How do combi boiler diverter valves work?

[Drake]

Hi, My Chaffateaux Britony 80 combi boiler has a recurring problem (as mentioned in an earlier post). A Chaffateaux tekkie thinks its the diverter valve. It's not easy to get detailed advice from him because I'm not a registered engineeer.

I can see the diverter valve in the diagram in my user booklet. It's part No.17 in the following illustration:

'm puzzled because there are no wires going to that component, apart from the CH control thermistor wires. (No.16 in the pic).

So how do these 3-way valves work? Electrically, or by some other means? What sort of fault could cause it to acasionally malfunction for seveal days on end and then clear up for a few days?

Thank you,

Drake

[Aidan]

It's a 3-way diverter valve, 1 inlet, 2 outlets. The water goes to either the CH or HW plate heat exchanger.

The actuator is usually a hydraulic diaphragm connected to the HW supply system. Opening a tap causes a drop in pressure on one side of the diaphragm, which is pushed by the pressure on the other side, operating 3-way valve. There are electric diverter valves (e.g., Honeywell) but they're far too slow for this application.

There's usually an electric switch on the actuator, which fires the boiler when the valve is in the HW position.

Electrically, or by some other

[Ed Sirett]

In this case it electrically operated. I've checked the manual. There is an electrical connection but you might not be able to see it until you've got the valve half out.

I strongly suspect that the only effective method of repair of this appliance is to replace this valve.

I possible cause of problems is the valve become stuck and then unsticking.

There are a lot of variations of diverter/3-way valves used in combi boilers.

The most common case is for the valve to be directly moved by the same components that detect the water flow.

Electrically is also used as in this case.

Wax pellet expansion is used on the Potterton Puma.

A 'standard' Honeywell type is used on some boilers (Pott. Lynx )

By using the circulator pressure and a reversing servo valve (Vaillant VCW 24x and Sine T3)

and probably others.