Grounding bolt through panel

[mhellx]

Hi,

I have design a motor control panel for a skid.
As per customer specs they want the grounding of the whole skid to be attached at the base corner of the steel frame of the skid.

We will just weld a grounding servit post to the steel frame as per equipment such as the Motor Control panel.

Our panel is a NEMA 4 type and I am thinking of installing a grounding bolt through it.
My idea is to connect the earth bar inside the panel to the grounding bolt and from the grounding bolt to the servit post welded to the skid frame.

My question is, will it ruin the NEMA 4 protection of the enclosure? Is there a grounding bolt that I can use that is made for this application to maintain my enclosure protection.

 

[petersonra]

You have to fasten the box to the skid. Those fasteners somehow manage to keep the rating of the box. Something similar would work for your grounding stud.

If it was me, I would just thread a bolt thru the box wall and put a nut on the outside. The chances of any water getting thru a threaded hole like that approaches zero if you silicon around it on the outside.

Another option is to weld a ground stud on the outside of the box. We have a stud welder for that kind of thing.