what does F5 mean?

make:glowworm
model:??
GCN:47-047-??
F5 refers to boiler overheating
overheat stat can be reset manually
would need to check why boiler is overheating
pressure OK?
can you hear pump running?
have you been removing any rads recently to do it bit of decorating?
had any plumbers in fitting new kitchen/bathroom recently?
noticed any leaks anywhere on rads or overflow/safety blowoff pipe?

muppet
May 2012