Photograph of a back wired aluminum wired electrical outlet by Roger Hankey.

Using CU-Only, COALR or CU-AL Electrical Outlets and Switches with Aluminum Wire
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Why we should not use CU-AL or AL-CU -marked electrical outlets, receptacles, or switches as a "repair" for aluminum wiring
What are the concerns with COALR or CO/ALR -marked electrical devices when used with aluminum wiring
The history, differences in performance, and significance of COALR, CO/ALR, CU-AL and AL-CU marked electrical devices in aluminum-wired homes
Questions & answers about using CO/ALR or CU-AL devices (electrical receptacles, "outlets", or switches) with aluminum electrical wiring

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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. Use the links at page left to navigate this document or to go to Other Resources. The Green links show where you are in our document & website. © Copyright 2007 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left.

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

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.

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

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.

The AL-CU or CU-AL marking was a manufacturer's option. Within a brand and model line - Leviton 5320 receptacle, for instance - there was no difference in design or construction (other than the stamped marking) between the devices that were marked "AL-Cu" and those that were not.
If the electrician and/or jurisdictional electrical or building inspector required the wiring devices to have the markings, they were available with the markings.
Since the markings were optional with the manufacturer, there was a wide variety, but most commonly either none or "Al-Cu", and, either way, the wiring devices were considered to be, promoted as, and sold as suitable for use with aluminum wire.
In about 1974 or so UL published a pamphlet on aluminum wiring which warned that the wiring devices with the "Al-Cu" marking should not be used with aluminum wire. [We are looking for a copy of this document - DJF]

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?

Make the proper repair: We 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
CU-AL or AL-CU marked electrical outlets, switches, or other devices should not be used as a repair for aluminum electrical wiring.
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.

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 this website. [If/when that topic is expanded we will provide notice of the update at this page and website.]

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.
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.
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.
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, 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

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

This aluminum-wired device was not installed according to the manufacturer's specifications and is a safety hazard. Some of the clients at this property wanted to simply replace the electrical outlets and switches with COALR or AL-CU devices. As we've explained above, that is not a recommended repair. Beyond the concerns with use of COALR devices with aluminum wiring in a building we note two additional worries:
What about all of the other electrical connections and splices in the building?. Even if these devices worked, which has not been demonstrated, I am concerned that any incomplete "repair" of aluminum wiring also risks creating a false sense of security among the building's occupants, possibly leading them to ignore dangerous warning signs of a problem or leading them to fail to complete the proper repair using approved, recommended methods and devices -- OPINION DJF.
Back-wiring any electrical receptacle that uses a simple spring-clip to contact the wire internally gives a poor and unreliable connection. In this case the receptacle was (1) back-wired which is a less reliable connection, and (2) was back-wired with aluminum wire specifically in contradiction to the instructions of the manufacturer. This is an improper and unsafe electrical connection. Some newer electrical receptacles that permit back-wiring use a connector that pinches the wire in a screw-tightened contact and may perform better when used with copper wire or a copper pigtail connected to aluminum wire by an approved connector. -- OPINION DJF

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 RISK REDUCTION 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-to-aluminm connections.

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

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ALUMINUM WIRING HAZARDS & REPAIRS

ALUMINUM WIRING REPAIR COALR & CU-AL DEVICES
  Devices marked CU-AL or AL-CU
  Devices marked COALR or CO/ALR
  Test Results Comparing COALR and CU-AL
  Should COALR or CO/ALR or CU-AL or AL-CU Be Used
  Examples of Improper COALR or AL-CU
DETAILED EXPLANATION

Reducing the Fire Hazards in Aluminum-Wired Homes, [.PDF document], Jess Aronstein, Ph.D., 21 May 2007. This document answers most technical questions about the hazards and remedies of aluminum electrical wiring and includes a report on independent test results of alternative products and methods for repairing aluminum wiring. Some of the sections of this very thorough document are listed below:
HOW TO REDUCE THE RISK of aluminum electrical wiring in buildings
ALUMINUM WIRING REPAIR ELECTRICIANS specializing in aluminum wiring repairs
ALUMINUM WIRING REPAIR, Other Products for aluminum wiring, ones that work, or don't
DETAILED EXPLANATION of the aluminum electrical wiring hazard

Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Daniel Friedman - principal editor, is the author of electrical and other topics at the InspectAPedia ^® Website
Dr. Jess Aronstein, Poughkeepsie, NY, - principal technical consultant. Dr. Aronstein is a Consulting Engineer, Mechanical amp; Materials Engineering, BME, MSME, Ph.D., N.Y. S. P.E. LIC. NO. 39860 845-462-6452 protune@aol.com. He has conducted and continues to conduct extensive testing of electrical devices and connections and works as a forensic engineering consultant.
Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com

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Recommended books on electrical inspection, electrical wiring, electrical problem diagnosis, and electrical repair can be found in the Electrical Books section of the InspectAPedia Bookstore. (courtesy of Amazon.com)
The Aluminum Wiring Information WebsiteAluminum Wiring Hazards and Repairs: in-depth info, photos, documents. Main Page.

The Aluminum Electrical Wiring Hazard Explained (in the document you are presently viewing)How to Reduce the Risk in buildings with Aluminum Electrical Wiring - Overview of Acceptable Repair Practices (in the document you are presently viewing)Aluminum Electrical Repair Method Details - "How to" details, how to identify, COPALUM repair, alternative repairs, history, products, research, source of special AMP TYCO COPALUM connectors & COPALUM Electricians (in the document you are presently viewing)COPALUM Electricians: Sources of TYCO COPALUM -Certified/Trained Aluminum Wire Repair Services (in the document you are presently viewing)
Other Products, Ideal 65 Purple Twister (not recommended), & other Aluminum Wire Products/Articles (in the document you are presently viewing)

The Aluminum Wiring Bibliography: extensive resources on Aluminum Wiring
Aluminum Wire Failure Reports & Photos: Real life aluminum wiring field failure reports
Reducing the Fire Hazards in Aluminum-Wired Homes, Jess Aronstein, Ph.D., This document answers most technical questions about the hazards and remedies of aluminum electrical wiring. Some of the sections of this very thorough document are listed below:
Fire Hazards With Aluminum to Copper Twist-on Connectors & Acceptable Aluminum Wiring Repair Practices Color Photos, Current Issues. 9/28/95 CPSC Meeting Minutes
"Is YOUR Aluminum Wiring Safe?" article discussing safety claims made by some people without looking at the wiring, J. Aronstein, 11/21/95
"Repairing Aluminum Wiring," U.S. Consumer Product Safety Commission Publication CPSC#516 available online
* Safety Hazards and Safe Inspection Procedures for Electrical and Home Inspectors at Residential Electric Panels
Electrical Panels, How to Inspect in buildings, safety for electrical inspectors, electrical panel, fusing, wiring defects, defective products. Inspection Class Presentation
Electrical System & Wiring Hazard Inspection, Detection, Cause, Remedy, Prevention - Main Electrical Page
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Use of COALR, CO/ALR, AL-CU or CU-AL or CU-Only Marked Electrical Devices, Switches or Receptacles with Aluminum Wiring

Electrical devices marked CU-AL or AL-CU

Electrical devices marked COALR or CO/ALR

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

Electrical devices marked CU-Only

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

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

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?

Reply: None

Questions & Answers regarding this article

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Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair