Reference NBS

Publications blftSM

NBSIR 81-2347

Field Measurement of Branch

Circuit Wire Temperatures

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Equipment Division

Washington, DC 20234

September 1 981

Issued November 1981 —ucluu

I i

Prepared for: The U.S. Department of Energy

Washington, DC 20461

ATIONAL BUBEAV

OV STANDA BUS LIBRARY NBSIR 81-2347

FIELD MEASUREMENT OF BRANCH

CIRCUIT WIRE TEMPERATURES

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Equipment Division

Washington, DC 20234

September 1 981

Issued November 1981

Prepared for: The U.S. Department of Energy

Washington, DC 20461

/4 /

Thomas K. Faison

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
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ABSTRACT

The National Bureau of Standards (NBS), under the sponsorship of the U.S. Department of Energy (DoE), planned and conducted a program to monitor temperature excursions of residential branch circuit wiring under field conditions.

This program was conducted to develop a field data base needed to determine the prevailing conditions in the field and to respond to various assertions that

the encapsulation of branch circuit wiring within thermal insulation is a potential hazard. It has been demonstrated through previous laboratory investigations that buried wires, when operated continuously at rated cimpaclty, will

exceed the thermal limit established by the National Electrical Code (NEC).

Approximately 2,800 circuits in 667 residences were monitored through a volunteer program with the utilities. The results of the study show that slightly

more than one-third of the circuits monitored operated at or above the thermal

limit established by the NEC, 60°C (140°F). Thermal distributions are shown

for variables such as: region, season, and age.

Key words: branch circuit; electric wire; field measurements; temperature

excursions; thermal insulation.

ill
PREFACE

This is one of a series of reports documenting National Bureau of Standards

(NBS) research and analysis efforts in developing energy and cost data. The

data supports the Building Energy Conservation Criteria Program sponsored by

the Office of Buildings and Community Systems, U.S. Department of Energy (DoE).

The work described in this report was supported by DoE/NBS Task Order No. A008-BCS under Interagency Agreement No. EA 77 A 01 6010.

iv
TABLE OF CONTENTS

Page

LIST OF FIGURES AND TABLES vl

1. INTRODUCTION 1

2. TECHNICAL APPROACH 2

2.1 Development of Thermal Indicators 2

2.2 Participation by Electric Utilities 2

2.3 Reporting and Analysis of Data 4

3. RESULTS 5

4. CONCLUSIONS AND RECOMMENDATIONS 8

5. ACKNOWLEDGEMENTS 8

6. REFERENCES 9

7. APPENDICES

A. Electrical Systems Check Points 17

B. Pamphlet In Field Measurements of Wiring Temperatures 18

V
LIST OF FIGURES AND TABLES

Page

Figure 1. Profile of wire temperature rise when encapsulated in

thermal insulation 10

Figure 2. Thermal indicator developed to measure branch circuit

wire temperatures in the field 11

Figure 3. Distribution of Indicated wire temperatures for all circuits

monitored 12

Figure A. Distribution of indicated wire temperatures as affected by

seasonal exposure 13

Figure 5. Distribution of indicated wire temperatures for those wires

covered with insulation and those either on or above the thermal insulation 14

Figure 6. Distribution of indicated wire temperatures near lighting

fixtures 15

Figure 7. Distribution of age of electrical systems monitored 15

Figure 8. Thermal distribution of branch circuit wire temperatures as a function of geographic regions 16

Table 1. Thermal Distribution Within Specific Age Increments (percent) 6

Vi
1 . INTRODUCTION

The National Bureau of Standards (NBS), under the sponsorship of the Department

of Energy (DoE), planned and conducted a program to monitor maximum temperature

excursions of branch circuit wiring under field conditions. This program was carried out to gain Information on In-service temperatures of branch circuit

wiring and to respond to the uncertainty that encapsulation of branch circuit

wiring within thermal insulation Is a potentially serious hazard. Through

previous laboratory experiments It was known that the rise in temperature of branch circuit wiring, when burled In thermal insulation, could exceed the National Electrical Code limit.

The National Electrical Code [1] requires that branch circuit wiring of the type generally found in residential applications be operated at temperatures

not exceeding 60°C (140°F). Under normal operating conditions, the maximum

rated continuous current allowed by the overcurrent protection device Is 110 percent of Its rating. A 20 ampere fuse or circuit breaker would be allowed

to operate continuously at 22 amperes. The overcurrent protection device could,

based upon the test standards for performance, operate without breaking the circuit for up to one hour at 135 percent of Its rating (27 amperes for a 20 ampere device [2, 3]). Under these loading conditions. It has been shown in

the laboratory [4] that the 60°C limit will be exceeded when the full ampacity

rating of the wire is applied to the conductor burled in thermal Insulation.

The temperature rise for selected wire sizes as a function of time under laboratory conditions Is presented in figure 1. The objective of the field measurements was to gain information on the actual maximum temperatures experienced

In the field under general usage conditions when the branch circuits are Installed or burled in thermal insulation.

1
2. TECHNICAL APPROACH

2.1 DEVELOPMENT OF THERMAL INDICATORS

In planning for the collection of field data on maximum temperatures produced

in the use of branch circuit wiring, it was necessary to identify or develop a cost-effective means of measuring temperatures of the wiring under conditions

of general use. Off the shelf data acquisition methods of sensing and logging

of temperature data as a function of time and load were available at the time the project was planned which could record time history and extent of thermal

excursion. The device was investigated but found to be far too expensive for

the scope of the proposed project.

Requirements for only the temperature indicators included: dependability, low cost (because of the large number to be used) and assurance that there would

be no degradation effects upon the wire to which the indicator was attached.

Several methods of measurement were considered prior to arriving at the final

selection. A commercially available adhesive-backed strip having thermal indicating phase change or color change material was investigated. Because of the limited range, cost, the possibility of leaving a residue of adhesive on the wire, and the potential for damage during the retrieval, the tape-on indicators were not selected. The indicator finally selected, custom designed by NBS staff

and a local specialty company, was made of a helical plastic strip with six waxes contained in metal eyelets. The waxes were color coded and were formulated to melt at discrete temperatures within the temperature range of Interest.

A series of tests was carried out to check the Indicated and actual melting

temperatures of the waxes and correlation was found to be acceptable within

3-A°F (1.6-2.2®C) of the indicated temperature. These indicators were given the name of thermal indicating flexible strips (TIFS). The Indicator is shown in

figure 2. Numbered identification tags were supplied with each indicator so that the records could be kept on individual indicators. The helical split in

the plastic strip allowed the indicator to be wrapped around the branch circuit

cable. The normal configuration of the indicator when wrapped around the cable

caused the waxes to be very close to the surface of the cable. The close

proximity of the waxes to the cable surrounded by thermal insulation provided

reasonable assurance that the cable temperature was near the Indicated temperature. Because there is not perfect contact between the waxes and the cable,

the cable temperature may be several degrees higher than indicated by the melted wax.

2.2 PARTICIPATION BY ELECTRIC UTILITIES

In order to carry out the program in a cost-effective manner and provide

representative distribution in the several geographic regions of the U.S. many

utilities across the country were contacted to gain an indication of interest

in voluntarily participating in the program of field temperature measurements.

It was planned that approximately 2,000 homes could be reached through a voluntary program involving the utilities. In each of the homes three to five indi- cators were to be placed on the wiring, thus the data base would be of significant size and geographically dispersed to give representative findings. A

meeting was called by DoE and NBS in March 1979 to describe the program and
discuss its objectives with the utilities. It was proposed that NBS would

supply the participating companies with the necessary field measurement materials and pamphlet for recording data (see Appendix B). The staff of the utility

companies would Install the temperature indicators on the branch circuits,

record specific data concerning the electrical system, retrieve the indicators

at specified Intervals, and return the indicators with the supporting data to NBS for analysis and final reporting.

The utilities which responded and participated in the program by installing and

retrieving the indicators include:

o Louisiana Power and Light Company

New Orleans, Louisiana

o New Orleans Public Service, Inc. New Orleans, Louisiana

o Public Service Company of Colorado

Denver, Colorado

0 Delmarva Power and Light Company

Salisbury, Maryland

o Dallas Power and Light Company

Dallas, Texas

Detroit Edison Company

Detroit, Michigan

o Public Service Company of New Hampshire

Manchester, New Hampshire

o Tennessee Valley Authority

Chattangooga, Tennessee

o Georgia Power Company

Atlanta, Georgia

o Philadelphia Electric Company

Philadelphia, Pennsylvania

o Gulf States Utilities

Beaumont, Texas

Q New York State Gas and Electric Company

Binghamton, New York

3
l.i lyiPoRTINO AND ANALYSIS OF DATA

The data provided by these utility companies was accepted by NBS without

screening the quality of input, some of the supporting data was very complete

and some responses had no supporting data (age, information on electrical

systems, etc.). Because of the amount of data and the problems of contacting

individuals in the field, along with problems of relying upon their memory for information, it was decided to accept the data on an "as received" basis with

no followup. Thus, there was no control on quality of the data beyond the instructions provided by the NBS pamphlet to individual companies participating

in the program. The individuals who collected the data for the utility companies did a commendable job of installing and retrieving the devices and recording

pertinent data.

Each of the thermal Indicators returned to NBS was analyzed to determine the maximum temperature within the range of 122 to 190 °F to which the indicator had been exposed. Each data pamphlet which accompanied the indicators was also

reviewed. The information was summarized to form the support data base and

Included such things as: maximum temperature for the branch circuit (indicated

by the melted wax); age of the wiring system; amount and type of thermal insulation; and information on the electrical system (type and size of overcurrent protection devices and wire systems, when provided). Generally, the installer

identified the location of the indicators on a diagram so that they could be found later for retrieval. Occasionally, Information such as the particular

circuit (HVAC, fan, light, etc.) on which the indicator was located was also

given.

4
3. RESULTS

From the total of 667 houses which were monitored in the program, 2824 thermal

indicators were returned. The majority of the houses had four individual

indicators installed on branch circuit cables generally in the attic space. The distribution presented in figure 3 represents the total sample of all indicators returned by the participating utilities. The major finding from

the analysis of this plot of wire temperature distribution is that 38 percent

of the circuits monitored were operating for some undetermined period of time at or above the 140 °F (60°C) NEC temperature limit. As indicated in the illustration, the largest individual segment of maximum temperatures was that

of the 140°F (bO^C) temperature range - 30 percent of the total sample; eight

percent of the total sample equalled or exceeded the 155°F (68.3°C) temperature indication.

The seasonal effect upon observed maximum wire temperature was of interest and

is illustrated in the distribution shown in figure 4. A distinct shift in the

distribution can be observed between the cooler months - March through October

- and the full year exposure. For the exposure which includes the warmer

summer months, there is a shift in the distribution toward the higher temperatures .

Occasionally, an indicator was installed on a wire which was indicated as not being covered with insulation. Approximately 10 percent of the indicators were

noted as being Installed on or above the insulation. Figure 5 presents the distribution of the observed maximum wire temperatures for wires covered with

thermal Insulation and those either on or above the thermal insulation. For

this very limited set of data the temperature distributions are very similar

for the wires covered (surrounded) by thermal insulation and those either in

free air or placed on top of the thermal insulation.

The supporting data reported that some of the Indicators were located near

light fixtures (within 12 inches of the fixtures). These data are plotted in

figure 6. At the higher end of the temperature range, a significant number of

the total high temperature readings are found to be near light fixtures. The

indicators which were located near light fixtures show that for all measured

wire temperatures greater than 180°F (82.2°C) but less than 190°F (87°C), one

out of five, or 20 percent, were near light fixtures, and 70 percent of all indicators recording temperatures of 190°F (87.8°C) or above were near light

fixtures

Figure 7 shows the age distribution of the wiring systems sampled. The average

of the wiring system was found to be 13 years. One-half of the samples fell

in the age bracket of 10 years or less with an even split between the 0-5 and

the 6-10 years. Approximately two percent of the samples exceeded 35 years of

age. The maximum age was indicated as being 72 years.

Having Information on the age of the wiring system along with the Indicated

temperatures, an analysis was made to determine if there is a correlation

between age of system and the thermal excursions. Table 1 presents the percentage distribution of temperatures for each of the age groups.

5
From the analysis of the wire temperatures as a function of age, it was found

that the age of the wire does not influence the observed thermal distribution.

Each of the age groups seem to have similar distributions.

To gain a feel for the affect of geographic location upon the temperature of the

branch circuit wiring, the temperature distributions of figure 8 are presented.

A major portion of the data base comes from the South/Southeastern states of

Texas, Tennessee, Louisiana, Mississippi, and Georgia. The North/Northeastern

states are comprised of the mid-Atlantic states (eastern shore) of Delaware,

Maryland, and Virginia in addition to Pennsylvania, New York, New Hampshire,

Michigan, and Colorado. There appear to be slight shifts to higher temperatures in both regions for the data which includes both summer and winter conditions. The South/Southeastern region has the more dramatic shift as might be

expected with the warmer summer exposures. The circuits monitored for the

South/Southeastern region, for the two exposure periods are approximately equal

in number. In the North/Northeastern region, there appears to be only a slight

shift to higher temperatures during the longer exposure period. The circuits

monitored for the longer period numbered approximately 20 percent more than

those monitored for the winter period only. This difference in data base size

could account for what appears to be a slight shift.

Table 1. Thermal distribution within specific age increments (percent)

1 r

1 Age 1

1 Increment | TEMPERATURES ("F)

1 (years) |

1 1 <122 H22 >133 >140 >155 M80 >_190

1 I

i i

1 1 <133 <140 <155 <180 <190

1 1 23 26.5 23 26.5 0 1 0

1 26-30 i

1 1 17 26 22 30 4 1 0

1 21-25

[ 22 20 22 31 3 1.5 .5

] 16-201 24 30 20 28 6 1.5 1

1 11-15 i

1 1 26 27 18 33 3 2 1

1 6-10 1

1 I 23 23 22 31 8 2 .5

1 0-5

1 17 25 23 27 6 1.5

6
The diversity of electrical loads patterns cannot be considered in the analysis of the data since the frequency, magnitude, and duration of the load

was not measured. This study provides only the maximum temperature experienced. There is no indication of the duration of the exposure at peak conditions. It is possible that the maximum temperature could have been a relatively short period* or it could have been a gradual buildup and sustained

for a considerable time period. It is possible and Indeed probable that some

of the indicators were Installed on circuits that were Inactive for the total

period, or at least drawing minimal loads during the period of test. A few

indicators, on the other hand, were reported to have been installed on circuits

drawing heavy loads, such as central air conditioning units in hot climates.

It was apparent, in some of these cases, that the length of exposure to these

heavy loads was over an extended period.

From the data collected in this "pilot study", there were very few cases which

could be classified as an immediate hazard. In one residence the Insulation

batt material was discolored from the heat of the wire. In another, heat from

the wire caused the resin sap to drip from the rafter to which the wire was

attached. The Installers noted these findings and advised the homeowner of the need to take corrective measures. As Indicated earlier, many of the Indicated higher temperatures resulted from heat generated by light fixtures.

Several of the higher temperatures were caused by combination heater/ventilator/

light fixtures. Care should be taken to prevent thermal insulation from coming

into contact with the fixture housings. Insulation if combustible, could present a potential fire hazard if placed in contact with lighting fixture. Also,

the thermal resistance of the insulating material can cause a build up of temperature if the heat generated by the lamp is not allowed to dissipate

through convection.

From the supporting data on the electrical system, there was sufficient data

on wire size, type of wire, and breaker or fuse size to gain some insight on

the issue of oversized overcurrent protection devices. It has been reported

in a recent investigation [5] for the Community Services Administration (CSA) that a substantial number of houses in the Weatherlzation Demonstration Project

had oversized overcurrent protection devices, i.e., a fuse or circuit breaker

of a larger size than required for the size wire used in the circuit. Of the total 667 residences reported, only 172 submittals had enough Information on

the electrical systems to assess compatibility of overcurrent protection and wire size. Of the 172 systems, there was evidence that 64 had at least one circuit with an oversized circuit breaker or fuse, thus there was a 37 percent occurrence of oversizing of fuses or circuit breakers for this small sample of

residential buildings. The CSA study indicated that 44 percent (two sets of

data) of the houses Included in that study had at least one circuit with an oversized fuse or circuit breaker. The age of systems was compared to the occurrence of oversizlng of overcurrent protection devices in the 172-house

sample and was found not to be a factor.

* The rise to near-equilibrium, or peak temperature conditions found in

laboratory experiments and computed temperatures from analytical modeling

required time intervals greater than 0.5 hours.

7
Analysts that "blindly" use this data base must do so with the knowledge that

the data base is subject to uncertainties which cannot be resolved. This statement in no way is meant to reflect on the character of the data source

but is Intended to make the point that there was no quality control on the data acquisition procedure. The sampling of homes in this "pilot project"

does not satisfy the statistical criteria for random sampling. There are regional biases because the volunteering utilities happened to fall primarily

in the eastern half of the nation. The information provided, although the best known to exist, was not complete with respect to individual data reports.

Some reports were very complete and some submittals were returned with only

the indicators and very little supporting data.

4. CONCLUSIONS AND RECOMMENDATIONS

It is evident from this study that there is a significant number of residential

branch circuits operating at or above the temperature limit of 140°F (60°C)

recommended by the National Electrical Code. The data from field measurements

indicated that at least 38 percent of the circuits monitored were operating at or exceeded the NEC temperature limit. Exceeding the thermal limit is technically a violation of the code. Many jurisdictions adopt the NEC as part of

their building code; thus any violations to the NEC necessarily become building

code violations in those jurisdictions. The severity of the hazard that may be posed by the violation is yet unknown. It is felt that operation of the branch

circuit wiring at temperatures above the recommended 140 °F (60°C) limit may, over the long term, cause problems of degradation of the electrical insulating

material. Future research should be directed toward measurement and better

understanding of the degradation process as may be caused by the buildup of heat. Both physical and electrical performance of the branch circuit wiring

must be investigated.

From analysis of the seasonal data the hot summer temperatures in the Southeastern states appeared to have some small effect upon the temperature

distribution. The temperature distribution which Included summer exposure

showed a slight shift toward higher temperatures.

Because of the small data base and the lack of controls on the sampling

techniques, further extrapolation of the material discussed in Section 3 "Results" is discouraged.

5. ACKNOWLEDGEMENTS

The author wishes to acknowledge the contributions of Dr. Lawrence S. Galowin

of the Center for Building Technology, NBS, and Ms. Shelly Launey of the Department of Energy for their efforts in developing and planning the program.

NBS' Dr. Galowin, and Mr. Henry Hahn of ARTEC Corporation are recognized for their development of the thermal indicating flexible strips (TIES) which

proved to be a very effective measuring tool. To the many field workers with

the utility companies, sincere appreciation is expressed in addition to management of the Individual companies who volunteered their services.

8
6 . REFERENCES

[1] National Electrical Code, 1981 Edition, National Fire Protection

Association 470, Boston, Massachusetts.

[2] U.L. 198.5, Plug Fuses, Underwriters Laboratories Inc., May 1973.

[3] U.S. 489, Moulded-Case Circuit Breakers and Circuit Breaker Enclosures,

Underwriters Laboratories Inc., November 1972.

[4] Exploratory Study of Temperatures Produced by Self-Heating of Residential

Branch Circuit Wiring When Surrounded by Thermal Insulation,

R. W. Beausoliel, W. J. Meese, and L. S. Galowin, NBSIR 78-1477, National

Bureau of Standards, July 1978.

[5] Electrical Aspects of the CSA/NBS Weatherlzatlon Study,

Marianne P. Valshnav, NBSIR 81-2203, National Bureau of Standards,

January 1981.

9
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Idol 3dniVll3dW3i 3dlM

Figure 1. Profile of wire temperature rise when encapsulated in thermal insulation

10

Figure

1.

Profile

of

wire

temperature

rise

when

encapsulated

in

thermal

insulation
THERMAL

INDICATING

FLEXIBLE

STRIP

ITIFSI

CD CO m CO

CM CO CO

B 1 1

B CM CO m

CM CO m

in m

UJ o ®

C9 flo

CD LU

oe eo ^

11

Figure

2.

Thermal

Indicator

developed

to

measure

branch

circuit

wire

temperatures

in

the

field
CIRCUITS

MONITORED

SUMMARY OF ALL INDICATORS

900

800

700

600

500

300

200

100

<122 2122 2133 2140 >155 >180 >190

<133 <140 <155 <180 <190

INDICATED TEMPERATURE |°F|

Figure 3. Distribution of indicated wire temperatures for all circuits monitored

12
SEASONAL EFFECTS UPON WIRE TEMPERATURES

600 -

500 -

400 -

300 -

200 -

100 -

WINTER MEASUREMENTS

, (first retrieval - liK Oct.-March|

WINTER & SUMMER

MEASUREMENTS

(second retrieval -

Oct.-Aug.)

122 >122 >133 >140

c133 <140 <155

;155 >180 >190

180 <190

INDICATED TEMPERATURE (°FJ

Figure 4. Distribution of indicated wire temperatures as affected by

seasonal exposure

13
CIRCUITS

IVIONITOREO

SUMMARY OF INSULATED vs. UNINSULATED INDICATORS

700

600

500

400

300

200

100

^ BURIED IN

THERMAL

INSULATION

UNINSULATED

<122 >122 >133 >140 >155 >180 >190

<133 <140 <155 <180 <190

INDICATED TEMPERATURE (°F)

Figure 5. Distribution of indicated wire temperature for those wires covered

with insulation and those either on or above the thermal insulation

14
INDICATORS LOCATED WITHIN 12” OF LIGHT FIXTURES

<122 >122 >133 >140 >155 >180 >190

<133 <140 <155 <180 <190

INDICATED TEMPERATURE [°f]

Figure 6. Distribution of indicated wire temperatures near lighting fixtures

AGE DISTRIBUTION OF WIRING SYSTEMS OBSERVED

(age given for 687 houses)

AVERAGE AGE: 13 yrs.

6-10 11-15 16-20 21-25 26-30 31-35 >35

AGE OF WIRING SYSTEM (years)

Figure 7. Distribution of age of electrical systems monitored

11
CIRCUITS

K^ONITORED

r

r—

SOUTH/SOUTHEASTER^ REGIQU

i

200 !-

100

E

i

i

i

i

I

mnm i^EASORE^Efiis

(Oct.-^arch)

i WINTER & SUMMER

i MEASUREMENTS (IQ months)

HORTH/NORTHEASTERPI REGiOl

=122 i122 >133 >140 >155 >180 >190

<133 <140 <155 <180 <190

<122 >122 >133 >140 >155 >180 >1

<133 <140 <155 <180

INDICATED TEMPERATURE (T)

Figure 8. Thermal distribution of branch circuit wire temperature as a function of geographic regions

16
APPENDIX A.

Electrical System Checkpoints :

Before adding thermal Insulation around existing wiring, the following

precautions should be taken (electrical modifications and/or Inspections should

be carried out only by qualified electricians).

° Make sure that the branch circuit of a given size wire Is protected

with the proper size fuse or circuit breaker.

° If screw base fuses are Installed In the residence, It Is recommended

that "Type S" fuses be used. This will prohibit larger size fuses

from being mistakenly used.

° Check the Illumination system - celling fixtures, wall fixtures, and

moveable lamps - to determine If they are over-lamped, that Is, do

they have lamp bulbs larger than recommended. If so, the lamp

should be replaced with the proper size bulb.

“ Check recessed lighting fixtures to make sure that thermal Insulation

Is not allowed to touch the fixture housing (three-inch minimum

clearance required)

° If the coating of the wire, the dielectric Insulating material. Is cracked or appears to be brittle, expert opinion should be obtained

before making the decision to cover the wire with thermal Insulation.

It Is generally recommended that wire In a deteriorated condition

be replaced.

17
Appendix B Pamphlet on Field Measurements of Wiring Temperatures

18
UNITED STATES DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington, O.C. 20234

May 1979

MEMO TO: Participants in Field Measurements of Wiring Temperatures

Your participation in assisting DoE/NBS in obtaining field measurements

of wiring temperatures in thermally retrofitted dwellings is greatly

appreciated. The correlation or variations between laboratory test

results with actual electrical loading conditions under normal usage

conditions in dwellings is critical to the success of the project.

The attached information package and forms which are supplied consist of:

A. Precautions

B. Instructions for Electrical Inspection Reports

C. Electrical Systems Inspection Forms

D. Temperature Indicator Mounting and Removal

E. Projected Schedule of Measurements

Also, a package of TIPS (temperature indicating flexible strips) and

numbered Identification tags are supplied. One form is provided for

each dwelling, the identification tag numbers must be noted in item

14 for each mounted TIPS. The dates on first page of the form D are filled in when the TIPS are mounted and removal date projected. The

actual removal date is entered when performed.

The safety of the installers, occupants of the dwellings and preventing

the introduction of new hazards are of foremost priority. Consequently,

where any situations develop which could be difficult to overcome it

is recommended the installation or searching for data to enter on the

forms be curtailed, i.e. do not fill out that portion of the form or stop installation of the TIPS. See the list of precautions.

The planning schedule for the groups are provided on attachment E

At the scheduled time intervals for removal of the TIPS the forms

and temperature indicators should be packaged together for delivery

to the above address.

FROM: Lawrence S. Galowin, Group Leader

Service Systems Program

Building 226, Room B306

National Bureau oT Standards

Washington, D.C. 20234

19
Mr. A.J. McCubbin

Baltimore Gas and Electric

P.O. Box 1475

Baltimore, MD. 21203

Mr. E.A. Hudge, Residential Manager

Consumer Service

Louisiana Power and Light Co.

P.O. Box 6008

New Orleans, LA 70174

Mr. J.F. O’Malley

Director of Marketing

Public Service Co., of New Hampshire

P.O. Box 330

Manchester, New Hampshire 03105

Mr. O.A. Dulle, Manager

Regional and Marketing Activities

Union Electric Company

P.O. Box 149

St. Louis, MO 63166

Mr. R.N. Arcari, Director

Central Commercial Services

Con Ed Company of NY, Inc,

4 Irving Place

New York, New York

Mr. E.G. Edison, Director

Residential Market Planning

The Detroit Edison Co.

2000 Second Avenue

Detroit, MI 48226

Mr. R. C. Bythewood

Assistant to the Vice President

Georgia Power Company

Atlanta, Georgia 30302

Mr. Dal J. Frandsen, Jr., Commercial Manager

Dallas Power and Light Co.

1506 Commerce Street

Dallas, Texas 75201

Mr. W.R. Coleman, Director

Residential and Commercial Services

American Electric Power Service

2 Broadway

New York, New York 10004

Mr. Richard Hallenus, Manager

Residential Division

New Orleans Public Service Inc.

P.O. Box 60340

New Orleans, LA 70160

Mr. William Bowers, Manager

Applications Department

Philadelphia Electric Company

P.O. Box 8699

Philadelphia, PA 19101

Mr, Dave R. Highland, Manager

Residential Department

Atlantic Electric Company

P.O. Box 567

Atlantic City, Ney? Jersey 08404

Mr. Jackson Mueller, Manager

Energy Conservation and Services

Pacific Gas and Electric Co.

77 Beale Street

San Francisco, California 94106

Mr, D.P. Kelley

New York State Electric and Gas

4425 Old Vestal Road

Binghamton, New York 13902

20
A. PRECAUTIONS

LOAD CENTERS, FUSE BOXES, WALL OUTLETS SHOULD BE OPENED BY ONLY

TRAINED STAFF AND/OR KNOWLEDGEABLE PERSONNEL.

CONSIDER POWER TURN OFF IVHEN MOUNTING TEMPERATURE INDICATOR FLEXIBLE

STRIPS (TIFS) PARTICULARLY IF VISUAL INSPECTION OF WIRING INDICATES

CRACKS OR SERIOUSLY AGED CONDITION (HARDENED, RIGID).

HANDLE WIRES WITH CARE - OLD WIRING MAY BE FRAGILE (ELECTRICAL INSULATION)

DO NOT CONTACT METAL DUCTS, PIPES, ETC., WHEN MOUNTING INDICATORS

TO ENERGIZED CABLES.

IN ATTICS DO NOT STEP ON GYPSUM OR PLASTER CEILINGS. PREVENT FALL THROUGH

USE PLATFORM OF WOOD PLANKS OR PLYWOOD SUFFICIENT TO SUSTAIN WEIGHT.

SUGGEST EYE PROTECTION, GLOVES, MASKS (PREVENT INHALATION OF FIBERS)

DO NOT SMOKE (PARTICULARLY IN ATTICS).

USE CARE WITH DROP LIGHTS TO AVOID CONTACT WITH OR RESTING ON ANY FLAMMABLE

MATERIALS OR THERMAL INSULATION - FLASHLIGHTS ARE GOOD SUBSTITUTES.

DO NOT USE OPEN FLAMES

TRY TO WORK IN A "BUDDY" SYSTEM.

DO NOT USE ELECTRICAL WIRES AS HANGER FOR LIGHTS, EQUIPMENT. DO NOT

USE WIRING AS A HANDHOLD.
B. INSTRUCTIONS FOR ELECTRICAL

INSPECTION REPORTS

PURPOSE OF INSPECTIONS

These electrical inspections are made to characterize electrical systems

in houses that are insulated.

ELECTRICAL DATA ASPECTS

The impact of thermal insulation on wiring systems is of concern,

(a) OVERFUSING

In residential occupancies branch circuits may be overfused

if wire sizes are larger than shown below. Wire sizes are usually marked with indelible stamp or pressed into the electrical

insulation.

Wire Size (AWG) Rated Size

of Fuse (in amperes)

Copper Aluminum

#14 #12 15

#12 #10 20

#10 # 8 30

If wiring size is not marked limit attempts to answer 3^C.

NOTE: Wires of a given size with some types of superior electrical insulations

may be rated at higher ampacities (current carrying capacity in amperes)

than shown above. However, nonmetallic-sheathed cable (romex) and

most other wiring used in houses (see C, Photographs) do not have these

superior electrical insulations.

(b) OVERLAMPING

Thermal insulation over surface-mounted ceiling lights is of concern. This is the reason for obtaining detailed information

on recessed and surface-mounted ceiling light fixtures. Unless

otherwise marked, most such light fixtures are overlamped if bulbs

larger than 60 watts are used.

RECORDING INFORMATION

A form on which to record information when marking electrical system inspections

is provided. Also provided are additional sheets on which to record notes

or comments. Please identify item on the form to which the comment applies.

Items No's are (1) through (14) and 3-A through 3-1, and 6-A through 6-M.

Blank sheets are provided to identify essential home plans, layouts and

locations of mounted TIPS.

22
INSTRUCTIONS CONCERNING SPECIFIC ITEMS FOR D

Fill out requested information above item 1, no names are requested.

Item (1) - SERVICE ENTRANCE CONDUCTORS

Please give information requested. Assess condition of conductors, their

fastenings, etc. Detail damage, any hazards, unusual situations, etc.

See Item 9.

Please estimate the length of service entrance cable which is inside of

the house. Indicate places within house (such as "unfinished attic',*

"exterior wall',' "interior wall',' etc.) where service entrance cables

are located. (We are concerned about heat dissipation after thermal

insulation is installed).

Item (2) - FUSE/CIRCUIT BREAKER ARRANGEMENT (See C Photographs)

Please draw sketch.

Example for fuse panel

Item (3) » BRANCH CIRCUIT INFORMATION

The cover of the fuse or circuit breaker panel (s) should be opened.

Information recorded for each circuit should be in accordance with

Che numbering on the fuse or circuit breakers in the sketch prepared

onder Item (2).

* Item 3-A - Type of Overcurrent Protection

Use the following symbols:

CB - Circuit Breaker

S - Type S Fuse

£ >, Edison Base Fuse

CART - Certridge Fuse

Identify any hazards, blown fuses, unusual conditions, etc. in Items 3-1 or on separate sheet.

23
Item 3-B Size of Fuse or Circuit Breaker (amperes)

Record the site of each fuse or circuit breaker presently used.

Item 3-C » Sire of Conductor

Please record (#14, #12, etc.) for each circuit.

Item 3“D “ Conductor Material

Use abbreviations:

C - copper

AL " aluminum

C"clad - Copper clad aluminum

Item 3”E - Insulation Material

Please try to determine if insulation is rubber or plastic (thermoplastic).

Use R for rubber, T for plastic.

Item 3-F - Wiring Method

Use symbols:

MM “ nonmetallic - sheathed cable (romex)

BX - armored cable

EMT - electrical metallic tubing

RC - rigid conduit

FMC - flexible metal conduit

Others - specify, use Item 3-I or separate (Item 9) if necessary.

Item 3-G - Grounding Conductor

Zadicate "y«s" or *'no*' for each circuit.

Item 3-H - Nominal Voltape

If circuit voltage is 110 to 125 indicate *'120", if circuit voltage is

220 to 240 (single phase) indicate ”240”. If circuit is three phase,

please indicate this. Most circuits will be ”120”.

Item 3-1 - Notes /Comments on Branch Circuit Items Listed Above

Indicate applicable information from Items 3-A through 3-H above. Identify

items being comBented on.

Example of filled out information

Circuit No. 3A 3B 3C 3D 3E 3F ' 3G 3H

Edison 15 Amp //14 Copper Plastic BX Armored 110

Fuse Sheath

24
Item (4) - BACK-UP/OTHER OVERCURRENT PROTECTION

List type, size and other applicable information on any fuses or circuit

breakers not listed in Item 3 above. Give appropriate details such as "current from circuits #1, 2, 3 and 4 pass through this fuseV

Item (5) - NAMEPLATE INFORMATION/CONDITION/LOCATION OF FUSE/CIRCUIT BREAKER PANEL

Please give any legible nameplate data and assess condition of panel. Detail

hazards, unusual situations, etc. Please indicate room (or basement) in

house where panel if located and indicate whether it is on an interior or exterior wall.

Item (6) - RECESSED AND SURFACE-MOUNTED CEILING LIGHTS

Please record data requested in Item 6-A through 6-M. Remove fixture

glass, etc., so that lightbulbs and other items can be observed (if feasible).

Item (6-A) - Location

Indicate room such as "kit" (kitchen). If in bedroom indicate specific

one, use Item 6-M if necessary.

Item (6-B) - Type of Fixture (Requires survey from within room(s) or living

areas under attic).

Only surface-mounted ceiling light fixtures of the types shown below

and recessed light fixtures are of interest:

TYPE A

TYPE B

25
Where there is considerable distance between lightbulbs and the ceiling

(such as with most chandeliers) do not list the fixture.

Use the following symbols;

R - Recessed light fixtures

A - Type A surface mounted ceiling fixture shown above

B - Type B surface mounted ceiling fixture shown above.

Item 6-C - Number of Lights

List the number of lights which can be used in the fixture.

Item 6-D - Size of Lightbulbs

List the wattage of each bulb now in the fixture. Use Item 6-M if necessary.

Item 6-E - Type of Bulbs

Are lightbulbs incadescent (use symbol I) , flourescent (use symbol F) or other (specify such as "heat" or "infrared")

,

Item 6-F - Scorching/Damage

Note if there is evidence of scorching or damage in fixture or ceiling or other surface above fixture. Indicate "yes" or "noV Detail any scorching

or other damage in Item 6-M or on separate sheet.

Item 6-G - Condition of Wiring

Examine and assess the condition of the fixture wiring. If there is

scorching or damage to the fixture wiring or to other parts of the fixture,

the ceiling, etc., be sure to also examine the wiring (including the building

supply wires) in the outlet box for the fixture. If the present condition

of the wiring is not satisfactory or "OK',' please give the details in

Item 6-M or on separate sheet.

Item 6-H - Size of Enclosure

Please indicate approximate length, width and depth dimensions, respectively,

of recessed and Type A surface-mounted ceiling light fixtures. If round,

indicate diameter and depth (such as 9 l/2"d x 3 3/A"). For Type B indicate

dimensions of glass or other bowl and its minimum distance to ceiling or other top surface.

Item 6-1 - Distance of Bulbs to Top Surface

Measure minimum dimension from top of bulbs to the ceiling or top surface

of the light fixture.

Item 6-J - Is Warning on Fixture?

Please indicate "yes" or "no'.' If "yes" please list warning in Item 6-M

or on separate sheet (i.e. "Do not use bulbs greater than 60 watts','" etc .

)

26
Item 6-K - Is Thermal Insulation Above Fixture Now?

Indicate "yes" or "no',' If "yes',' describe amount of coverage, any scorching or damage to insulation, outlet box, supply wiring, etc,, in Item 6-M or on separate sheet.

Item 6-L - Is Thermal Insulation Above Fixture Likely?

Indicate "yes" or "no" as to whether the addition of thermal Insulation would

cover the fixture or its outlet box unless precautions were taken. Generally,

fixtures in or on the surface of top floor ceilings are subject to being covered

by thermal insulation.

Item 6-M - Notes/Comments on Light Items Listed Above

If there is insufficient space for comments please use separate sheet of paper.

Item 9.

Item (7) - CONDITION OF BRANCH CIRCUIT WIRING

Please examine as much of the wiring as feasible and assess its general

condition. Detail any hazards or unusual conditions. Use Item 9 or separate sheet, if necessary.

If wiring appears to approach the condition of new wiring and does not have

fraying, cracking or other deterioration indicate "Good" or "G',' if no excessive fraying, cracking or other deterioration and wiring appears to

still be serviceable even though it looks old indicate "Satisfactory" or

"S',' if it is in such condition that it should be replaced indicate

"Unsatisfactory" or "U'.' If necessary indicate condition of each circuit.

Please indicate, if possible, whether grounding conductor is metallically

continuous to the fuse or circuit breaker panel. Please also indicate

whether receptacles have provisions to accept grounding-type attachment

plugs. If some receptacles are the grounding type and some are not,

please indicate locations of each type.

Item (8) - TEMPORARY/EXTENSION CORD WIRING

Please detail any unusual or extensive use of non-permanent wiring.

Item (9) - DETAILS ON OTHER ELECTRICAL HAZARDS

Please identify any other electrical hazard and their location. Some examples

of such hazards are:

® Loose/broken light fixtures

® Loss of electrical insulation or cracked electrical insulation around wires.

* Badly damaged/frayed wire

® Receptacles broken loose

“ Outside wires not of outdoor type

® Outside wire not properly buried or supported

® Shock hazard situations

“ Etc.

27
Two circuits of opposite polarity may share a common neutral. However, if two

circuits of the same polarity share a common neutral, the current in the

neutral will be the sum of the currents in the two circuits. Instances of

the current in the neutral conductors being large enough tc start fires have

come to our attention. Three-wire (with ground) cables were used for the

two circuits. If you see this situation please report it.

Items 10-13 - DWELLING INFORMATION

Item 14 - TEMPERATURE INDICATORS NUMBER RECORD

From "dog-tag" record numbers for each TIPS placed on wires.

28
c ELECTRICAL INSPECTION

DATE:

PROJECTED REMOVAL DATE:

ACTUAL REMOVAL DATE:

Dwelling Address : Inspection Performed by:

(1) SERVICE ENTRANCE CONDUCTORS (2) FUSE/CIRCUIT BREAKER ARRANGE^::::

Size

Material - Copper Alum.

Other (specify)

Norn. Voltage 110/120 220/240

Underground Overhead

Condition and Comments:

Sketch (see instructions)

(3) BRANCH CIRCUIT INFORMATION (SEE INSTRUCTIONS)

3-A 3-B 3-C 3-D 3-E 3-7

29
(3-1) Notes /Conjnents on Branch Circuit Itetns Listed Above

(4) BACK-UP/CTHER OVERCURRENT PROTECTION (see instructions):

(5) N;LMEPLATE INFORJIATION/CONDITION/LOCATION OF FUSE/CIRCUIT BREAKER PANEL;

(6) RECESSED AND SURFACE-MOUNTED CEILING LIGHTS

(6-M) Notes/Comnients on Lighting Items Listed Above:

(7-A) CONDITION OF BRANCH CIRCUIT WIRING:

(7-B) RECORD OBSERVATION OF CORROSION ON OR ABOUT SERVICE ENTRY BOX, JUNCTION

BOXES AND SWITCHES /RECEPTABLE PLATES DO NOT OPEN RECEPTACLE OR SWITCH BOXES.

(8) TEMPORARY /EXTENSION CORD WIRING (NUMBER OF ADD-ON WIRING CORDS)

30
(9) DETAILS ON OTHER ELECTRICAL HAZARDS;

SUPPLEMENTARY NOTES /COMMENTS ON ELECTRICAL SYSTE?-^ INSPECTION

(Please identify Items on "Electrical System Inspection" for which commenis

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10. Age of Dwelling years

Has home been rewired? Yes No If yes, when? ,

11. Has dwelling been retrofitted with thermal insulation? Yes No

If yes, indicate type ; Walls Attic . Rated ”R” value (s)

12. List major appliances (check if installed)

Refrigerator

Range (electrical)

Electric Clothes Dryer

Garbage Disposal

Dishwasher

Central Air Conditioner

Window Air Conditioner (s) How many?

Attic Fan

Freezer

Heating System (if electric) Where located?

Hot Water Heater (if electric) Where located?

Humidifier Where located?

13. Other Major Electrical Units (check or list)

Examples ; Space Heater

Hobby Shop

Attach Identification Tag to Temperature Indicator. List Locations

of Temperature Sensitive Indicator (Record number as tag is attached).

Attic, 5 9 9 9 9 9 Service box, , 9 9 9 9 9 9 Others , , , 9 9 9 9 /

Note: Groups of cables in close proximity under thermal insulation,

are also desirable.

32
FLOOR PLAN/WIRING

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Mark where wire Indicators are located and if enclosed or sitting on thermal

Insulation. Type of thermal insulation.
FLOOR PLAN/WIRING

Mark where wire indicators are located and if enclosed or sitting on thermal

insulation. Type of thermal insulation.

34
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I
D. TEMPERATURE INDICATOR-TIFS-MOUNTING

AND REMOVAL INSTRUCTIONS

The TIFS identification number tags are mounted to the coil by the "S" hook

enclosed in the transparent wrapper. The numbers are recorded under Item lA.

Mounting the TIFS is accomplished by either:

(a) Starting the end over the wire, slightly separting the end of the coil.

A twisting motion will cause the coil to wind around the wire. Care is

essential to keep the coil tip from "digging" into the wiring insulation,

(b) Untwist the coil TIFS in both hands and place against the wiring with

the "curling" toward the wire. Release the coil from one hand and restrain

the other end on the wire. The coil will tend to "snap" or wind around

the wire. A final twisting of the coil will complete the mounting.

Place the "S" hook and number tag away from the coil TIFS and wire.

Removal of the TIFS is accomplished by reversing (a) or (b) above. Leave

the number tag attached.

36
E. Planning Schedule

Projects Schedule of Measurements

i Utility Sample Size Approximate

Start Date

Approximate

Completion Date

Total Early Late 1 Early Group Late Group

1. Ga. Power 200 150

50

May 15 July 1 Aug 15

2. PG&E 500 400

100

May 15 July 15

Sept 1

3. Dallas

P&L

200 150

50

May 15 July 1 Aug 1

4. Louisiana

P&L

50 50 May 15 June 20 —

5. New Orleans 50 30 June 1 July 15

PS

20 ^ Sept 15

6. TVA 500 400

100

June 1 Aug 15

Sept 30

7. PS of NH 50 50 June 15 July 15

8. Con . Ed

of NY

50 50 June 15 Aug 1

9. Am Elec.P. 200 150

50

June 1 July 15

Sept 1 10. Union

Elec

50 50 June 1 July 1

11. Atlantic

Elec.

50 50 June 1 Aug 15

12. Phil. Elec. 50 50 June 15 Aug 1

13. Delmarva

Power

50 30

20

June 1 Aug 15

Sept 15

14. Detroit

Elec

50 50 June 1 July 15

37
NBS014A 'REV. 2 -ac) U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 81-2347

2. Performing Organ. Report No.1 3. Publication Date

1 October 1981

4. TITLE AND SUBTITLE

FIELD MEASUREMENT OF BRANCH CIRCUIT WIRE TEMPERATURES

5. AUTHOR(S)

Thomas K. Faison

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City, State. ZIP)

U.S. Department of Energy

1000 Independence Avenue, SW

Washington, D.C. 20585

10.

SUPPLEMENTARY NOTES

Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

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

bibliography or literature survey, mention it here)

The National Bureau of Standards (NBS), under the sponsorship of the U.S. Department

of Energy (DoE) , planned and conducted a program to monitor temperature excursions

of residential branch circuit wiring under field conditions. This program was conducted to develop a field data base needed to determine the prevailing conditions

in the field and to respond to various assertions that the encapsulation of branch

circuit wiring within thermal insulation is a potential hazard. It has been

demonstrated through previous laboratory Investigations that buried wires, when

operated continuously at rated ampacity, will exceed the thermal limit established

by the National Electrical Code (NEC). Approximately 2,800 circuits in 667 residences were monitored through a volunteer program with the utilities. The results of the

study show that slightly more than one-third of the circuits monitored operated at or above the thermal limit established by the NEC, 60°C (140°F) . Thermal distributions

are shovm for variables such as: region, season, and age.

12.

KEY WORDS (Six to twelve entries; alphabeti cal order; capitalize only proper names; and separate key words by semicolons)

branch circuit; electric wire; field measurements; temperature excursions;

thermal insulation

13. AVAILABILITY

Unlimited

I I For Official Distribution. Do Not Release to NTIS

f I Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

Order From National Technical Information Service (NTIS). Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

43

15. Price

$6.50

USCOMM-DC 6043-P80

I