Boiler cutting out - pleases help!!

[JamesM]

I'm a complete novice to heating and plumbing and am having terrible problems with my Worcester Bosch 24cbi boiler cutting out.

I moved to a new house in February and the heating was fine for the winter months. Lots of work was done to the house over summer and the boiler was completely off for a few months. When I came to turn it back on in October nothing happened. The heating engineer saids that he found a burnt out PCB and replaced it. Now the boiler came on, but only for 30 mins approx before it cut out and the warning light started flashing. You could restart it but the same thing happened. The engineer replaced a number of other components but this did not make it much better and he seemed at a dead-end. I called Worcester Bosch, who sent their engineer. He was at the house under 20 mins before he said that the boiler was functioning perfectly, the problem was that I had an open system which was gulping in air from the header tank which is only 5 ft or so above the boiler. He said to switch to a sealed system, replace the pump with a new one and flush through any old water/sludge and it will work. My doubts about this are: 1. The system has apparently been working well for 5 years. 2. I've bled the radiators and there is no air in there any more. It's a bit better than it was but a still have to restart it 3-4 times a day (and it's in the loft!). If you start it from cold it will stay on for 2 hours+. If you start it again while still warm it will cut out again in 30 mins - 1hr. Can you please give me some advice?!?[/b]

 

[Gasguru]

Is the lockout light definately flashing or is it constant ? Does it always flash (indicating lockout) or is it constant (indicating overheating).

If its definately lockout it sounds like the Worcester eng. was talking garbage or the diagnostic lights are wrong.

If it's lockout did they check the flue restrictor ring was fitted if a standard flue is installed?

The boiler should work with only 1.2m from the water level in the feed & expansion cistern to the top of the boiler ie 5ft should be sufficient.

Is it plumbed in correctly ie the pipework from the boiler flow pipe to the pump should have a close coupled vent and feed pipe. Has the pump been wired to the boiler? If the system has 2 x 2 port zone valves has a bypass valve been fitted?

Have a look at the manual or check the Worcester site to check the system is plumbed in correctly otherwise it may be overheating after the burner has sshut down.

 

[bengasman]

If the wb engineer says you should change to a sealed system, you should do so.
And have the system checked over completely by whoever is going to do the job for you.
Whoever stuck your boiler on the open vent without converting it was a cowboy
My tenner says the system was not flushed either, cowboys rarely do.
Another tenner says your earth is not up to spec, it never is in those cases
Another tenner says your controls are inadequate, either very old, or incorrectly installed or incomlete. cowboys are not interested in controls

 

[Gasguru]

If it's a genuine lockout faults then it has nothing to do with the system setup. There are plenty of these boilers on open vent systems.

 

[past3bar]

I encountered a 19/24 Cbi regularly going to lock out recently which was fitted to an open vented system (approx 4 years) and had previously worked fine. Someone had talked them into a new PCB but no improvement.
The problem was the APS pipes were perished and cracked (but not obvious till I inspected them closer. I cut them back & re-fitted, boiler is now fine.
I would have expected the Worcester engineer to check these but everybody makes mistakes.
Turn the power off before you go near this area!