by HB on Thu Mar 31, 2011 3:07 pm
If you open the steam wand valve and the boiler pressure drops, the vacuum breaker is sticking shut, resulting in false pressure. Mine does that regularly, despite that I've only used distilled water in the boiler. Tapping the pin on the vacuum breaker unsticks it for awhile.
If the pressurestat is reaching the red zone, it's failing in the closed position. This happens when the diaphragm is no longer flexible enough, or the contacts have welded themselves together. Replacement is the only fix.
For sake of completeness, the only other causes for a cold boiler I can think of are (a) over-temperature thermostat has tripped, (b) heating element has shorted out, and of course (c) it's unplugged and/or turned off.
Dan Kehn