OP
Engineer54
Whilst the straight sections of trunking could have a link either side, the bends and sets only have a knock out hole (usually with an earth adjacent), on the one side.
If you wanted to add another link, you would have to drill a hole, which would suggest that only the one link is deemed as being necessary.
No there doesn't appear to be a requirement for bonding across expansion joints in A/C ductwork.
That i would have thought, would be standard practice, when fabrication of sections are required on metal containment systems??
Why did i know that was going to be the feed back, on the A/C ductwork... lol!!