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Baxi DHW Flow Valve (sanitary section only)
The manifolds are of well-proven design, with thousands being installed in Combi boilers all over Europe and the UK. They are manufactured under strict quality controlled conditions, each and every manifold being fully tested for leakage and operation before being packed.
The complete manifold assembly used on the Baxi Potterton boilers is available in two sections: the \"Pressure Differential Assembly\" – Baxi Potterton part no. 248063 (Ezypart reference MF01) and the \"3 Way Valve Assembly – Baxi Potterton part no. 248062 (Ezypart reference MF03).
The entire manifold assembly performs a critical function within the overall operation of the boiler, being activated every time there is a demand for domestic hot water.
One of the main advantages of these combination boilers is that they provide domestic hot water at mains pressure, eliminating the need for cold-water tanks and shower booster pumps. This manifold assembly is the component within the boiler that responds when a hot water tap is opened and diverts primary (heating) water to a heat exchanger in which the mains pressure domestic water is heated to comfortable level.
The whole assembly is made up of two main brass sections: the first is the \"Pressure Differential Assembly\" (diaphragm chamber), identified by the six screws clamping the two parts together. Inside the chamber there is a flexible rubber diaphragm. The diaphragm is made from ethylene propylene WRAS (Water Research Advisory Service) or WRC (Water Research Council) approved rubber, specifically selected to comply with the UK water regulations.
On this section there are two small threaded connections to which the pressure pipes, which sense the flow of domestic water, are connected.
When a domestic hot water tap is turned on, the flow of water is sensed and causes the diaphragm, via a plastic plate, to act on two stainless steel shafts, one causing the 3 Way valve section to move to the hot water position, the second shaft projecting from the centre of the diaphragm chamber operating on the micro-switch.
Both shafts are located in PTFE bearings that contain rubber O-Rings that ensure no leakage.
The second section \"Valve – 3 Way assembly\" is secured to the \"Pressure Differential\" section by two clamp screws. As its name implies, this section is the 3-way valve section. This section has a G ¾\" primary water inlet connection, a G ¾\" primary outlet connection (to the heating circuit), and a pushfit primary outlet connection (to the plate heat exchanger). Two other connections are a pushfit connection for the by-pass tube & a threaded connection for the pressure gauge.
In the winter, the heating water flows in through the G ¾\" inlet connection, when the valve is in the non-actuated position. This heating water is discharged into the central heating system via the G ¾\" outlet connection and circulated around the heating system before returning to the boiler, where it re-enters the main heat exchanger.
When there is a demand for domestic hot water, the flow of cold mains water causes a differential pressure across the diaphragm via the two pressure pipes causing the valve to change position. Now the heating water flows in through the G ¾\" inlet connection and out the pushfit primary outlet connection passing through the secondary domestic hot water heat exchanger. In the summer, there is no flow of primary water until the boiler detects a requirement for domestic hot water.
This section also houses a primary water flow switch to ensure that the boiler does not operate without sufficient primary water flow.