The importance of tightening torque on electrical installations

Jan 22nd 2019

Often overlooked during the installation or replacement of electrical parts is the importance of tightening the wires to the terminals with the correct amount of torque.  While the focus may be on the wiring diagram and ensuring the correct connections, correctly tightening the terminals is just as important to ensure a safe and secure installation.  Incorrectly screwing terminals down without the correct pressure can lead to:

  • Electrical Fires - loose connections can lead to thermal runaway and very high temperatures with the real potential of causing an electrical fire
  • Contactor failure - improper torquing leads to a phase imbalance causing a contactor to burn up (example: a 3 pole 30 AMP contactor has 30 AMPS running to each L1, L2, and L3.  If one loose connection occurs, those 30 AMPS from the lost phase are distributed to the other 2 phases which far exceeds the contactors capabilities and quickly melts that contacts
  • Motor damage - phase loss without proper motor protection can damage a motor within minutes if not attended to immediately

Each contactor, overload, manual starter and circuit breaker has specifications listed on its side label as to the appropriate amount of torque needed to secure the terminals.  Also keep in mind, this is not just for replacement or new installation.  If you order a control box and have it transported to your facility, those connections could have some loose while in transit.  It's always a good idea to verify the connections prior to the initial start.