Screw to attach device into an enclosure

[Fred B]

Seen this the other day and can't find reference to say it right or wrong.
Guy attached a contactor into a box with Sheet metal self tapper. Seems to me it should be at minimum a Tapped hole with screw of a 32pi thread count. I don't see how the self tapper will securely fasten the contactor to the enclosure.

 

[Strathead]

Seen this the other day and can't find reference to say it right or wrong.
Guy attached a contactor into a box with Sheet metal self tapper. Seems to me it should be at minimum a Tapped hole with screw of a 32pi thread count. I don't see how the self tapper will securely fasten the contactor to the enclosure.

First off, self drilling and self tapping are two different things. There are self tappers that give you 32 threads per inch, for example the ones in the ears of a 4S box. I assume you mean a typical self drilling truss head screw. As long as it was installed well, I can't see any problem with it. It is about whether the contactor is secure. Can you shift it around? If not, then I would call it secure.

 

[Fred B]

typical self drilling truss head screw.

yes.

But will it attach firmly enough for the equipment ground bonding.

 

[ptonsparky]

yes.

But will it attach firmly enough for the equipment ground bonding.

IMO, I don't believe the mounting of the contactor requires the 2 threads of an EG. The EG to the enclosure would require the two threads.

 

[infinity]

You cannot use a standard self drilling screw to attach a bonding jumper to a box but it don't see that requirement as being the same as mounting a contactor to the box. All sorts of grounded electrical metal things are mounted with self-drilling or self tapping screws that do not have 32 threads per inch.

 

[Tulsa Electrician]

May not be a code item however good installation practice.
The 32 per inch would serve to bond the metal plate of the part to the enclosure which is bonded or should be.

I tell the guys by using a 32 per inch screw it would meet bonding requirements related to other parts of the code and a high quality of work.

If they attach with a sheet metal screw they tend to attach the ground lug with one as well. Now you have an issue.

I even have them use a ground screw. Remove the wire and use the 10/ 32 heck head screw. We always have them laying around. Yea it's green.

 

[Fred B]

You cannot use a standard self drilling screw to attach a bonding jumper to a box

This I know. This is my issue. Code reference?

but it don't see that requirement as being the same as mounting a contactor to the box. All sorts of grounded electrical metal things are mounted with self-drilling or self tapping screws that do not have 32 threads per inch.

Box is bonded at the bump-up attachment to the EGC with 10-32 screw. But the contactor frame (metal) seems to be the only ground bonding to box (no wire), that would be an issue. (metal box).

If they attach with a sheet metal screw they tend to attach the ground lug with one as well. Now you have an issue.

Exactly what they have.

 

[infinity]

This I know. This is my issue. Code reference?

250.8(A)

But the contactor frame (metal) seems to be the only ground bonding to box (no wire), that would be an issue. (metal box).

What code section would require something other than a self-drilling screw to mount the contactor?

 

[wwhitney]

So the question is whether the contactor is required to be bonded to the box, and if so whether the mounting screws are the only bonding connection.

Cheers, Wayne