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SCXG-SVX01B-EN
Diagnostic
Troubleshooting
W
WSM Communications Fail
Problem: The RTM has lost
communication with the WSM.
Check: Field/unit wiring between RTM
and WSM.
Reason for Diagnostic: The RTM has lost
communication with the WSM.
UCM's Reaction: The UCM will react as if
a freezestat has occurred by issuing:
• An "All Heat On" or "Mod Output Full
Open" request to "Heat Control"
• A "Fan off" request to "Supply Fan
Control"
• A "Close Damper" request to
"Economizer Actuator Control"
• The water pump to turn on and position
all water valves to provide maximum
flow through all water source heat
exchangers
• Disables preheat function if WSM Mixed
Air Temp Sensor is selected as Preheat
Sensor
Reset Required: An automatic reset
occurs after one complete set of IPC
packets is received.
WSM Mixed Air Temp Sensor Fail
b. Activation Conditions: temperature < -
50 F or temperature > 209 F , and sensor
is selected for use by "Water Side
Economizer Temperature Enable
Function" or "Preheat Function"
c. Time to React: 10 sec < T < 20 sec
e. Actions to be Initiated: "Water Side
Economizer Temperature Enable
Function" uses Supply Air Cooling
Setpoint instead of Mixed Air
Temperature. If Mixed Air Temperature is
being used for "Preheat Function", issue
a "Disable" request to "Preheat
Function".
f. Reset: An automatic reset occurs after
the Mixed Air Temp. input returns to
within range continuously for 10 seconds.
Water Flow Fail
a. Data used (module,packet,byte,bit):
WSM, 01,19,05
b. Activation Conditions: The water flow
input is detected open ;
1. at the end of precool water flow
initiation state, or
2. continuously for five minutes while:
Diagnostics
·water side economizer is open 100%,
· presetting of a Head Pressure Valve, or
· demand for mechanical cooling.
Unit must be: a. configured with water
cooled condenser and/or water
economizer and b. have water flow
switch installed.
c. Time to React: immediate
e. Actions to be Initiated: A "Lockout All
Ckts" request is issued to the
"Compressor Staging Function"
f. Reset: An automatic reset occurs after
the Water Flow input returns to within
range continuously for 3 seconds, the
water pump is requested OFF , or the
water flow switch becomes not installed.
Z
Zone Cool Setpoint Failure
Problem: The occupied zone cooling
setpoint is out of range.
Reason for Diagnostic: The input
designated as occupied zone cooling
setpoint source is out of range (temp. <
45 F or temp > 94 F).
UCM's Reaction: The active occupied
zone cooling setpoint reverts to the
default occupied zone cooling setpoint.
Reset Required: (PAR) an automatic reset
occurs after the designated occupied
zone CSP input returns to its allowable
range for 10 continuous seconds, or after
a different valid occupied zone CSP
selection source is user-defined.
119
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