3 point valve

[ursamajor]

Hope its the right termanology,but is it likely or possible for the valve to allow water to leak past,the reason I ask is,the hot water tank is set at 60c but the boiler is on 70c and as the day progrees's the water gets hotter without it being on.The valve is a switchmaster been there since the house was built in the eighties.

 

[45yearsagasman]

Yes it is possible for that to happen with these now obsolete valves.When the ch is on water can pass into the cylinder and heat it beyond the cyl stat set point.Change the valve for a modern 3 Port mid position valve,eg Honeywell 4073 for example.If you are not confident then a good heating engineer could change that in about an hour and a half and rewire the valve.A partial drain down may be required.

 

[ursamajor]

That was quick,thank you.If its a straight swap then I will do it myself.

 

[45yearsagasman]

It may require slight pipe alterations and the wiring is different.Can't remember the wiring changes off the top of my head but I'm sure someone on here will have a diagram.

 

[misterdubya]

It may require slight pipe alterations and the wiring is different.Can't remember the wiring changes off the top of my head but I'm sure someone on here will have a diagram.

S/Master Orange & Red = H/Well Orange
SM White = HW Grey
SM Yellow = HW White
SM Blue = HW Blue
SM Green/Yellow = HW Green/Yellow

Mr. W.

 

[ursamajor]

Thank you, have copied and pasted for future reference.