Terminal Block Grounding of DC Power Supply

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fredmellon

Joined Sep 15, 2017
1
I have a situation that I am hoping someone can confirm or exclude my thoughts on concept. I am distributing a 28V DC power supply through socket junction terminal blocks. The power return is also into the same type terminal block. I want to ground the system by connecting the returns to chassis. If I connect the return terminal block to a chassis grounded terminal block with a 16 AWG jumper, would this effectively be the same as running my return directly to a chassis grounded terminal block. Should I eliminate the two block scheme and just run ,y return to one block that is chassis grounded? I am thinking that the one chassis grounded block will do the trick but another EE poo pooed the idea saying that this would introduce 28V into the chassis. Thoughts and opinions?
 

nsaspook

Joined Aug 27, 2009
7,495
My 2c.
Your method might work but I would agree with the other EE. A bus bar/terminal strip (that could be bonded to the chassis ground) for each return wire back to the power supply and chassis grounding of load ground/shield point to a chassis ground point near the load.




If this chassis is primary electrical safety/shield earth ground then usually you don't want it to be a normal circuit current path (chassis return instead of ground return) for DC low voltage (and possible high current) too. I would not depend on chassis conductivity for powered DC circuits usually.



http://www.ese.upenn.edu/detkin/instruments/misctutorials/Ground/grd.html
 
Last edited:

Tonyr1084

Joined Sep 24, 2015
4,929
Running your return to a terminal block that is connected to a chassis grounded terminal block - it would be the same as just running your return to the chassis grounded terminal block.

Why some poo-poo the idea could be because your (lets call it) neutral (or negative) line might need to be isolated from chassis ground. However, chassis ground has been used for a long time. Of late it's becoming less common in power equipment because you want a separate return to ground (earth ground) in the event of a soft short circuit that could energize the chassis. For safety reasons you'll want the chassis to be grounded to earth ground to prevent any dangerous electrical power being present at the chassis. Should you come in contact with a live surface YOU could become the path of least resistance to ground, and you could be injured or killed.

I don't do much with power equipment. Mostly I work and play with low voltages such as 3.3 VDC up to 24 VDC. But even 24 VDC can be dangerous if there's enough current present. So having a safety ground isolated from the rest of the circuit is more of a protection to the user than to anything else.
 
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