grommets for elec cct backing boxes

[jim]

Open or closed grommets? Please, what is considered current or best practice spec?

TIA

[John Rumm]

Open generally - otherwise getting the cables through is a pain. All you are seeking to do is protect the cable from damage from the sharp edges of the box knockout - open does that and are cheaper and easier to insert to boot.

[Dave Plowman (News)]

Open are quicker to use. Although being softer can push out more easily. Were you thinking of flame retardation?

[jim]

TFT

Although being softer can push out more easily.

It's in the back of my mind that I picked up (?2 or 3 years ago) something about backing boxes needing to be completely sealed, including cable entry holes.

Probably misunderstood.

Thanks for the responses.

[Dave Liquorice]

As they are simply folded metal, "completely sealed" doesn't happen. There are cracks along the corners. And the holes where the tabs for the screws are pushed round. I'd fit a blind grommit to an open, but unused hole though.