Hello from KC. I have a question and this forum seems active. ........ Copper versus Alu busbar???

[cdherman]

Hello from Kansas City. I used to frequent Arizona Wind and Sun forum and gained (and contributed a bit) knowledge there through the years. Designed a system for my pole barn in 2008-09 but let an installer actually do the install, as here in KC there was serious money at stake from then KCP&L (now evergy) and I did not want to lose that. That system with Kyocera panels (manufactured in Mexico) and a Fronius inverter has been "Up" for 14 years. Aside from reseting the internet bridge, zero issues.

AZ wind and sun forum seems to be in decline.....

I am getting back into this again, this time around for my brother. System will be grid tie, but I am trying to leave some options open for batteries etc.

First things first. I need to get service to the shed and its a big one, 50x120. Future proof in order. Anticipate eventual EV Semi truck charging. So 200A at least. This is in a place in western KS where local electricians are rare and DIY is common, so spare me any comments about how I need a professional. If there were one, I'd be happy to hire them.....

Back to the title and what I really would like to know: I am a believer that a copper bus is better than Al. Better heat tolerance (higher melting point, in a SHTF event) and harder. Yes, since Al is actually PER WEIGHT UNIT more conductive than copper, you can design a robust Al bus, but the breakers that will back feed solar power, or feed a high amperage EVSE are the same size. Those contacts in the panel, made of copper, are just superior in my thinking... And solar as well as EV charging involves sustained high amperage loads that are prone to heat. Copper = better IMHO

I've been looking for some support of this opinion. Makes me feel better spending more $$ for a copper busbar.

Your thoughts?

 

[FilterGuy]

You are not likely to get very many folks on this forum to argue with you on that. Perhaps more important than anything you listed is that Aluminum Oxide is non-conductive. Consequently, it becomes too easy to get a bad connection.

 

[BentleyJ]

What FilterGuy said. Anodized aluminum is one the most nonconductive, noncorrosive finishes available. There are many examples of those dark bronze colored anodized aluminum hand rails at pedestrian beach walks all over CA. They don't corrode for years where in that environment even 316 SS will get rust spots. Copper is better than Al and Tin plated copper is even better depending on the humidity.
While aluminum may be better on a per weight basis, Al is 40% less conductive on a per volume basis and goes down from there as the oxide forms.

 

[SilverbackMP]

Bus bar for batteries? I am a big fan of MidNite Solar’s battery combiner boxes. They come in 1000 and 2000 Amp variations with big chonks of tinned copper. The 2000 Amp variant may just squeeze into your requirements.

They have punch outs for 12 large DC breakers. I used MidNite’s 250 Amp breakers which I’ve read are built by Carlyle.

Here’s one at my place a couple hours east of you:


That’s 4/0 wiring just for a sized perspective.

 

[SilverbackMP]

What kind of inverters are you planning? I would lean towards Victron which can be stacked to crazy amounts or for more money and complexity, SMA Sunny Islands with a Multicluster Box which can get you to the amps you need (at 208v three phase). You get AC coupling with that setup.

Schneider might do it too. IDK.

There’s also high voltage DC inverters available though there’s not many folks with them. “MikeG” on YouTube has such a setup. If I would have known about them before I went SMA, I might of considered them. Except electricity scares the crap out of me. And the DC power coming off all of those batteries at once could weld up a battleship.

I am far from an expert. Almost every thing I know comes from this forum or YouTube which helped me and an electrician (who didn’t have much knowledge of solar) figure everything out and install a quite robust SMA setup (not as much as you need. I have just under 100 amps @ 240v with the current setup; may add on to later. Use the existing SMA Sunny Island/Sunny Boys setup as “the grid” and feed “shore” power to Victron satellite clusters. User “Toms” on this forum has such a setup.

 

[Hedges]

Aluminum is of course common, and found in all my breaker panels. So long as it is tinned, I think it works well.
Bare aluminum I think is a problem. It is used in commercially assembled batteries by laser welding to terminals, which should be fine.

I've observed crimp terminals used by PG&E on aluminum wire, obviously that is reliable too.

Bolted connections, I don't want bare aluminum.

I don't think you've clarified what the busbar is to be for.

200A is typical electric service to a home. 400A panels are available of course, much more money.
Plan for how much PV backfeed you want to do, 120% rule etc. I use a 200A breaker at meter without busbar to avoid that.

Battery system for 200A 240V would be a larger size system, not clear you meant that.

Is this to be single phase or 3 phases? What voltage?

 

[SilverbackMP]

Aluminum is of course common, and found in all my breaker panels. So long as it is tinned, I think it works well.
Bare aluminum I think is a problem. It is used in commercially assembled batteries by laser welding to terminals, which should be fine.

I've observed crimp terminals used by PG&E on aluminum wire, obviously that is reliable too.

Bolted connections, I don't want bare aluminum.

I don't think you've clarified what the busbar is to be for.

200A is typical electric service to a home. 400A panels are available of course, much more money.
Plan for how much PV backfeed you want to do, 120% rule etc. I use a 200A breaker at meter without busbar to avoid that.

Battery system for 200A 240V would be a larger size system, not clear you meant that.

Is this to be single phase or 3 phases? What voltage?

On the AC side of my setup, we used a premium 200 Amp breaker box as the bus. Sunny Boys feed power in and the Sunny Islands and other loads pulls it out. This is OFFGRID though. Not sure how a grid connected setup would work.

I was hoping that I had an image of the breaker box, but I don’t. It’s located just to the right of the Sunny Boys (the top 3 are hooked up, the one on the bottom is a spare).

 

[ericfx1984]

I'm from the KC area too

 

[Copperman]

From the Lawrence area and grew up in western KS. If either of you are planning any panel purchases in the very near future, I would love to split a pallet. I'm looking for about 8 panels and hate to buy more than I need, but the minimums and shipping suck.\

 

[hwy17]

For an AC panel bus bar sure copper is better but who cares? If it's rated for then it's rated for it and it won't be a problem. I guess if I was building my dream home I'd want copper, but in real life I'll take whatever they got at Home Depot and not worry about it.

We're all gonna have to get over our copper preference sooner or later anyway when the EV's suck up all the supply of it and we'll learn to love aluminum romex again too.

 

[SilverbackMP]

For an AC panel bus bar sure copper is better but who cares? If it's rated for then it's rated for it and it won't be a problem. I guess if I was building my dream home I'd want copper, but in real life I'll take whatever they got at Home Depot and not worry about it.

We're all gonna have to get over our copper preference sooner or later anyway when the EV's suck up all the supply of it and we'll learn to love aluminum romex again too.

Maybe go one step ahead and hit up an electrical supply? Square D and others offers different lines of varying quality for the same ratings.

 

[hwy17]

Maybe go one step ahead and hit up an electrical supply? Square D and others offers different lines of varying quality for the same ratings.

I have considered QO. I have considered going to the supply house for Eaton. But ultimately I decided I would just be wasting a bit of money and a bit of time for no benefit to me other than some sort of status satisfaction.

If I was doing my outdoor main panel I would, but for subpanels I'm happy with a Homeline. Plus I think there's a benefit to going with the mass production stuff, it's well tested by mass use. My homeline AFCI/GFCI combo breakers have had zero nuisance trips even though they're feeding old ass 50's wires with some knob and tube mixed in.

 

[sunsurfer]

Melt yourself down some aluminum beer cans. Pour it into some C channel steel with the shape you want for bars.

Done.

 

[sunshine_eggo]

I'll argue Al vs. Cu.

I needed 107' of bus bars to join my 588 NMC cells (1,176 holes in bus bars). Materials + labor was $995 for Aluminum. Materials only for Cu was over $2000. The thickness of Aluminum has 20% better conductivity than the priced Cu.

Aggressively buffed the contact surface with scotchbrite, clean with acetone and apply a thin film of NO-OX-ID A-Special to the contact faces.

Here was a test fit of the bus bars:

 

[cdherman]

thanks for the comments and thoughts. I was referring to a busbar in a plain old load center, in this case, the sub-panel in the shed where the PV panels will be, as well as EV charging.

As others note, you can scale Alu to overcome its deficiencies if you have space, but the contacts inside a load center are fixed in size. They have to fit in a breaker. I just worry that a 100A breaker, used under continuous load at say 80A, if there is some corrosion, might start to see some heat. Then add another 100A breaker in the same load center. One feeding from PV, the other pulling to an EV.

Maybe I worry too much. I have seen one EVSE melt already in my 11 years of BEV use.......

 

[Hedges]

Deficiencies - lower conductivity of aluminum overcome with larger cross section.
Corrosion. Metal migration (if high current through small contact.)

The Homeline have a plug-on bus that other brands fit as well. Maybe there is a difference in performance under fault conditions (manufacturer would like you to use only their brand.)

QO has copper bus for > 100A, aluminum <= 100A. Lugs, neutral/ground busbars, breaker wire terminals, and other parts are all aluminum. At least some of that supposedly available as an option in copper but I haven't seen where.

I think the aluminum in both those models is all tin plated and rated for both copper and aluminum wire. Of course the aluminum wire itself is probably not plated, so have to get through the oxide and use goop.

I didn't know the differences before but now use QO panels exclusively.

I have had aged breakers trip well below rated current. It may be I had a PV circuit with the wire wedged under screw terminal rather than in the terminal so adding heat. Had to replace breaker.

Something I've found with QO is that when I paralleled inverters, with feed-through current balanced by resistance of 60' of 6 awg wire, the current imbalance was 3:1. about 15A through one and 45A through the other. This was due to different internal resistance of two QO270 breakers. I fixed that by using DIN rail breakers (and landing on lugs in the QO panel.)

 

[sunsurfer]

If silver doesn't go up this year I may have some nice high performance bus bars next spring.