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Technical Bulletin
Document Number 155-253P25
December 9, 2003
TH192 HC Heating/
Cooling Room
Thermostat
Sensitivity Adjustment
Limit Stop Adjustment
Thermostat Calibration
Page 18
The factory thermostat sensitivity setting is approximately 2.5 psi/°F (31 kPa/°C). To
change the sensitivity, use a flat-blade screwdriver to carefully move the sensitivity slide
(see Figure 16) to the desired position as follows:
Graduation closest to the rigid
end of the bi-metal element
4 psi/°F (50 kPa/°C)
CAUTION:
Thermostats must be recalibrated whenever sensitivity is changed.
Thermostat limit stops define the minimum and maximum thermostat set points. The
limit stops engage in the set point cam gear teeth and cause interference between the
set point cam gear and the adjustment knob gear.
To change the limit stop settings:
1. If not already done, remove the thermostat cover using the Cover screw and
calibration wrench.
2. Use a needle nose pliers to pull the limit stop tab (see Figure 16).
3. Rotate the limit stop to its new position.
4. Reposition between the setpoint cam gear teeth. Do not pull the limit stop any
more than necessary to clear the gear teeth.
5. Repeat with second limit stop tab.
NOTE:
Changing the limit stop position one gear tooth changes the limit stop setting
by 1-1/3°F (0.7°C).
The thermostat is factory calibrated to a control pressure of 7.5 psi (52 kPa) when the
setpoint and the ambient temperature are both at 72°F (22°C). No adjustments are
required if these settings are appropriate.
If the thermostat has been tampered with, the sensitivity changed, or it is out of
adjustment, use the following steps to recalibrate the instrument.
The output pressure test port (see Figure 16) is accessible without removing the
thermostat cover through the eighth opening:
NOTE:
For TH192 HC thermostats, the test port is on the left side.
CAUTION:
If you use the wrong test port, thermostat damage can occur and result in
replacement of the device.
Calibration Kit for Room and Duct Thermostats
Graduation closest to the
minimum (MIN) end of the bi-
metal element
1 psi/°F (12 kPa/°C)
Siemens Industry, Inc.
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