Glowworm xtrafast 96 overheating problem

[DaddyDurks]

Help needed !!!
i have a 5 year old Xtrafast 96 combi which up to now has given sterling service.
over the last month or so it has developed an overheating problem when i am running the hot water for any prolonged time ( a bath usually)
The boiler works perfectly on heating but once i start running the bath or shower it trips out on fault code 14 ctn2>97c-pump will run the boiler shuts down and you have to wait for it to cool sufficiently to reset
both clip on thermistors(heating and dhw) have been replaced but the problem hasnt gone away . the only way i have of running a bath is in one minute intervals and then turning the tap off for 10 seconds to let the boiler cool
any help would be appreciated before i call mr plumber !!!

 

[Agile]

Unless the secondary heat exchanger is blocked it could well be a gas related problem which will need a competent CORGI to diagnose.

You could do a gas rate check at the meter yourself to see if its in line with the specs.

Look at the FAQ and other postings for how to do it.

Tony

 

[DaddyDurks]

Agile
not sure how it could be a gas problem when the boiler performs fine when in heating mode
if i could find out how the boiler regulates the hot water output temperature then it may point to the cause.
there is a motorised valve within the unit and i have thought this may be the cause
if the water temperature is at its set limit what does the boiler do to prevent
a scalding water
b overheating !
and where does it "blend" the water to give a constant output..
what i cannot understand is that the central heating pipe thermistor is tripping the boiler out.

 

[gasgeezer]

F14 on this appliance usually means blocked or partially blocked secondary heat exchanger