Data Sheet for Product

Technical Instructions SW 251 Pressure Electric Switches
Document Number 155-057P25
Rev. 1, May, 2000
Page 4
Siemens Building Technologies, Inc.
Application
SingIe input models:
SPDT - See
Figure 2
N.O. - See
Figure 3
N.C. - See
Figure 4
DuaI Input Models -See
Figure 5
CONTROLN.C.
N.O.
COM.
PNEUMATIC
SIGNAL
ALARM
LINE
SW0083R1
Figure 2. SPDT Model.
N.C.
N.O.
COM.
PNEUMATIC
SIGNAL
TO
ELECTRICAL
EQUIPMENT
SW0084R1
Figure 3. Normally Open.
N.C.
N.O.
COM.
PNEUMATIC
SIGNAL
TO
ELECTRICAL
EQUIPMENT
SW0085R1
Figure 4. Normally Closed.
N.C.
FANLINE
EP
VALVE
321
S
S
T
COM.
SW0086R1
FROM NIGHT
THERMOSTAT
DAY/NIGHT
SUPPLY
Figure 5. Dual Input.
Day–Night Operation
Day Cycle [18 psi (124 kPa) applied to the "S" port] - Contacts 2 and 3 are closed. The
fan runs continuously and the EP valve is energized to open the outside air damper.
Night Cycle [25 psi (172 kPa) applied to the "S" port] - Contacts 2 and 3 are open. The
fan is actuated by Contact 1 through the "T" port. The night thermostat cycles the fan
intermittently to maintain a reduced night temperature. The EP valve is de-energized to
keep the outside air damper closed at night.
Discontinued