Wiring
Observe the following guidelines.
WARNING
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.
Avertissement
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: Use copper conductors only. Make all wiring in accordance with local, national,
and regional regulations.
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 input (sensor) cables that are exposed to high
electromagnetic or radio frequency noise.
Important: Electrostatic discharge (ESD) can damage A421 Controls. Use proper electrostatic
discharge precautions during installation and servicing to avoid damaging 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: 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 wire size restrictions listed in Table 2 and 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 6. See Technical specifications for more information.
5A421 Series Electronic Temperature Controls with Off-Cycle Defrost Installation Guide
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