Boiler is Myson Apollo 15/30.
All its components check out to be working OK but the system pumps over when hot and there does not appear to be any pump over run when the boiler stops firing. i.e. the circulation pump stops when the boiler stops firing. therefore, that residual heat can not get away and the hot water pumps over to the F & E tank.
Is there a reason for this that can be remedied? Also the heating clock has stopped working and the local boiler parts supplier says the boiler is obsolete and no parts available. Additionally, air is always being drawn in to the system.
Appreciate any feedback to above. Regards

Nigel Lynskey, April 2009

Question 1) Pumping over when shutting off - Sounds like the pump is sucking air into the system during use, could be lack of system head, F&E tank should be at least 750mm above the pump and preferably more,
when the pump the entrained energy is pushing water back into the F&E tank, try turning the pump speed down one setting, although the boiler might protest at this (Kettling)

Question2) Timeclock built in to apollo is obsolete, but you can always fit a stand alone programmer and wire it in to the system & over-ride the faulty built in unit
any decent heating maintenance engineer would be able to do this for you.

Most common parts such as thermostats and Thermocoulpes etc can still be sourced

www.elanar.co.uk, April 2009