Trane 4TTV7X48A1000A - Defrost Control (Heat Pump Only)

18-BC111D1-1A-EN
27
Defrost Control (Heat Pump only)
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The demand defrost control measures heat pump
outdoor ambient temperature with a sensor located
outside the outdoor coil. A second sensor located on
the outdoor coil is used to measure the coil
temperature. The difference between the ambient and
the colder coil temperature is the difference or delta-T
measurement. This delta-T measurement is
representative of the operating state and relative
capacity of the heat pump system. By measuring the
change in delta-T, we can determine the need for
defrost. The coil sensor also serves to sense outdoor
coil temperature for termination of the defrost cycle.
FFaauulltt IIddeennttiiffiiccaattiioonn
A fault condition is announced at the UX360 thermostat
and Diagnostic Mobile App.
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Demand Defrost is enabled with the following inputs to
the AOC:
• Outdoor ambient temperature sensor (ODS-B)
reporting an outdoor temperature at or below 52° F.
• Coil temperature sensor (CBS) reporting a coil
temperature at or below 35° F.
• Heat/Cool Demand (HCD) from the communicating
comfort control for at least two minutes or more.
DDeeffrroosstt IInniittiiaattiioonn
The calculated temperature difference between the
outdoor temperature sensor and the coil temperature
sensor is called Delta T. Defrost can occur once the
current Delta T exceeds the Delta T initiate value. This
adaptive logic assures a complete defrost for a range of
outdoor temperatures.
65ºF
60ºF
55ºF
50ºF
45ºF
40ºF
35ºF
30ºF
-40ºF -20ºF 0ºF 20ºF 40ºF 60ºF
FACTORY TERMINATION TEMP
AMBIENT TEMPERATURE
TERMINATION TEMPERATURE
MEDIUM TERMINATION TEMP
HIGH TERMINATION TEMP
DEFROST TERMINATION PROFILES
SOFTWARE 1.0/2.0
SOFTWARE 3.0 AND LATER
NNoottee:: A forced Defrost test can be entered through the
UX360 thermostats, the outdoor unit AOC or the
Link Diagnostic Mobile App.
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1. FRC DFT test can be run while in the heating mode
by pressing the S6 button on the top right of the
AOC. DFC TST can also be run while in the
Compressor Heating test mode found in the UX360
or Diagnostic Mobile App.
2. Press ENTER to begin forced defrost.
3. Execute Forced Defrost following Forced Defrost
(Defrost terminates on Coil Temperature or
maximum time override of 15 minutes).
4. When test begins, the Diagnostic Mobile App
monitor screens will update with coil temperatures
and operation.
NNoottee:: UX360 Screen, under System Status will display
DEFROST.
5. When test is complete, TEST COMPLETE displays
for 10 seconds.
6. If there is a defrost fault condition, test terminates
and sends alert to the alert menu in the UX360 and
Diagnostic Mobile App.
7. For more information, refer to the Alert Code Tables
in Service Facts and Technical Service Manual (Pub.
No. 34–4301–01 or newer) documents.
NNoottee:: Monitor screens will update as the test proceeds.
NNoottee:: Can enter Forced Defrost from UX360, AOC or
the Diagnostic Mobile App.