Assertion: boiler | /r/HasAspect | 2 or 3 pressuretrols
Facets:
value: generally
type: DEGREE
Source sentences:
text: Boilers generally have 2 or 3 pressuretrols: a manual-reset pressuretrol, which functions as a safety by setting the upper limit of steam pressure, the operating pressuretrol, which controls when the boiler fires to maintain pressure, and for boilers equipped with a modulating burner, a modulating pressuretrol which controls the amount of fire.