screw in this flange on the motor in a Honeywell valve. 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. Replacement Synchron valve motor which has been supplied with two types of connector. The orange connectors are not used in Honeywell valves. The two white connectors are crimps.
The wires to disconnect are the two wires which run from the motor. On earlier motorised valves, these were both joined to other wires using metal crimps encased in plastic. On more recent valves, one wire is joined with a crimp and the other is wired directly to the electrical components of the valve. Crimps are metal tubes within plastic insulation, which are flattened using pliers to trap two wires, joining them electrically. These crimps can sometimes be re-opened by using pliers to squeeze together the edges of the flattened tube.
This can be done with the plastic in place. If successful it frees the two wires.
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