My steam boiler, which supplies both heat and hot water, turned off a day or two ago, resulting in cold water. After some debugging, I found that the problem was with the pressuretrol, the device that turns the burner off when the boiler reaches operating pressure. It is a very simple device, as shown here:
The brown box is a microswitch. Below it is a lever. The lever is pushed from below on the right side by a piston, which in turn is pushed by the steam. On the left, the lever is anchored to an adjustable spring. When the steam pressure is great enough to pull the spring, the switch opens and turns off the burner.
The problem was that either the lever or the piston was stuck. A very gentle touch with the screwdriver was enough to loosen it, and bliss and hot water was restored.
My question is, do I have to worry about the pressuretrol getting stuck in the closed (“on”) position, causing the pressure to rise too much and blow a pipe or (much more likely) an old, rusty radiator? Should I have the pressuretrol replaced or inspected?