Trane VAV-SVX02B-EN - Manual (Page 3)

3 VAV-SVX02B-EN
Thermostat
Specifications
TP970 Series Pneumatic T-stats
Maximum Safe Air Pressure:
25psi (172 kPa)
Maximum Safe Air Temperature:
150°F (66°C)
Throttling Range:
2–10°F (1–5°C)
Gain:
2.5 psi/°F Adjustable
Operation
Pneumatic thermostats modulate
output air pressure in response to room
air temperature. Pneumatic thermo-
stats fall into two categories: direct-
acting or reverse-acting. This section
describes how thermostat output
pressure responds to changes in room
temperature.
Figure 3 graphically illustrates the
relationship between room
temperature and output pressure of a
direct-acting thermostat. The graph in
Figure 3 shows that as the room
temperature increases, so does the
output pressure of the thermostat.
Figure 4 illustrates the pressure/
temperature characteristics for a
reverse-acting thermostat. As room
temperature increases, the thermostat
output pressure decreases.
A thermostat in proper working order
will be able to output a pressure
ranging from approximately .5 psi to
supply air pressure depending on
distance from indicated setpoint.
Figure 4–Reverse-Acting
Thermostat Response
Output P
ressure
Input Temperature
Figure 3–Direct-Acting
Thermostat Response
Output P
ressure
Input Temperature