Chapter hvac engineering Fundamentals: Part 1 Introduction

Design Procedures: Part 6
241
Figure 8.22
Spiral bimetal mercury switch controller.
Figure 8.23
Nonbleed relay-type controller.
against the sensor action until the air supply valve closes at some new
balance point. This is internal feedback. When the sensor action is
upward, the exhaust valve opens and some air bleeds out, reducing
the pressure to a new balance point. The gain or sensitivity to change
in the sensed variable is adjusted by varying the length of the lever
Design Procedures: Part 6
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