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Thermostat A/C Penn A421


Only 4 left in stock (can be backordered)

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Thermostat A/C Penn A421

The A421 Series, Standard Electronic Temperature 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 touch pad for setup and adjustment. An LED indicates the On/Off status of the output relay.

The A421 Controls are available in low-voltage 24 VAC and high-voltage 120 VAC or 240 VAC models, which provide options for most refrigeration and HVAC applications.

The A421 Controls provide heating or cooling control, 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°F to 212°F or -40°C 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.

Features and benefits

Control front panel LCD
Displays the temperature, parameters, and status.
You can adjust the backlight intensity for ambient light conditions.
Custom icons display the system and control status.

Basic and Advanced programming menu

Provides two levels of parameter adjustment and control. You can set up advanced features in one
menu and easily adjust basic parameters in the other menu.

On/Off temperature adjustment

Select the temperature values at which the relay turns On and Off, which automatically defines the
Heating or Cooling mode of operation.

Switch-activated temperature setback
Shift the On or Off temperature by an adjustable setback value. When a user-supplied switch closes
the binary input control circuit, the control operates at the defined setback temperatures.

Adjustable anti-short cycle delay
Select the minimum time the output relay remains off before the next on cycle; avoiding short cycling, hard starts, and nuisance overload outages on compressors and other inductive applications.

Adjustable sensor offset
Adjust the displayed temperature to the actual sensed temperature.


– Height 5″
– Width 2-3/8″
– Depth 2-3/8″


1 Year

Additional information

Weight 0.45 kg
Dimensions 27.94 × 10.16 × 11.43 cm