[RE-wrenches] Attaching Ground To Steel Frame

[Mark Frye]

Thanks James. Very helpful. Got a source or spec for the bonding bar below?


From: RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> On Behalf Of James Jarvis via RE-wrenches
Sent: Tuesday, January 28, 2025 7:32 PM
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Cc: James Jarvis <jj at aprsworld.com>
Subject: Re: [RE-wrenches] Attaching Ground To Steel Frame

We use copper plated steel capacitor discharge weld studs for this application:
https://www.studweldprod.com/product/flanged-capacitor-discharge-studs/
They only take a few seconds to install and, as you can see, don't cost much. Of course you need a multi thousand dollar welder.

Generally using stainless steel hardware as your conductor is frowned upon. But it is okay if you are just using it to clamp something against something else conductor. In which case your weld shops recommended 309L stainless fill rod will work fine in welding 304 stainless steel hardware to a mild steel frame.

I think you are overthinking things quite a bit, however. I would just bolt a ground bar in a few places to the chassis. I like the heavy plated copper inter system bonding bars as a general purpose outdoor ground bar.
[cid:image001.png at 01DB725B.74B28AD0]
A couple of tapped #10-32 screws or 1/4"-20 and you can bolt that thing right down to your frame. Mask off or scrape off the paint underneath.

-James Jefferson Jarvis
APRS World, LLC
+1-507-454-2727
http://www.aprsworld.com/


On Tue, Jan 28, 2025 at 8:34 PM Mark Frye via RE-wrenches <re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>> wrote:
Thanks Everyone for your feedback.

I will try and respond to all here.

The skid is a stand-alone power supply for GPS equipment that will be deployed to large scale solar installation sites.

It will not be subject to UL or NEC requirements, all though I do try to keep them well in mind.

It will be a welded steel frame that will be dropped on the ground at a propitious location on a job site and left in operation for 3 to 18 months at a time.

The power supply is a AGM battery/PV system driving 12VDC and 24VDC busses for various radio equipment.

There will be two 8’ copper clad rods installed near the skid, about 6 feet apart to establish a system and a lightning grounding electrode.

The unit will have a UHF antenna lofted to 20 feet and the coax cable will lead to a lightning protection device with will in turn be connected to the lightning GE with a GEC.

The steel frame will have a stud for attaching a GEC that will run to the system GE.

The negative of the battery bank will attached to its own stud on the frame. An equipment grounding conductor will also run to this stub. This EGC and the Battery “-“ run back to a control panel that houses the power electronics including MorningStar Genstar DC System Controller.

My quandary is how to fabricate the two studs on the frame in a way that I can have durable connections to the GECs.

I like welding SS bolts to the mild steel frame and using SS hardware.

I have had one welding shop tell me that this is no big deal as long as you use a TIG and a 309L rod.

I can also just have a mild steel bolt welded to the frame, wire brush the stud before applying No-Ox, and tightening on a cable lug or compression lug with SS hardware.

That is the tempest which resides in in my tea cup.

Mark

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