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Cable Length Selection Tables
Table 1. Metal Pipe
Number of heating cable runs required
1/2 in
1/2 in
1
1
2
2
Pipe Size
Insulation
Thickness
20°F
(–10°C)
0°F
(–20°C)
–20°F
(–30°C)
–40°F
(–40°C)
3/4 in
1
1
2
2
1 in
1
2
2
2
1 1/4 in
1
2
2
3
1 1/2 in
1
2
3
3
1/2 in
3/4 in
1
1
1
2
3/4 in
1
1
2
2
1 in
1
1
2
2
1 1/4 in
1
2
2
2
1 1/2 in
3/4 in
1 in
1 1/4 in
1 1/2 in
2 in
3/4 in
1 in
1 1/4 in
1 1/2 in
2 in
1
2
2
3
1 in
1
1
1
2
1
1
2
2
1
1
2
2
1
1
2
2
1
2
2
2
1 1/2 in
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
2
2
Lowest Expected Temperature
Metal Pipe
Table 2. Plastic Pipe
Number of heating cable runs required
Lowest Expected Temperature
1/2 in
1/2 in
1
2
2
Pipe Size
Insulation
Thickness
3/4 in
1
2
2
3
1 in
1
2
3
3
1 1/4 in 2
2
3
1 1/2 in 2
3
3
1/2 in
3/4 in
1
2
2
2
3/4 in
1
2
2
3
1 in
1
2
2
3
1 1/4 in 1
2
3
3
1 1/2 in
3/4 in
1 in
1 1/4 in
1 1/2 in
2 in
3/4 in
1 in
1 1/4 in
1 1/2 in
2 in
2
3
3
1 in
1
1
2
2
1
1
2
2
1
2
2
3
1
2
3
3
1
2
3
3
1 1/2 in
1
1
1
2
1
1
2
2
1
1
2
2
1
1
2
2
1
2
2
3
Plastic Pipe
20°F
(–10°C)
0°F
(–20°C)
–20°F
(–30°C)
–40°F
(–40°C)
= Increase insulation thickness
1C. Calculate the total length of heating
cable required
Multiply the number of heating cable runs
by your pipe length. Add one extra foot
(30 cm) for each valve in your line. Add
one extra foot (30 cm) for the distance to
the power connection. For installations in
a crock, add an additional 2 feet (60 cm)
of heating cable. After cutting the Frostex
heating cable to the length you need,
proceed to Step 2.
Example:
Pipe size and
material:
1-inch diameter,
plastic
Lowest ambient
temperature:
–20°F (–30°C)
Pipe length:
16 feet (5m)
Valves:
1 ball valve is used
The water connection is in a crock.
From Table 2, Plastic Pipe, for –20°F
(–30°C), either two or three runs of Frostex
heating cable is required depending on pipe
insulation thickness.
Optimal pipe insulation thickness: 3/4 in
Selecting 3/4 in thick insulation requires two
runs of Frostex heating cable installed along
the entire length of the pipe (Table 2).
The total length of heating cable equals:
32 ft (10 m)
2 runs x 16 ft (5 m)
of pipe
+ 1 ft (0.3 m) for one ball valve
+ 1 ft (0.3 m) for one power connection
+ 2 ft (0.6 m) for installing in a crock
36 ft (11 m)
total length
Note:
Do not use more than
50 feet (15 meters) of heating cable
per plug. If the total
calculated length exceeds 50 feet
(15 meters), you will need additional
9800 FlexFit plugs and outlets.
Longer circuit lengths will blow the
nonreplaceable fuse in the 9800
FlexFit plug. If you require more than
50 feet per length
(15 meters), call nVent for
information on other products.
