ACSR or AAAC: how to tell them apart on a reel
Both are aluminum overhead conductor and both arrive on a wooden reel. The difference is a steel core, and it changes strength, sag, corrosion and how the lot is priced.
A transmission reel stored beside a line
Overhead conductor is chosen to do two jobs at once: carry current and hold itself up between structures. ACSR and AAAC are the two answers that dominate the work, and on a reel they look nearly identical until somebody examines the cut end. One uses a steel core for strength. The other uses an aluminum alloy strong enough that no second metal is needed.
For a seller the distinction is about identification and about how the lot will be priced. A reel tagged Drake is a known quantity. A reel with no tag and no recorded strand count is a question, and a magnet plus a photograph of the end usually answers it. Both materials are worth buying. Only one of them is quick to quote.
At a glance
- ACSR core
- Galvanized steel strands
- AAAC strands
- 6201 aluminum alloy throughout
- Quick test
- A magnet finds the steel core
- Code names
- Partridge, Hawk, Drake, Cardinal
Steel core or alloy strands
ACSR stands for aluminum conductor steel reinforced. The aluminum is 1350-H19, the hard-drawn grade used for overhead work, and it is stranded over a core of galvanized steel wires. The steel carries most of the tension and the aluminum carries the current, which is why the two metals are combined instead of one being made larger. The division of labor between core and conductor is the whole idea behind the design.
AAAC is all-aluminum alloy conductor, and every strand is 6201, a heat-treated aluminum alloy with magnesium and silicon that develops considerably more strength than 1350. There is no second metal anywhere in the conductor, so there is no core to fill with grease, no end cap to lose, and no interface between dissimilar metals to corrode while the reel waits in a wet yard. That alloy is what separates AAAC from plain all-aluminum conductor, which has no comparable strength.
The naming follows the same logic. ACSR is specified by a code name plus a stranding written as aluminum over steel, so 26/7 means twenty-six aluminum strands around a seven-strand steel core. AAAC carries its own set of code names, mostly place names such as Canton or Lima, followed by a plain count of identical strands. The two naming systems do not overlap, which is useful when a tag survives.
- ACSR: 1350-H19 aluminum strands over galvanized steel
- AAAC: 6201 alloy strands, no core
- Stranding is written aluminum first, steel second
- 26/7 means twenty-six aluminum over seven steel
- AAAC codes are separate from ACSR codes
One conductor carries current with steel. The other carries it with alloy.
What the difference does to a span
The advantage of ACSR is strength per unit of weight, and that is what lets a transmission line cross a long span with towers far apart. For a given diameter the steel core makes ACSR stronger than an all-aluminum conductor, and it can be strung at a tension that holds sag inside clearance without overstressing the aluminum strands at the clamps. Long crossings and steep terrain are where that margin is worth the most.
AAAC sits between plain aluminum and ACSR. It is stronger than 1350 all-aluminum conductor of the same size, which lets a utility work distribution and subtransmission spans without a steel core, and its sag is predictable because the whole conductor expands as one material. Where spans are longest, or ice and wind loading on the structures is heaviest, ACSR remains the usual answer. A distribution line with moderate spans rarely needs the extra strength that a steel core provides.
Weight runs the other way. Steel is much denser than aluminum, so an ACSR of a given diameter is heavier than an AAAC of the same diameter, and the structures carry that difference for the life of the line. The steel buys strength and the line pays for it in conductor weight, in tension, and in the effort of pulling the conductor during construction. That is also why an ACSR reel is heavier to handle in the yard than its diameter suggests.
Salt, industry and the galvanic couple
The bimetallic joint inside ACSR is where to look when a reel has been stored badly. Water sitting in the cut end, or between the aluminum layers and the steel core, sets up a galvanic couple, and aluminum is the metal that gives way first. That is why ACSR cores are galvanized, why many constructions fill the core with grease, and why end caps matter on a reel that will sit in a yard for a season.
AAAC avoids that particular problem because there is no second metal. In coastal air, and around plant with chloride or sulfur in the atmosphere, that is a real advantage, and it is one reason AAAC has a following on distribution lines near the coast where salt fog reaches the conductor. The conductor is only one part of the corrosion picture, but it is the part that cannot be painted or re-greased.
Neither metal likes chlorides, and both benefit from being stored off the ground with the ends sealed. A reel that has stood through several wet seasons will show pitting and white aluminum oxide on the outer layers, and the outer layers are what a buyer sees first. We will want that in a photograph before quoting, taken in daylight rather than under a shed roof. Photograph the worst face of the reel, not the cleanest one.
Strand count, core color and the tag
The cut end is the most reliable evidence and the cheapest to capture. ACSR shows a bundle of aluminum strands around a smaller group of steel wires that read grey rather than silver-white, often with grease at the interface and a visible step where the core sits inside the aluminum. AAAC shows one alloy throughout, with every strand the same color and the same diameter class. Take the photograph in daylight, close enough that the strand pattern can be counted.
A magnet confirms it. Held against the end, it will find a steel core through a little aluminum, and it will find nothing at all on AAAC. Where a tag survives, the code name settles the matter before you get that far. Partridge is 266.8 kcmil, Hawk is 477 kcmil, Drake is 795 kcmil, Cardinal is 954 kcmil and Bittern is 1,272 kcmil, all ACSR names in common use. If the tag has weathered away entirely, the magnet is the fastest answer available.
Do not confuse stranding with size. A 26/7 and a 54/7 can be close in overall diameter and nothing alike in strand count, and a tag reading 45/7 belongs to a different conductor than one reading 26/7. Copy the numbers exactly as they appear and photograph the flange, because a transposed digit changes the conductor and is an easy mistake to make on a faded stencil. Where two reels disagree with each other, treat them as separate lots.
- Photograph the cut end square on
- Count aluminum strands and steel strands separately
- Hold a magnet to the end to find a steel core
- Record the full code name, not just the first word
- Note any grease at the core interface
Questions about overhead conductor
What does 26/7 mean on a conductor tag?
It is the stranding: twenty-six aluminum strands laid over a seven-strand steel core. The first number counts the aluminum and the second counts the steel, and ACSR is normally written in that order. So a 54/7 has fifty-four aluminum strands over seven steel wires, and a 45/7 has forty-five over seven. AAAC tags usually give a single count because every strand is the same alloy.
Can a magnet separate ACSR from AAAC?
Yes, for practical purposes. The steel core in ACSR is magnetic, and a magnet held to the cut end will pull toward the center through the aluminum. AAAC is all 6201 alloy and will not attract a magnet at all. The test takes seconds and needs no tools beyond the magnet, though it will also react to steel armor or a steel messenger, so read the whole construction.
Is the steel core removed before the conductor is sold?
No, and it should not be. ACSR is bought as a composite conductor, and cutting the core out destroys the material and creates a mixed scrap problem worth less than the whole. The core is a small share of the weight and a large share of the strength. Leave the conductor as it came off the line and let the buyer decide how it is processed.
Why is AAAC preferred near the coast?
Because it has no bimetallic joint to corrode. In salt air the interface between aluminum and a steel core is where ACSR deteriorates first, even with galvanizing and grease. An all-alloy conductor removes that path entirely, so a coastal utility will accept a larger or heavier conductor in exchange for longer service. Inland, where salt is not a factor, the calculation often goes the other way.
Other seller guides
- Reading a reel tagWhat the markings on a flange actually tell a buyer
- Footage by weightTurning a weighed reel into a defensible length
- Copper and aluminumTwo conductor metals, and how to tell them apart
- High voltage safetyWhat not to touch before the clearance is issued
- Storing conductorKeeping reels saleable between projects
Send us your reel list
Six details are enough for a first review: what the cable is, the metal, the size, the footage or reel count, the condition and where it sits. Photographs can follow by text or email. There is no fee and no obligation, and nothing moves until written terms are agreed.
Ready to send the reel list?
Six details are enough for a first review: what the cable is, the metal, the size, the footage or reel count, the condition and where it sits. Photographs can follow by text or email. There is no fee and no obligation, and nothing moves until written terms are agreed.
Send the strand count
Photograph the tag and the cut end, note the stranding and the code name, and tell us how many reels are in the lot.
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