Leviton omnistat 3 Directives D'installation page 17

About 2-Pipe Systems
1) 2-Pipe systems require an external pipe temperature sensor to determine if the
thermostat will be calling for cooling or heating.
2) The external pipe temperature sensor connects to the two-position header
terminal marked J4 on the back of the thermostat printed circuit board (Refer to
Figure 12).
2-Pipe
24VAC
CONTROL
TRANSFORMER
Cool/Heat Valve
Fan
Fan Stage 3
Fan Stage 2
CONFIGURATION
• The "System Type" must be set to "2-Pipe" under "HVAC Settings".
POWER UP
1. Double check wiring, be sure that there are no stray wires or wire strands at the
connections.
2. Connect power to the transformer and system.
3. Attach the thermostat to the base, the display will show the current temperature
reading.
Connections for 2-Pipe thermostat
HVAC SYSTEMS
24VAC "HOT"
(RC)
24VAC Common
(C)
(Y1)
(G)
(G3)
(G2)
1 2 3 4 5 6 7 8
THERMOSTAT
Figure 10
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