hot water being fed into cold water header tank

[cjrboat]

hi all can anybody give me a reason for my central heating cold water tank is full of hot water causing a lot of condensation in the loft it apears
to come out of the exspantion pipe blow off when the pump comes on it starts to feed water in to the header tank slowly but enough to make the water hot can any one give me advise i think if i extend the pipe up another 2 ft higher will this be sufice or is their a valve i could put on the end of the pipe so it will still blow off on to much preasure but stop the water feeding into the tank all the time the heating is on thanks nobby

 

[KPlumbing]

Sounds like it's pumping over and the usual solution is to extend the open safety vent like you said but it could also be the pump speed is too high.

 

[anotherbgeng]

dont ever be tempted to block the open vent pipe with anything ..it is an open vent for a reason and that is to stop pressure and allow cold feed from the header tank..
4 possible reasons for pumping over ..
A. pump speed too high try a slower speed
B. boiler thermostat too high or out of range causing it to boil up through the open vent....
C. pipe work configuration is wrong not correctly close coupled etc
D. The favourite and most common is a restriction between open vent and cold feed ,when the pump kicks in it pushes the water up the open vent and down the cold feed so completing the circuit and giving circulation ,which will mean either the pipework between the cold feed and openvent needs cutting out or the air separator (if fitted )is blocked

 

[Agile]

The most common cause on an existing system which was previously OK under D above is cause by a partial blockage in the system.

Chemical cleaning or power flushing!

Tony