NBSIR 76-1184

Performance of Branch Circuit

Electrical Terminations of

Copper and Aluminum

Non-Metallic Sheathed Cable

Larry W. Masters

Elizabeth J. Clark

Edward J. Embree

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

November 1976

Final Report

Prepared for Naval Facilities Engineering Command

Department of the Navy

Washington, D. C. 20390

Directorate of Civil Engineering

U. S. Air Force

Washington, D. C. 20330

Office of Chief of Engineers

U. S. Army

Washington, D. C. 20314

1 NBSIR 76-1184

PERFORMANCE OF BRANCH CIRCUIT

ELECTRICAL TERMINATIONS OF

COPPER AND ALUMINUM

NON-METALLIC SHEATHED CABLE

Larry W. Masters

Elizabeth J. Clark

Edward J. Embree

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

November 1976

Final Report

Prepared for Naval Facilities Engineering Command

Department of the Navy

Washington, D. C. 20390

Directorate of Civil Engineering

U. S. Air Force

Washington, D. C. 20330

Office of Chief of Engineers

U. S. Army

Washington, D. C. 20314

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

Edward O. Vetter, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Acting Director

m.
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TABLE OF CONTENTS

Page

Abstract

1. INTRODUCTION 1

1.1 Background 1

1.2 Scope of Study 2

2. DISTRIBUTION OF ALUMINUM WIRED BRANCH CIRCUITS IN MILITARY BUILDINGS 2

3. LABORATORY TESTS AND RESULTS 2

3.1 Current Cycling Tests with Non-CO/ALR Receptacles 2

3.1.1 Scope 2

3.1.2 Procedure 3

3.1.3 Results and Discussion 4

3.2 Current Cycling Tests with CO/ALR Receptacles.. 5

3.2.1 Scope 5

3.2.2 Procedure 6

3.2.3 Results and Discussion 6

3.3 Comparison of Initial Termination Point Resistances for CO/ALR and

Non-CO/ALR Receptacles 6

3.3.1 Scope 6

3.3.2 Procedure 6

3.3.3 Results and Discussion 7

3.4 Measurement of Breakoff Tab Resistance 7

3.4.1 Scope 7

3.4.2 Procedure 7

3.4.3 Results and Discussion 7

4. CONCLUSIONS 8

5. GUIDELINES FOR THE USE OF ALUMINUM BRANCH CIRCUIT WIRING IN MILITARY BUILDINGS... 9

6. REFERENCES 10

iii
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Performance of Branch Circuit Electrical Terminations of Copper and Aluminum

Non-Metallic Sheathed Cable

Larry W. Masters, Elizabeth J. Clark and Edward J. Embree

ABSTRACT

A study was performed to provide the Tri-Services Committee on Building

Materials with guidelines regarding the use of aluminum branch circuit

wiring in military buildings. The first part of the study consisted of identifying military bases which contained buildings with aluminum wired

branch circuits. Personnel at a number of the bases were contacted in order

to estimate the extent of observed problems. Laboratory tests were performed

on CO/ALR and non-CO/ALR duplex receptacles wired with both aluminum and copper non-metallic sheathed cable. Overheating of aluminum wired termination points was observed with some receptacles in a current cycling test using non-CO/ALR receptacles at screw torque levels of 0.023 and 0.069 kg-m

(2 and 6 lb-in). Aluminum wired non-CO/ALR receptacles tested at 0.138 kg-m

(12 lb- in) screw torque showed no signs of overheating and copper wired non- CO/ALR receptacles showed no signs of overheating regardless of screw torque.

This report presents the findings of the study and includes guidelines

regarding the use of aluminum branch circuit wiring in military buildings.

Key Words: Aluminum wiring; branch circuits; copper wiring; military

buildings

.

1. INTRODUCTION

1.1 Background

Both copper and aluminum wire have been used for conducting current in electrical

branch circuits. Prior to the mid 1960's, copper wire was used almost exclusively in branch circuits but, in the mid to late 1960's, the use of aluminum wire in branch circuits

increased substantially. About that same time, the use of plated steel for wire binding

screws of receptacles and switches became prevalent. The substitution of aluminum for copper wire and of steel for brass wire binding screws was largely due to the increased

cost and limited availability of copper during the late 1960's.

By 1969, Underwriter's Laboratories Inc. (UL) had begun to receive reports of problems

in the field associated with aluminum electrical wiring [1]*. The reported problems were primarily overheating at points in branch circuits where the wiring was joined to receptacles

and switches (termination points) . As a result of these field reports, UL re-evaluated

and revised its test specifications and subsequently recommended that only those wiring

devices (receptacles and switches) with a "CO/ALR" label be used with aluminum wiring.

(The CO/ALR label means that the wiring devices have complied with the revised UL test specifications.) CO/ALR rated wiring devices can be used with copper as well as aluminum

wire. Devices which complied with the revised UL test specification all contained brass

wire binding screws and wire restraints. Some of the CO/ALR rated devices also contained

indium plated contact components.

In addition to the changes in wiring devices as a result of field problems, changes were also made in the alloys used for aluminum wiring. The aluminum wiring used prior to about 1972 has been shown by Battelle Columbus Laboratories [2] to exhibit high stress relaxation and to be physically difficult to work with. The post-1972 wiring was formulated

to overcome some of the problems observed with pre-1972 wiring.

*Numbers in brackets refer to references at the end of this paper.

1
In 1974, the Consumer Product Safety Commission (CPSC) requested that a study be

performed by the National Bureau of Standards (NBS) to determine if terminations of aluminum

electrical wiring produced a potential hazard in residential branch circuits. Reports

prepared for the CPSC presented the NBS findings in 1974 [1, 3]. Subsequent reports discussed conditions under which loose terminations (0 kg-m screw torque) of both copper and aluminum could overheat [4] and presented the results of cyclic tests of crimp connectors

[5].

In 1975, the Tri-Services Committee on Building Materials requested the Center for Building Technology of NBS to perform additional studies in order to provide guidelines on

the use of aluminum wiring in military buildings. The purpose of this report is to present

the findings of the latter study.

1.2 Scope of Study

This study had four objectives: 1) to estimate the extent of use of aluminum branch

circuit wiring in military buildings, 2) to identify military installations in which

problems had occurred, 3) to perform laboratory studies of electrical terminations and 4) to provide guidelines on the use of aluminum wiring in military buildings.

Prior laboratory studies [3, 4] had shown that totally loose termination points (0 kg-m

screw torque) could result in overheating with both copper and aluminum wire. Totally

loose terminations were not tested further in this study. This study consisted of identifying and contacting military bases where aluminum branch circuit wiring has been used and performing laboratory studies with both CO/ALR and non-CO/ALR duplex receptacles.

The laboratory studies were performed using aluminum wiring of the post-1972 type.

It would have been desirable to perform tests with pre-1972 wiring to provide guidelines

on actions to take regarding that type of wire. However, when the laboratory studies were

started, the pre-1972 alloys were not available.

2. DISTRIBUTION OF ALUMINUM WIRED BRANCH CIRCUITS IN MILITARY BUILDINGS

A Department of Defense (DoD) survey, performed in 1974, was used as the initial source of information to estimate the extent of use of aluminum branch circuit wiring in military buildings and to identify installations in which problems had been observed.

Personnel at a number of the bases where aluminum branch circuit wiring had been used were

then contacted by telephone to obtain additional information. Table 1 summarizes the information obtained from the DoD survey and the telephone contacts for Air Force, Army

and Navy residential units. The table includes data for aluminum and copper-clad aluminum

wire of sizes #6 AWG and smaller.

In addition to the use of aluminum wire in residential units, a number of bases have

a limited number of other types of buildings with aluminum wired branch circuits. These

include Cannon AFB, New Mexico; McChord AFB, Washington; Norton AFB, California; Rickenbacker

AFB, Ohio; Fort Polk, Louisiana (Army); Fort Rucker, Alabama (Army); and the U.S. Army

Aeronautical Depot Maintenance Center, Corpus Christi, Texas.

Based on the data in table 1, it is estimated that about 4100 military dwelling units

contain aluminum wired branch circuits. Approximately 2350 of these units are located on Air Force bases, 1300 on Navy bases and 450 on Army bases. Overheated termination points,

as determined by observations such as unusually warm receptacle or switch covers, degraded

wiring devices or degraded poly(vinyl chloride) wire insulation, have been observed by

base personnel in a number of installations as summarized in table 1. Overheated terminals

have generally been attributed by base personnel to loose connections and poor workmanship.

3. LABORATORY TESTS AND RESULTS

3.1 Current Cycling Tests with Non-CO/ALR Receptacles

3.1.1 Scope

Two types of typical non-CO/ALR duplex receptacles were installed in a laboratory

wall structure. One type of receptacle contained zinc plated steel wire binding screws

2
and the other type contained brass wire binding screws. The devices were wired with

either copper or aluminum non-metallic sheathed cable at three levels of screw torque. Current (15 amperes) was cycled through the circuit and the breakoff tab temperatures were monitored

The purpose of the test was to evaluate the performance of termination points under

conditions that simulate field conditions. The test was not designed to be an accelerated

test. Rather, it was intended to complement accelerated tests which had been performed in other laboratories [2, 6]. The test was started in July 1974 and continued for 27 months.

3.1.2 Procedure

Thirty-six non-CO/ALR grounding type duplex receptacles, which were rated for 15 ampere loads, were installed in a laboratory wall structure. The wall structure, which

was about 2.4 x 4.5 m (8 x 15 ft) in size, was constructed of 2 x 4's and plywood paneling

and included 8.8 cm (3.5 in) of foil faced fiberglass insulation. Half of the receptacles

contained zinc plated steel wire binding screws while the remainder contained brass screws. The wall had four rows (A, B, C and D) of nine receptacles, aligned in columns. Figure 1 illustrates the arrangement of the receptacles in the wall structure and figure 2 is a diagram of the circuit. Rows A and C contained receptacles with steel wire binding screws while Rows B and D contained receptacles with brass wire binding screws. Rows A and B were wired with #10 AWG aluminum non-metallic sheathed cable and Rows C and D with #12 AWG copper non-metallic sheathed cable. Both types of cable contained two conductors with a grounding conductor and the aluminum wire used in the test was representative of that commercially available in mid-1974. Three-quarter, planar wire loops were used in all terminations (e.g. the wire under the screw head formed a 3/4 loop and the plane of the loop was parallel to the plane of the screw head) . The screws of two receptacles (Columns

1 and 2) in each row were tightened to 0.023 kg-m (2 lb-in) torque. The screws of three

receptacles (Columns 3, 4 and 5) in each row were torqued to 0.069 kg-m (6 lb-in) and the remaining four receptacles (Columns 6, 7, 8 and 9) in each row were torqued to 0.138 kg-m

(12 lb-in) as illustrated in figure 1. In each case, the receptacles were installed in standard metal boxes having a volume of about 200 cm^ (12 in^) . The screw torque was applied after installing the receptacles in the boxes to ensure that the actual screw

torque was known. (If screws had been torqued prior to installing receptacles in the boxes, they may have been either tightened or loosened during the process of pushing the receptacle into the box.) Copper constantan thermocouples (28 gauge) were installed on the black wire (non-grounded) side breakoff tab of each receptacle and in the open space behind the receptacle in each box. An additional thermocouple was used to monitor the ambient air temperature in the wall structure. The voltage drop across the two black wire

termination points on each receptacle was measured prior to initiating the test. The procedure used was to apply a 10 ampere load, place probes on each of the black wires near

the termination point (note points A and B in figure 3) and read the voltage drop on a voltmeter. From the voltage drop reading, the resistance across the two termination

points was calculated. The voltage drop was then remeasured at the end of twenty cycles

and prior to removing receptacles from the wall.

The receptacles were wired to a load drawn by laboratory hot plates. The current

load (15 amperes) from the 120 volt, 60 cycle main supply was applied to the receptacles

in cycles of 3 1/2 hours ON and 1/2 hour OFF. Two ON/OFF cycles were completed each

working day. The cycling was not continued overnight or on weekends. Initially, temperature

readings were taken daily near the end of the ON period. After the completion of 20 cycles, temperatures were recorded in increments of ten cycles.

At the end of twenty cycles, twelve of the receptacles (one for each wire/screw/torque

combination) were removed from the wall structure and prepared for metallographic examination. No other predesignated time interval was assigned for removal of receptacles.

Rather, some receptacles were removed at various stages of overheating while others were

removed at similar time intervals for comparison. When receptacles were removed the wire

was cut 10-12 cm (4-5 inches) from the termination points and care was taken to avoid

disturbing the terminals. Replicate receptacles were installed to replace those that had

been removed.

3
3.1.3 Results and Discussion

The results for the four rows of receptacles are summarized in tables 2, 3, 4 and 5. The "Column Number" listed in the tables is the same as that in figure 1. The receptacles

installed in each "Column Number" for each row are assigned a number (i.e., "Receptacle

Number" 1 is the first receptacle installed; Receptacle Number 2 is its replacement,

etc.). The tables also include screw torque, number of cycles completed, and black wire

(non-grounded) breakoff tab temperature data. Several receptacles were also equipped with

thermocouples on the white wire (grounded) breakoff tab during the experiment. These are noted in the table footnotes. The third cycle temperature is included as a measure of the initial operating temperature because it was observed that two initial cycles were required

to obtain a stable operating temperature for many of the receptacles.

The tables also include the maximum recorded breakoff tab temperature and the cycle

on which the maximum temperature occurred. Typically, the temperatures varied from day to day and from cycle to cycle. Figure 4 is a plot of the black wire breakoff tab temperature

against the number of cycles for the aluminum wired brass screw receptacle (Row B, Column

1, Receptacle 1) that exhibited the maximum temperature in the wall experiment. It illustrates

the types of fluctuations observed in temperature from cycle to cycle.

For the purpose of this report, "overheating" is defined as an increase of 10°C

(18°F) or more above the average third cycle temperature for each row of receptacles.

Table 2 contains the test results for the Row A receptacles (steel screws/aluminum

wire). The average third cycle breakoff tab temperature for the Row A receptacles was

55°C (131°F). Of the four receptacles installed at 0.023 kg-m (2 lb-in) screw torque, one (Column 2, Receptacle 2) exhibited overheating according to the above definition. The

overheated receptacle exhibited a maximum black wire breakoff tab temperature of 110°C

(230°F) on the 210th cycle. During the experiment, infrared thermography using an infrared

(IR) television system was used to identify the termination points which were overheating.

It was determined by infrared thermography that a terminal on the white wire side of this

receptacle was overheating. At the end of 319 cycles a thermocouple was installed on the white wire breakoff tab. The white wire breakoff tab temperature was 88°C (191°F) on the 320th cycle and it remained relatively constant through the 390th cycle. The black wire

breakoff tab temperature, which was 76°C (169°F) on the 320th cycle, remained relatively

constant through the 390th cycle. The elevated temperature on the black wire side could

have been due to either an overheated terminal or to heat transferred from the white wire

side.

One additional Row A receptacle exhibited slight overheating. This receptacle (Column

4, Receptacle 2) was one of five installed at 0.069 kg-m (6 lb-in) screw torque. The

maximum black wire breakoff tab temperature recorded was 66°C (150°F) on the 210th cycle.

Infrared thermography studies showed that one white wire terminal on this receptacle was slightly overheating. At the end of 309 cycles, a thermocouple was installed on the white

wire breakoff tab. The temperature measured by this thermocouple was 67°C (135°F) on the 310th cycle and it remained relatively constant through the 390th cycle. From the 310th

through the 390th cycle the black wire breakoff tab temperature was slightly below the average third cycle temperature of the Row A receptacles. As shown in table 2, none of the five Row A receptacles tested at 0.138 kg-m (12 lb-in) screw torque showed signs of over- heating.

Test data for the Row B receptacles (brass screws/aluminum wire) are summarized in table 3. The average third cycle breakoff tab temperature for the Row B receptacles was

59°C (138°F). Four of the six receptacles tested at 0.023 kg-m (2 lb-in) screw torque

overheated. All four of the overheated receptacles were in Column 1 of the wall. The

first receptacle installed in Column 1 had a black wire breakoff tab temperature of 199°C

(389°F) after 68 cycles. At this point, the temperature decreased gradually to 57°C (135°F)

after 120 cycles and remained relatively constant until the receptacle was removed from the wall at the end of 280 cycles. The decrease in temperature after 68 cycles was attributed

to a wire to wire contact made about 2 inches from the termination points. The new contact was possible because of extensive degradation of the poly(vinyl chloride) (PVC) wire insulation.

Figure 5 is a picture of this receptacle prior to its removal from the wall. The PVC degradation can be observed in the figure.

4
The initial resistances of the Row B receptacles in Column 1, as measured across the two black wire terminations (from points A to B in figure 3), were 8.3, 7.6, 2.7 and 3.8 milliohms for receptacles 1, 2, 3 and 4, respectively. These resistances include the resistance of the breakoff tab which was located between the two termination points. The

breakoff tab resistance bf a replicate receptacle was measured and found to be about 0.33 milliohms. Measurements of breakoff tab resistance are discussed in Section 3.4 of this

report. The inital resistance values for the two receptacles in Column 2 were 2.0 and 1.2 milliohms, respectively. The initial values for all other Row B receptacles were less than 0.9 milliohms. Thus, all Row B receptacles with initial resistances of 2.7 milliohms

or greater exhibited overheating while those with initial resistances of 2.0 or less did not overheat. The Column 2 receptacle with an initial resistance of 2.0 milliohms was

cycled for .only 20 cycles. This cycling time may not have been great enough to produce

overheating. Based on these data, it appears that by measuring the initial resistance of brass screw receptacles wired with aluminum, there is a possibility of predicting whether

or not the terminals will overheat in a relatively short period of time (2 years). The

point above which overheating occurs is apparently between 1.2 and 2.7 milliohms, including

the breakoff tab resistance. Additional studies are needed to determine if such measurements

could be used as a tool in the field to identify potential future problems.

Row B, Column 1 receptacles 2 and 3 were also removed after overheating became obvious

but before extensive degradation took place in order to study the termination point interfaces at various stages of degradation. The screw head/wire/contact plate interfaces of the overheated termination point of Receptacle 1 of Column 1 are shown in figure 6. The figure shows arcing pits and corrosion products resulting from the corrosion products on the same wire shown in figure 5. Figure 7 is a closeup of the wire surface which shows

the corrosion products. Analysis of the surfaces in figure 6 by scanning electron microscopy

and X-ray emission showed that the surfaces of all the interface materials contained

aluminum, copper, zinc and large amounts of chloride [7], The source of the chloride was

almost certainly the degraded PVC wire insulation. No signs of overheating were observed

on the Row B receptacles with screw torques of 0.069 kg-m (6 lb-in) or 0.138 kg-m (12 lb-in).

Tables 4 and 5 summarize the data for steel and brass screw receptacles, respectively,

wired with #12 AWG copper wire. The average third cycle temperature of the Row C receptacles

(table 4) was 53°C (127°F) while that for the Row D receptacles (table 5) was 51°C (124°F). None of the receptacles in Rows C and D exhibited overheating during the test.

Table 6 is a summary of the data in tables 2-5. It can be seen in table 6 that all

the receptacles which exhibited overheating were wired with aluminum. However, replicate

test specimens did not necessarily yield replicate results as noted in the footnotes to table 6. A possible explanation for the lack of agreement among replicate receptacles

stems from the use of screw torque as a measure of screw head/wire/contact plate tightness

and, hence, contact area and pressure. Torque may not be a good measure of contact pressure, especially at low torque values, because frictional forces, such as those between the screw threads and the contact plate, are included in the measured torque. Also, if the wire loop is not planar, the contact area may be different for each terminal even though

the torques are equal. There was no attempt in these experiments to determine if torque measurements resulted in more than approximately equal metal to metal contact areas and pressures

3.2 Current Cycling Tests with C0/ALR Receptacles

3.2.1 Scope

A test was performed to study the performance of four types of aluminum wired CO/ALR

duplex receptacles using the maximum current for which they were rated. The receptacles were subjected to 15 ampere cycles of 3 1/2 hours ON and 1/2 OFF using a 120 volt ac supply.

5
3.2.2 Procedure

Six specimens of each of four types of CO/ALR receptacles were wired, using 3/4

planar loops, with #10 AWG aluminum non-metallic sheathed cable. The wire was one of the materials commercially available in 1975. A thermocouple was installed on the black wire

breakoff tab of each receptacle. A screw torque of 0.138 kg-m (12 lb-in) was applied to each termination point prior to installing each receptacle in a metal box. Resistance measurements were made across the two black wire terminals of each receptacle as illustrated

in figure 3. A plastic face plate was installed on each box and the boxes installed in open air on a laboratory bench. The receptacles were wired to a load consisting of 18-100 watt light bulbs. The current load (15 amperes) from the 120 volt, 60 cycle main supply was applied to the receptacles in cycles of 3 1/2 hours ON and 1/2 hour OFF. The breakoff

tab temperature was monitored each cycle for the first ten cycles and every tenth cycle

thereafter. The temperature was monitored near the end of the ON cycle.

3.2.3 Results and Discussion

The test results are summarized in table 7. The first column designates the four

manufacturers of the CO/ALR receptacles tested. The receptacles from Manufacturer 1 con- tained tin plated components while those from manufacturers 2, 3 and 4 contained either

indium plating or a combination of indium and tin plating on plated components. All four

types contained brass wire binding screws. The next column in table 7 is a specimen

number assigned to each receptacle from each manufacturer. Other columns present the initial resistance as measured across the two black wire terminals (including the breakoff

tab) and the breakoff tab temperatures during the first, 30th and 140th ON cycle.

The initial resistances varied from 0.24 to 0.67 milliohms with one exception. One receptacle from Manufacturer 2 (specimen number 3) had an initial resistance of 2.30 milliohms. The breakoff tab temperature of the latter receptacle was consistently higher

than that of other receptacles but it did not increase significantly during the period of the test. None of the CO/ALR receptacles exhibited signs of overheating during the test. The breakoff tab temperatures in table 7 cannot be directly compared with those of non- CO/ALR receptacles (tables 2, 3, 4 and 5) because the latter receptacles were tested in an enclosed wall. Thus heat was more easily dissipated from the CO/ALR receptacles than from

the non-CO/ALR receptacles.

3.3 Comparison of Initial Termination Point Resistances for CO/ALR and Non-CO/ALR Receptacles

3.3.1 Scope

A series of tests was performed to compare the initial termination point resistances

of four types of CO/ALR receptacles with that of two types of non-CO/ALR receptacles. The resistances were measured on newly made terminals that had not been subjected to current cycles

.

3.3.2 Procedure

Specimens of four types of CO/ALR and two types of non-CO/ALR duplex receptacles were wired to #10 AWG aluminum and #12 AWG copper non-metallic sheathed cable at screw torque

levels of 0.023, 0.046, 0.069, 0.092, 0.115, 0.138, 0.161, 0.184, 0.207 and 0.230 kg-m (2, 4, 6, 8, 10, 12, 14, 16, 18 and 20 lb-in). The aluminum wire and the CO/ALR receptacles were the same types used in the cyclic test described in 3.2. The non-CO/ALR receptacles were the same types used in the test described in 3.1. One receptacle of each type was

used with copper wire and a duplicate receptacle of each type was used with aluminum wire.

The procedure used was to insert a 3/4, planar wire loop under the screw heads,

tighten to 0.023 kg-m (2 lb-in) screw torque and measure the voltage drop across the two black wire terminals using a 10 ampere load. The probes were located at points A and B as shown in figure 3. The resistance calculated from the measurements included the breakoff

tab resistance. The screws were then tightened to 0.046 kg-m and the resistance measured

as before. This procedure was repeated for each torque level.

6
3.3.3 Results and Discussion

The results of the test series with CO/ALR receptacles are presented in table 8. Table 9 includes the results with non-CO/ALR receptacles. The data in table 8 show that the resistances measured ‘across newly made termination points of all four types of CO/ALR

receptacles are relatively independent of screw torque. Table 8 data also show that the resistances do not vary greatly with the type of wire. The resistances presented in table

9 for non-CO/ALR receptacles are somewhat more dependent on screw torque. The data in Table 9 also indicate that the resistance of aluminum terminations at low screw torque is higher than that of copper terminations at the same screw torque. For the non-CO/ALR Type

1 receptacle, aluminum and copper yield approximately the same resistances at screw torques

of 0.138 kg-m (12 lb-in) and greater. The resistance of aluminum and copper terminations

to the Type 2 non-CO/ALR receptacle are approximately equal at torques of 0.207 kg-m (18

lb-in) and greater.

During the tests, it was observed that tightening the wire binding screws of the CO/ALR receptacles in excess of 0.161-0.184 kg-m (14-16 lb-in) occasionally resulted in either buckling of the contact plate or stripping of the screw threads. The fact that CO/ALR termination point resistance is relatively independent of screw torque, as shown in table 8, indicates that it is not necessary to torque the screws above about 0.138 kg-m

(12 lb-in) to achieve the minimum initial resistance.

3.4 Measurement of Breakoff Tab Resistance

3.4.1 Scope

The resistances reported in tables 8 and 9 include the resistance of two black wire

terminations and the breakoff tab. Measurements were made in order to determine the magnitude of the breakoff tab contribution to the total measured resistance.

3.4.2 Procedure

Duplicate specimens of six types of duplex receptacles were selected for the test. The specimens included two types of non-CO/ALR and four types of CO/ALR receptacles. The

non-CO/ALR receptacles were the same types described in 3.1, while the CO/ALR receptacles were the same types described in 3.2 -and for which data are presented in tables 7 and 8. One specimen of each type was wired with #12 AWG copper non-metallic sheathed cable and the other specimen with #10 AWG aluminum non-metallic sheathed cable. The wire binding

screws were tightened to 0.138 kg-m (12 lb-in) torque. A current of 10 amperes was passed

through the receptacles and the voltage drop measured on both the black and white wire

sides. Measurements were made from points A to C and A to D as shown in figure 8.

The resistance calculated from the A-C measurement is indicative of the termination

point resistance. The A-D measurement includes the termination point resistance, the breakoff tab resistance and the contact plate resistance between the termination point and

the breakoff tab. The latter resistance was asssumed to be negligible for the purpose of this experiment. The breakoff tab resistance was obtained by subtracting the A-C resistance

from the A-D resistance.

3.4.3 Results and Discussion

The test results are summarized in table 10. The numbers assigned to the CO/ALR

receptacles are the same as used in tables 7 and 8. The non-CO/ALR receptacle numbers are

the same as those in table 9.

The data in table 10 show that the breakoff tab resistance varies with the type of receptacle and, when the wire to connector resistances are low, it can provide a substantial

contribution to the resistance across a receptacle. The Type 2 CO/ALR receptacle had the lowest breakoff tab resistance while the Type 2 non-CO/ALR had the highest. In each case, the breakoff tab resistance is higher than the initial termination point resistance.
The resistance of the breakoff tab is dependent largely upon its design. Thus it varies for each different type of receptacle. In addition, its resistance can vary with

different specimens of the same type. For example, the black wire breakoff tabs of the

two Type 4 CO/ALR receptacles (table 10) had resistances of 0.274 and 0.341 milliohms.

4. CONCLUSIONS

As mentioned in Section 1.2 of this report, the aluminum alloys used in the laboratory

tests of this study were of the post-1972 type. Since pre-1972 wiring was not available for

test, the conclusions must be limited to the materials tested.

The data obtained in the laboratory tests described in Sections 3.1 and 3.2 indicate

that lack of termination point tightness ih a major factor contributing to overheating.

For example, the data in tables 2 and 3 show that overheating (defined as a 10°C temperature

rise above the average breakoff tab temperature during the third cycle) occurred primarily

in receptacles with very low screw torque levels. The only receptacles that overheated to the point of extensive decomposition were at 0.023 kg-m (2 lb-in) screw torque. The

breakoff tab temperature of the one receptacle (aluminum wire/steel screws) at 0.069 kg-m

(6 lb-in) that overheated according to our definition increased only 11°C above the average third cycle temperature during 390 cycles in the wall test. Despite the problem

encountered in using screw torque as a measure of termination point tightness at a particular

torque level, the tightness, and hence the metal to metal contact, can be reasonably assumed

to increase progressively from 0.023 to 0.138 kg-m (2 to 12 lb-in) torque. It can be

concluded that, by maintaining a screw torque of approximately 0.138 kg-m (12 lb-in), the chance of obtaining overheated termination points is substantially reduced.

The type of wire used is another factor contributing to possible overheating. The data in tables 2-6 show that all instances of overheating occurred in receptacles wired

with aluminum while none of the copper wired receptacles overheated. These data indicate

that aluminum wired termination points at low screw torque are more susceptible to overheating

than those wired with copper. The difference in electrical conductivity of the oxide

coatings on the two wires may contribute to this. Aluminum oxide is less conductive than copper oxide. Thus, it is more important to obtain good metal to metal contact (by applying

higher screw torques) with aluminum than with copper wire.

The decomposition of poly(vinyl chloride) (PVC) wire insulation is another factor that may contribute to overheating. It is not known if traces of PVC which remain on the wire

after stripping the insulation contribute to the initial overheating. It is also uncertain

if traces of PVC decomposition products which may be expelled by prolonged exposure to normal operating temperatures contribute to initial overheating. Previous studies using

thermogravimetric analysis have shown that the plasticizer component of some specimens of PVC can be lost at temperatures of 85°C. PVC degradation resulting from long exposures to lower temperatures was not studied. The scanning electron microscopy and x-ray studies of components of overheated terminals, however, have shown that large quantities of chloride

are present at component interfaces. The resultant products could contribute to the corrosion of termination point interfaces.

The comparison of initial resistances across newly made terminations of CO/ALR and non-CO/ALR receptacles (tables 8 and 9) indicate that CO/ALR receptacles provide terminations with lower resistance, particularly at the lower torque levels. The initial resistance

is important because the lower the resistance the lower the termination point temperature.

Higher temperatures could result in more rapid termination point changes which could enhance

degradation with time. The termination point resistances at 0.138 kg-m (12 lb-in) included

in table 10 show that the initial resistances of aluminum wired terminations of CO/ALR

receptacles are lower than those of non-CO/ALR receptacles. The table 10 values for copper wired terminals show that the resistances of CO/ALR terminations are less than or equal to those of non-CO/ALR terminations. The results obtained in this study and those

from previous studies (3) indicate that terminations of lower resistance can be made with

CO/ALR receptacles than with non-CO/ALR receptacles. In addition, CO/ALR receptacles are designed with wire restraints to help hold the wire loop under the wire binding screw

head. Although laboratory and field data are not yet available to ensure the satisfactory
performance of CO/ALR receptacles and switches for long periods of time, i.e., 10-20 years, it can be concluded based on the results of this study and those of other studies

[2, 3, 6] that CO/ALR devices provide improved termination points over those made with

non-CO/ALR devices.

5. GUIDELINES FOR THE USE OF ALUMINUM BRANCH CIRCUIT WIRING IN MILITARY BUILDINGS

One of the objectives of the study has been to provide the Tri-Services Committee on Building Materials with guidelines for the use of aluminum branch circuit wiring in military

buildings. The guidelines presented in this Section are based upon the knowledge available

at this time. However, the data limitations resulting from testing only post-1972 aluminum

alloys must be kept in mind.

The guidelines for the use of aluminum branch circuit wiring are as follows:

1. For aluminum branch circuit wiring in new installations, Underwriters'

Laboratories, Inc. (UL) recommends that CO/ALR rated receptacles and switches be

used. It is suggested that this UL recommendation be followed. It is also

suggested that the wire binding screws be tightened to and maintained at 0.127-

0.150 kg-m (11-13 lb-in) screw torque.

2. Where the terminals of existing aluminum branch circuit wiring, show signs

of possible overheating (such as decomposed connector components, odors from

overheated organic materials, receptacle and switch covers that are warm when

touched etc.), it is suggested that the overheated receptacles and switches be

replaced with CO/ALR wiring devices and that the terminations be made to fresh

wire by clipping off any PVC wire insulation that shows deterioration plus 5 to

7 cm (2-3 in) of the old wire and making a new 3/4 loop; it is also suggested

that the screw should be tightened to and maintained at a torque of 0.127-0.150

kg-m (11-13 lb-in)

3. Where the terminals of existing aluminum branch circuit wiring, connected

to non-CO/ALR receptacles and switches, have NOT shown signs of overheating, it is suggested that the screw torque be checked by an electrician periodically to ensure tightness to 0.127-0.150 kg-m (11-13 lb-in). (Electricians who check screw torque should take precautions to avoid loosening of the screws while

reinserting connectors into the metal boxes.) It is also suggested that building

occupants be alerted to signs of possible termination point overheating such as odors from overheated organic materials, interference with radio or television,

receptacle and switch covers that are warm when touched and flickering lights

not due to major appliances. In addition, it is suggested that occupants be

given guidelines for having problem terminations repaired. For safety reasons,

a qualified electrican should carry out all checks and repairs.

4. Where aluminum branch circuit wiring is terminated to receptacles or switches

using techniques such as push or backwiring, it is suggested the devices be

replaced with CO/ALR devices. It is further suggested that the new terminations

be made by clipping off the old exposed wire, making a 3/4 loop and tightening

the screw to a torque of 0.127-0.150 kg-m (11-13 lb-in).

An alternative to suggestion 3, above, would be to replace all non-CO/ALR receptacles

and switches with CO/ALR devices (as in suggestion 2) , even if they have not shown signs

of overheating.

9
6 . REFERENCES

1. Bunten, Elaine D., Donaldson, John L. and McDowell, Eugene C., "Hazard Assessment of Aluminum Electrical Wiring in Residential Use," NBSIR 75-677, National Bureau of Standards, Washington, D.C., December 1974.

2. Series of Quarterly Reports on Electrical Connector Characteristics of Aluminum and

Aluminum-Based Alloys, Battelle Columbus Laboratories, Columbus, Ohio 43201.

3. "Aluminum Branch Circuit Wiring in Residences, Summary Report for the Consumer Product

Safety Commission, January - September 1974," NBSIR 75-723, National Bureau of Standards

Washington, D.C., June 1975.

4. Meese, W. J. and Beausoliel, R. W., "Exploratory Study of Glowing Electrical Connections

NBSIR 76-1011, National Bureau of Standards, Washington, D.C., August 1976.

5. Laug, Owen B., "Evaluation of Selected Connectors for Aluminum Wire in Residential

Structures," NBSIR 76-1039, National Bureau of Standards, Washington, D.C., March

1976.

6. Private communication. Underwriters' Laboratories, Inc.,, Melville, Long Island, NY.

7. Clark, E. J., Ballard, D. B and Embree, E. J., "SEM Examination of an Overheated

Aluminum Wired Electrical Receptacle," 34th Ann. Proc. Electron Microscopy Soc. Amer .

,

Miami, Florida, Edited by G. W. Bailey, page 454 (1976).

10
Figure

1.

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of

Non-CO/ALR

Duplex

Receptacles

ina

Laboratory

Wall

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Figure

2.

Circuit

Diagram

of

Wall

Test
BREAK

OFF

TAB

x

<i Q_

U

£

z

o

13
14

Non-CO/ALR

Receptacle

Installed

in

the

Test

Wall
Figure

5*

Receptacle

1,

Column

1,

Row

B

Before

Removal

from

the

Wall

Structure.

PHHMHi

17

Figure

7

.

Corrosion

of

Wire

Loop

from

Receptacle

1,

Column

1,

Row
CO<I—

u_ 5

Q_

h—u<

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18

Figure

8.

Probe

Locations

for

Measuring

Voltage

Drops

to

Determine

the

Breakoff

Tab

Resistance.
Table

1.

Aluminum

Branch

Circuit

Wiring

in

Military

Residential

Units

(#6

AWG

and

smaller) i x

Clx

QJ

X

a S

00 (0 4J QJ GO 2 P co x

co etf QJ X) rH <£

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co

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19
Table

1.

Aluminum

Branch

Circuit

Wiring

in

Military

Residential

Units

(#6

AWG

and

smaller)

(cont.

c

o

oo

3 3 X *H 3

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20

buildings

have

had

overheated
Table

1.

Aluminum

Branch

Circuit

Wiring

in

Military

Residential

Units

(#6

AWG

and

smaller)

(cont.

co

oo

p

<U -H pd > P ,-1 P P <C H O U

CU lU C 4J £

C Qj 4J O P *H

CO ^ P X

cu <u co co a. co a) cu o o a

>-> P- *H *H e o > >

P P <U 03 <C ft Tl Tj

> 4- 03 4- 42 T

CX *H *H O > >

P CD CD

(2- X X

U

> P “H O

03 03 O 4-i CO 2 Q) (1) 0} 42 P- rH 00 42 CU CO CU P

4-1 42 4-1 p -H

0j CO 4-1 O C P 4-1 • 4-4 P -H O 03 CO 00 P P 03 CO (U P

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42 O P *H P > p P -H CU P <U P QJPCOPCU^iPO

> 03 4) p H p U O P O 42 42 42

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P

CU O

4-J *H P 4-1 P

E O P

•H i—

X CU i—

O P P

P P P a Q co a p < w

o

4-1o

P

(U 42E

CO

<U

o

oCM O

m

CM

CM B o o

o o

On r—

4-1O

CU

CU P

P- -H

X

P

P

CU£

P2

4HO

P

O

•H CU P CO P P

U PQ O

hJ

CU X

P X

CU p E P

r~H P

P P O P

Pn S

p p P cu p >

p p

> P P P P P Z P 2

P -H P

> P P

P O CU 2 < c/d

p * 2 2 0 a oo oo

Po

P x

p i—

CO <D

p

p

42o

pp

H

CQ eP<

>>>

PE

21
Table 2. Wall Structure Test Results for Non-CO/ALR Receptacles wiyh

Steel Wire Binding Screws Wired with Aluminum (Row A Receptacles)-^

Column

Number

Receptacle

Number

Torque

(kg-m)

Breakoff Tab Temperature

During Third

Cycled/

°C

Maximum Breakoff Tab Temperature Observed

°C

Number of Cycles

Completed

Cycle on Which

Maximum Temperature Occurred

1 1 0.023 58 - 58 20 3

2 0.023 52 59 650 330

2 1 0.023 55 56 280 240

2 0.023 60 110^ 390 210

3 1 0.069 56 56 20 3

2 0.069 51 57 650 480

4 1 0.069 55 58 280 73

2 0.069 60 66^ 390 210

5 1 0.069 53 56 670 73

6 1 0.138 55 55 20 3

2 0.138 51 58 650 330

7 1 0.138 55 58 670 500

8 1 0.138 53 57 670 500

9 1 0.138 54 57 670 500

1/ Ambient air temperature around wall was 24 ± 1°C (76 ± 2°F)

.

2/ For thermocouples installed on black wire side.

3/ After 319 cycles, a thermocouple was added to the white wire breakoff tab. The temperature on the 320th cycle was 88°C. It remained relatively constant through the 390th cycle.

4J After 309 cycles, a thermocouple was added to the white wire breakoff tab. The temperature on the 310th cycle was 67°C. It remained relatively constant through the 390th cycle.

22
Table 3. Wall Structure Test Results for Non-CO/ALR Receptacles with

Brass Wire Binding Screws Wired with Aluminum (Row B Receptac les) 1

/

Column

Number

Receptacle

Number

Torque

(kg-m)

Breakoff Tab Temperature

During Third

Cycles./

°C

Maximum Breakoff Tab Temperature Observed

°C

Number of Cycles

Completed

Cycle on Which

Maximum Temperature Occurred

1 1 0.023 99 199 280 68

2 0.023 78 88 110 78, 90

3 0.023 59 101 60 60

4 0.023 64 80 220 78

2 1 0.023 61 61 20 1, 14

2 0.023 51 55 650 53

3 1 0.069 56 56 20 3

2 0.069 51 56 650 480

4 1 0.069 55 57 280 73

2 0.069 51 58 390 210

5 1 0.069 53 56 670 500

6 1 0.138 56 56 20 3

2 0.138 50 54 650 480

7 1 0.138 56 58 670 500

8 1 0.138 55 58 670 500

9 1 0.138 55 57 670 500

1 / Ambient air temperature around wall was 24 ± 1°C (76 ± 2°F)

For thermocouples installed on black wire side.

23
Table 4. Wall Structure Test Results for Non-CO/ALR Receptacles with

Steel Wire Binding Screws Wired with Copper (Row C Receptacles)^/

Column

Number

Receptacle

Number

Torque

(kg-m)

Breakoff Tab Temperature

During Third

Cycle2/

°C

Maximum Breakoff Tab Temperature Observed

°C

Number of Cycles

Completed

Cycle on Which

Maximum Temperature Occurred

1 1 0.023 54 54 20 3

2 0.023 51 57 650 480

2 1 0.023 54 55 280 90

2 0.023 54 57 380 210

3 1 0.069 54 54 20 3

2 0.069 49 54 650 480

4 1 0.069 53 55 670 500

5 1 0.069 52 54 670 500

6 1 0.138 54 54, 20 3

2 0.138 49 54 650 480

7 1 0.138 54 54 280 3

2 0.138 52 54 380 60

8 1 0.138 53 54 670 500

9 1 0.138 52 54 670 500

1/ Ambient air temperature around wall was 24 ± 1°C (76 ± 2°F)

.

2J For thermocouples installed on black wire side.

24
Table 5. Wall' Structure Test Results for Non-CO/ALR Receptacles^yith

Brass Wire Binding Screws Wired with Copper (Row D Receptacles)

Column

Number

Receptacle

Number

Torque

(kg-m)

Breakoff Tab Temperature

During Third

Cycled/

°C

Maximum Breakoff Tab Temperature Observed

°C

Number of Cycles

Completed

Cycle on Which

Maximum Temperature Occurred

1 1 0.023 54 54 20 3

2 0.023 48 52 650 480

2 1 0.023 54 54 280 3

2 0.023 49 53 380 210

3 1 0.069 51 51 20 3

2 0.069 48 53 650 480

4 1 0.069 54 56 670 500

5 1 0.069 54 56 670 50

6 1 0.138 54 54 20 3

2 0.138 49 52 650 480

7 1 0.138 53 53 280 3

2 0.138 47 49 380 60

8 1 0.138 52 54 670 500

9 1 0.138 48 52 670 500

3./ Ambient air temperature around wall was 24 ± 1°C (76 ± 2°F)

2J For thermocouples installed on black wire side.

25
Table 6. Summary of Observations on the Performance of Non-CO/ALR Electrical Terminations in the Wall Structure

Screw Torque Screw Type of Wire

(kg-m)i:/ Composition #12 AWG Copper #10 AWG Aluminum

0.023 Brass No overheating ^ . 2/ Overheating—

Steel No overheating 3 / Overheating—

0.069 Brass No overheating No overheating

Steel No overheating 4 / Overheating—

0.138 Brass No overheating No overheating

Steel No overheating No overheating

1/ 1 lb-in = 1.,15 x 10

-2 kg-m.

2/ Overheating observed on 4 of 6 receptacles tested

.

3/ Overheating observed on 1 of 4 receptacles tested .

4/ Overheating observed on 1 of 5 receptacles tested

.

26
Table 7. Results of Cyclic Tests of CO/ALR Receptacles

from Four Manufacturers

Breakoff Tab Temperatures

CO/ALR

Manufacturer

Specimen

Number

Initial

Resistance

(milliohms)

First

Cycle

°C

30th

Cycle

°C

140 tl Cycli

°C

1 1 0.40 31 32 33

2 0.40 32 32 34

3 0.41 32 32 34 4 0.36 32 33 34

5 0.35 33 33 35

6 0.38 33 34 36

2 1 0.24 34 36 37

2 0.26 33 34 36

3 2.30 44 44 46

4 0.29 33 33 34

5 0.35 33 33 34

6 0.30 32 32 33

3 1 0.49 33 33 34

2 0.46 34 33 34

3 0.55 33 34 34

4 0.49 33 33 34

5 0.67 36 36 37

6 0.55 35 36 37

4 1 0.51 37 38 37

2 0.54 36 38 36

3 0.54 34 37 34

4 0.56 36 37 34

5 0.54 34 37 34

6 0.52 34 36 34

27
Table

8.

Effect

of

Applied

Torque

on

Resistances

Across

Newly

Made

Terminations

Points

of

CO/ALR

Duplex

Receptacles

from

Four

Manufacturers.^

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>> H

U

CL) T3

CL 0) CL C O -H O ^

Xl

<UU

•H

U

0> X

CL QJ CL Ci O *H

B

d

c: •H X

E (U d c

r—I *H < ^

u

<U X)

cl a) cl u

o -H u ^

B

d

a

•H X

6

d ci

i—I *H <

M

0) X)

CL (U CL L-i O -H O ^

X

<u

Ci

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a)d

cr

CiO'"". Hcm|

S 9<D I Ci 00 O ^

CO W

O rH C M

M-d M-(O

nJ

<u , Ci CN

I <U C

0) Ci a o

c

00

•H CL

CO CL

<0 *H

Ci Ci

CO <U

CU Cl

i—I o

a co

cl cu (U rC

CU *H

Ctf <u

28
Table 9. Effect of Applied Torque on Resistances Across Newly

Made Terminations Points of Non-CO/ALR Duplex Receptacles

V

Resistances (milliohms) for Non-CO/ALR Receptacle Type

Screw Torque Aluminum Copper Aluminum Copper

(kg-m)—' Wired Wired Wired Wired

0.023 1.83 0.83 2.06 1.30 0.046 1.13 0.77 1.56 1.05 0.069 0.88 0.72 1.21 0.89 0.092 0.79 0.69 1.09 0.87 0.115 0.75 0.68 1.02 0.80

0.138 0.71 0.68 0.95 0.73

0.161 0.67 0.66 0.86 0.69

0.184 0.65 0.64 0.81 0.68 0.207 0.62 0.70^ 0.68 0.64 0.230 0.60 — 0.64 0.62

Resistances include breakoff tab and 2 wire /connect or terminations

2J 1 lb-in = 1.15 x 10 ^ kg-m.

3/ Type 1 receptacle contained brass wire binding screws.

4/ Type 2 receptacle contained steel wire binding screws.

5/ Screws thread stripped at 0.207 kg-m.

29
Table

10.

Calculated

Resistances

of

Breakoff

Tabs

and

Termination

Points

I,

CJ-4 <4-1

CD o

03

U

CD *H U ^

PQ

a

cd

cd <D d u

•H *H a 3

cd

m

H c>

cd

0) CD a m

-h

H 3

cda

CD <D a a

0)

ctfH

ON rH CM o CM ON r- On UO <r CO CD <r CO ON ON vO CO O O uo vO vO UO U

co CO CO CO i-H i—1

r—1 l—1

CM CM CO CO

d

00 o O o o O O o o O O o o •r4doOou

vo ON o CO CO ON uo 00 CM CM •<r i-H cm i—H O 00 vo <r ON o 4n kO < CO CO <f CO 1 1 T—1 O rH CM CM CM CO

CO o o o o o o o o o o O o 4—1 r-» d

•H

<DO

U

a

d

00

X

•rH

d

fi* cd d Q o O

CJ 4-J vO uo CO vo <r r- co 1"- CO O o rH rH CO <r CO CM vo uo r^. r*. uO CO o < I—1 i—1 CM rH o o O O o o O o -U

CO o o o o O O O O o o o O < 4-1 C

co •H

4H

O

d

a

•Ho d

Cl CD

(D e 3

CM CM 00 ON CO vO i-H i-H 00 <r ON

O 4-1 CM 00 CM o <3- co rH o rH CM (D i—1 rH CM t—1 O O o o rH rH rH o <4H JC o o o o o o o o o o o o X CO

(D CD U a d d

CO CD

cd

p

CD CD a <4H

<4-4 CO •rH cd X) e a a i a B O- a d d d d d d o o d u a u d o d u d u d u u p

•rH 0) •H CD •H CD •H (D •H CD •H 0)

X XJ

a Cl e aB Cla

a

B cl s CL

d cl

d cld Pd cld cl o CL CD CD «—i o r—1 o rH O «H o rH O rH O 00 00 < cj < CJ < CJ < cj < CJ c CJ cd cd u 4-J 1—1 rH o o

/—

N > > ct)

co 3 3 a

B

CD (D o o u P u u

CJ CJ <4-4 <4-4 co CO X X U)

I—1i-H CM CO (D CD

CO <D 4-J 4-* cd CD CD 0) CD CD cd cd H Pi U cl CL CL CL 1—1 i—i J PO CO >> d d < H H H H u CJ i—i i—i o rH o CM pi Pi Pi P1

cd cd cj CJ hJ kJ L CJ CJ 1 CD 1 CD < < < < d a d a '

o o o O o o 

H H CJ CJ CJ CJ ^ 1

30
||3S-1 14A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLIC ATION OR RHPORT NO. NBSIR 76-1184

2. Gov’t Accession

No.

title ano subtitle:

Performance of Branch Circuit Electrical Terminations of

Copper and Aluminum Non-Metal lie Sheathed Cable

3. Recipient’s Accession No.

5. Publication Date January 1977

6. Performing Organization ( ode

. AUTHOR(S)

Larry W. Masters, Elizabeth J. Clark and Edward J. Embree

8. Performing Organ. Report No.

PER EORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

2. Sponsoring Organization Name, and Complete Address (Street, City, State, ZIP) Naval Facilities Engineering Command, Dept, of the Navy,

Washington, DC 20390; Directorate of Civil Engineering, U.S.

Air Force, Washington, DC 20330; Office of Chief of Engineers,

U.S. Army, Washington, DC 20314

13. Type of Report & Period Covered

Final Report

14. Sponsoring Agency Code

5. SUPPLEMENTARY NOTES

6. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) A study was performed to provide the Tri-Services Committee on Building Materials with

guidelines regarding the use of aluminum branch circuit wiring in military buildings.

The first part of the study consisted of identifying military bases which contain

buildings with aluminum wired branch circuits. Personnel at a number of the bases

were contacted in order to estimate the extent of observed problems. Laboratory

tests were performed on CO/ALR and non-CO/ALR duplex receptacles wired with both

aluminum and copper non-metallic sheathed cable. Overheating of aluminum wired

termination points was observed with some receptacles in a current cycling test using

non-CO/ALR receptacles at screw torque levels of 0.023 and 0.069 kg-m (2 and 6 lb-in).

Aluminum wired non-CO/ALR receptacles tested at 0.138 kg—m (12 lb— in) screw torque

showed no signs of overheating and copper wired non-CO/ALR receptacles showed no

signs of overheating regardless of screw torque.

This report presents the findings of the study and includes guidelines regarding the

use of aluminum branch circuit wiring in military buildings.

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 wiring; branch circuits; copper wiring; military buildings.

18. AVAILABILITY [XX Unlimited 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

For Official Distribution. Do Not Release to N 1 IS UNCLASSIFIED

33

Order From Sup. of Doc., U.S. Government Printing Office Washington, D.( . 20402. SD Gat. No. C13

20. SECURITY CLASS

(THIS PAGE)

22. Price

[X 1 Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151 UNCLASSIFIED

$4.00

USCOMM-DC 29042-P74
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