Important: Use copper conductors only. Make all wiring connections in accordance with local, national, and regional regulations. Do not exceed the A421 Control's electrical ratings.
Important: Do not exceed the A421 Control’s electrical ratings. Exceeding the electrical ratings can result in permanent damage to the control and void any warranty.
Important: Run all low-voltage wiring and cables separate from all high-voltage wiring. It is best practice to use shielded cable for input (sensor) cables that are exposed to high electromagnetic or radio frequency noise.
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 connect supply power to the A421 Controls before checking all wire connections. Short circuits or improperly connected wires can result in damage to the modules and void any warranty.
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.
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 for more information.
- 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.
|Maximum sensor cable length1
|500 ft (150 m)
|300 ft (100 m)
|200 ft (60 m)
|125 ft (40 m)
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.