Trane RTWA 70-125 TON - Manual (Page 41)

RLC-SVD03A-EN 41
Module Power and Miscellaneous I/O
This section will detail the normal voltage levels present on each of the
modules inputs and outputs under various conditions or states. Typical
operation of the I/O will be discussed in terms of chiller operation. This should
help the serviceman determine when and how they should function. Certain
inputs have been presented in greater detail in earlier sections and these are
referenced where applicable.
Power Supply
All of the modules are powered from 115 VAC 50/60hz Control Power except
the CLD and the IPCB, which are powered by 24 VAC. This power is provided
by either a control power transformer or is customer supplied. With the
exception of the CLD, LCI-C and the IPCB modules, the other modules have
incoming power connected to the upper-most terminal on the right hand side
of the module, just below the fuse. The terminal is arranged with two hot
pins (1 and 2), a keying pin (3), and two neutral pins (4 and 5), for ease of
“daisy chaining” power from one module to another. Incoming power can be
verified by measuring the voltage between the fuse bottom (hot side) and the
connector's neutral (pins 4 or 5). The voltage should read between 97.8 to
132.2 volts AC rms. Refer to
Figure 7 . (The ±15% voltage criteria is most
important for the EXV module's operation, as the Electronic Expansion
Valve's available torque is directly related to this value).
The fuses can be checked by looking for the supply voltage at the top of the
fuse (fused side) with respect to the connector neutral.
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 CPM. Refer to Section 2
Interprocessor Communication for more information about Communication
(IPC) diagnostics. If the CLD's display is blank, 24 VAC power should be
checked at the CLD.