Using Stainless Steel Hardware To Attach A Copper Lug To A Copper Buss

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Ravenvalor

Ravenvalor

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Piedmont region of NC
Hello Everyone,

Does anyone here know If stainless hardware is good for mounting a copper lug to a copper buss bar?

I have to attach a #1 THWN CU conductor to a copper buss bar. I already have a copper lug but unsure what type of material I should use for the nut and bolt. Yesterday I picked up some stainless steel hardware but I am unsure whether or not it's a good choice for preventing corrosion with copper. It looks like the existing hardware on the buss bars in this panel may be galvanized steel bolts with copper nuts but that doesn't seem to make sense due to corrosive factors. The panel is a SQUARE-D 120/208V 1600A Service Main Breaker Distribution Panel. It may be 75 years old. It's located in a room that is being used for storage of non-corrosive material like furniture.

Thanks for the help. It's good to know there are electrical industry experts here on this forum that I can rely on for good advice.
 
Galvanized or stainless is unlikely to cause any kind of galvanic corrosion with copper. I'm not a big fan of copper lugs though. More common is tin plated aluminum.
 

Copper or type 410 stainless are the most compatible with copper in terms of corrosion.

Plain steel will sacrifice itself to protect the copper, so with a plain steel or galvanized fastener the copper will be fine but the fastener will be at risk.

Of course if there is no electrolyte present to cause corrosion then this might not be a significant issue. If the area is always dry (including condensation) then you don't have to worry about corrosion. If the area is unheated and subject to temperature swings where you might get condensation, then you have a small worry. If the area is exposed to salty moisture then you want to be really careful about compatibility.

-Jon
 
Stainless is higher resistance (electrically) than copper. But, if the copper lugs are touching each other then stainless is fine to clamp them. The stainless is not part of the current carrying path.

If a stainless stud is used to carry the current, it does not work so well in very high current applications. I'm speaking over 100 amps or so.
 
Ravenvalor said:
Hello Everyone,

Does anyone here know If stainless hardware is good for mounting a copper lug to a copper buss bar?

I have to attach a #1 THWN CU conductor to a copper buss bar. I already have a copper lug but unsure what type of material I should use for the nut and bolt. Yesterday I picked up some stainless steel hardware but I am unsure whether or not it's a good choice for preventing corrosion with copper. It looks like the existing hardware on the buss bars in this panel may be galvanized steel bolts with copper nuts but that doesn't seem to make sense due to corrosive factors. The panel is a SQUARE-D 120/208V 1600A Service Main Breaker Distribution Panel. It may be 75 years old. It's located in a room that is being used for storage of non-corrosive material like furniture.

Thanks for the help. It's good to know there are electrical industry experts here on this forum that I can rely on for good advice.
Click to expand...
Chart at the bottom
 
Switchboard and switchgear bus is bolted together with standard plated hardware. SS would be more expensive but unless required by a specification I wouldn't waste any extra money on it.
 
In the panels we used to build, we used galvanized grade 5 hardware, a weak loctite, and a Belleville washer. Our stuff was relatively small; 1/4, 5/16, and 3/8 covered everything.
 
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