18
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™ communi-
cations address (see section 3.9.2 on page 43). Once the start-up delay has timed out, the con-
troller will begin normal operation.
2.9 Setup for the 920
The 920 may be programmed using the optional 920 Operator Console, or a Group Communica-
tions Controller (
GCC) if the modem communications option is installed. For instructions on the
operation of these devices, refer to the corresponding operating manuals. For complete instruc-
tions on programming the 920, see the Section 3 on page 18.
2.9.1 VOLTAGE READING SETUP
The 920 series control module is tested, calibrated, and ordered separately from the switch
interface modules which contain the voltage sensing circuitry. This prevents Tyco Thermal
Controls from calibrating the control modules to specific switch interfaces and removing any
component inaccuracies. Generally, the voltage readings will be within 3 Vac to 5 Vac when
shipped from Tyco Thermal Controls. If more accurate voltage readings are desired, they may be
adjusted as part of the initial setup of the controller. This requires measurement of the trace volt-
age using a multimeter and adjusting the
VOLTAGE TURNS RATIO setting to arrive at more accu-
rate voltage readings. See section 3.5.21 on page 26.
2.9.2 SWITCH RATING SETUP (SSR ONLY)
The 920 series control module is ordered and shipped as a separate item from the enclosure
assembly. This prevents Tyco Thermal Controls from predetermining the
SWITCH CURRENT
RATING
settings since various types of output switches are available.
The user should verify that the switch current ratings are set properly for the rating of the solid-
state relays that are included as part of the enclosure assembly. Refer to section 3.5.7 on
page 22 for more information on the
SWITCH CURRENT RATING setting. Tyco Thermal Controls
default setting is defined in Appendix F on page 76.
Section 3 Programming and Configuration
3.1 Introduction
This section provides complete operating and setup instructions for the 920 Series Heat-Tracing
Controller. The text describes each available function in detail, its purpose, valid range settings,
the procedure for use, and some operational tips and suggestions.
While configuring the controller, it is important to remember that the 920 series controller is a
two control point device. Both control points allow completely independent operation and, as
such, have their own individual settings that must be configured. Throughout the text, the first
control point is referred to “Point A” and the second as “Point B.”
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