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
4˝
100 mm
6˝
150 mm
8˝
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