Defrost Controls

Surplus City Liquidators sources surplus defrost control boards directly from manufacturers as overstock, brand-new components that came to market because a manufacturer overproduced a run or phased out a model line. "Surplus" describes how the inventory was acquired, not the condition of the board. These are the same discount HVAC control boards you'd buy through a traditional distributor, arriving in original manufacturer or blister packaging where available, at a lower price point.

Surplus City carries a rotating selection of board types, including timed defrost boards with pin-selectable 30/60/90-minute intervals, time-and-temperature combination boards, demand defrost boards that initiate the defrost cycle based on coil temperature rather than a fixed timer, and defrost timer control boards compatible with multiple voltage inputs. Brand-specific OEM replacement boards are available for major manufacturers including Carrier, Trane, Lennox, and Rheem, alongside universal aftermarket boards. The heat pump defrost control board inventory rotates based on manufacturer overstock availability, so specific part numbers vary (check the Defrost Controls collection for current listings).

Start with your unit's model number and the existing board's part number, then cross-reference against the listing's "Replaces" field, which lists the OEM part numbers a given board is confirmed to substitute as an OEM defrost board replacement. Verify input voltage (typically 18 to 30 VAC), defrost interval settings, output type (triac or relay), and whether the board supports the reversing valve wiring configuration your unit uses. It’s O terminal for most systems and B terminal for some Trane and American Standard units. For demand-style boards, confirm whether your system requires a separate coil temperature sensor and that the replacement lists a compatible one.

Universal defrost control boards are a practical option when an original part is discontinued or difficult to source, as they are designed to replace multiple OEM part numbers across different manufacturers, making them a flexible defrost board for heat pump applications. Before ordering, match the universal board's voltage range, defrost interval options, and terminal layout to your unit's wiring diagram. Boards from manufacturers like ICM Controls often include configurable settings and built-in diagnostics that can offer additional flexibility compared to a fixed-spec OEM replacement.

Confirm the replacement part number or "Replaces" cross-reference against your unit's existing board, and double-check input voltage, output type, and defrost interval pin settings before placing the order. Review any packaging condition notes on the listing, as some surplus components ship without original manufacturer packaging, which does not affect product quality but is worth knowing in advance. If your unit uses a demand defrost board with separate coil or ambient temperature sensors, verify whether those sensors are included in the kit or need to be sourced separately.

Surplus City ships small components and control boards to all 48 contiguous states via standard ground shipping, with freight options available for larger orders. Shipping charges are calculated based on package dimensions, weight, and carrier fuel surcharges. Local pickup is available Monday through Friday at all five Surplus City showrooms. Our locations are in Lebanon, IN, Lafayette, IN, Grand Prairie, TX, Greenville, SC, and Lebanon, PA.

Defrost control boards are components and parts that fall outside the categories currently covered by Surplus City's optional $30/30-day startup warranty. That warranty applies to eligible major equipment: AC and heat pump units, air handlers, evaporator coils, and furnaces. Manufacturer warranty terms, if applicable, depend on the specific board and brand; check individual product listings for any available documentation.