Data Sheet for Product

Technical Instructions Free Energy Band TH 193 HC Heating/Cooling Room Thermostat
Document Number 155-068P25
February 14, 2022
Page 10 Siemens Industry, Inc.
Troubleshooting
Before troubleshooting thermostat (see Table 4), ensure that there is clean, dry supply air
at 18 psi (124 kPa) minimum. Use the test probe gauge and needle adapter to measure
the control pressure at the thermostat test port.
The output pressure test port is accessible without removing the thermostat cover through
the 8th opening from the top. For one-pipe thermostats, the port is on the right side. For
two-pipe thermostats, the port is on the left side.
Figure 9. Accessing the Output Pressure Test Port.
CAUTION:
If you use the wrong test port, thermostat damage can occur and result in
replacement of the device.
Table 3. Troubleshooting Guide.
Problem
Check
Cause
Action
Control pressure
stays at
approximately zero
Air supply
Low supply pressure
As required
Nozzle or flapper
Dirt on nozzle or
flapper
Clean nozzle or
replace thermostat
Restrictor
Clogged restrictor
Replace restrictor
Calibration
Out of calibration
Recalibrate
Control pressure
stays at
approximately
supply pressure
Nozzle
Clogged nozzle
Clean nozzle or
replace thermostat
Calibration
Dirt on either supply or
exhaust valve seat
Alternately close and
open nozzle by gently
pushing down the
bimetal
Excessive air
leakage from
exhaust port on left
side of thermostat
Supply and return
line connection
Connections are
interchanged or
connection to port is
incorrect
As required