What’s Wrong With Using Twist On Connectors For Aluminum Wire Repairs?
The Consumer Product Safety Commission, in its report entitled, Repairing Aluminum Wiring, made a very straight forward statement regarding the use of twist on wire connectors.
They say, “It is possible that some pigtailing ‘repairs’ made with twist-on connectors may be even more prone to failure than the original aluminum wire connections. Accordingly, the Commission staff believes that this method of repair does not solve the problem of overheating present in aluminum branch circuits.” (Read the full report here).
To understand how they came to this conclusion, it’s helpful to understand the 2 primary causes to aluminum wire danger:
- Oxidation
- Dissimilar metals coming into contact with each other
Oxidation – Oxidation occurs when metal comes into contact with oxygen. On aluminum wire, this “oxidation layer” builds up over time and can ultimately result in excessive heat build up, melted twist on wire connectors, or even fire.
Dissimilar metals coming into contact with each other – Often, it is necessary to splice copper wires with your existing aluminum wire. When you splice these two metals under the same termination point (as you do in a twist on connector), it poses a problem because the aluminum and copper wires expand and contract at different rates (as they heat and cool). So, even if you install a twist on connector correctly, it’s possible that the connection could loosen over time as these two metals expand and contract at different rates. The loosening can cause the current to arc and potentially start a fire.
The following photo was taken by an electrician out of California. They dedicated a page on their website to this issue. You can see the page here.
What Do Others Say About Use of Twist On Wire Connectors To Repair Aluminum Wire?
The Washington Post, January 13, 2007 Five that Failed; These Building Practices Used to Be Popular, Now They’re Nothing but Trouble.
“… in practice, many more of these [aluminum branch circuit wiring] systems seem to have been retrofitted with a product called the Ideal Twister Al/Cu (aluminum-copper) connector… The Twister complies with the National Electric Code and has been Underwriters Laboratories-listed… However, the CPSC does not approve that fix, agency spokesman Scott Wolfson said. “We know that there are those in the electrical safety community who disagree with us, but we remain firm in our position.”
Letter to UL President Thomas Castino, 1996 from Dr Jesse Aronstein, Consulting Engineer http://www.inspect-ny.com/aluminum/ideal65-1.txt
“The purpose of this letter is to bring to your attention the results of tests on a connector that UL recently listed for aluminum wire applications. The connector, the Ideal #65, does not meet the UL486C heat-cycle test performance requirements when tested with splices representative of the common pigtailing combination used in aluminum-wired homes, even though the connector is UL listed for those wire combinations.”
From Inspectapedia.com – http://www.inspect-ny.com/aluminum/aluminum.htm
“Other methods – not recommended: Warnings regarding other “repair” methods which
are not recommended… such as the Ideal 65 purple “Twister” connector…”
Letter to Dr Jesse Aronstein, Consulting Engineer, from the Consumer Product Safety Commission – http://www.inspect-ny.com/aluminum/twistcpsc.htm
“… the U.S. Consumer Product Safety Commission (CPSC) staff does not consider
the use of the twist-on connector (including the Ideal No. 65) to be a suitable repair
for aluminum wiring in residences.”
From Inspectapedia – http://www.inspect-ny.com/aluminum/aluminum.htm#otherconn
“Independent Tests indicate Ideal-65 Twist-on retrofit connector fails UL 486C Safety Standard despite UL listing.”