Wiring - PENN Controls - A421ABG - A421ABJ - A421AEJ - Electronic Temperature Control - A421 Standard Model

A421 Series Standard Electronic Temperature Controls with Power Cords Installation Guide

Product name
A421 Standard Model
Document type
Installation Guide
Document revision
Revision date
  • Risk of Electric Shock
  • Disconnect or isolate all power supplies before making electrical connections. More than one disconnection or isolation may be required to completely de-energize equipment. Contact with components carrying hazardous voltage can cause electric shock and may result in severe personal injury or death.
  • Risque de décharge électrique
  • Débrancher ou isoler toute alimentation avant de réaliser un raccordement électrique. Plusieurs isolations et débranchements sont peut-être nécessaires pour -couper entièrement l'alimentation de l'équipement. Tout contact avec des composants porteurs de tensions dangereuses risque d'entraîner une décharge électrique et de provoquer des blessures graves, voire mortelles.
Important: Do not exceed the A421 Control’s electrical ratings. Exceeding control electrical ratings can result in permanent damage to the control and void any warranty.
Important: Make all wiring connections in accordance with the National Electrical Code and local regulations. Use proper Electrostatic Discharge (ESD) precautions during installation and servicing to avoid damaging the electronic circuits of the A421 Controls.
Important: Do not overtighten the terminal screws. Excessive torque can damage the electronic board. The recommended torque is 3 in.•lb.
Important: When you connect an A99 sensor with a shielded cable to an A421 Control, connect the cable shield drain lead to the common (COM) terminal on the sensor and binary input terminal block (TB3). Do not connect the shield at any other point along the cable, and isolate and insulate the shield along the entire length of the sensor cable. If you connect a cable shield at more than one point, transient currents can flow through the sensor cable shield and cause erratic control operation.

The A421 Electronic Temperature Controls with Integral Power Cords are prewired for 120 VAC plug-in applications only. Observe the electrical ratings listed in Technical specifications.

Observe the following guidelines, procedures, and illustrations when you wire an A421 Series Control and A99 Series sensor.

  • Select the appropriate A99 sensors for the ambient operating range that the A421 Control monitors and controls, as shown in Table 2. See Technical specifications.
  • Keep the sensor leads as short as possible in your application. The additional resistance in long sensor cables creates an offset between the actual temperature and the displayed temperature. See Table 1 when you extend sensor leads.
  • A99 sensors are not polarity specific. You can connect either lead to the SEN or COM terminals.
  • It is best practice to use 22 AWG, stranded, twisted-pair cable with a shield to extend sensor cable runs.
    Table 1. Maximum sensor cable lengths and wire sizes
    Wire gauge Maximum sensor cable length1
    16 AWG 500 ft (150 m)
    18 AWG 300 ft (100 m)
    20 AWG 200 ft (60 m)
    22 AWG 125 ft (40 m)
    Table 2. A421 Control Sensor and Binary Input wiring terminals and wire size information
    Terminal block Label Description, function, and requirements Wire sizes
    TB3 BIN Detects a switch closure between the BIN and COM terminals and implements the selected temperature setback (tSb) value. 22 AWG (0.34 mm²) stranded, shielded cable
    COM Connects low-voltage common from the sensor and binary input.
    SEN Connects low-voltage input signal wire from control sensors.
1 At the listed maximum cable lengths, there is less than 1Fº (0.6Cº) error between the temperature sensed at the A99 sensor and the temperature displayed on the LCD.