Hi Patrick,
You've probably sorted out your boiler by now. But if not, I hope this helps.
To sense there is sufficient air to ignite the burner, there is a small diameter plastic tube with a vacuum sensor to detect if it blocked, usually with condensation. The sensor activates the gas valve. If this is the case, unblock the tube. If the burner still doesn't ignite. there is a restriction in the flue.
This is basically a safety device to ensure a good clean gas
burn.
As I am writing from memory, I haven't the installation manual to hand, this the theory but the might not have the detail quite right.
When I had mine install, they had this problem. I had to read the manual to sort it out for them.
I want to replace my Miami 4 front with a Chatsworth. I'm "Googling" to find one as these back boilers are obsolete now. Any ideas?
Regards,
Tony
Tony, November 2007
