Install Instructions

RP970A PNEUMATIC CAPACITY RELAY
Operation
Figs. 4 and 5 show typical operation. When pilot pressure
increases, the exhaust tube raises the diaphragm off the
branch chamber port and main air flows into the branchline,
pushing against Diaphragm 2, (Fig. 4A). This pressure
forces the exhaust tube down and closes the branch
chamber port. Branchline pressure now equals pilot
pressure (Fig. 4B). As pilot pressure drops, the branchline
pressure against Diaphragm 2 forces the exhaust tube
down, which opens the exhaust port (Fig. 4C). This function
allows branch air to bleed out through Port 4. When
branchline pressure equals pilot pressure, the exhaust tube
rises and the exhaust chamber port closes (Fig. 4D).
You can use Exhaust Port 4 in other ways. For example, if
Port 4 is fed with a regulated pressure, the branch does
not bleed below the switch setting.
RP970A
1
3
PILOT
CHAMBER
2
4
EXHAUST
MAIN
TUBE
DIAPHRAGM 1
BRANCH
BRANCH CHAMBER
DIAPHRAGM 2
EXHAUST
PILOT
A
RP970A
1
MAIN
2
BRANCH
EXHAUST
3
4
PILOT
B
RP970A
1
MAIN
2
BRANCH
EXHAUST
3
4
PILOT
C
RP970A
1
MAIN
2
BRANCH
EXHAUST
3
4
PILOT
D
C4295
Fig. 4. Typical RP970A Operation.
Application
Fig. 5 shows a typical RP970A application. The device
increases and repeats the output signal from the bleed-
type duct thermostat, improving signal response over a
long transmission line or high-capacity load (additional
actuators).
BLEED-TYPE DUCT
M
DAMPER OR
VALVE
ACTUATOR
RESTRICTOR
THERMOSTAT
RP970
41
3
2
EXH
M
TO ADDITIONAL ACTUATORS
OR LONG TRANSMISSION LINE
C4479-1
Fig. 5. RP970 Typical Application.
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