Combi Boiler problem

[ellal]

I've got a fairly new Halstead combi boiler ( just out of warranty ), and it's developed an annoying fault. The boiler fires up ok, on hot water demand, but after a minute or so cuts out, and the water cools, and then the boiler fires up again. this just repeats. It also does it to a lesser extent on the heating system.
On recommendations, have checked the following:
Mains stopcock fully open so boiler receives adequate supply.
Pressure for heating system at required 'Bar'.
Boiler 'reset' tried.

Any ideas? Thanks in advance.

 

[DP]

Pressure for heating system at required 'Bar'.

Ellal, What is the pressure? There may be one hand or two hands on the pressure gauge

 

[ellal]

1 and 1/2 Bar at 'idle'

 

[ellal]

sorry, that didn't look right...

single hand at 1.5 Bar

 

[ChrisR]

WHICH BOILER?!! How old is it? (Wtees vary) Did the fault come quickly? How big is the CH system?
Measure the flow rate (litres per minute) of shower temp water from a good flowing tap. Use a bucket for that. Do you know if the system was cleaned/inhibited with chemicals?

 

[ellal]

it's a 'halstead aces high' boiler. 10 rad system. problem appeared quite quickly, as it's very noticeable in the shower! boiler is 15 months old (1 yr warranty). no chemicals used