Boiler lock out

[bennyxf1]

Bosch Worcester 280RSF, In hot water mode temperature at hot tap is a steady 50 deg C. IT DOES NOT INCREASE IN TEMPERATURE. It runs fine for approx 5-10mins (at around 12 l/m). Boiler then locks out, and needs resetting.

THANKS IN ADVANCE

 

[namsag]

50 degrees would be about right 35 degree temp rise and water coming in around 15 degrees .
cutting out then it could be a faulty sensor that is not allowing boiler to modulate down and is staying on high flame.
Would not suspect faulty calorifier as it appears to be transfering heat into the hot water

 

[bennyxf1]

50 degrees would be about right 35 degree temp rise and water coming in around 15 degrees .
cutting out then it could be a faulty sensor that is not allowing boiler to modulate down and is staying on high flame.
Would not suspect faulty calorifier as it appears to be transfering heat into the hot water

If the sensor were faulty, and the boiler was staying on high flame (and not reducing output), would this not create an increase in flow temperature before the boiler locks out?

 

[namsag]

Not necessarilly the calorifier can only get rid of so much heat into the incoming cold water by its design which yours appears to be doing by it reaching 50 degrees

 

[bennyxf1]

sorry namsag, not sure if we've crossed lines or not here, but i presume your aware that its a combi boiler I've got. Not sure what you mean in stating calorifier???

 

[namsag]

Yes i know its a combi a calorifier is the name they use on this model for the water to water heat exchanger, days before plate heat exchangers.
Not unless the 280 used a bi flow heat exchanger which if memory serves me right it didn`t.

EDIT
memory does seve me wrong these did use a plate heatexchanger which is listed as a water to water heat exchanger but fault would still be same.

simple way to check is let it be cold then run hot water at full flow for a minute then cut it right down and you should see the flame go down from high flame to low flame

 

[bennyxf1]

Ok, ive run the test (from cold). Ran the kitchen tap on full for a couple of minutes which controlled fine around 50 deg (without boiler going off), then reduced flow from tap by approximately 50%, and boiler controlled very well at around 60 deg (on lower flame) for over 5 minutes (without boiler going off). I then reduced flow out of tap even lower (which would never happen), and temperature exceeded 70 deg, and boiler did not lock out, but stopped, and re-ignited after a few seconds. I presume this proves the overall control of the boiler is good i.e water to water exchanger not blocked??? After use of the tap, the diverter valve traveled, and htg pump kicked in - i suppose to dissipate the heat out of primary heat exchanger (gas to water). I am bemused at to what is causing the boiler to lock out, and am getting ever more annoyed at having to reset the damn thing. We are not using the boiler for heating at present, so assume the problem is connected to hot water. It locks out randomly - was fine all day yesterday, and this morning with a fair amount of use, then go to use it this afternoon and its locked out.

Any suggestions please.

Was thinking along the lines of the fan maybe???? Is there any way to check this?

 

[bennyxf1]

Is there anyone out there who can help?