User Guide

ManualsBrandsBarber Colman ManualsHVAC Replacement PartsThree Stage Thermostat w/ 20' Capillary (10-90F)

4. To check differential between stages:

a. Turn regulating knob well above calibration point.

b. Start turning know slowly toward calibration point until the first stage switch just

clicks (makes to “B”) and note dial reading at this point.

c. Continue turning knob in same direction until the second stage switch clicks (makes

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

d. Continue turning knob in the same direction until the third stage switch clicks (makes

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

e. Again, turn knob in the same direction until the fourth stage switch just clicks (makes

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

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

For example, if the fourth, third, second, and first stages click (make to “B”) at 84°,

80°, 77°, and 71°, respectively, then the differential between the fourth and third

stages is 4° (84 – 80), between the third and second stages is 3° (80 – 77), and

between the second and first stages is 6° (77 – 71). Total differential between the

first, or low, stage and the fourth, or high, stage is then 13° (84 – 71).

5. If it is desired to raise or lower all four switch actions, and the differential between all

stages is satisfactory, turn the calibrating screw to the left to raise the setpoints and to

the right to lower the setpoints. All four switches will retain their differentials and will

remain in sequence.

N O T E

If differential between stages is changed after the control has been calibrated, the calibration

will have to be rechecked to make certain that the change in differential did not affect the

calibration. Recheck calibration point (steps 1, 2, and 3).

Use caution in handling this instrument and when changing differential. Carelessness can

result in erratic operation.

Figure-17 Part Identification of Four Stage Thermostats.

Dial (a)

Dial Screw

Calibrating

Screw (DD)

Thermostat

Arm (c)

Cover Screw

Bellows Plunger

Tension Spring

Plunger Spring

Thermal

Element

First Stage

Switch (Fixed)

Second Stage

Switch

Second Stage Differential

Adjustment Screw (AA)

Terminal Block

Differential Contact

Springs (b)

Lock Screw (CC)

Fourth Stage Switch

Positioning Plate

Third Stage Differential

Adjustment Screw (BB)

Differential Nut (d)

Third

Stage

Switch

Fourth

Stage

Switch