Billy, "rgi" is shorthand for registered Gas Installer and it may well be wise to call a certified enginer in.
The fault you have may be due to a defective pressure switch or a defective control board.
You are not obliged, however, to call in a Gas Safe Engineer - it is perfectly legal - unless you're a landlord - to attempt a repair yourself - weather it's a wise thing to do is another matter. You are not allowed to interrupt the gas way unless qualified - that would definately be illegal.
Good luck...
Peccavi, March 2010
