HARTING Technology Group

In and outs of control panel wiring. What it does, and how it’s done.

Industrial control panels come in many sizes and shapes. Their purpose is to provide power  and execute control and monitoring functions for operating simple or complex machinery. The UL standards organization defines a closed industrial control panel as comprising “the enclosure, all components located within the enclosure, and all components mounted to the walls or cover of the enclosure.” The cabinet might contain motor controllers, switches, overload and control relays, circuit breakers, timers as well as push buttons or HMI touch screens to initiate control commands, and more. The necessary wiring from control, sensing and safety features in the panel to devices inside the machine is installed in one of two ways – by hard-wiring or by connectorization.

Hardwiring (point to point wiring)

A hard-wired connection is a dedicated wire from an individual connection point in the panel associated with a particular function to the corresponding device inside the machine that provides that functionality. There can be hundreds of such individual connections for a major piece of machinery. Hardwiring is a proven technology that has been used since the advent of electric-powered machinery.

Connectorized wiring

With connectorization, connector housings are affixed to the side or front of the panel and to the machine. These connectors are comprised of a hood and housing that can be mated and unmated as necessary. The signal path between the connection point in the control panel enclosure to the device on the machine follows an internal wire to the panel-side connector, then an external cable running between two connectors, then an internal wire in the machine. The signal transfers between internal and external wiring are effected via male/female contacts in the connectors. Industrial connectors have been a marketplace staple for over half a century.

Summary

In building and installing a new machine, including the controls panel(s), the major difference between the two wiring approaches comes if a machine is dismantled to facilitate shipping. With hardwiring, each wire inside the panel and sometimes the machine has to be disconnected so the machine and panel or panels can be shipped in sections. Shipping in sections is less costly with less risk of damage to the machine. Panels are particularly vulnerable and are often crated separately. However, the reassembly process with hard-wiring takes more time and runs up more labor cost than re-installing connectorized wiring which is plug & play. And any wiring errors remaking hard-wired connections can stretch out the installation process and in extreme circumstances, damage the machine or panel.

With connectorization, none of the wiring inside machine sections or panels is disconnected for shipping, only the connectorized cable between them. Reattaching that external cable during re-assembly at the end user takes virtually no time or effort and entails no cost or error risk.

Hardwiring’s main virtue is that its initial cost is lower than connectorization for the first installation, so where breakdown and reassembly of the machine is not required for shipping, it’s often the go-to approach, preferred by those OEMs basing their sales pitch on offering the lowest up-front sticker price rather than lowest possible total cost of ownership (TOC).

However, in most other scenarios, including anywhere hard-wired connections must be done at least twice by the OEM, connectors are more cost-effective, and allow for faster machine setup. For the end user, connector-based wiring can contribute to a lower TOC because it is generally faster to troubleshoot and fix maintenance problems than it is with a comparable system that is hard-wired. That lower TOC should be a unique selling feature and customer loyalty builder for the OEM.