Raychem MI Surface Snow Melting Installation guide

Installation and Operation Manual

forSurface Snow Melting

MI Heating Cable System

ii | nVent.com

Important Safeguards and Warnings

WARNING: FIRE AND SHOCK HAZARD.

nVent RAYCHEM Surface Snow Melting Systems must

be installed correctly to ensure proper operation and to

prevent shock and fire. Read these important warnings

and carefully follow all the installation instructions.

• To avoid damage to the heating cables, do not energize

cables until they have been completely embedded and

the installation has been completed.

• To minimize the danger of fire from sustained electrical

arcing if the heating cable is damaged or improperly

installed, and to comply with the requirements of nVent,

agency certifications, and national electrical codes,

groundfault equipment protection must be used on each

heating cable branch circuit. Arcing may not be stopped

by conventional circuit protection.

• Heating cables must be spaced at least 1/2 in (1.3cm)

from any combustible surface.

• Approvals and performance of the Surface Snow Melting

Systems are based on the use of approved components

and accessories.

• Cable terminations must be kept dry before, during, and

after installation.

• Damaged heating cable can cause electrical arcing or

fire. Damaged heating cable or terminations must be

repaired or replaced. Contact factory for assistance.

• If the heating cable sheath is stainless steel, the

cable must be grounded, but must not be used as the

grounding means.

• Reinforcing rod, mesh or other materials used for the

support of, or on which the heating cables are installed,

must be grounded in accordance with CSA Standard

C22.1, Section 10 or the National Electrical Code as

applicable.

• Megohmmeters operate at high voltage. This voltage

is hazardous and possibly lethal. Read and follow all

instructions included with the instrument you are using.

nVent.com | iii

Table of Contents

1

General Information 1

1.1 Use of the Manual 1

1.2 MI Applications 2

1.3 Safety Guidelines 2

1.4 Electrical Codes 2

1.5 Approvals 2

1.6 Warranty 3

1.7 Heating Cable Construction 3

1.8 Heating Cable Identification 4

1.9 Heating Cable Catalog Number Decoder 6

2

General Installation Guidelines 7

2.1 Before You Start 7

2.2 Materials Specifications 8

2.3 Heating Cable Storage 8

2.4 Tools Required 8

2.5 Cable Testing Guidelines 8

2.6 Heating Cable Handling 9

2.7 Junction Boxes and Electrical Enclosures 11

2.8 Protecting the Heating Cable 11

2.9 Check Materials Received 11

2.10 Review the Design 12

2.11 Slab Temperature Sensor 18

2.12 Waterproofing Membranes 19

2.13 Drainage and Trench Drains 20

2.14 Visual Inspection 20

3

Heating Cable Installation 22

3.1 Heating Cables Installed in Concrete 22

3.2 Heating Cables Installed in Asphalt 31

3.3 Heating Cables Installed in Mastic Asphalt 35

3.4 Heating Cables Installed Under Brick

and Concrete Pavers 40

3.5 Concrete and Asphalt Wheel Tracks 44

3.6 Concrete Stairs 46

4

Accessory Installation 51

4.1 Junction Boxes 51

4.2 Slab Thermostat Installation 61

iv | nVent.com

5

Control, Monitoring and Power Distribution 63

5.1 Manual On/Off Control 63

5.2 Slab Sensing Thermostat 63

5.3 Automatic Snow Controller 63

6

Power Supply and Electrical Protection 65

6.1 Voltage Rating 65

6.2 Circuit Breaker Sizing 65

6.3 Ground-Fault Protection 66

6.4 Junction Box Wiring 68

6.5 Typical Wiring Diagrams 68

7

Commissioning and Preventive Maintenance 76

7.1 System Tests 76

7.2 Preventive Maintenance 77

8

Test Procedures 79

8.1 Visual Inspection 79

8.2 Insulation Resistance Test – Test 1 79

8.3 Continuity (Resistance) Test – Test 2 80

8.4 Insulation Resistance and Continuity

Test Procedure 80

8.5 Power Check 82

8.6 Fault Location Testing 85

9

Troubleshooting Guide 86

10

Installation and Inspection Records 90

1

General Information

nVent.com | 1

1.1 Use of the Manual

This manual covers the installation of nVent

RAYCHEM Mineral Insulated (MI) heating cables for

surface snow melting in concrete, asphalt, and sand

or limestone screenings under paving stones*.

The manual covers general heating cable installation

procedures and specific installation details and

provides information on available accessories.

The manual also provides information on controls,

testing, and periodic maintenance.

This manual assumes that a proper snow melting

or anti-icing design has been completed according

to nVent's recommendations. Only the applications

described in this manual are approved by nVent for

nVent RAYCHEM MI Surface Snow Melting Systems

and only when used with approved accessories.

The instructions in this manual and the installation

instructions included with the control systems,

power distribution systems, and accessories must

be followed for the nVent warranty to apply.

For design assistance, technical support, or

information regarding other applications not shown

here, please contact your nVent representative or

nVent directly.

nVent

7433 Harwin Drive

Houston, TX 77036

USA

Tel +1.800.545.6258

Fax +1.800.527.5703

[email protected]

nVent.com

Important: For the nVent warranty and agency

approvals to apply, the instructions that are included in

this manual and product packages must be followed.

* Special permission for paver snow melting is

required from the Authority Having Jurisdiction.

1

General Information

2 | nVent.com

1.2 MI Applications

Surface Snow Melting

Surface Snow Melting Systems prevent the

accumulation of snow on ramps, slabs, driveways,

sidewalks, platform scales, and stairs under typical

snow conditions.

Anti-Icing

Anti-icing systems keep the surface temperature

above freezing to prevent ice formation.

1.3 Safety Guidelines

As with any electrical equipment, the safety and

reliability of any system depends on the quality

of the products selected and the manner in which

they are installed and maintained. Incorrect design,

handling, installation, or maintenance of any of the

system components could damage the Surface

Snow Melting System and may result in inadequate

snow melting, electric shock, or fire. To minimize

these risks and to ensure that the system performs

reliably, read and carefully follow the information,

warnings, and instructions in this guide.

Pay special attention to the following:

Important instructions are marked Important

Warnings are marked WARNING

1.4 Electrical Codes

Article 426 of the National Electrical Code (NEC) and

Section 62 of the Canadian Electrical Code (CEC)

govern the installation of fixed outdoor surface

snow melting and de-icing systems. All installations

must be in compliance with these and any other

applicable national and local codes.

1.5 Approvals

MI heating cables are approved for use in

nonhazardous and hazardous locations.

1

General Information

nVent.com | 3

For a complete list of approvals, refer to the product

data sheets available on our web site at

nVent.com or contact your nVent representative.

• H57796 – MI Heating Cable for Surface Snow

Melting – MI data sheet

• H56990 – MI Heating Cable for Commercial

Applications data sheet

Important: Types SUA and SUB heating cables are

approved for use in nonhazardous areas only.

1.6 Warranty

nVent’s standard limited warranty applies to Surface

Snow Melting Systems.

An extension of the limited warranty period to ten

(10) years from the date of installation is available,

except for the control and distribution systems,

if a properly completed online warranty form is

submitted within thirty (30) days from the date of

installation. You can access the complete warranty

on our web site at nVent.com

1.7 Heating Cable Construction

The MI heating cables are comprised of one or

two conductors surrounded by magnesium oxide

insulation and a solid copper or Alloy 825 sheath.

nVent RAYCHEM Copper sheath cables are covered

with an extruded low-smoke zero-halogen (LSZH)

jacket that protects the copper sheath from

corrosive elements that can exist in surface

snow melting applications. All of the cables

include both a heated section (heated length) and

a nonheating cold lead section. These sections

are joined at the hot/cold joint where the heating

element is spliced into larger bus wires. A final

transition at the end of the cold lead section

provides an environmental seal and tails for the

electrical connection. The heating cables are

available as factory-terminated configurations

shown in Table 1.

1

General Information

4 | nVent.com

TABLE 1:

MI HEATING CABLE CONFIGURATIONS

MI cable

design

Number of

conductors

Configuration

Heated length

Cold lead length

NPT threaded

connector

Hot/cold

joint

NPT threaded

connector

Hot/cold

joint

Heated length

Cold lead length

NPT threaded

connector

Hot/cold

joint

A Single

conductor

(61 series)

B Single

conductor

(61 series)

D Dual

conductor

(32 & 62

series)

(SUA)

(SUB)

1.8 Heating Cable Identification

Each MI heating cable is supplied with an

identification tag on which the heating cable catalog

number is permanently printed. In addition to its

identification purposes, the catalog number provides

information regarding the heating cable length,

power output, and operating voltage. Also printed on

the tag are the serial number and temperature code.

If the cable has been designed for a hazardous

location, the area classification is printed in the

“Haz. Locations” section of the tag (for custom

engineered cables only).

Important: If the metal tag is removed during cold

lead installation, it must be reinstalled on the cold lead

within 3 in (7.5 cm) of the end of the cold lead/power

connections.

Figure 1 shows a typical identification tag supplied

with pre-engineered SUA/SUB heating cables

(SUA1 through SUB22). These heating cables

are designed to be used for several different

applications depending on the supply voltage

selected. In Figure 2, a typical identification tag

supplied with custom engineered heating cables

is shown.

1

General Information

nVent.com | 5

Figure 1: Typical SUA/SUB MI heating cable identifica-

tion tag (front)

Important: Several SUA and SUB series of heating

cables are designed for use on either 208, 240, or 277

volts when used in surface snow melting applications.

For these cables, the catalog number printed on the tag

will show only the highest voltage to which the cable

may be connected, and the highest wattage produced.

The wattages produced at other supply voltages are

shown in the area below the catalog number and

across from the “SNOW MELTING / PS,C” heading

(see Figure 1).

Figure 2: Typical custom engineered heating cable

identification tag (front)

1

General Information

6 | nVent.com

1.9 Heating Cable Catalog Number Decoder

The heating cable catalog number may be broken

out as follows:

Gland size

(N12 = 1/2 in NPT)

Cold joint ‘Y’ is standard

for copper sheath heating

cables

Cold joint ‘X’ is standard

for Alloy 825 sheath

heating cables

Cold lead code

Cold lead length (in feet)

(4.6M = 4.6 meters)

Heating cable voltage

Heating cable wattage

Heated cable length

(in feet)

(97.6M = 97.6 meters)

Heating cable reference

Heating cable design

configuration (A, B, D)

B/61RE4300-RD/320/8000/277/15/R30A/Y/N12

Figure 3: MI heating cable catalog number

2

General Installation Guidelines

nVent.com | 7

The guidelines in Section 2 are provided to assist

the installer throughout the installation process and

should be reviewed before the installation begins.

2.1 Before You Start

The Surface Snow Melting System is an engineered

system that has been designed for your application.

To ensure a smooth, efficient installation and start-

up, obtain all the relevant engineering information

before commencing work. Contact the general

contractor, owner, or owner’s representative to

obtain a statement of the project design basis,

project specifications, and the heating cable layout

drawings.

It is important that the heating cable depth and

spacing be maintained for proper operation of

the system for all concrete, asphalt and paver

installations. For sloping ramps, such as a ramp

to an underground parking garage, serpentine the

cables across the width of the ramp to improve

snow melting effectiveness.

To ensure that the installation proceeds smoothly

and meets the design objectives, the following

questions should be answered.

• What are the exact dimensions of the area to be

heated?

• What is the supply voltage and phase?

• Are the heating cables being installed in concrete

or asphalt, or if paver area, in limestone screenings

or sand?

• Where are the control joints, expansion joints, and

construction joints located?

• What is the heating cable spacing?

• Is a waterproof membrane being used?

• What is the depth of burial of the heating cable?

• Where are the junction boxes located?

• Is there adequate drainage for melted snow and ice?

Important: Fuel storage areas and aircraft

hangar doors are classified as hazardous areas.

Heating cables installed in these areas must be

approved for the area classification.

2

General Installation Guidelines

8 | nVent.com

2.2 Materials Specifications

Install the heating cables in concrete, asphalt, or

other materials that have been designed to handle

the expected load and environmental conditions, and

for long term structural stability. The quality of the

granular base materials, concrete, and asphalt must

conform to generally accepted standards and

specifications set by the American Society for

Testing and Materials (ASTM) and/or Canadian

Standards Association (CSA). Site preparation

and material selection should be done under the

direction of the Soil Consultant, Engineer, Architect,

or Landscape Architect.

2.3 Heating Cable Storage

• Store heating cables in a clean, dry location and

protect from mechanical damage. Temperature

range: –40°F to 140°F (–40°C to 60°C).

• Store heating cables in their shipping container

until ready to install.

2.4 Tools Required

The following tools are recommended for installing

MI heating cables:

• Pliers

• 1000 Vdc megohmmeter

• Multimeter

• Large adjustable wrench

• Torque wrench

• Pay-off reel (to uncoil long cables)

2.5 Cable Testing Guidelines

Insulation resistance (IR) testing is recommended

at four stages during the installation process and

as part of regularly scheduled maintenance. Further

details on IR testing can be found in Section 8.

• When received – minimum 100 MΩ

• After the cables have been installed – minimum

20 MΩ

• Continuously during placement of concrete,

asphalt, etc. – minimum 20 MΩ

2

General Installation Guidelines

nVent.com | 9

• Prior to initial start-up (commissioning) –

minimum 20 MΩ

• As part of the regular system inspection

• After any maintenance or repair work

2.6 Heating Cable Handling

Avoid damage to the MI heating cable as follows:

Important: Do not energize the heating cables

before they have been completely embedded and the

installation has been completed.

• Use a pay-off reel to uncoil heating cable

during installation; do not pull cable out into a spi-

ral (Figure 4).

Right Wrong

Figure 4: Unreeling/uncoiling cable

• Do not alter cable length.

• Avoid damaging heating cables by cutting or crush-

ing (Figure 5).

Figure 5: Avoid cutting and crushing the heating cable

• Do not install cables if the temperature is below

–4°F (–0°C) for UL, and –2°F (–0°C) for CSA.

Important: Do not install so that heating cables

are crossed, overlapped, or grouped (Figure 6).

Grouped heating cables can cause localized

overheating with a risk of fire or cable failure.

2

General Installation Guidelines

10 | nVent.com

Figure 6: Figure 6: Do not cross, overlap, or group heat-

ing cables

• Do not repeatedly bend and straighten the cable.

• Do not install heating cable in contact with

insulating materials.

• Install heating cable at the recommended spacing

to ensure correct watt density.

• Use a plank to tip wheelbarrow on.

• Handle the hot/cold joint carefully. Support the

joint on both sides when moving and positioning

the cold lead.

• Position hot/cold joints 6 in (15 cm) in from edge

of snow melted area and spaced at least 6 in (15

cm) apart from each other (do not bunch hot/cold

joints – see Figure 7).

Wrong

hot/cold joints

installed on

slab edge

Wrong

hot/cold joints

bunched

Right

hot/cold joints

6 in (15 cm) apart

and 6 in (15 cm)

from slab edge

Figure 7: Positioning hot/cold joints

• During installation, protect tails from breaking

where they emerge from brass pot by taping over

tails and pot with electrical tape.

• Do not bend the heating cable or cold lead within

6 in (15 cm) of a splice, the hot/cold joint, or the

end cap.

• Do not bend cable to an inside radius less than

6times the outside diameter of the cable.

• Do not space runs of heating cable closer than

3in (7.5 cm) together.

2

General Installation Guidelines

nVent.com | 11

• Do not use sharp objects such as shovels, rakes,

etc. when installing the cable (Figure 8).

Figure 8: Avoid damage by not using shovels or rakes

2.7 Junction Boxes and Electrical Enclosures

• Junction boxes and enclosures used for electrical

connections to the heating cables must be listed

and approved for the environment in which they are

installed.

• Junction boxes should be mounted indoors or

above grade when possible. For electrical connec-

tions made outdoors at grade level, use a handhole

type grade mounted enclosure.

• Keep covers on junction boxes to prevent moisture

from entering them.

2.8 Protecting the Heating Cable

On many projects, there is a delay between

installation of the heating cables and placement

of the topping course (concrete, asphalt, limestone

screenings/sand). If there is any delay at all, take the

following precautions to protect the installation until

the heating cables can be completely covered.

• Do not energize the heating cables

• Mechanically protect the heating cables so that

they cannot be damaged by being walked on, run

over, painted, sandblasted, burned, welded, or cut.

2.9 Check Materials Received

Review the project specifications, drawings, and

schedules and compare the list of materials to the

catalog numbers of heating cables and components

received to confirm that proper materials are on site.

The heating cable catalog number, voltage, wattage,

and length are printed on the metal tag attached to

the cold lead.

2

General Installation Guidelines

12 | nVent.com

• Ensure that the heating cable voltage rating is

suitable for the power supply voltage available.

• Inspect the heating cable and components for

in-transit damage.

2.10 Review the Design

Hold a project coordination meeting. Review the

design at this meeting and ensure that the cables

supplied meet the design requirements and conform

to the watt density (watts per square foot/watts per

square meter) requirements for the project at the

specified cable spacing. This can be verified in

conjunction with the MI Surface Snow Melting

Design Guide (H57045).

Review the installation steps in Section 3 for the

particular application as several trades may be

involved in the system installation. Review Section 4

on accessory installation including the location of all

junction boxes. During the meeting, discuss the role

of each trade and the contractor.

Spacing and watt density may be confirmed as

follows:

English

Cable Spacing (in) = Heated Area (ft

2

) X 12

Heating Cable Length (ft)

Watt Density (W/ft

2

) = Heating Cable Wattage (W)

Heated Area (ft

2

)

Metric

Cable Spacing (cm) = Heated Area (m

2

) X 100

Heating Cable Length (m)

Watt Density (W/m

2

) = Heating Cable Wattage (W)

Heated Area (m

2

)

2

General Installation Guidelines

nVent.com | 13

For three-phase supply voltages, the total area is

generally divided into multiples of three equal

subsections, allowing for installation of a single

cable in each subsection. Heating cables of the

same length and wattage, installed in each

subsection, will provide a balanced electrical load.

It may not be possible to use a balanced electrical

load for small areas, therefore one or two heating

cables, single-phase connected, must be used.

Ensure that the cold lead length is sufficient to reach

the junction box. The standard cold lead length for

pre-engineered (SUB) cables is 15 ft (4.6 m), but

heating cables may have been custom designed

using longer cold leads. Plan the location of all

junction boxes and supply points so that they are

located within reach of the heating cable cold leads.

Typical junction box installation details are shown in

Section4.

The location of all joints in the ramp or slab

should be recorded on the layout drawing. Plan the

general layout of the heating cables to avoid cross-

ing control and expansion joints. In some cases, the

placement of these joints may have to be relocated

in order to divide the area equally since the quantity

of heating cables supplied may have been based

on equal subsection areas. If necessary, control

joints can be crossed using one of the two methods

shown in Figure 9. Crossing expansion joints should

be avoided, but if this is not possible, use the

method shown in Figure 10.

Types of Joints

Control joints are intended to control where the slab

will crack. Their exact location is determined by the

concrete installers before the concrete is poured.

Because of the reinforcement in the base slab, there

is rarely a shearing action caused by differential

vertical movement between the concrete on either

side of the crack. As a precautionary measure, how-

ever, either of the two methods of crossing control

joints shown in Figure 9 should be used. Minimize

the number of times the joint is crossed as shown in

Figure 9. When installing cables using the two-pour

2

General Installation Guidelines

14 | nVent.com

method, control joints must be placed in both the

base slab and the surface slab.

WARNING: Use caution when saw cutting the

control joints to avoid damaging the heating cables.

Consult with the electrical contractor or cable

installer before cutting or drilling to find out cable

depth.

2

General Installation Guidelines

nVent.com | 15

Angle iron

Hot/cold joints

Cold leads

Control joints

(cut into both bottom

and top slabs for two

pour installations)

Well-drained base

Nonmetallic

conduit

Base slab

Heating cable

1 x 1 x 12 in

(2.5 x 2.5 x 30 cm)

angle iron filled

with RTV or silicone

rubber caulk

Control joint

Steel rebar

Heating cable secured

to rebar with plastic

tie wraps

Concrete

Figure 9: Crossing control joints

Construction joints are joints that occur when the

concrete pour is going to stop but will resume at

a later date. Therefore, their location may not be

known beforehand. However, the reinforcement

is left protruding out of the first pour so that it

enters the next pour and therefore shearing action

2

General Installation Guidelines

16 | nVent.com

rarely occurs due to differential vertical movement

between the concrete on either side of the joint. As

a precautionary measure, either of the two methods

of crossing control joints shown in Figure 9 should

be used.

Expansion joints are placed where a concrete slab

abuts some structure, such as a building, a slab, or a

foundation, etc. Because the reinforcement does not

cross expansion joints, differential movement will

occur between the slab and the adjoining structure.

Avoid crossing expansion joints with the heating

cable. If this is not possible, expansion joints can be

crossed using a sand filled metal box as shown in

Figure 10.

Well drained

gravel base

Concrete slab

Expansion

joint

Heating

cable

Heating

cable

Metal

box

6 in x 6 in x 4 in

(15 cm x 15 cm x 10 cm)

metal box filled with sand

Figure 10: Crossing expansion joints

Refer to the installation instructions in Section 3

for your specific application. This section gives

details on the minimum and maximum concrete

or asphalt cover required over the heating cables

and maximum paver thickness, cable testing

requirements during installation, and other specific

installation details.

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Raychem MI Surface Snow Melting Installation guide

Raychem MI Surface Snow Melting Installation guide

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