Module Power and Miscellaneous I/O
RTHC-SVD01B-EN 67
Section 13 Module Power and Miscellaneous I/O
13-1. General
This section details the normal voltage levels present on each of the
module inputs and outputs under various conditions or states. Typical
operation of the I/0 will be discussed in terms of chiller operation. This
should help the serviceman determine when and how the modules
should function. Certain inputs have been presented in greater detail in
earlier sections, and these are referenced where applicable.
13-2. Power Supply
All of the modules are powered from 24 VAC control power. This power
is provided by a factory installed control power transformer. The mod-
ules have incoming power connected to J2. The terminal is arranged
with two hot pins (1 and 3) and two neutral pins (4 and 2), for ease of
“daisy chaining” power from one module to another. Pins 1 and 3 and
pins 2 and 4 are internally jumpered. Incoming power can be verified
by measuring the voltage between J2-1 or 3 to J2- 2 or 4. The voltage
should read be approximately 24 VAC rms.
If some modules have power and some do not, the “daisy chain” wiring
or power connections should be suspected. Refer to the Unit Wiring
diagrams for the specifics on the power wiring.
Generally a power loss to a particular module will first be noticed as a
communications loss with that module. The module can be identified
by analysis of the IPC diagnostics as displayed by the UCP2. Refer to
Section 8 Interprocessor Communication for more information about
communication diagnostics. If the Clear Language Display(CLD) is
blank, 24 VAC power should be checked at the CLD.
13-3. Clear Language Display (CLD) Keypad
Overview (1U4)
13-3 a. General
Local operator interface with the system is accomplished using the 16
keys on the front of the CLD panel. The readout screen is a two line,
40 character liquid crystal display with a backlight. The backlight allows
the operator to read the display in low-light conditions. Depressing any
key will activate the backlight. The backlight will stay activated for 10
minutes after the last key is pressed.
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