EKS-HUM-036 / Dehumidification technology and performance
Defrost
化霜
Defrost is an operating action or cycle that removes frost from a refrigeration evaporator so that airflow and heat transfer can continue.
- Aliases
- defrost cycle, coil defrost
QUANTITY, SYMBOL AND UNIT
Quantity / objectDefrost operation
UnitNot applicable
Definition
Defrost is an operating action or cycle that removes frost from a refrigeration evaporator so that airflow and heat transfer can continue.
In refrigerant dehumidifiers, a cold evaporator can accumulate frost under low-temperature or low-load conditions. Controls may interrupt or alter refrigeration operation until the coil is cleared, temporarily changing moisture removal and power use.
Relations and distinctions
Defrost and normal condensate drainage
Normal drainage removes liquid water formed on a coil above freezing. Defrost addresses solid ice that obstructs operation.
Frost protection and defrost
Protection may prevent severe frost by changing airflow or capacity; a defrost cycle clears frost that has formed.
Engineering meaning
- Check the approved entering-temperature range and the defrost control sequence for the application.
- Use time-averaged capacity where frequent defrost cycles are expected rather than assuming continuous rated output.
Common misconceptions
MisconceptionDefrost adds extra dehumidification because it melts collected ice into drain water.
Accurate explanationIt restores coil operation, but moisture removal is reduced or altered during the cycle and meltwater includes previously captured moisture.
Application boundaries
- Defrost strategy varies by refrigeration circuit and control design; the term does not identify the mechanism.
- Repeated frosting can also indicate unsuitable entering conditions, airflow or equipment selection and should not be treated only as a maintenance event.
Supporting sources
-
ASHRAE / SRC-ASHRAE-S20-CH25
ASHRAE Handbook - HVAC Systems and Equipment, Chapter 25: Mechanical Dehumidifiers and Related Components ↗
2020 SI edition / Chapter 25, low-temperature operation and defrost-control discussion
Supports: Frost can form on a dehumidifier evaporator at low entering conditions; Defrost control can interrupt or change compressor operation to clear frost; Defrost reduces time-averaged dehumidification while it is active
Maintenance record
Defrost
- Maintained by
- Yakeclimate Engineering Team
- Authoritative sources verified
- August 3, 2026
- Terminology checked
- August 3, 2026
- Last updated
- August 3, 2026