System pressure should be set cold at approx 1.2 - 1.5 bar on the guage. when heating is on, pressure will rise upto 1.8/2bar. If pressure reaches towards 3bar, water will discharge from the pipe outside to protect boiler. when it cools pressure will be down because water has been lost. If this is the case, expansion vessel is at fault
chris m - ravenheat specialist, November 2009
