# Fenix ELSR-M User Manual

## Page 5

3. USE OF TEMPERATURE REGULATION TO PROTECT PIPES AGAINST
FREEZING

• Heating cables placed on metal or plastic pipes provide protection against the

freezing of liquids in the pipes when the surrounding temperature is lower then
0°C.

3. a) Dimensioning
The required performance of the cable per 1 m of length can be determined by a
calculation using the following formula:
For the determination of the needed performance of the cable it is necessary to multiply
the heat loss by the coefficient 1.3 and the length of the pipe.
EXAMPLE: a pipe with an inner radius of 25 mm, 13 m long, and insulated with 20 mm
Mirelon needs to be protected against freezing according to the following calculation:

)

(

*

)

(

*

2

2

p

m

t

t

d

r

r

Q

+

=

λ

π

down to a lowest surrounding temperature of -20°C (we always consider the non-
freezing temperature to be +5°C).

Pk = Q*1.3*l Pk – performance of the cable
l – length of the cable

Q – heat loss per 1 m of pipe (W/m)

l – coefficient of the heat conductivity of the insulation (W/m*K)

r – radius of the pipe (m)

d – thickness of the insulation (m)

tm – temperature of the medium (°C)

tp – temperature of the environment (°C)

Interior diameter of pipe

½˝ 15

mm

¾˝ 20

mm

1˝ 25

mm

1¼˝ 32

mm

1½˝ 40

mm

2˝ 50

mm

2½˝ 65

mm

3˝ 80

mm

100 mm

150 mm

200 mm

10˝

250 mm

SOLUTION:
The total wattage of the heating cable must be 171 W or higher. We will use 13 m of self-insulating cable
ELSR – M – M15-2-BO

)

(

*

)

(

*

2

2

p

m

t

t

d

r

r

Q

+

=

λ

π

=

1

.

10

))

20

(

5

(

05

.

0

*

02

.

0

)

025

.

0

025

.

0

(

*

2

2

=

+

π

W/m

Pk – Q*1.3*l = 10.1*1.3*13=170.69 W