nVent.com | 5
HEATING CABLE DESIGN
Only WinterGard Wet H612 120 V heating cable is suitable for
use with the H908 power connection kit for roof and gutter
de-icing applications.
1. Calculate the heating cable length required.
Length = A + B + C + D + E + F + G
A Roof edge length (ft) x feet of heating cable per foot of roof edge
(From Table 5)
B Roof edge length (ft) x 0.5*
C Total gutter length (ft)
D Total downspout length (ft) + 1 (ft)
E 1 ft for each power connection
F 2 ft for each splice connection
G 3 ft for each tee connection
= Total heating cable length (ft)
* Roof extension: This length allows the heating cable to extend into the gutter
to provide a continuous drain path, or where no gutters are present, extends
beyond the roof edge to form a drip loop.
Table 5. WinterGard Wet cable length for roof de-icing
Standing seam metal roof:
Eave overhang
Shingle roof
18 inch seam 24 inch seam
0
2.0 ft
2.5 ft
2.0 ft
12 in
2.8 ft
2.8 ft
2.4 ft
24 in
3.8 ft
3.6 ft
2.9 ft
36 in
4.8 ft
4.3 ft
3.6 ft
Note: nVent recommends a gutter and downspouts to provide a continuous
path for melted water.
Important: For the nVent warranty to be valid, you must comply
with all the requirements outlined in these guidelines.
All design information provided here is based on a “standard”
shake or shingle roof application. For any other application or
method of installation, consult nVent at (800) 545-6258.
HEATING CABLE INSTALLATION
1. Prepare for installation.
• Store the heating cable in a clean, dry place.
• Use only the following RAYCHEM accessories to satisfy code
and agency requirements:
- H908 Plug-in Power Connection Kit (with end seal)
- H910 Splice and Tee Kit (if splicing or teeing)
- H915 Downspout Hangers
- H913/H914 Roof Clips
• Carefully plan the routing of the heating cable for roof and
gutter de-icing.
• Make certain gutters and downspouts are free of leaves
and other debris.
2. Cut the heating cable to length.
• Cut the heating cable to the length required before or after
it is installed. Leave a minimum of 1 foot extra heating cable
for connection to power. For splice and tee connections
leave a minimum of 1 foot for each section of heating cable.
WinterGard heating cable can be cut to length without affecting
its heat output per foot.
• Protect the heating cable ends from moisture and mechanical
damage if they will be left exposed before connection.
3. Position and attach the heating cable.
On roofs
• Loop the heating cable on the overhang area of the roof. This is the
part that extends past the building wall. Extend the bottom of each
heating cable loop over the roof edge and, using a UV-resistant
cable tie, connect the bottom of each loop to the cable running in
the gutter to ensure a drainage channel off the roof and into the
gutter and downspout. The cable running in the gutter should remain
against the bottom of the gutter. Extend the top of each heating
cable loop beyond where the wall joins the roof. nVent recommends
2-foot clip-spacing along the roof edge. See the “Heating cable
design” section (Table 5) for spacing and layout information.
• Use WinterGard H913/H914 roof clips to attach heating cable
to the roof surface. One kit contains ten double roof clips for
approximately 7 linear feet of roof edge. One H914 kit contains
50 roof clips for approximately 35 linear feet of roof edge.
For flat roofs, the heating cable can be spaced as needed to
create runoff paths for melting ice and snow. Use single-ended
clips located at 3-foot intervals to secure the cable to the roof.
Roof clips may be attached to a shake or shingle roof with nails
or screws. Roof clips may be attached to a metal roof using
screw, nail or adhesive. (See H56723 installation instruction for
more details.) Reseal the nail or screw holes if necessary before
installing heating cable in the clips.
• A barrier (snow fence) can be placed on the roof above the
heating cable. This prevents damage to the cable and keeps the
installation from coming loose due to ice slides. The heating
cable can be attached to the barrier with UV-resistant cable ties,
instead of using roof clips, if desired. Do not use wire or other
materials because they may damage the heating cable.
In gutters and downspouts
• Run heating cable along gutters and into downspouts, ending
below the freezing level. Permanent attachment of the cable to
the gutter bottom is not necessary. Loop the heating cable in
downspouts if convenient, such as when the downspout is not
at the end of the run, or use the H910 splice and tee kit to tee
down the downspout.
• Use WinterGard H915 downspout hangers to protect the heating
cable from fraying and from damage from sharp edges and
to provide strain relief. Refer to the H915 kit instructions for
installation details.
• Use WinterGard H913/H914 roof clips to route heating cable
into and out of the gutter in such a way as to prevent abrasion
to the cable. Protect all cable that protrudes past the lower
opening of the downspout.
H908 DESIGN AND INSTALLATION INFORMATION FOR ROOF AND GUTTER DE-ICING ONLY
(WinterGard Wet H612 Heating Cable)
Example:
Roof edge:
20 ft
Roof overhang:
1 ft
Roof gutter:
20 ft
Downspout:
15 ft
Power connection:
1 ea
Tee connection:
1 ea
Voltage available:
120 V
CB Size Available:
15 A
Start-up temperature: 0 °F
WinterGard Wet heating cable required:
A Roof edge:
20 ft x 2.0
(from Table 5) = 40 ft
B Roof extension:
20 ft x 0.5
= 10 ft
C Roof gutter:
= 20 ft
D Downspout:
= 15 ft + 1 ft = 16 ft
E Power connection:
1 ft x 1 ea
= 1 ft
F Splice connection:
= 0
G Tee connection:
3 ft x 1 ea
= 3 ft
Total WinterGard Wet
heating cable required:
90 ft**
**This total is less than 100-ft maximum circuit length
(see Table 6), therefore a single circuit is required
