Aluminium Busbars

[RaymondR]

In a thread titled " How many cables fit on a busbar" I lodged the following post:

Quote:
Originally Posted by Singularity View Post
FWIW...an aviation perspective.
FAA allows 4 lugs per stud, but:
-there needs to be a physical divider between studs
-some type of locking device required (lock washer/nut, not just Loctite)
-2-3 threads should show above nut after all torqued on (standard aviation practice)
-current should be carried by terminal bar (or sandwiched components, not relying on stud; maybe this is was addressed differently up-thread)

Not saying the above is required, and planes +/- have more vibration issues. Here's an FAA best practices document, terminal strips starting at page 101 (obviously references to aluminum and steel don't apply to boats):
https://www.faa.gov/training_testing..._printable.pdf

I found the aircraft recommended practices very interesting in that they address aluminium conductors.

A couple of years ago I expanded my solar farm and when it came to rewiring the new installation I became very dissatisfied with the amount of wiring and connections required. Consequently I decided to utilize aluminium bus bars. I was unable to find much information on the use of alloy in this application other than to find that it's use therein is becoming more common.

Being a suck it and see sort of bloke I decided to forge ahead and just see how it turned out. There is little risk in doing so as the solar farm is an all alloy construction.

I was concerned about potential dissimilar metal problems until I went to an electrical warehouse and found a paste used to prevent the problem with alloy bus bars.

I've not had any problems with the solar farm and am now considering rewiring the mess of cables in the battery box using aluminium bus bars. It is heartening to see that alloy is used in aircraft. I believe it has about 64% the conductivity of copper but is much more readily available and much lighter and less expensive."

The responses were generally negative and cataclysmic.

However I believe there are some fairly major advantages to the use of the subject material for electrical work in the marine environment. For example two of the reasons I implemented the solar farm wiring with alloy busbars were that I could reduce the overall number of connections significantly and that it was structurally much simpler to support the busbars. And that consequently the subject deserved a separate thread.

[a64pilot]

Aluminum wire used to be used in houses, but due to the excessive number of fires it’s use has been discontinued, it is much less expensive, or was anyway when copper prices were high.
An issue of aluminum wiring is it expands when heated and that loosens connections, loose connections mean higher resistance and that means heat, enough heat and you have a fire.

You will still find aluminum wire in a house, it’s the wire that comes into the house from the power company and it stops there, that is where the paste is used.
https://en.wikipedia.org/wiki/Aluminum_building_wiring

Aluminum can be used safely but be real sure it’s the proper alloy, and there are special precautions and different terminations etc.
In short it’s not easy to do safely, requires special equipment and knowledge, and by the time it’s all said and done, what’s the advantage?
On aircraft it’s weight, weight is paramount, every ounce you save, is another ounce you can carry plus enhanced performance. In order to save weight the AH-64 Apache ran 110VAC three phase 400hz current to power things, the weight savings of the smaller wire from the high voltage AC was significant.
400hz 110 VAC is an aircraft standard, but a pound of wire just isn’t going to make any difference in a cruising boat.

[Reefmagnet]

Aluminum 1100 series is a decent electrical conductor and is used in heaps of applications, but it's oxide isn't (in fact, it acts as a semiconductor of sorts). It also won't like being in contact with most other metals, especially copper where it makes a great sacrificial anode. It melts at just over half the temperature of copper and it won't dissipate heat from arcing as quickly as copper will. It's generally considered to be inferior to oxygen free copper for bus bars. I'd probably use it in the right situation, but certainly not in locations where it may be exposed to a corrosive environment.

Here's an interesting factoid. Aluminium can be arc welded to copper. A main application is the fabrication electrical components, including bus bars.

[Frankly]

I designed and specified commercial electrical sytems for 30 years. My designs were always predicated on the use of copper conductors and copper bus bars in the panels. On some occasions (when copper prices elevated) the electrical contractors would offer an aluminum alternative bid. I always recommended against the aluminum choice but left the final decision to the client I was representing. On a few ocassions the client decided on the less costly aluminum (we are talking about the larger conductors, not the 10 and 12 AWG branch wiring). I watched the electrical contractors a little closer (often bringing my own tools to check connections). Never had any problems but aluminum does require extra care, and in 50 years might be a bad choice. The local electrical utility avoids aluminum within 1,000 or so yards of the coast.

Having said all that, the only place on a sea going vessel for aluminum is the mast or underwater anodes. Maybe an arch or bimini frame if money is tight. Using aluminum in an electrical application would fall just right line with using PVC plumbing valves for thru hulls.

And aluminum hulls if so inclined. Was aboard the ALCOA Seaprobe once (impessive no paint) and if my memory is correct it was actually scrapped many years later here in Panama City.

Frankly

Over the years I did do a few fire investigations on aluminum wired houses (including branch wiring). Have not heard of that in years, think I would feel more secure living in a tent on the Gulf Coast during hurricane season.

[Manateeman]

Well I love aluminum. My whole boat is aluminum. But this is one thing I’ve learned. Aluminum protects itself within minutes. I do a lot of TIG welding on aluminum. Weathered aluminum, new material and anodized. TIG welding is the controlled flow of electrons from the tungsten through the aluminum back into the welder. It takes a lot of work to prepare the aluminum even new material.
The wire brush cannot be used on other metals, the rods must be stored to prevent corrosion, clean gloves. You just can’t clean one day and weld the next.
Just the oil from your fingers will contaminate the weld.
The oxidation of even 5000 series (marine) occurs very quickly. I try to weld within a half hour of cleaning.
I would guess that the electrical Conductivity of an aluminum buss bar would decrease with oxidation. I have not had time to research to what degree but I can attest to two things I’ve learned. The surface of aluminum oxidizes very quickly and keeping aluminum clean requires attention to detail and speed.
Anodized aluminum is interesting.
It’s a super hard layer and very thin, which protects the aluminum but it’s difficult to TIG. You can grind it off to weld or set an inverter machine with very specific settings which kinda blows off this otherwise impenetrable layer.
I don’t know if anodized aluminum would be better or worse for a buss bar in terms of conductivity but anodizing really protects the aluminum from salt air.
There certainly is a way to measure this I just can’t find the data.
I’ve never tried Boshield on anodized alu but I know some builders wax it.
Happy trails to you
Mark and the Argon Army of manatees

[Wotname]

Apart from a possible small $ saving, I'm hard pressed to see any advantage in using Al busbars on a cruising sailboat but I can see disadvantages.

[Reefmagnet]

Originally Posted by Manateeman

Well I love aluminum. My whole boat is aluminum. But this is one thing I’ve learned. Aluminum protects itself within minutes. I do a lot of TIG welding on aluminum. Weathered aluminum, new material and anodized. TIG welding is the controlled flow of electrons from the tungsten through the aluminum back into the welder. It takes a lot of work to prepare the aluminum even new material.
The wire brush cannot be used on other metals, the rods must be stored to prevent corrosion, clean gloves. You just can’t clean one day and weld the next.
Just the oil from your fingers will contaminate the weld.
The oxidation of even 5000 series (marine) occurs very quickly. I try to weld within a half hour of cleaning.
I would guess that the electrical Conductivity of an aluminum buss bar would decrease with oxidation. I have not had time to research to what degree but I can attest to two things I’ve learned. The surface of aluminum oxidizes very quickly and keeping aluminum clean requires attention to detail and speed.
Anodized aluminum is interesting.
It’s a super hard layer and very thin, which protects the aluminum but it’s difficult to TIG. You can grind it off to weld or set an inverter machine with very specific settings which kinda blows off this otherwise impenetrable layer.
I don’t know if anodized aluminum would be better or worse for a buss bar in terms of conductivity but anodizing really protects the aluminum from salt air.
There certainly is a way to measure this I just can’t find the data.
I’ve never tried Boshield on anodized alu but I know some builders wax it.
Happy trails to you
Mark and the Argon Army of manatees

Anodising is aluminium oxide. The colour traditionally comes from the chemistry of the alloy.



Aluminium should be welded within 20 minutes of cleaning, because that's the maximum amount of time where it's safe to assume a contaminating layer of oxide has not formed sufficiently enough to cause problems. And at 3x the melting point of the base metal and funky conductivity characteristics, it does need to be clean when welding with TIG.

[RaymondR]

Various dyes are used with anodized aluminium to give it colour.

I have another shocking confession to make.

Rather than drilling, tapping and screwing the terminals to the alloy bus bars when I wired the new solar farm, I used alloy blind rivets. When I need to remove any wiring I will just drill out the alloy rivet. I originally intended to put the wire through the holes in the alloy bar and solder them however I found that the wiring was soldered at the panel end in the junction box and decided one end should be readily dis and reconnected.

[jamhass]

As Reefmagnet said. To reiterate:

Aluminum oxide is an insulator. Even with "paste" it will be very difficult to prevent in a seawater environment.

Copper and aluminum do NOT like to coexist. Again, the paste is only marginally effective, especially in a situation where current is flowing. Put a copper penny (if you can find one!) on an aluminum tank and watch it eat a hole in the tank.

Even using brass/bronze fittings on aluminum tanks is strongly discouraged.