King Electric SR self-reg, cut to length User Manual
Page 7
Use the number in the table and multiply it by the length of the roof edge.
CALCULATIONS FOR GUTTERS, DOWNSPOUT AND VALLEYS:
1. For standard non-metal roofs, add 1 foot of heating cable for
each foot of gutter.
2.
Add 1 foot of heating cable per foot of downspout.
3.
If the downspout is in the middle of the run, loop the cable
down and back up. Double the length of the downspout for
determining the length of cable to install.
4.
For valleys, run the heating cable two thirds of the way up and
down the valley. Add this additional length to the overall cable
needed.
5.
For gutters 6 inches wide use two cable runs.
Selecting the Required Heating Cable Length for Roof and Gutter Deicing
Eave
Overhang
Standard
Roof
Metal Roof
18” Seam
Metal Roof
24” Seam
None
2.0
2.5
2.0
12”
2.8
2.8
2.4
24”
3.8
3.6
2.9
36”
4.8
4.3
3.6
Table 6: Heating Cable Multiplier
GENERAL INFORMATION
1. SR cable is designed
to remove ice, not
accumulated
snow.
2. SR cable will not keep snow or ice from falling off
of
the
roof
. Snow fences or snow guards should be used to
eliminate snow movement.
3. SR heating cables may be used on:
- Roofs made from all types of roofing materials, such as
shake, shingle, rubber, tar, wood, metal, and plastic.
- Gutters made from standard materials, such as metal
and plastic.
- Downspouts made from standard materials, such as metal
and plastic.
CALCULATION FOR HEATING CABLE LENGTH:
Use the formula below to determine the amount of heating
cable required.
Total heating cable length = A+B+C+D+E+F+G
A (Roof edge) × (heating cable multiplier)
B (Roof edge x 0.5)
C (Total gutter length)
D (Total downspout length + 1 ft)
E (1 ft for each power connection)
F (2 ft for each splice)
G (3 ft for each tee connection)
= Total heating cable length required
Example:
1.
Roof edge = 48 ft
2.
Eave overhang = 1 ft (Refer to Table 6)
3.
Gutter = 48 ft
4.
Downspout = 22 ft
5.
Power connection = 2 each
6.
Splice = 3 each
Heating Cable Required:
A Roof edge:
48 ft × 2.8 (From table 6)
= 134.4 ft
B Roof extension*: 48 ft x 0.5
= 24.0 ft
C Roof gutter:
48 ft
= 48.0 ft
D Downspout:
22 ft + 1 ft
= 23.0 ft
E Power Connection: 2 x 1 ft
= 3.0 ft
F Splice Connection: 3 x 2 ft
= 6.0 ft
G Tee Connection: 0 x 3 ft
= 0.0 ft
Total heating cable length required:
= 238.4 ft
*Roof extension is the length of cable required to prevent ice
dams between the roof edge and the gutter. When there are
no gutters present it forms a drip loop to prevent ice dams at
the roof edge.
4. Do not install the heating cable underneath any roof
covering.
5. Install only in accessible locations; do not install behind
walls or where the cable would be hidden.
6. Do not run the heating cable through walls, ceilings, or
floors.
7. Connect only to ground-fault protected circuit breakers or
outlets that have been installed in accordance with all
national and local codes and standards
and that are
protected from rain and other water sources such as
melting ice water.
8. Do not exceed the amp rating of the over current
protection device.
SR Heating Cable Design for Roof and Gutter Applications
DESIGN NOTES:
1.
In-line splices and tee splices should be avoided where
possible.
2.
Heating cable in downspouts should be looped and extend
below the frost line if tied into a drainage system.
3.
End terminations should not be located in an area where
moisture is present. End terminations should not be located at
the lowest point of downspouts.
4.
·For roof drains leading into a heated area, a loop of heating
cable should be installed to a depth of 3 ft.
Rev 11.04.12
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