Rotor turndown sensor and control

Rotary regenerative heat exchange apparatus having a central rotor post, a rotor shell concentrically around said rotor post to provide an annular rotor therebetween, a mass of heat absorbent material carried by said rotor, a rotor housing having apertured end plates at opposite ends of the rotor adapted to direct a heating fluid and a fluid to be heated to and through the rotor, means for rotating the rotor about its axis to align the heat absorbent material of the rotor with the heating fluid and the fluid to be heated, a sector plate intermediate an end of the rotor and an end plate adapted to separate the heating fluid from the fluid to be heated, means supporting the inboard end of the sector plate, an axial projection carried by the end edge of the rotor, an actuating means connected to the outboard end of the sector plate to drive it axially toward said projection, means for motivating the actuating means, a limit switch actuated by axial movement of said projection, and an axially disposed sensor rod intermediate the projection and the limit switch adapted to actuate the switch in response to axial movement of the projection.