24VDC To Ground or Not to Ground

[natfuelbill]

Any experiences, or recommendations, on whether it is"better" to ground a 24VDC power plant, or not. Primary concern is safety, secondary concerns are process continuation and equipment protection. The 24VDC system supplies power to engine control panels (PLCs), relays, displys, and solenoids; and usually has rectifiers and battery strings with 100's of AH.

Issues identified include:
short circuit protection
voltage stabilization
lighting protection
noise

 

[tom baker]

Its not a requirement for under 50 volts. Some DC power supplies are grounded some are not.
However, some DC systems are required to be grounded such as device net.
Some are not allowed to be grounde such as Allen Bradley panelview supplies.
Some users always require it
Some never allow it

 

[dereckbc]

I have a lot of experience in 24 VDC battery plants, but not in your industry, mine is with Telephone companies where AH exceed 40,000 AH

As Tom pointed out there is no requirement, only options. In the Telco biz we reference the neg polarity on 24 volt systems and positive on 48 volt systems.

For conductor protection there are two options:

1. Bond 1 polarity to something like earth or a point in space isolated from everything. Use OCPD on the hot side in primary and secondary distribution. This is what the Telco industry does.

2. Utilities and UPS systems float both polarities, install GFD and OCPD on both polarities in primary and secondary distribution.

 

[dereckbc]

Should have added for lightning and noise issues we use Single Point Ground schemes which make it impossible for lightning or noise to flow. Or the oppisite approach of multi-point ground which provides such a low impedance the voltage developed is well below thresholds of operation.

 

[hockeyoligist2]

Something you might also consider, We try to always try to ground any low voltage power because it will help with toubleshooting. We have a lot of proxy's and micro switches and there will not be a common, so it's almost impossible to tell if you are getting the power to the switch.