Evaporator Defrost Control

Frostat is standard on all 6 to 25T units. To prevent frost build-up on the indoor coil during low ambient conditions, compressor operation is monitored and controlled accordingly relative to outdoor air temperature.

Evaporator Defrost Control can be initiated through two means, based on the FroStat input.
FroStat Installed (default):

• 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 as “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.

Application Guide Link

• https://support.trane.com/hc/en-us/articles/44468444639245-Precedent-Symbio-700-controller-Application-Guide

WARNING:

Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.