Install Instructions

RP470A AND B PNEUMATIC SELECTOR RELAYS
5
RP470A
3
2
5
RP470A
PILOT INPUT A
PILOT INPUT B
BRANCH OUTPUT
PILOT INPUT B
3
2
PILOT INPUT A
BRANCH OUTPUT
A
B
C4293-1
Fig. 4. RP470A operation.
RP470B
When the pressure at Port 2 is greater than the input
pressure at Port 5 (Fig. 5A), Port 2 supplies output
through Port 3. When the pressure at Port 5 is greater
than the pressure at Port 2 (Fig. 5B), the diaphragm
closes off the output (Port 3.) This action prevents the
Port 2 signal from passing through Port 3.
BRANCH OUTPUT
OR VENT
SIGNAL INPUT OR
BRANCH OUTPUT
BRANCH OUTPUT
OR VENT
SIGNAL INPUT OR
BRANCH OUTPUT
A
RP470B
3
2
RP470B
3
2
PILOT INPUT
5
LOCKOUT
PRESSURE
PILOT INPUT
5
LOCKOUT
PRESSURE
B
C4294
Fig. 5. RP470B operation.
Applications
RP470 A and B Pneumatic Selector Relays are used in
HVAC systems to perform several relay functions.
RP470A - Higher-of-Two Pressures Relay
CAUTION
Accuracy decreases when used with circuits
having 0.005 restrictors; for example, TP974
(0.30 psi [2.07 kPa]) compared with those
having 0.007 restrictors (0.15 psi [1.03 kPa]).
Fig. 6 shows a typical application using three zone
thermostats and two RP470A for control. Each zone is
controlled by a separate thermostat. The thermostat that
calls for the most cooling (transmits the highest
branchline pressure) controls the cooling valve through
one or both RP470A.
ZONE 1
DA
THERMOSTAT
ZONE 2
DA
THERMOSTAT
ZONE 3
DA
THERMOSTA
T
N.C.
DAMPER
A
CTUATOR
ACTUATOR
RP470A
RA
VALVE
N.C.
DAMPER
ACTUATOR
N.C.
DAMPER
ACTUATOR
3
5
2
RP470A
3
5
2
M B M B
M M
M B
M
C4492
Fig. 6. RP470A typical application.
RP470B - Lockout Relay or Repeater
Fig. 7 shows a typical lockout application. When outdoor
air temperature is higher than return air temperature, it
disables the mixed air controller.
0.005 IN.
BLEED
RETURN AIR
SENSOR
–40 TO 160°F
(–40 TO 71°C)
OUTDOOR AIR
SENSOR
–40 TO 160°F
(–40 TO 71°C)
RP470B
RP471A
MIXED AIR
ACTUATORS
MIXED AIR
CONTROLLER
INPUT
(0.013 MM)
8
7
RESTRICTOR
EXH
6
3
2
5
3
M
M
SNAP-ACTING RELAY
SET AT 3 PSI (21 kPa)
C4491-1
Fig. 7. RP470B typical lockout application.
Fig. 8 shows the RP470B piped as a repeater. This
application provides circuit isolation by repeating the
input pressure with a second air source. The signal at
3 95-7231EF