Trane RTWA 70-125 TON - Manual (Page 11)

RLC-SVD03A-EN 11
Interprocessor Communication
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3. Loss of power to a module:
Generally a power loss to a particular module will only affect communica-
tions with that module. The module can usually be identified by analysis
of the IPC diagnostics. (When the display is blank, check power at the
CLD). Loss of power can most directly be diagnosed by measuring the
AC voltage at the top of the fuse with respect to the neutral of the power
connection (pins 4 or 5) on the terminal just below the fuse:
4. Internal module failure:
Internal module failures usually result only in communication loss to the
failed module, but could, in some cases, affect all the modules because
the failed module may “lock up” the IPC bus and prevent all communica-
tions. The former can be identified by analyzing all of the active IPC diag-
nostics. The latter can be identified in a process of elimination, whereby
each module, in turn, is taken out of the IPC link and a jumper installed in
its place. See
Figure 3 . The CPM can then be reset and the new IPC diag-
nostics that result can be analyzed.
Table 2 IPC Address Dip Switch (SW1) Settings for MCSP an EXV Modules
MODULE DESIG. CONTROLLING DIP SWITCH SETTING
SW1-1 SW1-2
MCSP “A” 1U4 COMPRESSOR A OFF OFF
MCSP “B” 1U5 COMPRESSOR B OFF ON
EXV 1U3 CKTS. 1 & 2 OFF OFF
Figure 2 Module Fuse and Power Connection, Except CLD
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