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114 SCXG-SVX01B-EN
Diagnostic
Troubleshooting Diagnostics
this input (temp < -55 F or temp > 209 F).
UCM’s Reaction: The functions that
designated the heat module auxillary
temperature input as their input are
disabled.
Reset Required: (PAR) An automatic reset
occurs after the heat module auxillary
temperature input returns to its allowable
range for 10 seconds.
Heat Module Comm Failure
Problem: The RTM has lost
communication with the heat module.
Check: Check field/unit wiring between
RTM and heat module.
Reason for Diagnostic: The RTM has lost
communication with the heat module.
UCM’s Reaction: An “all heat off” request
is sent to the heat operation function.
If the unit has staged gas or electric heat,
all heat module outputs will be zeroed
and deenergized.
If the unit has hydronic heat or chilled
water installed, the unit will turn off the
supply fan and close the outside air
damper upon the occurrance of a heat
module comm failure. A failsafe function
in the heat module will cause all water
valves to be set to 100% to provide full
water flow. Unless used for switching
purposes (air handlers with chilled water
and mod gas, or chilled water and
hydronic heat) all binary outputs will be
deenergized.
Reset Required: (PAR) An automatic reset
occurs after communication has been
restored.
L
Low Air Temp Limit Trip
Problem: The low air temp limit has
tripped. (Units with steam or hot water
heating, or air handlers with chilled water
cooling)
Reason for Diagnostic: A low air temp
limit trip is detected continuously for
more than one second. This can occur if
the hydronic heat low air temp limit input
closes for > 1 second, or if the chilled
water low air temp limit trip input opens
for > 1 second. On units with both
hydronic heat and chilled water, both low
air temp limit inputs are active, and the
unit will respond in the same manner
regardless of which input is used.
UCM’s Reaction: The UCM will initiate the
following actions;
a. An “open all water valves”request is
issued to the heat module function,
causing any steam, hot water, or chilled
water valves on the unit to open.
b. An “all heat off” request is issued to
the heat control function.
c. A “fan off” request is sent to the supply
fan control function.
d. A “close damper” request is sent to
the economizer actuator control
function.
Reset Required: (PMR) A manual reset is
required after the low air temp limit trip
condition clears. The diagnostic can be
reset at the unit mounted human
interface, by Tracer Summit
®
, or by
cycling power to the RTM.
Low Pressure Control Open - Circuit 1, 2,
3, or 4
Problem: The Low Pressure Control (LPC)
for Ckt #1, 2, 3, or 4 is open.
Check: State of refrigerant charge for ckt
#1, 2, 3, or 4.
Reason for Diagnostic: The Ckt # 1 LPC
input is detected open as described in the
compressor protection function.
UCM’s Reaction: A “Lockout Ckt # 1, 2, 3,
or 4” request is issued to the compressor
staging control function.
Reset Required: (PMR) A manual reset is
required anytime after the diagnostic is
set. The diagnostic can be reset by the
human interface, Tracer Summit
®
, or by
cycling power to the RTM.
M
Manual Reset SA Static Press Limit
Problem: The supply air static pressure
went too high for the third consecutive
time.
Reason for Diagnostic: The auto reset
supply air static pressure limit diagnostic
has occurred for the third time while the
unit is operating in occupied mode.
UCM’s Reaction: A "supply air pressure
shutdown" signal is sent to the following
functions;
a. Compressor staging control,
b. Economizer actuator control,
c. Heat operation,
d. Supply fan control,
e. IGV/VFD control,
f. Exhaust fan control
g. Exhaust actuator control
Reset Required: (PMR) A manual reset is
required and can be accomplished at the
HI, Tracer Summit
®
, or by cycling power
to the RTM.
MCM Communications Failure
Problem: The RTM has lost
communication with the MCM.
Check: Check field/unit wiring between
RTM and MCM.
Reason for Diagnostic: The RTM has lost
communications with the MCM.
UCM’s Reaction: A “Lockout” request is
sent to the compressor staging control
function. And a failsafe function in the
MCM will cause all MCM outputs to be
zeroed and deenergized.
Reset Required: (PAR) An automatic reset
occurs after communication has been
restored.
Mode Input Failure
Problem: The RTM mode input is out of
range.
Check: Sensor resistance should be
between 1 ohm and 40 Kohms. If so,
check field/unit wiring between sensor
and RTM.
Reason for Diagnostic: The mode input
signal on the RTM is out of range
(resistance < 1k ohm or resistance > 40k
ohms).