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I'm starting my shopping for our construction project this summer.

After being sent away from an electrical supply place - they said it was a 4-6 month wait to get a panel from them*, I was looking at the following 2 panels at my local big-box:

They're both 40 space/40 circuit panels good for either flush or surface mounting. They're both PON ready (does "ready" mean I can use a PON *FCI breaker or does it mean something else?) The only difference I see is that the SN series has an aluminum bus while the PN has a copper bus.

  • What are the advantages of a copper over an aluminum bus that makes it cost more?
  • What are the other advantages of the PN over the SN series that I'm not seeing that make it cost more?

*It was nearly closing time on a Friday evening. I'll certainly check other local places before pulling the trigger at the big-box.

FreeMan
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    Question quibble - The cost of the actual metal makes it cost more, regardless of advantages. The advantages might help to sell at the higher price, but the fact is copper is stupid expensive .vs. aluminum for a couple of decades, at least. And a pair of busses that handle 200A are not tiny amounts of metal. – Ecnerwal Feb 12 '22 at 01:28
  • The question still stands, @Ecnerwal, is copper worth spending the extra money on? I understand that for wiring itself, AL is significantly cheaper, even when going up a size to handle the same ampacity. Are there other advantages to the copper bus (or to the PN vs SN series) that make it worth the extra? – FreeMan Feb 12 '22 at 01:42
  • I figured certain other parties will have more data and experience of failures for the answer to that, as well as being able to answer your "What is PON-ready" question. A bus is different from wire in important ways that do, IMHO, favor spending the extra $25. IIRC, one issue is that if the plating is damaged on an aluminum bus it's a big deal. Never-the-less, the pricing is almost certainly about metal cost, not advantages, given the relative prices. – Ecnerwal Feb 12 '22 at 01:58
  • Thanks for the input! I wasn't really doubting your point about pure material cost, TBH, that hadn't even really occurred to me. I was just curious why that seems to be the one difference that's a big enough deal that it's listed on the packaging in addition to the spec sheets I linked. – FreeMan Feb 12 '22 at 02:05

2 Answers2

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The #1 use is to avoid hypocrisy. It looks dumb to insist on copper wire, and then, buy the cheapest panel and not realize it has aluminum buses. (as well as aluminum lugs).

The lugs are aluminum for a very good reason - due to thermal expansion differences, this plays to aluminum's advantage, making it the "universal donor". Copper lugs play badly with aluminum wire (hence the famous trouble with That 70's small branch circuit wiring).

However the bus bars can go either way. One thing for sure - when things fail, we see a lot of reports of it on here. I don't see too many bus stab failures that have no other reason to have happened. Lots due to alien breakers, some due to misfit (the breaker wouldn't seat all the way because of an alien breaker next to it, user pushing the breaker off the stab to make the wrong cover fit, etc.)

One case where I would stick to copper is a panel that lives in rough conditions like outdoors. The tin plating can be exhausted, and aluminum would corrode with pitting - just what you don't want on a bus stab. Copper does not corrode easily - in fact, it's one of only a few metals found in nature in its metallic form (i.e. 4 billion years and it never oxidized).

Harper - Reinstate Monica
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Why use copper rather than aluminium as the conductor in power cables? – help.leonardo-energy.org

when looking at lifetime costs, there is no economic advantage to using the initially less expensive aluminium rather than the more technically performant copper.

Copper:

  1. does not creep.
  2. does not react with water.
  3. corrosion is not an issue.
  4. is less brittle.

From personal observation: does not pit as bad during an arc flash. I've seen marred copper buses. And I've seen aluminum ones missing chunks. With 60% less thermal capacity, that's what happens.

And according to Woodworking, aluminum has a hardness of 15 and copper 35, so it's more resistant to physical damage. Substituting aluminum for copper when it's better than gold is just silly when over the course of 100y we're talking about $.25 per year.

In 100y that copper bus will still be as good as the day it went in, and an aluminum one will still be as questionable. It's the one thing you can cheat on that you shouldn't.

Mazura
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    This got a down vote. Someone please explain what's wrong with it - I'm not questioning the vote, I'm trying to learn. – FreeMan Feb 12 '22 at 14:36
  • @FreeMan Not my down vote but the answer paraphrases the link from an advocate of copper. If I wasn't familiar with the OP, I might have marks this as spam. Plus, this deals with cables, not bus bar in panels, so not really an answer. – JACK Feb 12 '22 at 22:12
  • Thanks, @JACK. Not wrong, per say, just not a quality answer. – FreeMan Feb 13 '22 at 17:39