Technical Instructions
Document Number 155-067P25
October 28, 2010
Page 6
Siemens Industry, Inc.
Operation
Day-Night Operation
The TH 192 DN thermostat is either direct or reverse acting for both day and night
operating modes. In a direct acting thermostat, an increase in temperature increases
the control air pressure and a decrease in temperature decreases the control pressure.
In a reverse acting thermostat, an increase in temperature decreases the control air
pressure and a decrease in temperature increases the control pressure.
The TH 192 DN provides two separate bimetal elements; one for day temperature and
one for night temperature. Each bimetal element operates independently of the other.
Use of two different supply air pressures accomplishes changeover from day to night
temperature. A supply pressure of 18 psi (124 kPa) or 25 psi (172 kPa) positions a
changeover switch so a changeover relay operates in the day or night mode
respectively.
Figure 5. TH 192 DN and DNV Input/Output Characteristics.
Manual Selector Switch
A manual selector switch allows an individual thermostat to control at its day setting
even though the remainder of the system is controlling at its night setting.
•
In the normal AUTO position, the manual selector switch does not interfere with air
passage to the changeover relay.
•
To manually set the selector switch to the DAY position, push the selector in until it
latches and the handle points downward. In the latched DAY position, the manual
selector switch seals off air to the changeover relay.
•
To manually reset the selector switch, rotate the handle until it unlatches and returns
to the normal AUTO position.
•
Manual Selector Switch resets automatically when supply pressure changes back to
day time control.
Day-Night-Vent
Operation
The TH 192 DNV provides a supplementary air line connection at the back of the
thermostat.
NOTE:
This third line feature cannot be added to a TH 192 DN in the field.
The vent line provides either 0 or 25 psi (0 or 172 kPa) pressure via the manual selector
switch to pilot auxiliary controls. For example, a unit ventilator can provide continuous
full day operation when the space is occupied and intermittent night operation when the
space is unoccupied.