24VDC Class 2 Power Supplies

[ncs]

We normally ground the -24VDC side of a control systems power supply. What are you folks thoughts about grounding the -24VDC side of a class 2 power supply?

 

[OkiePC]

Two articles for reference on this topic from Control dot com

Grounding DC Power Supplies - Technical Articles

Should you connect a DC power supply to ground or not? The answer is not a straightforward yes or no. This article explores the benefits and drawbacks of grounding DC power supplies.

control.com

Negative Effects of Grounding (Earthing) a DC Power Supply - Technical Articles

DC voltage systems exist to provide controllers and field devices with stable power, but it is not always clear when these systems should be bonded with the earth ground of the AC line voltage supply.

control.com

We typically leave them floating. We've experienced fewer problems with analog signals and devices where there is a nearby VFD ground fault, for example. I have one system of about 16 small panels that we commissioned but were built by a subcontractor who grounded the 24VDC common. They were installed in multiple pump stations and water tower monitoring applications. We've had more problems with failed sensors and analog cards at that customer than most of the others we built in house with floating DC voltage. I have since removed the connection from DC- to ground on some of them and it seems to have helped. This is just anecdotal and somewhat subjective support for floating, but isn't really substantial.

In the few cases where we have 240vac or 480vac input to the power supplies, we do ground them.