I just drained my central heating system to install a new radiator. When I refilled it, bled all the air out and turned the heating back on, the boiler only stayed lit for a few minutes than cut out before the radiators were hot. The pipes around the pump in the airing cupboard are scorching but the radiators are cold. Any suggestions?
You've got an airlock somewhere. Possibly around the main pump area - could be it is just spinning air around.
The boiler went off because the water in the heat exchange was hot enough.