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Switches
70
customer.honeywell.com
70-6925
SP970 Operation
SP970 Typical Piping
Operation
SP970A Three Port Switches
PRESSURE REGULATOR OPERATION
Main line air flows through the restriction into the branchline
chamber and out the nozzle. Branchline pressure increases
until it is strong enough to compress the spring and lift the
diaphragm off the nozzle. Air flow out the nozzle is controlled by
the balance between the branchline pressure and spring force.
See Typical Piping Diagram A Above.
MINIMUM POSITION OPERATION
See Typical Piping Diagram B above. An external signal is
connected to Port 4 (Exhaust Port). When the external signal is
greater than the spring load, the nozzle opens and branchline
pressure is the same as the external signal. When the external
signal is less than the spring load, branchline pressure is
controlled as described above. See Operation Diagram below.
SP970A operation
SP970C 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 to the SP970A 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 Operation Diagram below.
Piping Diagram C above shows a typical four-port SP970C
application. The minimum-position switch keeps the pneumatic
actuator at a minimum position until the thermostat pressure is
greater than the minimum position valves. The thermostat then
controls the actuator.
SP970C Operation
C4471A
C. MINIMUM POSITION APPLICATION WITH
BLEED TYPE THERMOSTAT INPUT (LP916)
A. MANUAL POSITION APPLICATION
2
1
4
BRANCH
M
SP970A
EXH
DAMPER
ACTUATOR
2
1
4
BRANCH
M
SP970C
3
EXH
INSERTION
THERMOSTAT
M
DAMPER
ACTUATOR
1 2
M
CONTROLLER
DAMPER
ACTUATOR
2
1
4
BRANCH
SP970A
B. MINIMUM POSITION APPLICATION WITH
CONTROLLER INPUT
M
2
PILOT
SP970
SP970A
1
BRANCH
MAIN
4
C4298A
2
PILOT
1
BRANCH
MAIN
4
3
2
PILOT
SP970C
A. BUILDING TO MINIMUM SETTING
B. BALANCED AT MINIMUM SETTING
D. BALANCED AGAINST PILOT
1
BRANCH
MAIN
DISC
VENT
4
C4300A
PILOT
CHAMBER
3
2
PILOT
SP970C
1
BRANCH
MAIN
VENT
4
3
2
PILOT
SP970C
1
BRANCH
MAIN
VENT
4
3
2
PILOT
SP970C
C. PILOT BUILDING BRANCH ABOVE
MINIMUM SETTING
1
BRANCH
MAIN
VENT
4
Содержание VP525C
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