f7 error code-no heating/hot water?

F7 = FLAME DETECTED ALTHOUGH APPLIANCE IS SWITCHED OFF Check electrode assembly, dry pcb. Flue clear?

FA = FLAME DETECTED AFTER GAS SHUT OFF
Check gas valve and wiring to gas valve. Clean condensation trap and check electrode assembly. Flue clear?

If your gas safe registered engineer hasn't got clue then get yourself a different engineer - you pay them for their expertise in diagnosis and repair - it's called professionalism.

F7 and FA appear to be the same fault - flame detected - clearly there will be no flame because your boiler does not ignite - so the flame detection is a false message.

There will be a flame detector electrode (which you have cleaned) that communicates to the control board - the fault condition happened immediately after the pcb was changed so it's easy to assume that work somehow caused the faults you see - either the new pcb is faulty or an electrical connection to it is bad or the flame detection electrode is giving a false signal.

I have several clues and I have no experience with boilers.

Good Luck...
December 2015

Some interesting stuff here (May be worth oosting on this forums as it's specialist:

http://www.diynot.com/diy/threads/problem-with-combi-boiler-bg-worcester-bosch-rd532i.193778/

and

http://www.ultimatehandyman.co.uk/BOSCH%20_WORCESTER_CONDENSING_BOILER_FAULT_CODES.htm

XXX
December 2015