equipment ground/bond outside of conduit

Is an equipment ground/bond wire ever allowed to run along the outside of the conduit containing the feed wires for distances exceeding six feet (whether new or as a supplement to an existing installation)? BTW, replacing an ungrounded receptacle with a grounded one does not apply to this situation.

Thanks

Bonding jumpers can only be max 6' 250.102(E)

... but see what you make of 250.120(C)

Quote

(C) Equipment Grounding Conductors Smaller Than 6 AWG. Equipment grounding conductors smaller than 6 AWG shall be protected from physical damage by a raceway or cable armor except where run in hollow spaces of walls or partitions, where not subject to physical damage, or where protected from physical damage.

... so you can run a ECG outside a raceway/cable if it is 6 or larger or otherwise protected from damage.

To be honest I have never seen it.

I did see this discussed once in reference to adding grounds to a house that was ungrounded and it was surmised that you could run a bus of #6 through the crawlspace, attic or whatever was accessible and tap off #12 or #14 drops into the wall cavities to the boxes if the unprotected portion was very short, basically directly into the wall from the tap.

It seemed reasonable to me.