User Guide

d. Continue moving dial in same direction until high stage switch just clicks (makes to

“B”) and note dial reading at this point.

e. The difference in dial readings, as noted, indicates the differential between stages.

For example, if the high, middle, and low stages click (make to “B”) at 71°F, 77°F,

and 84°F, respectively, then the differential between the high and middle stages is

6°F (77 – 71) and between the middle and low stages is 7°F (84 – 77). Total differ-

ential between the low and high stages is then 13°F (84 – 71).

N O T E

If differential between stages is changed after the instrument is calibrated, the calibration

has to be rechecked to make certain that the change in differential did not affect the calibra-

tion. Recheck calibration point (step 3).

Figure-15 Part Identification of Three Stage Thermostats.

Dial

Calibration Screw

Dial Screw

Thermostat Arm

Cover Screw

Tension Spring

Plunger Spring

Thermal Element

High Stage

Switch

Differential

Clamp Nut

Switch

Insulator

Between Differential

Eccentric Stud

Middle Stage

Terminal Block

Lock Screw

High Stage

Terminal Block

Differential

Contact Spring

Low Stage

Terminal Block

Middle Stage

Switch

Low Stage

Switch (Fixed)

Middle Stage

Differential

Adjustment Screw