The A421 Series controls are single stage, electronic temperature controls with a single-pole, double-throw (SPDT) output relay. The controls feature an adjustable backlit LCD for viewing the temperature and status of other functions, and a three-button touchpad for setup and adjustment. An LED indicates the On/Off status of the output relay. The A421 controls are available in 120 VAC and 240 VAC models.

The A421 Control with Defrost allows you to set up regular, passive defrost periods of 1 to 99 minutes. The defrost interval can range from 2 to 24 hours, or be set to 0 (no defrost interval). You can also start or stop a defrost cycle in two ways: using the three-button touchpad on the Advanced Menu or connect a momentary switch to the Binary Input (BIN).

This A421 Control with Defrost also provides sensor offset, temperature setback, adjustable anti-short cycle delay, and a restricted user adjustment mode. The temperature units can be displayed in °F or °C. The temperature adjustment range is -40 to 212°F or - 40 to 100°C.

The A421 controls are available in Type 1/IP20 high-impact plastic enclosures suitable for surface or DIN rail mounting and Type 4X/IP66 watertight, corrosion-resistant surface mount enclosures.