Chromalox Heat Trace Design Guide

Insulation
Factor

Pipe Insulation TypePipe Insulation Type

Insulation
Factor

Glass fiber (ASTM C547) 1.00
Calcium silicate (ASTM C533) 1.48
Cellular glass (ASTM C552) 1.48
Rigid cellular urethane (ASTM C591) 0.64

Foamed elastomer (ASTM C534) 1.16
Mineral fiber blanket (ASTM C553) 1.16
Expanded perlite (ASTM C610) 1.90

A

Pipe Temperature (ºF)

Maintenance Temperature

0 10 20 30 50 60 70 80 90 100 110 120 130 140 150

Thermal Output (W/ft)

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

4.88

SRL10 & HSRL10

SRL8 & HSRL8

SRL5 & HSRL5

SRL3 & HSRL3

Cable Output
versus
Temperature

40

0 10 20 30 50 60 70 80 90 100 110 120 130 140 15040

Pipe Temperature (ºF)

SRL10 & HSRL10

Thermal Output (W/ft)

9

8

7

6

5

4

3

2

1

0

SRL8 &
HSRL8

SRL5 & HSRL5

SRL3 & HSRL3

Cable Output
versus
Temperature

Pipe Temperature (ºF)

Heat Output (W/ft)

21
20
19
18
17
16
15
14
13
12
11
10

9
8
7
6
5
4
3
2
1
0

15 W/ft

10 W/ft

5 W/ft

Cable Output
versus
Temperature

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230

0 50 100 150 200 250 300

Pipe Temperature (ºF)

SRM/E20 &
HSRM20

Power Output (W/ft)

24

20

16

12

8

4

0

SRM/E15 &
HSRM15

SRM/E10 &
HSRM10

SRM/E8& HSRM8

SRM/E5& HSRM5

SRM/E3& HSRM3

Cable Output
versus
Temperature

Pipe Heat Loss Calculations

1.Basic Heat Loss: After determining the difference between the ambient and desired pipe maintenance

temperature, T

, use Table 1 to figure the basic heat loss for the pipe size and insulation thickness.

m

2.Insulation Adjustment: Using Table 2, find the type of insulation being used and its insulation factor.

Table 1 Pipe Heat Loss Q

Nominal

Pipe Size,

in. (ID)

DegºF 40ºF 50ºF 60ºF 70ºF 80ºF 90ºF 100ºF 120ºF 140ºF 160ºF 180ºF 200ºF 220ºF 240ºF 260ºF

1

/2" W/ft 1.4 1.8 2.1 2.5 2.8 3.2 3.5 4.2 5.1 5.9 6.6 7.7 8.5 9.2 10.0

3

/4" W/ft 1.6 2.0 2.4 2.8 3.2 3.6 4.0 4.8 5.9 6.7 7.6 8.8 9.7 10.6 11.4
1" W/ft 1.8 2.3 2.8 3.2 3.7 4.1 4.6 5.5 6.8 7.7 8.7 10.1 11.1 12.1 13.2

11/2" W/ft 2.4 3.1 3.7 4.3 4.9 5.5 6.1 7.3 9.0 10.2 11.5 13.4 14.8 16.1 17.4

2" W/ft 2.8 3.5 4.1 4.8 5.5 6.2 6.9 8.3 10.1 11.6 13.0 15.2 16.7 18.2 19.7

21/2" W/ft 3.2 4.0 4.8 5.6 6.4 7.2 8.0 9.6 11.8 13.4 15.1 17.6 19.4 21.1 22.9

3" W/ft 3.7 4.7 5.6 6.5 7.4 8.4 9.3 11.2 13.7 15.6 17.6 20.5 22.5 24.6 26.6
4" W/ft 4.6 5.8 6.9 8.1 9.2 10.4 11.5 13.8 16.9 19.3 21.7 25.3 27.8 30.4 32.9
6" W/ft 6.4 8.0 9.6 11.2 12.8 14.4 16.0 19.2 23.5 26.9 30.2 35.2 38.7 42.2 45.8

8" W/ft 8.1 10.1 12.1 14.1 16.2 18.2 20.2 24.2 29.7 33.9 38.2 44.4 48.9 53.3 57.8
10" W/ft 9.9 12.4 14.8 17.3 19.8 22.2 24.7 29.6 36.3 41.5 46.7 54.3 59.8 65.2 70.6
12" W/ft 11.6 14.5 17.4 20.3 23.2 26.1 29.0 34.8 42.6 48.7 54.8 63.8 70.2 76.6 82.9
14" W/ft 12.6 15.8 19.0 22.1 25.3 28.4 31.6 37.9 46.5 53.1 59.7 69.5 76.5 83.4 90.4
16" W/ft 14.3 17.9 21.5 25.1 28.7 32.3 35.9 43.0 52.7 60.2 67.8 78.9 86.8 94.6 102.5
18" W/ft 16.0 20.1 24.1 28.1 32.1 36.1 40.1 48.1 58.9 67.4 75.8 88.2 97.0 105.9 114.7
20" W/ft 17.7 22.2 26.6 31.0 35.4 39.9 44.3 53.2 65.1 74.4 83.7 97.5 107.2 117.0 126.7
22" W/ft 19.4 24.3 29.1 34.0 38.8 43.7 48.5 58.2 71.3 81.5 91.7 106.7 117.4 128.0 138.7
24" W/ft 21.1 26.4 31.6 36.9 42.2 47.4 52.7 63.2 77.5 88.5 99.6 115.9 127.5 139.1 150.7

1

/2" W/ft 1.1 1.4 1.7 2.0 2.2 2.5 2.8 3.5 4.1 4.7 5.5 6.2 6.8 7.4 8.0

3

/4" W/ft 1.2 1.6 1.9 2.2 2.5 2.8 3.1 3.9 4.6 5.2 6.1 6.8 7.5 8.2 8.9

1" W/ft 1.4 1.8 2.2 2.5 2.9 3.2 3.6 4.5 5.3 6.0 7.1 7.9 8.7 9.5 10.3

11/2" W/ft 1.8 2.3 2.8 3.2 3.7 4.1 4.6 5.8 6.8 7.7 9.1 10.1 11.1 12.1 13.2

2" W/ft 2.1 2.6 3.1 3.6 4.2 4.7 5.2 6.6 7.6 8.7 10.3 11.4 12.6 13.7 14.9

21/2" W/ft 2.4 3.0 3.5 4.1 4.7 5.3 5.9 7.4 8.7 9.9 11.7 13.0 14.3 15.6 16.9

3" W/ft 2.7 3.4 4.1 4.8 5.4 6.1 6.8 8.6 10.0 11.4 13.5 15.0 16.5 18.0 19.4

4" W/ft 3.3 4.2 5.0 5.8 6.6 7.5 8.3 10.5 12.2 13.9 16.4 18.3 20.1 21.9 23.7

6" W/ft 4.5 5.7 6.8 7.9 9.0 10.2 11.3 14.2 16.6 19.0 22.4 24.9 27.3 29.8 32.3

8" W/ft 5.6 7.1 8.5 9.9 11.3 12.7 14.1 17.8 20.7 23.7 27.9 31.0 34.1 37.2 40.3
10" W/ft 6.8 8.0 10.3 12.0 13.7 15.4 17.1 21.5 25.1 28.7 33.9 37.6 41.4 45.1 48.9
12" W/ft 8.0 10.0 12.0 14.0 16.0 18.0 20.0 25.2 29.4 33.6 39.6 44.0 48.4 52.8 57.2
14" W/ft 8.7 10.9 13.0 15.2 17.4 19.5 21.7 27.3 31.9 36.5 43.0 47.7 52.5 57.3 62.1
16" W/ft 9.8 12.3 14.8 17.2 19.7 22.1 24.6 31.0 36.2 41.3 48.7 54.1 59.5 64.9 70.4
18" W/ft 11.0 13.7 16.4 19.2 21.9 24.7 27.4 34.5 40.3 46.0 54.3 60.3 66.3 72.3 78.4
20" W/ft 12.1 15.1 18.1 21.1 24.2 27.2 30.2 38.1 44.4 50.7 59.8 66.4 73.1 79.7 86.4
22" W/ft 13.2 16.5 19.8 23.1 26.4 29.7 33.0 41.6 48.5 55.4 65.3 72.6 79.9 87.1 94.4
24" W/ft 14.3 17.9 21.5 25.1 28.6 32.2 35.8 45.1 52.6 60.1 70.9 78.8 86.6 94.5 102.4

in W/ft Based on Temperature Differential and Insulation Thickness

P

Temperature DifferenceBetween Pipe and Ambient

1" Insulation Thickness

1.5" Insulation Thickness

3.Calculate Q

calculate the estimated heat loss, Q

4.Correct for Indoor Location/ Wind Speed: If location is indoors, multiply Q

: Multiply the basic heat loss figure from Table 1 by the adjustment factor from Table 2 to

F

, in watts per foot of pipe length.

F

by 0.9. Table 1 is based on

F

10% safety factor and 20 mph wind speed; add 5% margin for each 5 mph over 20 mph wind speed.

Nominal

Pipe Size,

in. (ID)

DegºF 40ºF 50ºF 60ºF 70ºF 80ºF 90ºF 100ºF 120ºF 140ºF 160ºF 180ºF 200ºF 220ºF 240ºF 260ºF

1

/2" W/ft 1.0 1.2 1.4 1.7 1.9 2.2 2.4 3.0 3.5 4.0 4.8 5.3 5.8 6.3 7.2

3

/4" W/ft 1.1 1.4 1.6 1.9 2.2 2.4 2.7 3.4 4.0 4.5 5.3 5.9 6.5 7.1 8.1
1" W/ft 1.2 1.5 1.8 2.1 2.4 2.7 3.0 3.8 4.4 5.0 5.9 6.6 7.3 7.9 9.0

11/2" W/ft 1.5 1.9 2.3 2.7 3.0 3.4 3.8 4.8 5.6 6.4 7.5 8.4 9.2 10.0 11.4

2" W/ft 1.7 2.2 2.6 3.0 3.4 3.9 4.3 5.4 6.3 7.2 8.5 9.5 10.4 11.4 12.9

21/2" W/ft 1.9 2.4 2.9 3.4 3.8 4.3 4.8 6.0 7.1 8.1 9.5 10.6 11.6 12.7 14.4

3" W/ft 2.2 2.8 3.3 3.9 4.4 5.0 5.5 6.9 8.1 9.2 10.9 12.1 13.3 14.5 16.4
4" W/ft 2.6 3.3 4.0 4.6 5.3 5.9 6.6 8.3 9.7 11.1 13.1 14.5 16.0 17.4 19.7
6" W/ft 3.6 4.5 5.3 6.2 7.1 8.0 8.9 11.2 13.1 15.0 17.6 19.6 21.5 23.5 26.6

8" W/ft 4.4 5.6 6.7 7.8 8.9 10.0 11.1 14.0 16.3 18.6 22.0 24.4 26.9 29.3 33.2
10" W/ft 5.3 6.7 8.0 9.3 10.6 12.0 13.3 16.8 19.6 22.3 26.3 29.3 32.2 35.1 39.8
12" W/ft 6.2 7.8 9.3 10.9 12.4 14.0 15.5 19.5 22.8 26.0 30.7 34.1 37.5 40.9 46.3
14" W/ft 6.7 8.4 10.1 11.8 13.4 15.1 16.8 21.2 24.7 28.2 33.3 37.0 40.7 44.4 50.2
16" W/ft 7.6 9.5 11.3 13.2 15.1 17.0 18.9 23.8 27.8 31.8 37.4 41.6 45.7 49.9 56.5
18" W/ft 8.4 10.5 12.6 14.7 16.8 18.9 21.0 26.5 30.9 35.3 41.6 46.2 50.8 55.4 62.8
20" W/ft 9.2 11.6 13.9 16.2 18.5 20.8 23.1 29.1 34.0 38.8 45.7 50.8 55.9 61.0 69.1
22" W/ft 10.1 12.6 15.2 17.7 20.2 22.7 25.3 31.8 37.1 42.4 50.0 55.6 61.1 66.7 75.5
24" W/ft 11.0 13.7 16.4 19.2 21.9 24.7 27.4 34.5 40.3 46.0 54.3 60.3 66.3 72.3 81.9

609.6 mm W/m 36.1 44.9 53.8 63.0 71.9

1

/2" W/ft 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.5 2.9 3.4 4.0 4.4 4.8 5.5 6.0

3

/4" W/ft 0.9 1.1 1.3 1.5 1.8 2.0 2.2 2.8 3.2 3.7 4.4 4.8 5.3 6.1 6.67

1" W/ft 1.0 1.3 1.5 1.8 2.0 2.3 2.5 3.2 3.7 4.2 5.0 5.5 6.1 6.9 7.5

11/2" W/ft 1.2 1.5 1.8 2.1 2.4 2.7 3.0 3.8 4.4 5.0 5.9 6.6 7.3 8.3 9.0

2" W/ft 1.3 1.7 2.0 2.3 2.6 3.0 3.3 4.2 4.9 5.5 6.5 7.3 8.0 9.1 9.9

21/2" W/ft 1.5 1.9 2.2 2.6 3.0 3.3 3.7 4.7 5.4 6.2 7.3 8.1 9.0 10.2 11.1

3" W/ft 1.7 2.1 2.5 2.9 3.4 3.8 4.2 5.3 6.2 7.1 8.3 9.2 10.2 11.6 12.6

4" W/ft 2.0 2.5 3.0 3.5 4.0 4.5 5.0 6.3 7.4 8.4 9.9 11.0 12.1 13.8 15.0

6" W/ft 2.6 3.3 3.9 4.6 5.2 5.9 6.5 8.2 9.6 10.9 12.9 14.3 15.7 17.9 19.4

8" W/ft 3.2 4.0 4.8 5.6 6.4 7.2 8.0 10.1 11.8 13.4 15.8 17.6 19.4 22.1 23.9
10" W/ft 3.8 4.8 5.7 6.7 7.6 8.6 9.5 12.0 14.0 16.0 18.8 20.9 23.0 26.2 28.4
12" W/ft 4.4 5.5 6.5 7.6 8.7 9.8 10.9 13.7 16.0 18.3 21.6 24.0 26.4 30.1 32.6
14" W/ft 4.7 5.9 7.1 8.3 9.4 10.6 11.8 14.9 17.3 19.8 23.4 26.0 28.6 32.6 35.3
16" W/ft 5.3 6.7 8.0 9.3 10.6 12.0 13.3 16.8 19.6 22.3 26.3 29.3 32.2 36.7 39.8
18” W/ft 5.9 7.4 8.8 10.3 11.8 13.2 14.7 18.5 21.6 24.7 29.1 32.3 35.6 40.6 44.0
20" W/ft 6.4 8.1 9.7 11.3 12.9 14.5 16.1 20.3 23.7 27.0 31.9 35.4 39.0 44.4 48.1
22" W/ft 7.0 8.8 10.5 12.3 14.0 15.8 17.5 22.1 25.7 29.4 34.7 38.5 42.4 48.3 52.3
24" W/ft 7.6 9.5 11.3 13.2 15.1 17.0 18.9 23.8 27.8 31.8 37.4 41.6 45.7 52.2 56.5

Temperature Difference Between Pipe and Ambient

2" Insulation Thickness

3" (76.2 mm) Insulation Thickness

3” Insulation Thickness

Table 2

Insulation Adjustment Factors

B

Chromalox Cable Selection

1.Select Heating Cable Family: Based on the maximum maintenance temperature rating, maximum

exposure temperature rating, and area classification, select the heating cable family from Table 3. (See
Chromalox Heat Trace Cable Product Information Sheets for cable construction options, voltage ratings,
and wattage outputs available.)

2.Select Thermal Output Rating:

(a) For Metal Pipes – Use Figures 1, 2 or 4
(b) For Plastic Pipes – Use Figure 3 by finding the intersection of the calculated heat loss, Q

maintenance temperature, Tm. Select the cable with a thermal output that equals or exceeds QFat Tm.

Table 3

Heating Cable

Family

SRL
(Self-Regulating
Low Temperature)

SRM/E
(Self-Regulating
Medium
Temperature)

SRP
(Self-Regulating
Medium
Temperature)

HSRL
(H-Self-Regulating
Low Temperature)

HSRM
(H-Self-Regulating
Medium
Temperature)

CWM
(ConstantWattage)

MI (Mineral
Insulated)

NOTE: It is the responsibility of the facility manager or engineer to determine the classification of an area where heat trace will be installed. The factory can help determine a suitable
cable based on the information provided.

Figure 1

Heating Cable Families

Area

Classification

Ordinary
Class I, Div.2, Gr. B, C, D CSA, FM, (Gr.A, CSA Only) GOST, Cenelec,CE, ATEX
Class II, Div.2, Gr. E, F,G CSA, FM, (Gr. E, CSA Only) GOST, Cenelec,CE

Class III, Div.2 FM Only GOST,Cenelec,CE, ATEX

Ordinary

Class I Div.2, Gr. A, B, C, D CSA, FM, (Gr.A, CSA Only) GOST, Cenelec,CE, ATEX

Class II, Div.2, Gr. F, G CSA Only GOST,Cenelec,CE, ATEX

Ordinary
Class I, Div.2, Gr. B, C, D

Class II, Div.2, Gr. F, G

Class III
Class I, Div.1, Gr. B, C, D
Class II, Div.1, Gr. E, F,G CSA, FM

Class III, Div.1 CSA, FM
Class I, Div.1, Gr. B, C, D
Class II, Div.1, Gr. E, F,G CSA, FM

Class III, Div.1 CSA, FM

Ordinary

HazardousArea, Consult Factory

Ordinary
Class I, Div.2, Gr. B, C, D CSA, FM
Class II, Div.2, Gr. E, F,G CSA, FM

Class III CSA, FM

Pipe

Material

Plastic/Metal 150ºF / 65ºC 185ºF / 85ºC

Metal Only 302ºF / 150ºC 420ºF / 215ºC

Metal Only 225ºF / 110ºC 275ºF / 135ºC

Plastic/Metal 150ºF / 65ºC 185ºF / 85ºC

Metal Only 302ºF / 150ºC 420ºF / 215ºC

Metal Only Consult Factory 392ºF / 200ºC

Metal Only Consult Factory 1,100ºF / 595ºC

Maximum
Maintenance
Temperature

SRL & HSRL – Thermal Output
Ratings on Insulated Metal Pipe

Maximum Exposure

Temperature

(Power Off)

Figure 2

U.S. Other

UL, CSA, FM GOST, Cenelec,CE, ATEX

UL, CSA, FM GOST, Cenelec,CE, ATEX

UL, CSA, FM

Pending

CSA, FM

CSA, FM

UL, CSA

CSA, FM

SRM/E & HSRM – Thermal Output
Ratings on Insulated Metal Pipe

, and pipe

F

Approvals

GOST,Cenelec,CE, ATEX

Pending

3.Determine Total Cable Length: In addition to pipe length, in-line components such as valves, flanges,

and pipe supports require additional heat tracing to maintain T
cable length required by combining the pipe length with the additional lengths needed for all the
other components.

Additional Cable Lengths Required for In-Line Components

Globe Valve

on Pipe Size)

Ball Valve

Butterfly Valve

ft

Table 4

Piping Size

1

in. 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0.30

2

/

3

in. 1.50 1.00 1.00 1.00 1.50 1.00 1.00 0.30

4

/

1 in. 2.00 1.00 1.00 1.00 1.50 1.00 1.00 0.30

1

1

in. 2.50 1.50 1.50 1.50 2.00 2.00 2.00 0.30

2

/

2 in. 2.50 2.00 2.00 2.00 2.00 2.00 2.00 0.30

1

2

in. 2.50 2.00 2.00 2.00 2.00 2.00 2.00 0.30

2

/
3 in. 3.00 2.50 2.50 2.50 2.00 2.00 2.00 0.50

4 in. 4.00 3.00 3.00 3.00 2.50 2.50 2.50 0.50

6 in. 5.00 3.50 3.50 3.50 2.50 2.50 2.50 0.80

8 in. 7.00 4.00 4.00 4.00 2.50 2.50 2.50 0.80

10 in. 8.00 4.50 4.50 4.50 3.00 3.00 3.00 0.80

12 in. 9.00 5.00 5.00 5.00 3.00 3.00 3.00 0.80

14 in. 10.00 5.50 5.50 5.50 3.00 3.00 3.00 1.00

16 in. 11.00 6.00 6.00 6.00 3.50 3.50 3.50 1.00

18 in. 12.00 7.00 7.00 7.00 3.50 3.50 3.50 1.00

20 in. 13.00 7.50 7.50 7.50 3.50 3.50 3.50 1.00

22 in. 13.00 7.50 7.50 7.50 3.50 3.50 3.50 1.00

24 in. 15.00 8.00 8.00 8.00 4.00 4.00 4.00 1.00

Figure 3

Based on Pipe IPS (Ir

Gate Valve

SRL & HSRL – Thermal Output Ratings
on Plastic Pipe with Aluminum Tape

. See Table 4. Calculate the total

m

Shoe Support

Figure 4

Hanger Support

SRP – Thermal Output Ratings
on Insulated Metal Pipe

Sleeper Support

Flange Pair