Grounding Hardware Stack?

[daver01]

Some time ago I heard that a proper hardware stack for a ring terminated ground strap consists of a star washer next to the ground plane, on top of which is stacked a ring terminal, flat washer, split lockwasher and finally the screw or nut. Is there a source for this if it is correct, or has it been improved upon? Thanks.

 

[itsmoked]

Boy... This will probably get into a religious fervent. lol

I think it probably depends on every little bit of a particular situation. I have heard of no "correct way". If a fault current is large enough the steel star washer could represent a higher resistance. If you have some larger ring terminals they should probably be in direct contact with the ground structure.

On the other hand for a run-of-the-mill small ground your stackup sounds very good to me! The star will make gas tight scratches into both the ring and the surface. The flat washer will limit the ring's distortion on top of the star. The split will lock the fastener. I would consider skipping the split as it may cause the star and ring to rotate ruining the star's points. Furthermore, split washers are weak and fail often. If you must I'd just use another star.

Hope to see some further comments.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

Hi Keith;
I agree with you 100%.
For older equipment, and where low level currents may be an issue and must be drained, and where there may be slight surface contamination or oxidation, the star washer is a good idea.
For power circuits where high fault currents may be encountered I would skip the star washer, but spend some extra time cleaning the contact areas prior to making the connection.
Respectfully

 

[zappedagain]

"...spend some extra time cleaning the contact areas prior to making the connection."

and maybe add some dielectric grease to keep the contact clean if the environment is nasty.


daver01's technique is the only one that I've heard over the years (with a disclaimer that I don't work in high power electronics). Now I've heard two!

 

[richs]

Hi-

The star washer is a good idea as there are a lot of racks
of equipment that are painted........

The star tends to cut through the paint. Sometimes teaching
"craft" people can be a little tedious, so it is better
to err on the safe side.

The second (or split) lockwasher might be a tad overkill.
What you want with the lockwashers from a mechanical
standpoint is to have some tension on the bolt or screw.
The star washer will do double duty, the electrical and
the mechanical. But it shouldn't hurt anything, other than
if one gets lost and gets across some buss bars......

There might be some galvanic action to take into account
so I would suggest materials accordingly.

But basically, yep, I agree with Keith.

Just one more voice out in the wilds of the internet.

Cheers,

Rich S.

 

[ScottyUK]

For a bond earth to a cabinet frame or door I wouldn't have a problem with the star washer in the conducting path. For a utility power earth to, for example, structural steel or a main earth bar I would be mortified to see one. Depends on the situation, as do so many other things.

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I don't suffer from insanity. I enjoy it...