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SP970A, B, C AND D MANUAL AND MINIMUM POSITION PRESSURE REGULATORS
SP970C and D: Four Port Switches
These minimum position devices have a separate dead
ended chamber connected to port 3 to receive an
external signal. When the external signal is less than the
spring load, the signal has no effect and functions similar
PILOT
CHAMBER
PILOT
BRANCH
1
VENT MAIN
3
3
SP970C,D
4
A. BUILDING TO MINIMUM SETTING
SP970C,D
PILOT
BRANCH
3
3
4
1
VENT MAIN
B. BALANCED AT MINIMUM SETTING
to the SP970A, B as a pressure regulator. When the
external signal is greater than the spring load, the spring
load is isolated and the device duplicates the input
signal. See Fig. 7.
SP970C,D
DISC
PILOT
BRANCH
3
3
4
1
VENT MAIN
C. PILOT BUILDING BRANCH ABOVE
MINIMUM SETTING
SP970C,D
PILOT
BRANCH
1
VENT MAIN
3
3
4
D. BALANCED AGAINST PILOT
C4300
Fig. 7. SP970C and D operation.
Application
Fig. 8A shows a typical manual position application using
the three port SP970A, B. This control system manually
positions a damper between OPEN and CLOSED.
Turning the setpoint knob clockwise increases the
branchline pressure to the damper actuator and opens
the damper. Turning the position knob counterclockwise
decreases the branchline pressure and closes the
damper.
The three port SP970A, B is also used with a controller
for automatic damper positioning with minimum position.
See Fig. 8B. When the external signal is less than the
knob setting, the spring maintains the branchline
pressure as previously described. When the external
signal rises above the knob setting, air from the signal
flows directly to the branch. During steady state
conditions, the external automatic controller must be
capable of exhausting the air flowing through the exhaust
(pilot) port 4.
Fig. 8C shows a typical four port SP970C, D application.
The minimum position switch keeps the pneumatic
actuator at a minimum position until the thermostat
pressure is greater than the minimum position valve. The
thermostat then controls the actuator.
DAMPER DAMPER
M
M
1
2
1
2
4
DAMPER
ACTUATOR ACTUATOR ACTUATOR
M
M
SP970C OR D
INSERTION
THERMOSTAT
1
2
3
4
BRANCH BRANCH
EXH
SP970A OR B
CONTROLLER
B. MINIMUM POSITION C. MINIMUM POSITION
APPLICATION WITH APPLICATION
CONTROLLER INPUT WITH THERMOSTAT
C8279
Fig. 8. Typical SP970 application.
BRANCH
2
1
EXH
M
4
SP970A OR B
A. MANUAL POSITION
APPLICATION
Automation and Control Solutions
Honeywell Honeywell Limited-Honeywell Limitée
1985 Douglas Drive North 35 Dynamic Drive
Golden Valley, MN 55422 Scarborough, Ontario
M1V 4Z9
Printed in U.S.A. on recycled
95-7237EF J.H. Rev. 2-02 customer.honeywell.com
paper containing at least 10%
post-consumer paper fibers.