Icm Controls 300c Heat Pump Defrost Timer Control

Product Description

The ICM CONTROLS 300c is a time-and-temperature defrost control designed as a direct OEM-style replacement for Type 621 defrost timer applications in residential and light commercial heat pump systems. Operating on 18 to 30 VAC at 50 to 60 Hz with a maximum power draw of 1 watt, it monitors compressor run time through a HOLD input and triggers a fixed 10-minute defrost cycle when both time and temperature conditions are met. Defrost intervals are pin-selectable at 30, 60, or 90 minutes, giving technicians flexibility to match the control to the system's demand profile. Test pins reduce test cycle time by a factor of 256, simplifying field verification.

The 300c is suited for residential and light commercial heat pump installations where a time-and-temperature defrost strategy is required. It features stable pin post construction and carries a high installed base across a wide range of equipment. Note that this control requires external relays for the condenser fan motor, reversing valve, and auxiliary heat circuits — these are not integrated into the board. It is installed and serviced by licensed HVAC technicians during defrost control replacement or system commissioning.

Key Features

• Direct replacement for OEM Type 621 defrost controls including 90-621, DT2-1000, 47-21776-01, and others
• Pin-selectable defrost intervals: 30, 60, or 90 minutes
• Fixed 10-minute defrost termination time (+/- 5%)
• HOLD input tracks compressor run time for accurate cycle timing
• Test pins reduce test time by 256x for faster field diagnostics
• Stable pin post construction for reliable long-term connection
• Requires external relays for fan motor, reversing valve, and auxiliary heat — not included

Compatibility

The 300c replaces the following OEM part numbers: 90-621, DT2-1000, B12260-06, C64310-1, 621-110, 621-111, 10321-00, 621-310-110, 47-21776-01, 33G9501, 840-4-5548, 3030A374, 621-10, C64301-1, 621-1, 1395-329, 26E-10, and TD-10.

Installation Notes

Installation should be performed by a licensed HVAC technician. Disconnect all power to the heat pump system before removing or installing the defrost control. Verify that external relays for the condenser fan, reversing valve, and auxiliary heat are present and properly rated before energizing the replacement board. Consult the equipment manufacturer's wiring diagram and applicable local codes to confirm proper termination of all control circuit connections.

Technical Specifications

• Voltage: 18 to 30 VAC
• Frequency: 50 to 60 Hz
• Power Consumption: 1 watt maximum
• Relay Type: SPST, N.O.
• Relay Rating: 1 amp
• Defrost Time: Fixed 10 minutes (+/- 5%)
• Power On Reset Time: 500 ms
• Interval Time Between Defrosts: Pin-selectable 30, 60, or 90 minutes

Standard Information

• Brand: ICM CONTROLS
• Manufacturer Part Number: 300c