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tained. Be certain to use the proper size screwdriver for the terminal blocks to minimize the
chance of damage to the terminals.
If the controllers are installed in either a metallic or non-metallic enclosure, follow the enclosure
manufacturer’s recommendations for proper grounding. Do not rely on conduit connections to
provide a suitable ground.
Grounding terminals/screws are provided for connection of system ground leads. Proper system
grounding is required for safe and correct operation of the controller’s protection features.
2.7.6 INPUT POWER
The 920 controller may be powered directly from the trace voltage (120 Vac to 277 Vac),
through a step-down transformer, or from a separate circuit. The same wiring terminal assign-
ments are used in all configurations, as defined below:
Note that terminals 5 and 8 are only used for implementing 3-phase switching (this is true for
both SSR and contactor configurations).
When powering the controller directly from the incoming trace power (120 Vac to 277 Vac),
jumpers are installed between terminals 1 and 2 and 3 and 4. This is the standard factory config-
uration. When the controller is to be powered from another voltage source, the jumpers between
terminals 1 and 2 and 3 and 4 should be removed, and the controller power connected to termi-
nals 2 and 4.
In applications where a neutral-based 4-wire 3-phase source is available, the controller may be
powered from one line to neutral connection, while the trace is operated from the line-to-line
connection, eliminating the need for step-down transformers or separate power sources. This
can be accomplished by removing the jumper between terminals 3 and 4 only. Controller power
can then be derived from the L1 trace power on terminals 1 and 2 and the incoming neutral con-
nection for controller power would be connected to terminal 4.
Wiring diagrams for typical 1- and 2-pole configurations are included in Appendix C on page 68.
Note: The contactor version Switch Interface modules provide a switched line voltage signal to
drive the contactor coil. This is derived from the control power and, as such, requires that the
contactor coil voltage be specified to match the control voltage present on terminals 2 and 4.
Caution: Many wiring configurations will use more than one power source and all must be de-
energized prior to performing any maintenance on a controller circuit. When servicing one con-
trol point, remember that power may also be present on the second control point.
2.8 Initial Power-up
Caution: Before applying power to the controller, ensure that powering the circuit will not dam-
age it if power limiting or the setpoint temperature have not been set correctly. If there is any
doubt, the load should be disconnected until the 920 has been suitably programmed for correct
and safe operation.
Power Connections Terminal No.
Line/L1 power input 1
Line/L1 Control Power Input 2
Neutral/L2 Power Input 3
Neutral/L2 Control Power Input 4
L3 Power Input (3Ph only) 5
Line/L1 Output to Trace 6
Neutral/L2 Output to Trace 7
L3 Output to Trace (3Ph only) 8
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