TH 192 DN Day-Night and DNV Day-Night-Vent Room Thermostat
Technical Instructions
Document Number 155-067P25
October 28, 2010
Siemens Industry, Inc.
Page 11
Troubleshooting
Before troubleshooting thermostat per Table 5, make certain there is clean dry supply air
at 18 psi (124 kPa) for day control and 25 psi (172 kPa) for night. Use test probe gauge
and needle adapter to measure control pressure at thermostat test port.
The output pressure test port is accessible without removing the thermostat cover
through the 8th opening from the top left side.
Figure 10. Accessing Output Pressure Test Port.
Table 4. Troubleshooting Guide.
Problem Check
Cause
Action
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
Control pressure
stays at
approximately zero
Calibration
Out of calibration Recalibrate
Nozzle Clogged
nozzle
Clean nozzle or
replace thermostat
Control pressure
stays at
approximately
supply pressure
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
