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Operation
When the pilot pressure exceeds the preset spring
pressure, port 8 opens and connects to port 7 and port 6
closes. See Fig. 5A. When pilot pressure is less than the
preset spring pressure, port 8 closes and port 6 opens
and connects to port 7. See Fig. 5B.
SPRING
COMMON
7
PILOT
3
A
COMMON
7
PILOT
3
B
Fig. 5. RP670 operation.
RP670A
NORMALLY
6
CONNECTED
6
NORMALLY
8
DISCONNECTED
8
RP670A
NORMALLY
6
CONNECTED
6
NORMALLY
8
DISCONNECTED
8
RP670A AND B PNEUMATIC SWITCHING RELAYS
Application
Fig. 6 shows a typical heating and cooling application
using an RP670A. During the cooling cycle, pilot
pressure (port 3) is below the relay minimum switching
pressure. Ports 6 and 7 are connected and port 8 is
blocked, removing the low-limit controller from the
system.
During the heating cycle, the pilot pressure is above the
preset switching pressure. Ports 7 and 8 are connected
A
and the low-limit controller resumes its override
operation. Port 6 is blocked.
7
3
THERMOSTAT
M
13/18 PSI
B
(90/125 kPa)
7
3
Fig. 6. RP670A typical application.
C4287
3
DISCHARGE
NORMALLY
RP670A
M B
DISCONNECTED
8
PILOT
COMMON
3
7
NORMALLY
6
CONNECTED
RESTRICTOR
COIL
LOW LIMIT
C4485
95-7232EF–1
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