Grounding Electronic Enclosures

All devices and signals within a panel should be tied back to one single location. It is common to see several different devices within a control panel that need to be grounded. No matter the number of devices, it is essential to ensure that everything comes together in one location. This location is where the main utility power and grounding conductor  enters the panel. It can also be where the enclosure is grounded to an exterior ground rod. Tying everything to the utility ground or ground rod, allows any short circuits and surges to be dissipated out of the control panel, protecting sensitive equipment. It can also help to reduce any chances of creating ground loops within the enclosure.

Analog signal grounding. Typically, analog signals have shielded wire to protect the signal from “noise” or distortion that could potentially corrupt the signal.  This shielding needs to be grounded in order to dissipate that “noise”. It is important to know that this shielding should only be grounded at one location along the circuit, typically within the control panel where the conductors are being terminated, and not on the field side of the device. If both ends of the shielding are terminated, it can cause issues with the signals as well as create potential ground loops.  

AC and DC circuit grounding. In some cases, it is necessary to isolate the AC ground from the DC ground, but in the case of most industrial control panels it is common to see these two types of power share a “common ground”. This is done by tying the DC negative portion of the DC bus to the AC ground bus within the control panel. This allows everything, including all AC and DC circuits, to be tied back to one single location within the panel. 

Outdoor enclosure grounding. When an industrial control panel is being installed in an outdoor location, or anywhere that it might be exposed to the elements, it is critical to install a ground rod and ensure that the enclosure is tied to that ground rod. In the event of a lighting strike, the ground rod will allow the bulk of that energy to be dissipated directly into the ground, while protecting the hardware within the panel.