SCXF-SVX01T-EN
95
Category Diagnostic
H
Heat Failure
Problem
The heat has failed. (Electric heat unit)Typically, this is because the electric heat section became too hot.
Reason for
Diagnostic
The heat fail input on the heat module was closed:
• For more than 80 seconds,
• For ten consecutive occurrences (each lasting five seconds or more) within a 210 second period.
Controls
Reaction
A n information only diagnostic is set.
Reset
Required
(INFO) An automatic reset occurs after the heat fail input remains open for 210 seconds continuously.
Heat Module Auxiliary Temperature Sensor Fail
Problem
The heat mod aux temp sensor input is out of range.
Check
Sensor resistance should be between 830 ohms (200°F) and 345.7 ohms (-40°F). If so, check field/unit wiring between sensor and heat
module.
Reason for
Diagnostic
At least one enabled unit function has the heat module auxiliary temperature input designated as its sensor, and the unit is reading a signal that
is out of range for this input (temp < -55°F or temp > 209°F).
Controls
Reaction
The functions that designated the heat module auxiliary temperature input as their input are disabled.
Reset
Required
(PAR) An automatic reset occurs after the heat module auxiliary 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.
Controls
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 de-energized.
• 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
occurrence of a heat module comm failure. A fail-safe 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 de-energized.
Reset
Required
(PAR) An automatic reset occurs after communication has been restored.
L
Low Air Temperature 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.
Controls
Reaction
The UCM will initiate the following actions:
• 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.
• An “all heat off” request is issued to the heat control function.
• A “fan off” request is sent to the supply fan control function.
• 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.
Diagnostics
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