Initial Power-Up - Pentair 920 Series Installation, Operating And Maintenance Instructions

2.8 InItIaL poWer-up

INDUSTRIAL HEAT TRACING SOLUTIONS
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 sepa-rate circuit. The same wiring terminal assignments are
used in all configurations, as defined below:
power Connections
Line/L1 power input
Line/L1 Control Power Input
Neutral/L2 Power Input
Neutral/L2 Control Power Input
L3 Power Input (3Ph only)
Line/L1 Output to Trace
Neutral/L2 Output to Trace
L3 Output to Trace (3Ph only)
Important: 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 configuration.
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 terminals 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 connec-tion, 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 connection
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.
Important: 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 control point,
remember that power may also be present on the second control point.
CAUTION:
Before applying power to the controller, ensure that powering the circuit will not damage 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.
2.8.1 InItIaL CabLe test
To minimize the risk of damage to the controller due to a cable fault, the integrity of the heating
cable should be verified by:
1. Using a megger to perform a high-voltage insulation test
2. Using an ohmmeter to ensure that the heating cable is not shorted
These tests must be performed with the controller output disconnected. Once the cable has been
checked, it may be reconnected to the controller and power applied.
2.8.2 random start deLay
All 920 series control modules incorporate a RANDOM START-UP DELAY feature, ensuring that
all units do not power on at the same time. When power is first applied to a controller, it will
hold its output off for a random time (0 to 9 seconds), equal to the last digit of the HTCBUS™
communications address (see section 3.9.2 on page 43). Once the start-up delay has timed out, the
controller will begin normal operation.
EN- Raychem920series-IM-H56874 05/15
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