NBSIR 76-1039

Evaluation of Selected

Connectors for Aluminum Wire

in Residential Structures

Owen B. Laug

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

March 1 976

Final

Prepared for

Consumer Product Safety Commission

5401 Westbard Avenue

Bethesda, Maryland 20016

NBSIR 76-1039

EVALUATION OF SELECTED

CONNECTORS FOR ALUMINUM WIRE

IN RESIDENTIAL STRUCTURES

Owen B. Laug

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

March 1 976

Final

Prepared for

Consumer Product Safety Commission

5401 Westbard Avenue

Bethesda, Maryland 2001

6

U.S. DEPARTMENT OF COMMERCE, Elliot L. Richardson. SBentmy

James A. Baker. Ill, Under SecrBtary

Dr. Betsy Ancker-Johnson, Assistant Sacratary for Sdaitea and Tachnohgy

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Acting Diractor

Table of Contents

Page

1. Introduction 1

2. Heat Cycling Tests - General 2

2.1 Heat Cycle test on direct wired receptacles 2

2.2 Heat Cycle test on terminal A 3

2.3 Heat Cycle test on terminals B&C 4

2.4 Heat Cycle test on splices D&£ 5

3. Interface Photomicrography 6

4. Mechanical Tests 7

5. Bend Tests 8

6. Conclusions & Recommendations 12
List of Tables

Table I Heat Cycle Data for Terminal A

Table II Heat Cycle Data for Terminals B ?c C

Table III Heat Cycle Data for Splices D & E

Table IV Results of Tensile Tests of Aluninum Wire and Wire-Terminal

Types b & C

Table V Destructive Bend Tests on Wires Tenninated With Terminals

B & C and Splices D & E

ii
List of Figures

Fig. 1 Terminals fastened to the ends of alarninam wire. The tongues

of the terminals are fastened under the binding screws of a

wiring device.

Fig. 2 oplices used to connect aluminum wire to copper wire pigtails

i^hich are fastened under the binding screws of a wiring device.

Fig. 3 The five connectors selected for evaluation.

Fig. 4 Cross section through the crimp of TenTiinal A.

Fig. 5 Cross section of Terminal A through the longitudinal axis of

the wire.

Fig. & Cross section through the crimp of splice E with a #10 aluminum

and a ^^12 copper wire.

Fig. 7 Cross section of splice £ through the longitudinal axis of the

aluminum v;ire.

Fig. o Application of splice D with two itl2 aluminum and one Itm copper

wire all entering one end of the splice.

Fig. 9 Application of splice D with two #12 aluminum wires entering one

end and one #14 copper wire entering the other end.

Fig. 10 Crimping tool used on splice D.

Fig. 11 Heat gun is used to shrink insulation sleeve over splice.

Fig. 12 Application of butt splice E with iHO aluininum v/ires and one #12

copper wire.

Ill

Summary

Systems of connecting aluminum wire for possible use in receptacle

outlets and elsewhere in 15 and 20 ampere branch circuits in residences are

available as practical alternatives to the presently used mechanisms such

as the wire binding screw and the twist-on "wire nut" connector. The

alternative systems are based on the principle of high defonnation of the

wire in the connection to achieve more permanent metal-to-metal fittings

and/or wire splice devices of several designs. They involve either

crimping the device around the wire or swaging the wire into the device

with special tools.

Based on tests, basic connection perfonnance of several highdeformation connectors has been established. The results indicate that

certain designs of connectors operate with stability and without

dangerously over-heating under accelerated laboratory tests.

The tools, however, to be used to crimp terminals are not only bulxy

and awk'ward to use but quite expensive. Moreover, they must be correctly

coordinated with the terminals and sizes of wires used. There is danger

that a misadjusted or improper tool and/or terminal may be used with

particular wire or wires which could result in a poor connection. Some

improvements in the design of the assembly tools and in the devices

themselves would reduce certain installation difficulties encountered

during testing, and certain connectors could be slightly modified to avoid

human errors during assembly.

Use of these systems and conformance with established codes and

standards does not appear to present major problems.
)
1, INTRODUCTION

This report describes the results of tests on a variety of terminals

and splices to be used primarily with aluminum wire. The tests were

performed to evaluate the suitability of these terminals and splices as a

potential "fix" for residences with 15 and 20 ampere branch circuits wired

with "older technology" aluminum wiring systems . Of particular importance

are those branch circuits employing a combination of "old technology" wire

and receptacle devices with steel wire binding screws. This combination is

known to be most prone to failure. The use of the terminals and splices

described in this report has also been considered as an alternative to

present termination methods.

Two techniques of connection were evaluated. The first is a terminal

device which is fastened to the end of a wire by a crimping or swaging

operation and the tongue of the terminal fastened under the binding screw

of a wiring device. See Fig. 1. The second type is a splice which

connects one or two aluminum wires to a copper wire "pigtail", which in

turn is fastened under the binding screw of a wiring device in the usual

manner. See Fig. 2. Each terminal or splice that was evaluated will be

referred to throughout this report by a letter which designates the device

type as shoi-m in Fig. 3.

Suitability of installed electrical devices in most jurisdictions in

this country is evidenced by the listing of a testing laboratory such as

Underwriters Laboratories (UL), The manufacturer of devices B, C, 0 and E

has indicated that the UL listing has been or is being obtained for these

products.

Host jurisdictions follow the requirements for electrical

installations as detailed in the National Electrical Code (NEC). Except

for the possible lack of an approval (such as the UL listing) for a device,

the general use of the connection devices as described in this report would

not involve any known conflicts with the NEC.

Since the binding screws on a wiring device are generally not

ranovable, the original ring- tongue configuration of terminals B & C had to

be modified by cutting through a section of the ring to fonn a J-hook

configuration.

* "Older technology" aluminum wiring system refers to the use of an

aluminum conductor which does not meet the Underwriters Laboratories (UL)

requirements for solid aluminum wires which became effective Nay 1, 1971

and/or the use of outlet wire terminal devices not rated CO/ALR.
In accordance with the requests of the Consumer Product Safety

Commission (CPSC) the following tests were performed on each of the devices

where applicable:

1. Heat cycling test

2. Interface photomicrography

3. f-techanical tests

4. Bend tests

Although an evaluation of constriction resistance was requested by CPSC,

early investigation shov/ed that comparative evaluation of constriction

resistance of crimp and screw connections was not feasible within the scope

of this project, and therefore not undertaken. This was indicated in our

proposal of laboratory tests.

2. HEAT CYCLIiMG TESTS - GENERAL

A heat cycling test was performed on all the devices (A thru E). In

addition, to provide comparative data, receptacles wired directly (without

terminal connectors, i.e., wire wrapped around screw) were subjected to the

heat cycling test. Any device which did not pass the heat cycling test was

not further evaluated. Also, it was arbitrarily decided to limit the test

to approximately 5000 cycles of operation.

The heat cycling test is a form of accelerated aging intended to

simulate extended service performance. The test consists of subjecting the

connection or tenninal device to an overload current which is 2.67 times

the rated current of the conductor. Thus, for a 20 ampere rated conductor

(No. 10 American Wire Gage (AWG), aluminum) the overload test current Ls 53

amperes and 40 anperes for a 15 ampere conductor rating (No. 12 AWG,

aluminum). The current is cycled "on" for a period of 20 minutes and

"off" for a period of 10 minutes. The devices and conductors were tested

in the open ambient, that is, they were not enclosed in outlet boxes.

Initially and at intervals during the test, temperatures at the connection

interface and voltage drops across the connections were measured.

2.1 Heat Cvcle test on direct wired receptacles

A total of ten duplex receptacles were wired in a series arrangement

that permitted current to pass through each screw terminal of the devices.

Five were wired with #10 AWG EC-H19 (older technology) aluminum wire and

five were wired with a new alloy aluminum wire. This configuration

resulted in a total of 20 terminations for each type of wire. Each binding

head screw was torqued to 6 inch pounds (0.7 newton meter).

-2-

* Wire numbers hereinafter do not have the "AWG" reference, but they continue

to represent wire sizes in accordance with the American Wire Gage.
Data was usually taken near the end of the 20 minute "on" cycle and

the "on" condition extended until the measurements were completed. This

insured thermal equilibrium of the connection during the measurement

interval. Since there generally is little thennal resistance between the

upper and lower screw heads of a duplex receptacle, tanperature data was

taken on only one screw head. Voltage drop measurements were made across

the two connections at points on the wire located 20 mm from the center of

each screw head.

The results of the heat cycle test on receptacles wired directly

became evident almost immediately. All of the connections failed in less

than 100 cycles with the first failure occurring in 3 cycles. Failure was

defined when the temperature increased 125 C above the temperature of the

wire. At temperatures above 300 C the insulating material of the

receptacle begins to smoke and char. Many of the connections were allowed

to continue overheating until the insulating material around the screw

terminals became completely charred. There was, however, a distinct

difference in the failure rate of the connections for the two types of

wire. Those wired with EC-H19 aluminum wire failed in an average of 18

cycles, whereas connections made with the new alloy wire failed in an

average of 42 cycles. Regardless of this, it is clear that receptacles

with steel screws wired with #10 EC-H19 or new alloy aluminum wire fail the

heat cycling tests. Although there are still no definite data which

indicate that this particular accelerated test can in an absolute sense

predict the potential life of a connection in service, it is an accepted

industry qualification test procedure and does provide comparative

information that allows new termination techniques to be evaluated against

known methods of tenninations.

2.2 Heat Cvcle test on terminal A

Terminal type A was subjected to the same heat cycling test. A rack

of 10 receptacles was employed for each type of wire. The terminals were

crimped at the ends of both types of #10 aluminum wire and the split tongue

of the terminal fastened under the binding screws of the receptacles. Each

screw was torqued to 6 inch pounds (0.7 newton meter). The results of the

heat cycle tests on terminal A are shown in Table I. The average

temperature was obtained by averaging the readings of temperature from 20

screw head terminals. The maximum and minimum values of temperature

indicate the extremes. After 443 cycles, the terminals connected to the

EC-H19 wire were well on their way to failure. At 490 cycles the entire

set had to be removed from test because of the high incidence of failure.

Terminals on the new alloy wire began to fail at about 1000 cycles and

subsequently the number of failures increased to five at which point the

entire set was removed from test at 1410 cycles

-3-
Voltage drop measurements taken between various connection interfaces

showed that the maximum voltage drop occurred between the wire and the

terminal. Thus, all the overheating was due to a failure in the crimp

connection. Voltage drop measurements between the terminal body and the

receptacle binding screw remained low and relatively constant.

The source voltage in the current cycling test is in the order of a

few volts, hence, when terminations begin to fail, the current in the

series group of devices under test will decrease. The current is initially

adjusted for the test value and regulated manually. However, when a

connection begins to fail the increased voltage drop causes the current to

decrease and therefore the source voltage must be readjusted to obtain the

original test current. Finally as more and more connectors fail, manual

regulation of current becomes difficult to maintain, hence, the test is

discontinued

.

The manufacturer of terminal A was informed of the high failure rates

that were experienced with both types of aluminum wire. An engineer from

the company visited the test facility at NB3, examined the crimping tool,

and measured the crimped terminals. He found the crimp tool and terminals

to be within specifications, but was unable to offer any explanation for

the failures. Thus, based on the failure of terminal A to pass the heat

cycle test, no further tests were made except that photomicrographs of the

crimped cross section were examined.

2.3 Heat Cyclg test on terninals 6 4 C

Terminals B & C were subjected to the same heat cycling tests as

terminal A and measurements made in the same manner. A rack of ten

receptacles was used to test each terminal type with both types of wire.

This resulted in 20 terminations for each terminal type and wire type. The

results of the data are shown in Table II. From cycle one to cycle 5080

(when the test was stopped) the temperature data indicates that both

terminals are remarkably stable. There are no excessive temperature rises

or wide fluctuations indicative of failure. The average was computed from

the individual temperature readings for a given terminal and wire type.

The minimum and maximum tonperatures indicate the extremes of the

individual readings. There is a slight increase in temperature from the

first cycle, but thereafter the temperature remains relatively constant.

Terminal C in which the wire is swaged into an undercut slot on the

terminal body operates 15 to 13 degrees higher than terminal B which is a

crimp type. This difference can be attributed to the fact that the wire to

terminal resistance for terminal C is approximately 50% greater than for

terminal 3. Typically the resistance from the wire to the terminal body is

-4-
60 r.iicroolTns for the b terminal and yO microohins for the C terminal.

Tnis difference in resistance, however, is small in relation to the total

resistance of the connection at the duplex receptacle.

2.4 Heat Cvcle test on Splices D & S

Splice type D, which is an in-line splice, is designed for a range oV

circular mil area (ChlA) which permits two //12 aluminum and one iflH copper

wire to be crimped together in parallel. A total of ten splices were

arranged in a series configuration so that five devices provided a current

path from one aluminum conductor to the other and five devices provided a

current from the aluminum wire to the copper wire. Splice type D was

tested only with the #12 new alloy aluminum wire because #12 EC-H19 wire

was not available for the test. Table III shows the results of the heat

cycle test on splice D. There are no excessive temperature rises or wide

fluctuations indicative of failure. The voltage drop across the splice

averaged 0.0077 volts after 5000 cycles which for the 40 ampere test

current results in an average resistance of 0.19 millioiims.

Splice is a two-crimp butt splice with an aluminum wire CMA range of

13100 to 20800 and a copper CMA range of 5130 to 13100. This splice was

chosen to splice together two #10 aluminum wires and one #12 copper wire.

Although the maximum Ci'lA range for aluminum would allow two #10 wires to be

inserted in one end of the splice, this was not physically possible because

the inside diameter of the splice was insufficient to accept two iflO wires.

The only configuration possible was to place one #10 aluminum and one /;12

copper wire in one end and a single ii/10 aluminum wire in the other end of

the splice. However, a single //lO aluminum wire in one end is smaller than

normally recommended by the manufacturer. This exception, according to the

manufacturer, was not expected to affect the performance.

For the heat cycle test a total of 20 type E butt splices were

arranged in the following manner. Ten splices were used with the H;C-ril9

wire and ten with the new alloy wire. For each type of wire half the

number of devices were wired so that current would pass from one aluminum

wire to one copper wire. The results of the heat cycle test on splice E is

shown in Table 111. Again there are no excessive temperature rises or wide

fluctuations over the cycling period. There is a 5 to 7 C difference

between the two types of wire but of more importance is the stability after

the first cycle. There was one failure which was evident In the first few

cycles of operation. An excessive voltage drop developed between the body

of the splice and the single #10 EC-H19 wire. Examination of the splice

revealed that the integral perforated metal sleeve was missing from the end

that was overheating. A splice with a missing, removable sleeve was

-5-
unnoticed before crimping. This experience did, however, dramatically

demonstrate the functional requirement of the perforated sleeve.

3. INTliHFACE PHOTOMICROGRAPHY

Each of the terminals and splices was photomicrographed in order to

examine the effectiveness of the wire-connector interfaces. Samples were

made with older technology (EC-ril9) and new alloy aluminum wire, and in the

case of splices a copper wire was included. Each of the samples was

sectioned normal to the long axis of the wire and through the long axis of

the wire at the wire- terminal interface. Color photography was employed to

enhance the contrast of the various metal interfaces. Figures H thru 7 are

a selected number of photomicrographs of the various terminals and splices

chosen to illustrate generally the type of information revealed. Fig. 4

shows a cross section through the crimp on terminal type A with ^^1Q EC-H19

wire. Although the aluminum conductor appears to be in good contact and

defonned into the perforations of the wire barrel, this connection failed

the heat cycling test. This view does show one possible reason for the

failure. Note that the geometry of the formed crimp is such that there is

no means for it to retain pressure on the wire after numerous cycles of

thermal expansion. It is surmised that the heat cycling causes the wire to

expand which in turn may slightly open the crimp and loosen the wire

terminal interface. Fig. 5 shows the same device sectioned through the

longitudional axis of the conductor. This view shows that the conductor is

deformed to about one half its diameter and extruded into the perforations

of the wire barrel. Further investigation would be required to determine

the actual cause of failure.

Fig. D sliows a cross section of device type E which is a butt splice

with a #10 EC-H19 aluminum and a #12 copper wire crimped together in the

same barrel. This view shows that the aluminum has been extruded through

the thin brass liner perforations. This should allow clean aluminum metal

to be brought into direct contact with the liner and wire barrel, i^ote

that the copper wire does not appear to extrude into the perforations. It

is interesting to note the shape of the outer surface produced by this

crimp. The geometry is such that a reverse curved surface is produced on

one side with respect to the other side. This tends to lock the crimp and

make it act like a spring so that the crimp maintains constant pressure.

Figure 7 shows the cross sectional viev/ through the longitudinal axis of

the aluminum conductor in one end of the type E splice. This view shows

thiat the crimp has considerably reduced the cross section of the wire and

the brass perforated liner appears to be split in the area of greatest

deformation. All of the samples employing this type of crimp seemed to

have a split liner and occasionally the aluminum conductor would become

separated in the region of greatest deformation.

-6-
The manufacturer was made aware of these observations but maintained

that the electrical interface is not affected. This seems to be verified

by the successful heat cycle tests on all terminals and splices employing a

brass perforated liner and the reverse curved crimp. Of the five types of

devices evaluated, types B, D, and E are supplied by the same manufacturer

and employ the same crimp. Terminal C relies on deforming the aluminum

wire into an undercut channel on the terminal. The aluminum is apparently

wiped clean by the edge of the channel as it is forced in. This is

referred to by the manufacturer as a tamp crimp. Examination of its cross

section under magnification showed no obvious defects. Most of the contact

seems to be at the bottom and bottom sides of the channel.

Generally the photomicrographs revealed no significant difference

between the EC-ril9 and the new alloy wire. The photomicrograph analysis of

the devices in this study did not appear to be particularly useful for

prediction of performance in their ultimate use.

4. FECriMICAL TESTS

Axial and right angle load tests were performed on samples of EC-H19

and new alloy wire with and without terminals to determine the tensile

strength of the terminal and wire. The tests were made on a tensile

testing machine in which the specimen is clamped at one end and pulled from

the other end by a moving cross head until a fracture occurs. For axial

tests the tongue of the terminal was clamped and for right angle tests the

tenninal was clamped across the wire barrel near the tongue. The machine

records the force and the elongation (i.e. stress/strain). For this test

the maximum force required to fracture the sample was reported. In

addition, the machine has a variable cross head speed v/hich can be adjusted

to accommodate the ductility of the sample. The new alloy aluminum wire is

far more ductile than the EC-H19 wire and therefore the cross head speed

was selected arbitrarily for each sample type to complete the testing in a

reasonable time.

Terminal type A was not tested because it failed the heat cycling

test. Only terminals b & C were tested for tensile strength. The results

on samples of these terminals showed that in all cases the wire fractured

and not the connector. This result coupled with the fact that splice types

L) & £ employ the identical crimp design of terminal 6 led to the decision

not to test types D & E for tensile strength. Furthermore, the bending

tests relate more to the actual service perfonnance of these devices than

tensile loading tests. The following is a brief description of the results

based on the tensile test data shown in Table IV:

1. All of the wire samples tested Vxfithout connectors (speciments 1-10)

fractured within the 10-inch gauge length except for specimen no. <3.

-7-
Since this specimen fractured outside the guage length, no elongation

is reported.

2. Three of the five EC-H19 wire specimens (12, 13, and 15) tested axially

with terminal B fractured where the wire entered the tenninal. The

wire in specimens 11 and 14 fractured at the crimp in the terminal.

3. kll the alloy wire specimens (16-20) tested axially with terminal B

fractured where the wire entered the terminal.

4. All of the EC-H19 wire specimens (21-25) tested axially with tenninal C

fractured where the wire entered the terminal.

5. All the alloy wire specimens (26-30) tested axially with terminal C

fractured several centimeters from the connector.

6. All of the wire specimens (31-40) tested at right angles to terminal

B fractured where the wire entered the tenninal. In each case the body

of the wire barrel cracked on the back side.

7. Four of the five EC-H19 wire specimens (41-44) tested at right angles to

tenninal C fractured near the tongue of the terminal. The wire pulled

completely out of the terminal in specimen 45.

8. For the alloy wire specimen tested at right angles with terminal C, the

wire pulled out in two tests (specim.ens 46 and 47), one wire fractured

about midv/ay in the swage (specimen 48), and two vdres fractured near

the tongue end of the terminal (specimens 49 and 50).

It is interesting to note from Table IV that the two sets with alloy wire

on terminals B & C (specimens 16-20 and 36-40) failed in axial tensile

tests at consistently greater loads than alloy wire specimens without

tenninals.

5. BEND TESTS

Bending tests were performed on wires terminated with terminals or

splices to determine their ability to withstand the typical manipulation of

the wires in the installation process. Two types of bending tests were

performed. The first test consisted of subjecting samples to destructive

bend tests. The second test was an investigation of the bending stresses

that might occur in a typical installation process. This test provided

mostly qualitative information on the problem of retrofitting existing

wiring to the tenninal or splice approach.

The destructive bend tests on terminal devices were made by fastening

the tongue of the terminal under the head of the wire binding screw of a

-8-
receptacle device and bending the wire through alternating 90 degree bends

until failure occurred. The bend was nade by holding the wire about 5 cm

from the terminal end and pushing the wire in a plane normal to the

rotational axis of the screws. In addition, comparative tests were made in

the same manner on a typical old style receptacle with the wires connected

directly under the binding head screws. The results of the destructive

bend tests with and without terminals showed that the follov/ing three types

of failures occur:

1. wire broke

2. terminal or wire loosened under screw

3. tongue of terminal opened

It was found that often the difference between the wire breaking and the

terminal loosening under the screw depended on whether it was the upper or

lower screw terminal of a receptacle. This difference is apparently due to

the breakoff tab which can interfere with the rotation of the terminal or

wire in the loosening direction.

The destructive bend tests for splices was made by clamping the

splice, holding the wire at a point about 5 cm from the splice, and bending

the wire through alternating 90 degree bends until the wire broke. Each 90

degree excursion is defined as one bend. Table V shows the average number

of ninety degree bends required to break the wire. If the terminal did not

loosen under the screw, the average number of bends required to break the

EC-H19 wire is 3, whereas, direct connection of the wire under the screw

head required an average of ^ bends to break the wire. Also, the new alloy

wire directly connected under a screw head can withstand more bending than

various terminals and splices before breaking. For the terminals and

splices which are crimped to the wire, the point of bending usually begins

just inside the wire barrel where the constriction of the wire begins. The

stress is concentrated at this point whereas a wire under a screw head is

not constricted to bend at one point. Of more importance than breaking is

the tendency for terminals B & C to loosen under the screw as a result of

bending the wire. Terminals d & C have a J-hook tongue configuration which

seems to be worse with respect to loosening than direct wiring to the screw

terminals, ^'ith the J-hook terminals it was not uncommon for the screw to

loosen in the first or second bend. Furthermore, the hook tongue on these

tenninals often opened with a subsequent loosening of the screw. Since

there is no means on the receptacle to limit the rotation or restrain the

wire, the hook can open up in one direction and loosen the screw in the

other direction.

Terminal devices B & C were subjected to a typical retrofitting

installation exercise in order to discover the practical problems. It was

assumed that the terminals would be used with a typical old style

-9-
receptacle mounted in a standard 2x2 1/2 inch (5 cm x 6.3 cm) steel

outlet box with an average length of wire folded in the box behind the

receptacle with wires wrapped around the screw terminals. The receptacle

was pulled out, the wires cut as close to the receptacle as possible, the

wire loops removed, the terminal connected to the ends of the circuit

wires, and the tongue of the terminal fastened under the screws. The

receptacle v;as pushed back into the box and fastened. The sides of the box

were removed to expose the condition of the wiring. This exercise was

repeated several times. The follov;ing are typical of the condition of the

completed wiring:

1. The body of the terminal, which is not insulated, was often found to be

contacting the inside surface of the box. This condition was due

primarily to the connector bending outward slightly in the process

of pushing the receptacle back in the box. The strength of the terminal

tongue is insufficient to prevent it from bending outward.

2. The tongue often became loosened under the screw or opened up as a

result of pustiing the receptacle back into the box.

3. With the EC-H19 wire there was one instance were the wire broke off

at the terminal.

From the conditions cited above it is doubtful that the terminals in

their present form would be practical as a "fix" for residences with

aluriinurn branch wiring. In general, more care than conventional wiring

techniques is required for these terminals. However, the use of a heavy

insulating sleeve which is shrunk over the terminal wire barrel and the

wire would probably alleviate the shorting problem and prevent sharp bends

of the wire at the terminal. The weakness of the terminal tongue may be

due in part to the cutting away of tongue material to fonn the J-hook

configuration.

Splices D & E were also subjected to the same retrofitting

installation exercise. Splice D is an in-line crimp splice designed to

splice two #12 aluminum and one //14 copper wire together. See Figure 3.

Splice E is a butt crimp splice for splicing two //lO aluminum and one #12

copper wire together. The idea with both of these devices is to splice a

pair of aluminum wires together with a copper pigtail which in turn is

connected to the receptacle device in the normal manner.

The type D splice can be used in two ways; all three wires entering

from one end or two wires entering from one end and one from the other.

Figures 8 and 9 each show the completed connections of the two possible

configurations. There did not seem to be a preferable configuration,

except that when all the wires enter one end the manipulation of the wires

-10-
into the box is similar to the familiar "wire nut" splice. The time

required to complete the retrofitting job for each configuration averaged

about seven minutes. Much of the time is taken with positioning the wires

for crimping and shrinking the insulation over the splice. Figure 10 shows

the crimping operation and Figure 11 shows the use of a heat gun to sl-irink

the insulation over the splice. In general there were no problems

associated with the type D splice even when a full-sized ground wire is

employed. There seemed to be ample room in the box to accommodate up to

three splices. It should be mentioned that for this exercise only the new

alloy wire was available in the /^12 size. It would be expected that wire

similar to the EC-H19 characteristics would be more difficult to manipulate

and perhaps more care would need to be taken to insure that sharp bends do

not occur at the splice. The shrink tubing, if it extends over the wire,

is very helpful in preventing sharp bends at the splice.

The crimping tool provided by the manufacturer for splices D and E is

pneumatically powered and heavy. It is intended for industrial production

where the tool can be supported while the splice vath the wires is

positioned in the jaws. In a typical field installation the tool was found

to be bulky and cumbersome to use because it must be held with one hand

while the splice and wires emanating from the box are positioned in the

jaws. Many of the field installations would involve receptacle wiring

which is located approximately 30 cm above the floor, a position which

makes the crimping operation even more awkward. A crimping tool of a

different design to overcome the above described objectionable

characteristics appears technically feasible. However, despite any

improvements that could be made there exists the practical field problems

of insuring correctly coordinated tools and terminals with the wire sizes

used. There is danger that the improper or misadjusted tool and/or

terminal may be used with particular wire or wires which could result in a

poor connection.

An additional problem requiring some attention is that the perforated

inner sleeve of the splice often has a tendency to be pushed out when

inserting the wires. This is particularly so for the type D splice. In

some samples the insert had fallen out. As mentioned previously, this was

the reason for one failure in the heat cycling test.

The results of subjecting the type £ splice to the same retrofitting

exercise was less favorable than the type D because the type E is larger.

Figure 12 shows the completed splices ready to be installed in the box.

The length of the shrink tubing supplied for the type E splice was only the

length of the splice. It would be desirable to employ a slightly longer

tubing so that it could shrink over the wire. The reason again is to

prevent sharp bends at the ends of the splice. Although the splices and

wires can be folded into the box and the receptacle mounted in place, the

additional volume occupied by the three splices crowds the box and probably

-11-
would affect the number of allowable conductors in a box as established by

the National Electric Code, 1975 (Paragraph 370-6). This may necessitate

the use of an outlet box with an extension ring to provide the required

volume. If there exists older technology wire with the old sized ground

wire (usually two sizes smaller than the current carrying conductors) then

the ground conductor could be spliced with the type D in-line splice which

is much smaller.

6. COtCLUSIONS AND RECOMMENDATIONS

Based on the test results the following are conclusions and

recommendations on each of the five terminal devices:

1) Wiring devices with steel screws connected directly to either

"new" or "old" technology aluminum wire did not pass the heat

cycle test. Although the heat cycle test does not quantify

the potential life of a connection in service, it is an accepted

industry qualification test procedure and does provide

comparative information that allows new termination

techniques to be evaluated against known methods of termination.

2) Device A, which is a crimp terminal with a locking-spade

tongue, failed the heat cycling test for both old and new

technology aluminum wire. The geometry of the crimp is

such that there is no means for it to retain the pressure

on the conductor. This tenninal is not recommended for

service with aluminum wire in residential branch circuits.

3) Device B, which is a crimp terminal with the tongue modified

into a J-hook configuration, was cycled over 5000 cycles in

the heat cycling test without failure or excessive temperature

excursions. The tongue of the terminal tends to loosen or open

up under the receptacle binding screw as a result of bending

the wires into a receptacle box. The weakness of the tongue often

permits the body of the terminal to bend outward and cause it to

contact the sides of the box. If this terminal is to be used in

residential aluminum wiring, it is recommended that an insulating

sleeve be positioned over the terminal body and wire, and that

care be exercised in the installation to prevent loosening

and/or opening of the terminal tongue under the screw,

4) Device C, which is a swage crimp tenninal with the tongue modified

into a J-hook configuration, was cycled over 5000 cycles in the

heat cycling test without failure or excessive temperature

excursions. Right angle axial tensile- tests on the wire and

-12-
tenninal showed that this is its weakest mode, but still quite

adequate for its intended use. The tongue of the terminal

tends to loosen or open up under the receptacle binding screw

as a result of bending the wires into a receptacle box. The

weakness of the tongue often permits the body of the terminal

to bend outward and cause it to contact the sides of the box.

If this terminal is to be used in residential aluminum v/iring,

it is recommended that an insulating sleeve be positioned

over the terminal body and wire, and that care be exercised in

the installation to prevent loosening and/or opening of the

tenninal tongue under the screw.

5) Device D is an in-line crimp splice designed for connecting

together two #12 aluminum and one it^l^ copper wire pigtail

which in turn is connected to the wiring device. This splice

was cycled over 5000 cycles in the heat cycling test without

failure or excessive temperature excursions. The bend and

simulated retrofitting tests indicated that there are no serious

problems in its use in standard receptacle boxes. The crimping

tool provided by the manufacturer, however, is bulky and awkward

to use in a field environment. It is recommended that the shrink

type insulating sleeve extend over the wires as well as the body

of the splice to prevent sharp bends at the wire splice interface.

6) Device E is a butt crimp splice designed for connecting together

two #10 aluminum and one #12 copper wire pigtail, which in turn

is connected to the wiring device. This splice was cycled over

5000 cycles in the heat cycling test without failure or excessive

temperature excursions. This device is much larger than the type

D, hence, the additional volume occupied by them creates a

marginal situation with respect to the general requirement in

the 1975 National Electrical Code, Paragraph 370-6 (Boxes shall be of

sufficient size to provide free space for all conductors enclosed in the

Sox) . The crimping tool provided by the manufacturer is bulky

and awk-ward to use in a field environment. It is recommended that

the shrink type insulating sleeve extend over the wires as well as

the body of the splice to prevent sharp bends at the wire splice

interface.

-13- USCOMM-NBS-DG

Table I Heat Cycle data for terminal A

Cycle No> Wire Type iMin. Temp. °C Max> Temp. ^C Avg. Temp °C

1 #10 EC-H19 80 95 89

4^43 no EC-H19 Ick 315 188

490 #10 EC-H19 Entire Set Removed From Test

1 no I>;ew Alloy 75 86 81

443 no fjew Alloy 83 109 91

1089 #10 New Alloy 82 320 102

1410 #10 New Alloy Entire Set Removed From Test

*53 amperes "on" 20 minutes, "off" 10 minutes
Table II Heat Cycle Data for Tenninals B & C

Min. Temp (lax. Temp Avg. Temp

Cycle No. Tenninal Wire Type 2c 2c_

1 B #10 EC-H19 99 106 102

50 a #10 b:C-H19 103 106 105

^17 B #10 EC-H19 101 110 105

1475 B #10 EC-H19 96 102 99

5080 B #10 EC-H19 103 111 107

1 B #10 New Alloy 96 106 99

50 B #10 New Alloy 98 110 102

417 B //lO New Alloy 96 115 103

1475 B #10 New Alloy 96 107 101

5080 B no New Alloy 96 112 102

1 C #10 EC-H19 110 128 116

50 C #10 EC-H19 112 13^ 119

417 C #10 EC-H19 111 131 118

1475 C #10 EC-H19 108 133 116

5080 c #10 EC-H19 111 137 120

1 c #10 New Alloy 111 113 113

50 c #10 New Alloy 110 126 118

417 c #10 New Alloy 112 129 121

1475 c #10 New Alloy 110 129 120

5080 c #10 New Alloy 112 128 121

53 anperes "ON" 20 minutes "OFF" 10 minutes
Table III Heat Cycle Data for Splices D & E

Cycle No. Splice Wire Type Min. Temp Max. Temp Ave. Temp

OC °C °C

1 n

^^^12 New Alloy ca 70 a:j ^ ^ #14 Copper ^6 72 63

570 D " " 61 68 65

3457 D " " 61 76 66

4642 D " " 64 74 67

5314 D " " 64 71 68

,

• p #10 New Alloy „^ ^ ^ ^ #12 Copper ^4 72 60

508 E

It ti 58 73 64

2272 E " " 58 73 62

5024 E " " 59 72 63

T

p, #10 EC-H19 7, .7

^ ^ #12 Copper 73 67

508 E " " 58 73 71

2272 E " " 59 74 70

5024 E

II II 58 74 70
Table IV Results of Tensile Tests of Aluminun Wire

and Wire-Terminal Types B & C

tests on wire WX Oil ilU UvJllItCC l/Ul o

\iire Tvoe

1 EC-H19 223 2.2

2 EC-H19 226 2.2

3 EC-H19 227 2.2

i\ EC-H19 219 1.3

c;J EC-H19 228 2 1 u alloy

7 alloy

8 alloy

Q alloy

10 oil rjv 126 2"^ 4

Avi ?il I'pn^^ilp tests on wire u/i t'h Tpprninfll R nn nnp pnH

11 EC-H19 193

12 EC-H19 199

1 7.

1-

J

EC-H19

14 EC-H19 139

15 EC-H19 183

16 alloy 1 <4

17 alloy

18 alloy

19 alloy J- jJ20 alloy

Axial tensile tests on wire WX L'll XOllllXIlCt J- O ^li KZH\X ^ ^UX J C^vi wx connector clamped

21 EC-H19 178

22 EC-H19 182

23 EC-H19 180

24 EC-H19 186

25 EC-H19 182

26 alloy 137

27 al loy 135

28 alloy 134

29 alloy 136

30 alloy 135
lable IV continued

Right angle tensile tests on wire with Terminal B on one end

31 EC-H19 116

32 EC-H19 90

33 EC-H19 97

34 EC-H19 132

35 EC-H19 86

36 alloy 113

37 alloy 110

38 alloy 103

39 alloy 86

40 alloy 91

Right angle tensile tests on wire with Terminal C on one end

41 EC-H19 76

42 EC-H19 57

43 EC-H19 72

44 EC-H19 72

45 EC-H19 46

46 alloy 52

47 alloy 68

48 alloy 96

49 alloy 56

50 alloy 62

Cross Head Speads:

EC-H19 Samples 0.05 inches per minute (1.3 mm per minute)

Alloy Samples 0.2 inches per minute (5 ram per minute)
Table V Destructive Bend Tests on Wires Terminated

With Terminals B & C and Splices D & E

Terminal or Splice Wire Tvoe Avg. No. of Bends

B #10 New Alloy 15

C #10 New Alloy 10

£ #10 New Alloy 11

D #12 New Alloy 8

Direct Under Screw #10 New Alloy 18

B #10 EC-H19 3

C #10 EC-H19 3

E #10 EC-H19 3

Direct Under Screw #10 EC-H19 5
jFig, 2 Splices used to connect aluminum wire to copper wire pigtails which are

fastened under the binding screws of a wiring device.
Terminals fastened to the ends of aluminum wire. The tongues of the

terminals are fastened under the binding screws of a wiring device.












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NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR RI-:POR'r NO.

NBSIR 76-1039

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLF-: AND SUBTITLE

Evaluation of Selected Connectors For Aluminum Wire in

Residential Structures

5. Publication Date

March 1976

6. Performing Organization ('ode

7. AUTHOR(S) 8. Performing Organ. Report No. NBSIR 7b-1039

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Projocr/Task/Work Unit No.

11. Contract/(jrant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Consumer Product Safety Commission

5401 Westbard Ave.

Bethesda, Maryland 20016

13. Type of Report & Period

Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT Ci4 200-word or less factual summary of most si^ilicant information. If document includes a significant

bibliography or literature survey, mention it here.)

Systems of connecting aluminum wire for possible use in receptacle outlets and elsewhere in 15 and 20 ampere branch circuits in residences are available as practical

alternatives to the presently used mechanisms such as the wire binding screw and the

twist-on "wire nut" connector. The alternative systems are based on the principle of

high deformation of the wire in the connection to achieve more permanent metal-to-metal

fittings and/or wire splice devices of several designs. They involve either crimping

the device around the wire or swaging the wire into the device with special tools.

Based on tests, basic connection performance of several high-deformation connectors

has been established. The results indicate that certain designs of connectors operate

with stability and without dangerously over-heating under accelerated laboratory tests.

The tools, however, to be used to crimp terminals are not only bulky and awkward to

use but quite expensive. Moreover, they must be correctly coordinated with the

terminals and sizes of wires used. There is danger that a misadjusted or improper tool

and/or terminal may be used with particular wire or wires which could result in a poor

connection. Some improvements in the design of the assembly tools and in the devices

themselves would reduce certain installation difficulties encountered during testing,

and certain connectors could be slightly modified to avoid human errors during

assembly. Use of these systems and conformance with established codes and standards

do not appear to present major problems.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Aluminum wire; splices; terminals

18. AVAILABILITY^Unlimited 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

1

' For Official Distribution. Do Not Release to NTIS

UNCL ASSIFIED 37

1

1 Order From Sup. of Doc, U.S. Government Printing

Washington. D.C. 20402. SD Cat. No. C13

Office 20. SECURITY -CLASS

(THIS PAGE)

22. Price

|jQj[ Order From National Technical Information Service

Springfield, Virginia 22151

(NTIS)

UNCLASSIFIED ^4.00

USCOMM-DC 29042-P74