Evaporator Defrost Control; If Configured For Evaporator Defrost Control = Enabled; If Configured For Frostat = Installed - Trane SYMBIO 700 Troubleshooting Manual

Evaporator Defrost Control

Evaporator Defrost Control can be initiated through two means, based on configuration.

If configured for Evaporator Defrost Control = Enabled:

When the unit is operating in a "Cool" mode with a valid Outdoor Air Temperature, the EDC function will
keep track of the amount of time that at least one compressor in a unit is commanded ON and the
Outdoor Air Temperature Active is less than the low ambient temperature defined in table 3. If the
Accumulated Compressor On Time reaches 10 minutes, the EDC function will cause the Compressor
Output(s) to de-energize for three minutes. The supply fan continues to operate during this three-
minute interval at 100% capacity. After the three-minute EDC timer has expired, the EDC function is
ended and compressors are allowed to operate as requested by the algorithm.
Low Ambient Temperature Setpoints:
Single Compressor Systems – 55F
Multi-Compressor Systems – 40F

If configured for FroStat = Installed:

A FroStat input can also be used to directly request the Evaporator Defrost Control function
When the unit is running in an effective "Cool" mode, the FroStat input will directly control the FroStat
diagnostic. If the FroStat input CLOSES, the diagnostic will be annunciated.
When the unit is running in an effective "Heat" mode, and the Refrigeration System == Heat Pump, the
FroStat diagnostic will be controlled "Inactive" until the following are true:
FroStat input is CLOSED
One or More Compressors have been active for Heat Pump Heating for more than 30 seconds.
Once the above two conditions are met, the FroStat Diagnostic will become Active.
The FroStat diagnostic is an Auto-Reset diagnostic such that it will be reset when the FroStat input is
OPEN in either effecting unit mode.
If the FroStat diagnostic becomes active, the Compressor Output(s) will de-energize until the FroStat
diagnostic is cleared. The supply fan continues to operate during the FroStat diagnostic, so long as it is
still requested by a heating or cooling function.
FroStat and Evaporator Defrost Control can both be configured on a unit, although in most cases, only
one should be necessary.
Note: The actual EDC Switch on the Evaporator Coil is Demand Limit in the menu!
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