Photograph of a back wired aluminum wired electrical outlet by Roger Hankey. Do Not Use CU-Only, COALR or CU-AL Electrical Outlets and Switches as a "Repair" for Aluminum Wire

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Safety advice about using COALR type devices with aluminum electrical wiring: this article explains why COALR, CO/ALR, AL-CU or CU-AL marked devices are not recommended for use with aluminum wiring as a "repair" for aluminum wiring. We explain the differences between COALR, CO/ALR devices and AL-CU or CU-AL devices - they are not equivalent!

Aluminum wire connections can overheat enough to start a fire without ever drawing enough current to trip a circuit breaker. Making proper repairs to aluminum electrical wiring, using the proper electrical wire connectors and methods, can bring the level of electrical wiring safety in building to about the same as a copper-wired building.

Making improper repairs to aluminum wiring might actually increase the level of risk. The history, differences in performance, and significance of COALR, CO/ALR, CU-AL and AL-CU marked electrical devices in aluminum-wired homes. What are the concerns with COALR or CO/ALR -marked electrical devices when used with aluminum wiring.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Use of COALR, CO/ALR, AL-CU or CU-AL or CU-Only Marked Electrical Devices, Switches or Receptacles with Aluminum Wiring

Photo of a back-wired electrical receptacle Photograph of aluminum wire on a CU device

Independent tests support the US US CPSC recommendations for repairing aluminum electrical wiring: only the AMP TYCO COPALUM or the King Innovations AlumiConn connector repair - or re-wiring with copper

Electrical Receptacles and switches marked COALR, CO/ALR, AL-CU or CU-AL or CU-Only (photo above right) have not been recommended by the US CPSC for aluminum wiring repairs.

However COALR or CO/ALR - marked devices are not and should not be treated identically with electrical devices marked CU-AL or AL-CU.

Also, devices marked CU-only are intended for use only with copper wire.

Article Contents

Prior to the introduction of the "CO/ALR" wiring devices in about the 1973 timeframe, UL did not have any standard or standard tests for wiring device terminals for aluminum wire. The markings prior to that time regarding type of wire were optional for the manufacturer to apply as they wished. UL considered all wiring devices with screw terminals as suitable for aluminum wire, even if the devices also had push-in backwired terminals.

The photograph shows a back-wired electrical receptacle with an aluminum-wired branch circuit. In the case in these photos the electrical receptacle was marked as "AL-CU" but was further marked as Backwire CU-ONLY by its manufacturer.

["Electrical receptacle" as used in our articles is a synonym for "electrical outlet" or what some people inaccurately call a "wall plug" or "wall socket". "Electrical devices" include receptacles, switches, and possibly other electrical components which are connected to the electrical wiring in a building.

Technical content courtesy of Dr.Jess Aronstein. Photographs courtesy of Roger Hankey. Contributions of photos of CU-AL and COALR receptacles are sought by the author.].

Electrical devices marked CU-AL or AL-CU

Photograph of aluminum wire on a CU device.

The CU-AL and AL-CU markings were applied by the wiring device manufacturers at their option, without any special testing for compatibility with Aluminum Wire. This was allowed (by UL) until about 1972.

Most of the devices marked this way are identical to those (of the same model # "family" from the same manufacturer) that are not marked AL-CU or CU-AL.

Electrical devices marked COALR or CO/ALR

In about 1972, UL and the wiring device manufacturers agreed on a test standard for receptacles for use with Aluminum Wire. The devices that passed the standard were marked CO/ALR.

Five manufacturers initially manufactured "CO/ALR" wiring devices (receptacles and switches), and we believe that one or two continue to manufacture them today.

Since devices marked COALR or CO/ALR conform to the UL standard for compatibility with aluminum wire, the devices with CO/ALR markings must be considered differently - they are not the same as the AL-CU or CU-AL devices.

Summary of Test Results Comparing COALR and CU-AL Electrical Devices

Wright-Malta Corporation conducted long-term tests of "old technology" (including "CU-AL") wiring devices and CO/ALR devices for CPSC.

A total of 1000 receptacles (4000 wire terminations), were tested, including 500 of the CO/ALR (100 of each brand. All of the testing was done within the ratings for the wire size and receptacle application.

[Aronstein reports in summary that there were] "... many failures and burnouts of the "old technology" receptacles, and one failure (burnout) of a CO/ALR device."

Electrical devices marked CU-Only

Electrical devices that are stamped CU-Only are intended only for use with copper wiring and should not be used with aluminum electrical wiring.

Should COALR or CO/ALR or CU-AL or AL-CU -Marked Devices Be Used With or as a "Repair" for Aluminum Wiring?

Electrical wire repair not recommended (C) Daniel Friedman
  1. No. Make the proper aluminum wiring repair instead: experts including the US CPSC, Aronstein and others recommend that aluminum-wired homes be repaired using only one of the approved, recommended measures described at HOW TO REDUCE THE RISK of aluminum electrical wiring in buildings
  2. CU-AL or AL-CU marked electrical outlets, switches, or other devices should not be used as a repair for aluminum electrical wiring.
  3. COALR or CO/ALR marked electrical devices as tested by Wright Malta Corporation performed better than CU-AL devices when used with aluminum branch circuit wiring provided that the connections and wiring were installed properly.

    Aronstein has not [yet] commented, for example, on aluminum wiring and back-wired receptacles with COALR devices nor on field reports of aluminum wiring failures with either type of marked electrical device.

    [Other research by Aronstein found poor performance at back-wired electrical devices, most likely because of the very limited contact surface between the spring end and the wire surface. - Ed.]

    The replacement of receptacles with CO/ALR devices is treated to some extent in the report "Reducing The Fire Hazard in Aluminum-Wired Homes" a document available at REFERENCES .

    One might reasonably infer that it may be the case that an aluminum-wired home which has properly installed, not-backwired COALR or CO/ALR electrical outlets and switches might be at a lower risk level of an incident than homes without these devices, and such a home is probably at lower risk of an electrical incident than homes wired with CU-AL or AL-CU marked devices.

    But risk assessment of the condition of aluminum wiring in any individual building is more complex than just this. Relying on the observation of the presence of COALR devices alone to assess risk is questionable at best.
  4. Don't guess about aluminum wire safety: We recommend against guessing about the condition of aluminum wiring in a building or making any assumption about its safety if the wiring has not been repaired using an approved method. We also recommend against relying on superficial and possibly technically un-sound safety surveys using test instruments in buildings as a way to assess the risk of aluminum electrical wiring and as a way to decide whether or not to repair it.
  5. The level of risk in an aluminum-wired building: Assessing the actual level of risk associated with aluminum wiring at any individual building is difficult, highly technical, requires special equipment and procedures, and should not simply be "guessed" based on casual observations like "no problems have been reported" or " we have COALR devices already installed" or "the workmanship here was good".

    The risk of an overheating connection in an aluminum-wired building varies with many factors which are difficult to assess because many of the variables are simply not visible, and because any individual risk assessment, even using special equipment, cannot predict future changes in building conditions, changes that could occur moments after the assessor left these building.

    Some of these variables include changes in use of an electrical circuit by a new occupant, changes in the condition of an electrical connection, say at a receptacle, as the device is used, increased deterioration of an individual electrical connection in a building with age or time, variations in electrical installation workmanship from one part of a building to another. we have received mail from readers reporting that a home inspector or electrician has "looked at the wiring" and has proclaimed it "safe". Such assessments are nonsense, irresponsible, and are potentially dangerous.
  6. The US CPSC has recommended only re-wiring or use of the AMP TYCO COPALUM connector and the "copper pigtailing" repair approach for aluminum wiring, and that there is one additional newer product, the AlumiConn, which appears to perform well in this application and is now also recommended by the US CPSC., Readers should note that no authority has recommended use of electrical switches or outlets of any kind as a "repair" method for aluminum wiring

Examples of Improperly-Wired COALR or AL-CU Devices with Aluminum Wiring

Photograph of aluminum wire on a CU device. Photograph of aluminum wire on a CU device

These photographs from a large condominium complex wired with aluminum show aluminum wiring connected to an electrical outlet marked CU-ONLY.

Reader Questions & Comments on Aluminum wire and CO/ALR CU-AL Devices

Question: What switches or receptacles are OK to use with Solid Conductor Aluminum Electrical Wiring?

Are switches and receptacles marked with Solid Core Wire Only suitable for use with Aluminum Wire? - D.C.

Reply: None

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with wiring, use of aluminum wire, and with the connectors, pigtails, or other repairs that have been attempted or that are needed.

That said, the short answer to your question is NO.

Here are some things to consider:

Even CO/ALR devices that the manufacturer has stamped as intended for use with AL wire are not suitable according to industry experts and according to research already performed and documented here. See ALUMINUM WIRING REPAIR NOT-Recommended.

If your building has solid conductor AL wiring the proper repairs are either re-wire with copper or pigtail with copper using a CPSC recommended connector. See ALUMINUM WIRING REPAIR METHODS for details.

Watch out: some "approved" aluminum wire to copper wire connectors that the manufacturer has tested as meeting the appropriate standard in fact do not work, melt, catch fire. And there are no connectors currently sold intended for straight aluminum connections.

Stick with what the CPSC recommends and you'll be ok.

Aluminum Wiring Repair Articles


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