Ed Sirett wrote:

The prime suspect is a scaled up secondary heat exchanger that won't allow
enough heat to go from the boiler into the HW.

If the model is a Puma then the CH delay is normal on-off 30seconds - on.
Longer than that it'll be the wax pellet actuator.
However it should not fire up and down repeatedly until the radiators are
hot.

The second British Gas engineer stated my water pressure was fine and
that the heat exchanger would need replacing due to limescale build up.


Before I get the quote, can anyone provide any insight as to what a
reasonable quote would be for parts and labour? Previous quotes from
British Gas have been halved by me obtaining the parts myself and
getting a local plumber/electrician to fit.