28cdi, gaining pressure?

[pete_the_heat]

hi guys, got called to a w/bosch 28cdi yesterday, apparently gaining pressure overnight and opening the p.r.v.
filling key was not left in, expansion vessel is ok, p.rv is operating correctly (obviously!).
watched it running for about half' hour yesterday, and pressure seemed stable under all conditions, and its not a large install, so the expansion vessel is more that enough, so the only conclusion i can come to is that the cold feed is passing through to the heating circuit within the boiler.

Diverter valve?
D.H.W heat exchanger?

anyone who's had this before, you comments would be great!!

cheers pete

 

[ollski]

calorifier passing mains pressure into heating circuit usually.

 

[PEDANTICVINDICTIVEMAN]

Who makes these calorifiers then, calor gas ?

 

[kevplumb]

fink he means the DHW heat ex

 

[ollski]

calorifier
plate heat exchanger
secondary heat exchanger
water to water heat exchanger

call it what you will I just go for the quickest one to type
If you ring worcester they list it as a plate heat exchanger.