Defrost Heating Control

Control Triac for Defrost Heating

Design Notes:

Protection Application:
Control Triacs and Alternistors are used to switch AC currents through for defrost heating respectively. The Triac for heating and the Alternistor for compressor motor are turned on alternatively, and could share the same heat sink.
Solution Description:
Triac selection depends on the line voltage, nominal load current, maximum surge load current and the specific trigger circuit employed. For the defrost heating, typical triac part number as Q8008L5, For the Compressor, typical Alternistor Part number Q6008LH4.
Companion Solutions:
Other packages and current rating Triacs, Min /Max Alternistor current rating from 6 to 10A , Voltage rating from 200Volts in a 800 volts
Regulatory Issues:
For both Isolated tab devices must be qualified to rigorous UL insulation standards.
Unique Features:
The LF method of isolating the tab is state-of-the-art.
Application Warnings:
Does not apply.



  • Q8008L5

    8 Amp Sensitive, Standard, & Alternistor (High Commutation) Triacs

  • Q8008LH4

    8 Amp Sensitive, Standard, & Alternistor (High Commutation) Triacs

  • P4KE250CA

    400W Axial Leaded Transient Voltage Supressors

  • P6KE510CA

    600W Axial Leaded Transient Voltage Suppression (TVS) Diode