AlumiConn torque tests by D Friedman (C) Daniel FriedmanComparison of Torque-Setting Methods for the AlumiConn™ splicing connector
Independent test results

  • AlumiConn TORQUE TESTS - CONTENTS: independent test compares measured torque with the manufacturer's alternative torque method of counting screw turns
  • POST a QUESTION or READ FAQs about how to repair aluminum electrical wiring to reduce the risk of overheated connections or building fires
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AlumiConn™ splice connector torque settings during installation:

This article compares two methods for achieving the required torque for secure aluminumn-wire connections when using the AlumiConn splice connector. Using a manufacturer-provided SK 73004 torque measuring screwdriver we compared the torque achieved when making aluminum wire connections when using the SK73004 versus counting a manufacturer-specified number of screw turns past first wire contact.

We found that generally the screw-turn counting method resulted in torque that met or exceeded the manufacturer's specifications, but we were left with some questions about field installation quality. For safe aluminum wiring repairs, readers must follow the manufacturer's instructions provided by King Innovations, the AlumiConn™ manufacturer as well as recommendations from the US CPSC for aluminum wiring repair.

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Testing AlumiConn™ Splice Connector Torque Test Results

AlumiConn torque tests by D Friedman (C) Daniel Friedman


The AlumiConn™ connector shown at left is used to splice a copper "pigtail" wire together with one or two aluminum wires as a step in reducing the fire hazard associated with aluminum electrical wiring.

[Click to enlarge any image]

Our photo (left) shows the bit of a torque screwdriver inserted into the screw in the AlumiConn™ terminal block. Click any image to see an enlarged, detailed version.

Results of independent testing indicate that this product "... is predicted to have a high probability of failure-free long-term safe performance, PROVIDED THAT THE SETSCREWS ARE CAREFULLY TIGHTENED TO THE MANUFACTURER'S RECOMMENDATION".

Reading the UL document recommending use of the AlumiConn™, we found no mention whatsoever of torque specifications - those are particularly important for this particular connector as it involves tightening a screw in a terminal block to secure the aluminum or copper wire being spliced. But as quoted above, Aronstein emphasized that the connector's acceptable performance relied on using the proper torque settings.

AlumiConn torque tests by D Friedman (C) Daniel FriedmanThe maufacturer lists two methods for achieving the required splice connector torque, a measure of turning force that in turn reflects how securely the screw is pressed against the wire that has been inserted into the splice terminal block.

  1. Use a torque measuring screwdriver and set the AlumiConn screw against the electrical wire to 10 inch pounds on aluminum solid conductor wires, or 15 inch-pounds on #10 aluminum or any solid stranded copper wire.
  2. Use a specified number of turns of the setscrew past "first contact" with the wire in the connector.

We were concerned that there is subjectivity in deciding exactly when "first contact" between the setscrew and the wire has been achieved.

To compare these procedures I (Daniel Friedman for performed simple torque measurement experiments using AlumiConn™ connectors and the SK 73004 torque measuring screwdriver (about $100) provided courtesy of King Innovations.

Results of all tests performed (n=10) showed that the "specified number of turns" method always exceeded the inch-pounds of torque specified by the manufacturer. We conclude that as long as the installer does not so over-tighten a setscrew so as to damage the connector, strip the screw, or excessively compress and damage the wire, this method will meet the required torque specifications.

Watch out: only the measured-torque method of installation is officially a "listed" and CPSC recommended application of the AlumiConn device.

However in an interview of more than 50 licensed electricians conducted by the autor in Dallas TX, not one electrician owned a torque-setting screwdriver measuring in the inch-pounds range and not one electrical supply store had the SK 73004 torque measuring screwdriver in stock. [The product is available online, from the manufacturer, and in some auto supply and hobby stores].

Watch out: For a safe proper installation follow the complete AlumiConn installation instructions provided by the manufacturer and found at

A companion discussion, AlumiConn Torque settings, explains why torque is important in electricalconnections & how the necessary torque settings are achieved when installing splices using the AlumiConn™

AlumiConn & SK 73004 torque measuring screwdriver Torque Test Experimental Design

Experiment Objective

AlumiConn torque tests by D Friedman (C) Daniel FriedmanDetermine whether or not the turn-count method of torque setting would reach or exceed the measured-torque setting method for the AlumiConn connector.

Equipment & Materials:

AlumiConn Torque Test 1: Turns past first wire contact

Using AlumiConn splice connectors provided by the manufacturer, we installed both aluminum and copper wires into the connectors.

Using a conventional screwdriver we turned the setscrew until we detected or felt (manually) that the screw requred more force to continue turning at the same rate - defining this as "first contact with the electrical wire".

Using a fine felt tip marker we marked the position of the screw head at point of first wire contact. The photo at below left shows the position of the set-screw before attempting to turn it. We marked both the screw head (black dot inside the screw-head slot) and its position in the terminal block.

AlumiConn connector at start of torque test (C) Daniel Friedman AlumiConn connector at start of torque test (C) Daniel Friedman

Using the conventional screwdriver we turned the screw 1/2 or one full tyrn past initial contact as specified by King Innovations. We marked the final position of the screw head at this point. The photograph at above right shows the position of the screw after a 1/2 turn using a conventional screwdriver. The arrow indicates the clockwise direction of tightening rotation.

AlumiConn Torque Test 2: Torque to Specified Inch-Pounds using the SK 73004 torque measuring screwdriver

SK 73004 Torque Screwdriver needed for AlumiConn Repairs (C) Daniel FriedmanBecause the SK™ 73004 torque measuring screwdriver only measured torque in the tightening direction we could not easily use this device to measure reverse torque or loosening force required on the screws set by Torque Test1 above. Instead we performed the following procedure:

Starting with a new AluimiConn™ splice connector and using a conventional screwdriver we turned the setscrew until we detected or felt (manually) that the screw requred more force to continue turning at the same rate - defining this as "first contact with the electrical wire" just as in Test 1.

Using a fine felt tip marker we marked the position of the screw head at point of first wire contact.

Using the SK 73004 torque measuring screwdriver we turned the screw until reaching the 10 or 15 inch-pounds of torque specified by the manufacturer.

We marked the final position of the screw head at this point.

Comparing Torque Tests 1 & 2

By simple visual observation it was easy to compare the final position of the setscrew as torqued by test method 1 and test method 2 above.

If the final position of the set-screw in Test 1 had been turned visibly past the final position of the set screw for the same wire brand and type in the terminal block of the AlumiConn, we concluded that the manual torquing method provide by Test 1 exceeded the measured torqu set by Test 2.

AlumiConn & SK 73004 torque measuring screwdriver Torque Test Experiment Results


AlumiConn™ Torque settings specified by King Innovations

SK 73004 Torque Screwdriver needed for AlumiConn Repairs (C) Daniel Friedman

Binding of the screw

A difficulty in both subjective measurement of screw-turn resistance and in precision instrument measurement of torque in the same device is that in some electrical components (connector terminal blocks in electrical panels, for example, and in earlier versions of the AlumiConn product) a steel binding-head screw is used in an aluminum terminal block.

The dissimilar metals and manufacturing details can result in the steel screw head binding in the aluminum terminal block due to resistance in the threaded female opening in the block before the required pressure has been obtained between the screw end and the wire against which is supposed to press.

Mr. King informed us that they have addressed this concern by plating the screws in nickel and plating the lug block in tin, thus eliminating the galling found in other lugs. Also there is a very small gap at the back of the wire terminal block where the installer can see the wire (coated in sealant) coming through. This provides visual confirmation that the wires came all the way through.

at LOST NEUTRAL SHOCKS HOMEOWNER - where just this problem occurred, we report a case history of a neutral wire failure, improper joining of neutral and ground wiring in a sub panel, burning-up electrical ground wires, and a homeowner who received a nasty electrical shock.

When I examined that electrical panel I found that the main neutral wire, though properly stripped and inserted into the terminal block, had never been properly connected and could be easily pulled right out of the block by hand. The steel screw had bound in the aluminum block, "fooling" the installing elecctrician.

Using the SK 73004 torque measuring screwdriver

This too is easy to set (an allen key inserted into the end of the handle sets the inch-pounds of torque required) and use (like a normal screwdriver, turn until the device "clicks" like other torque wrench type tools.

It is possible to detect that a screw had not been tightened enough using the manual method, since using the SK73004 on such a screw would result in further turning of the screw.

But the slip-clutch in this tool only operates in the clockwise or tightening turn direction. Therefore it was not possible to use the tool to make a direct measurement of the existing torque of a screw that has already been tightened by a conventional screwdriver for cases in which the screw torque already exceeds the torque setting of the SK 73004.

For this reason we resorted to using actual physical markings to compare screw ending positions.

Based on our tests we conclude that the "alternative method" described by the manufacturer for tightening the screws produces torque close to or exceeding the actual torque specified numbers (according to some preliminary tests we have done in our lab) - photo at left.

But we are not completely confident that that approach would be adequate for general field use where individual human performance may vary considerably.

For example, you may not be exactly sure just when the setscrew "... comes into contact with the solid conductor". King is confident of this approach but is careful to point out that it is not associated with the UL listing for the product.


In every test conducted on both aluminum and copper wire and the AlumiConn splice connector for aluminum wire repair, we found that the manual method (Test 1) always produced more torque (more screw turns) than the measured torque method (Test 2).

The manufacturer's advice to tug to check the security of wires adds an additional measure of security against under-tightening of the setscrew. And the absence of any field reports of field-failures of the AlumiConn splice connector in service (though early in the product life) adds confidence to its performance, with the caveat that absence of evidence is not evidence of absence of failures in any device or study.

Further study on a larger number of devices in lab or field tests and making use of an instrument that can measure reverse or loosening torque resistance could improve the confidence of our initial findings.

Watch out: the manufacturer makes clear that their installation instructions for the AlumiConn without using a torque-setting screwdriver are not included in the CPSC recommendations, but the " manufacturer (King Innovation) stands firmly behind this installation method." [1]

WALL-NUTS [New U.S. product application, Not UL Listed, undergoing testing before UL application] spring-clamp terminal blocks available from Wago Corporation have is being tested by that company for a connector for aluminum-to-copper pigtailing for aluminum wiring repair.

The company informs us that a similar product use with aluminum wire conductors has been approved and used in Europe for over 20 years. The company is conducting further testing before submitting the product to UL to obtain a listing. Significantly, the company indicates that this connector is suitable for connecting multi-stranded (copper) as well as solid conductor conductors.

If approved by UL and if test results are satisfactory, this product would, in addition to providing standard solid CU to solid AL connections, address the wiring of a twisted-copper-wire light fixture to a solid conductor aluminum branch circuit wire. This connector has not been recommended, nor recommended against, by the US CPSC, and is currently undergoing testing. Results will be reported here ASAP. Product description information for the copper to copper wire connection use of this connector is available at the Wago website.


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