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Cable Length Selection Tables
Table 1. Metal Pipe
Number of heating cable runs required
Lowest Expected Temperature
Metal Pipe
Insulation
Pipe Size
20°F
Thickness
(–10°C)
1/2 in
1/2 in
1
3/4 in
1
1 in
1
1 1/4 in
1
1 1/2 in
1
3/4 in
1/2 in
1
3/4 in
1
1 in
1
1 1/4 in
1
1 1/2 in
1
1 in
3/4 in
1
1 in
1
1 1/4 in
1
1 1/2 in
1
2 in
1
1 1/2 in
3/4 in
1
1 in
1
1 1/4 in
1
1 1/2 in
1
2 in
1
Table 2. Plastic Pipe
Number of heating cable runs required
Lowest Expected Temperature
Plastic Pipe
Insulation
Pipe Size
20°F
Thickness
(–10°C)
1/2 in
1/2 in
1
3/4 in
1
1 in
1
1 1/4 in
2
1 1/2 in
2
3/4 in
1/2 in
1
3/4 in
1
1 in
1
1 1/4 in
1
1 1/2 in
2
1 in
3/4 in
1
1 in
1
1 1/4 in
1
1 1/2 in
1
2 in
1
1 1/2 in
3/4 in
1
1 in
1
1 1/4 in
1
1 1/2 in
1
2 in
1
= Increase insulation thickness
4 | nVent.com/RAYCHEM
0°F
–20°F
–40°F
(–20°C)
(–30°C)
(–40°C)
1
2
2
1
2
2
2
2
2
2
2
3
2
3
3
1
1
2
1
2
2
1
2
2
2
2
2
2
2
3
1
1
2
1
2
2
1
2
2
1
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
2
1
2
2
0°F
–20°F
–40°F
(–20°C)
(–30°C)
(–40°C)
2
2
2
2
3
2
3
3
2
3
3
3
2
2
2
2
2
3
2
2
3
2
3
3
3
3
1
2
2
1
2
2
2
2
3
2
3
3
2
3
3
1
1
2
1
2
2
1
2
2
1
2
2
2
2
3
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:
Lowest ambient
temperature:
Pipe length:
Valves:
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:
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.
1-inch diameter,
plastic
–20°F (–30°C)
16 feet (5m)
1 ball valve is used
3/4 in
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