OIL BOILER

摘要

PURPOSE:To lessen dust attachment to a sensor element by mounting a number- of-revolutions sensing element to sense the number of revolutions of a blower fan in the neighborhood of the fan case wind starting point within a fan case. CONSTITUTION:A number-of-revolutions sensing element 5 to sense the number of revolutions of a fan 12 is fixed to a fan case 13, wherein the sensing part protrudes into the fan case 13. The sensing element 5 is located in the position with smaller air passage in the neighborhood of the fan case wind starting point 22 between a throat 21 and a suction hole 19. Thereby dust attachment to the number-of-revolutions sensing element can be extremely lessened to lead to prevention of any failure in sensing of the number of revolutions.