Fire-Rated Fire Alarm and
Power Cables
This section provides an overview of general circuit design considerations and installation
guidelines for Pyrotenax® and Raychem® Fire-Rated Cables. For additional information,
contact your Tyco Thermal Controls representative or phone Tyco Thermal Controls at
(800) 545-6258. Also, visit our web site at www.tycothermal.com.
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Typical Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Typical Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pyrotenax System 1850™ Fire-Rated Mineral Insulated Cable . . . . . . . . . . . . . . . . . . . . 3
Cable construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Raychem RHW and Raychem MC Fire-Rated Polymer Insulated Cable . . . . . . . . . . . . . 4
Raychem RHW Cable Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Raychem MC Cable construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Raychem CI Fire-Rated Polymer Insulated Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Cable construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Approvals and Certifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Pyrotenax System 1850 MI cable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Raychem RHW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Raychem MC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Raychem CI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Outside North America. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Fire Alarm Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Pyrotenax System 1850 and Raychem CI Fire Alarm Circuit Design Considerations. . . . 8
Cable sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Equipment bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Cable termination and splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Installation Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Supporting fire alarm cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Seismic considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Terminating fire alarm cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Connecting fire alarm cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Critical Power Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Circuit Design Considerations – Pyrotenax System 1850 . . . . . . . . . . . . . . . . . . . . . . . 11
Cable sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Voltage drop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Equipment bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Short circuit capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Expansion and vibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Corrosion and MI cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Cable termination and splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Typical system installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Installation Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
H57573 12/05 (800) 545-6258 www.tycothermal.com Tyco Thermal Controls 1 of 22
FIRE-RATED FIRE ALARM AND POWER CABLES
Supporting System 1850 MI cable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Seismic considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Cable layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Terminating System 1850 MI cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Connecting System 1850 MI cable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Circuit Design Considerations – Raychem RHW and MC cables . . . . . . . . . . . . . . . . . . 19
Cable sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Voltage drop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Equipment bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Cable termination and pull boxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Installation Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Supporting Raychem fire-rated cables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Supporting Raychem RHW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Terminating Raychem RHW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Connecting Raychem RHW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Supporting Raychem MC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Terminating Raychem MC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Connecting Raychem MC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Seismic considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Cable layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2 of 22 Tyco Thermal Controls www.tycothermal.com (800) 545-6258 H57573 12/05
Introduction
Introduction
Tyco Thermal Controls Pyrotenax® System 1850™ mineral insulated (MI) wiring cables and
Raychem® polymer insulated cables (RHW, MC, and CI) meet the relevant requirements of
the U.S. National Electrical Code (NEC), the National Fire Alarm Code, the Canadian Electrical
Code (CEC), and the Canadian National Building Code for fire protection of emergency power
feeders and fire alarm circuits. The codes stipulate that a reliable source of power is required
to operate all critical life safety circuits necessary to provide time for a safe evacuation of
building occupants and to allow emergency crews to effectively control the fire. Fire resis-
tance ratings of 1-hour or 2-hours are required depending on national and local codes, the
type of circuit, and the environment.
Typical Applications
Tyco Thermal Controls fire-rated wiring cables meet the most stringent requirements for
2-hour fire rating, allowing for the highest degree of fire protection for emergency back-up
power supply systems, emergency equipment, and fire alarm systems. In the event of a fire,
electrical power and communication is preserved for critical life safety circuits. These critical
circuits provide power for:
• Fire pumps – to maintain pressure in the sprinkler system
• Firefighters’ elevators
• Smoke dampers and pressurization fans – to maintain smoke-free areas for egress
• Smoke extraction fans
• Emergency lighting and exit signs
• Fire alarm and voice communication systems
Typical Locations
Typical locations requiring emergency power feeders include:
• High-rise buildings
• Hospitals and other institutions
• Historic buildings
• Tunnels and subways
• Airports, stadiums, hotels, banks, etc.
Pyrotenax System 1850™ Fire-Rated Mineral Insulated Cable
System 1850 2-hour fire-rated MI cable offers a unique combination of dependability,
versatility, and permanence while withstanding continuous operating temperatures as high
as 250°C (82°F) and intermittent exposure temperatures as high as 1010°C (1850°F).
Featuring “zero smoke, zero flame spread, zero fuel contribution” and up to 80% space
savings compared to conventional conduit and wire systems, System 1850 MI cable is the
preferred choice for many specifiers. The ease with which this tough cable can be pulled into
difficult runs with tight corners makes it an ideal choice for many applications. System 1850
MI cable may be installed in virtually any location: outdoors, submersed or buried with a
protective over-jacket. The cable can be bent, twisted, or pulled, and can withstand
mechanical abrasion while remaining fully functional.
System 1850 MI cable is 2-hour fire-rated to UL 2196 / ULC S139-00, which utilize the ASTM
E-119 time-temperature curve. The test requires that cables remain operational after
H57573 12/05 (800) 545-6258 www.tycothermal.com Tyco Thermal Controls 3 of 22
FIRE-RATED FIRE ALARM AND POWER CABLES
exposure to temperatures up to 1010°C (1850°F) for two hours followed by the full force of a
firefighter’s hose stream. System 1850 MI cable passes this rigorous circuit integrity test
without additional mechanical protection.
CABLE CONSTRUCTION
Pyrotenax System 1850 MI cables are manufactured using only inorganic materials, copper
and magnesium oxide. This construction is inherently tough, yet allows the cable to be bent
and molded to fit into tight spaces. In addition, the totally inorganic construction of
unjacketed System 1850 MI cable allows for an environmentally clean electrical cable that
does not burn, produce smoke, or contribute fuel when exposed to fire conditions.
Seamless
copper sheath
Magnesium
oxide (MgO)
insulation
Solid copper
conductors
Fig. 1 System 1850 MI cable construction
For superior corrosion protection, an optional polymer jacket is available and is suitable for
use in temperatures as low as –40°C (–40°F).
CONFIGURATIONS
System 1850 fire-rated MI cables are available in a range of sizes and conductor
configurations for power feeders and in twisted pair configurations for fire alarm circuits.
600 V cables are approved for power feeders; 300 V cables are approved for signal
applications.
Raychem RHW and Raychem MC Fire-Rated Polymer Insulated Cable
Raychem RHW and Raychem MC are 2-hour fire-rated cables capable of withstanding expo-
sure temperatures up to 1010°C (1850°F). Raychem RHW achieves its fire rating when
installed in conduit. Raychem MC is a stand-alone fire-rated system that can be installed in
cable tray, in conduit, or directly supported. Featuring the familiarity and ease of installation
and termination of conventional conduit and wire systems, Raychem RHW cable is preferred
by many installers. Single and multiconductor Raychem MC offers the benefit of single-pull
installation and ease of pulling into locations with restricted space and runs with tight corners.
All Raychem fire-rated cables are 2-hour fire-rated to UL 2196 and ULC S139, which utilize
the ASTM E-119 time-temperature curve. The test requires that cables remain operational
after exposure to temperatures up to 1010°C (1850°F) for two hours, followed by the full
force of a firefighter’s hose stream. Raychem MC cable passes this rigorous circuit integrity
test without additional mechanical protection.
RAYCHEM RHW CABLE CONSTRUCTION
Raychem RHW cables are NEC Type RHH/RHW constructed to UL 44, and CEC Type R90,
constructed to CSA C22.2 No.38. Through unique design parameters and the use of highest
quality materials, this cable may be installed in wet locations and provides a 2-hour fire rat-
ing when installed in conduit. The conductor material is designed to withstand the tensile
stresses in a vertical run and is covered with a helically applied tape fire barrier. The silicone
insulation is a special type that provides electrical protection under fire conditions. The outer
4 of 22 Tyco Thermal Controls www.tycothermal.com (800) 545-6258 H57573 12/05
Introduction
jacket is a cross-linked polyolefin (XLPO) that gives superior abrasion protection and has a
low coefficient of friction for easy pulling into conduits. Both insulation and jacket are made
from “low smoke zero halogen” material and meet the low toxicity index per NES 713 (Naval
Engineering Standard 713).
Low smoke, zero halogen
(XLPO) jacket
Silicone rubber insulation
Fire barrier tape
Annealed copper conductor
Fig. 2 Raychem RHW cable construction
CONFIGURATIONS
Raychem RHW fire-rated cables are available in a range of sizes in single conductor
configuration only. This cable is 600 V rated and may be used in any application allowed by
electrical codes for Type RHH or RHW (Type R90 in Canada). For specifications, see the
product data sheets in the Technical Data section.
RAYCHEM MC CABLE CONSTRUCTION
Raychem MC cables are constructed to UL 1569 and are unique in this cable type in
providing a 2-hour fire rating. This metal-clad cable provides fire resistance without conduit
protection and the copper armor of Raychem MC cable meets the code requirements of the
NEC for an equipment grounding conductor.
For superior corrosion protection, an optional flame retardant polyvinyl chloride (PVC) or
low smoke, zero halogen polyolefin jacket is available.
Continuously welded and
corrugated copper armor
Silicone rubber inner jacket
Silicone rubber insulation
Annealed copper conductor
Fig. 3 Raychem MC cable construction
CONFIGURATIONS
Raychem MC fire-rated cables are available in a range of single and multiconductor sizes and
conductor configurations. For specifications, see the product data sheets in the Technical
Data section.
H57573 12/05 (800) 545-6258 www.tycothermal.com Tyco Thermal Controls 5 of 22
FIRE-RATED FIRE ALARM AND POWER CABLES
Raychem CI Fire-Rated Polymer Insulated Cable
Raychem CI polymeric cable is a line of fire alarm cable that is ideal for twisted pair commu-
nication wiring and also meets the survivability requirements of NFPA 72. It is a UL Listed
2-hour fire-rated cable requiring no conduit protection. It is also listed as a 2-hour fire-rated
Electrical Circuit Protective System when installed within the specified protective conduit.
CABLE CONSTRUCTION
Raychem CI meets the requirements for FPL cables to UL 1424, NPLF cables to UL 1425,
and FAS cables to CSA C22.2 No.208. The conductors for both shielded and unshielded
cables are insulated with silicone rubber and twisted together to form a single pair. In the
shielded design, the pair is wrapped with a copper/polyester tape shield and bare copper
drain wire. In both designs, the assembly is covered with a low smoke, zero halogen polyole-
fin jacket. The construction of Raychem CI allows the installer to strip the cable with minimal
effort.
Unshielded cable Shielded cable
Low smoke, zero
halogen polyolefin jacket
Copper/polyester tape shield
Low smoke, zero
halogen polyolefin jacket Stranded copper drain wire
Silicone rubber insulation Silicone rubber insulation
Annealed solid copper conductor Annealed solid copper conductor
Fig. 4 Raychem CI cable construction
CONFIGURATIONS
Raychem CI fire-resistant cable is a stand-alone 2-hour fire-rated cable, requiring no conduit
protection to achieve the fire-rating when tested to UL 2196. However, it is also 2-hour
fire-rated when installed in 1/2" minimum electrical metallic tubing (EMT) or rigid metal
conduit (RMC) and is ideal for retrofit applications in existing conduit. Raychem CI is fire-
rated with a utilization voltage of 72 V and is available in shielded and unshielded twisted pair
configurations, 18 AWG through 12 AWG. For specifications, see the product data sheet in
the Technical Data section.
Approvals and Certifications
PYROTENAX SYSTEM 1850 MI CABLE
Pyrotenax System 1850 MI cables meet the requirements of the circuit integrity fire test,
UL 2196 (ULC S139 in Canada), and are UL Listed and CSA Certified in North America.
The details of this system appear in the UL and ULC Fire Resistance Directories, in the UL
Directory as Electrical Circuit Protective System (FHIT), System No. 10, and are Factory
Mutual (FM) 2-hour fire rated.
Factory preterminated MI cable sets are approved for both nonhazardous locations and
hazardous locations. For specific approval information, see the product data sheets in the
Technical Data section.
6 of 22 Tyco Thermal Controls www.tycothermal.com (800) 545-6258 H57573 12/05
Introduction
RAYCHEM RHW
When installed in conduit as specified, Raychem RHW cables meet the requirements of the
circuit integrity fire test, UL 2196 (ULC S139 in Canada), and are UL Listed and CSA Certified
in North America. They are listed in the UL and ULC Fire Resistance Directories. For specific
approval information, see the product data sheets in the Technical Data section.
RAYCHEM MC
Raychem MC cables meet the requirements of the circuit integrity fire test, UL 2196, and are
UL Listed. They are listed in the UL Fire Resistance Directory. Note: 'MC' is not a CEC cable
type. For specific approval information, see the product data sheets in the Technical Data
section.
RAYCHEM CI
Raychem CI cables are UL Listed as stand-alone fire-rated cables requiring no conduit
protection when tested to UL Standard No. 2196. However, they are also listed in the UL and
ULC Fire Resistance Directories as fire-rated systems when provided with conduit protection.
They are CSA Certified and UL Listed fire alarm cables, NEC Type FPL and NPLF, and CSA
Type FAS. Cables are also UL listed as Type CL3 (Class 3 cables for remote control, signaling
and power limited circuits). For specific approval information, see the product data sheets in
the Technical Data section..
OUTSIDE NORTH AMERICA
Pyrotenax fire-rated fire alarm and power cables are also available for use outside North
America, and are LPCB certified to BS 6387, Categories C, W, and Z, and to BS 5839-1:2002
for standard and enhanced grades of cable. These products carry the CE Mark, and are
approved to local standards. Contact Tyco Thermal Controls for information on our range of
cables certified for use worldwide.
H57573 12/05 (800) 545-6258 www.tycothermal.com Tyco Thermal Controls 7 of 22
FIRE-RATED FIRE ALARM AND POWER CABLES
Fire Alarm Circuits
Fire alarm circuits may utilize Pyrotenax System 1850 MI cables or Raychem CI polymeric
cables. The following general guidelines relate to the design and installation of fire alarm
circuits using either cable technology.
Pyrotenax System 1850 and Raychem CI Fire Alarm Circuit Design Considerations
Fire alarm systems should only be designed by professionals familiar with generally
accepted design practices. The information provided below relates specifically to designs
using Tyco Thermal Controls fire alarm cables and must be followed, along with all relevant
local codes and standards, to ensure that the systems are designed properly. For additional
information, contact your Tyco Thermal Controls representative or phone Tyco Thermal
Controls at (800) 545-6258.
CABLE SIZING
Primarily data and signal communications, these circuits are low voltage and low current,
utilizing 18 AWG through 12 AWG conductors.
Cable sizing should be in accordance with the fire alarm system manufacturers’
recommendations.
EQUIPMENT BONDING
The copper sheath of System 1850 cable meets North American code requirements for an
equipment grounding conductor.
CABLE TERMINATION AND SPLICES
When using Raychem CI or Pyrotenax System 1850 shielded cables, the drain wire is
connected to the metallic foil or shield. At each junction box, the drain wires are connected
together, but not grounded; the shield drain wire is only grounded at one point in the circuit.
Raychem CI polymeric cable
Special terminations are not required for Raychem CI cable. A 2-hour fire-rated slice box
is available for use with this cable.
System 1850 MI cable
System 1850 MI fire alarm cables are approved as a complete system only when used
with the appropriate Pyrotenax termination and splice kits. The use of nonapproved
components may compromise the reliability of the system and will invalidate approvals
and warranties.
Brass
gland
Pot
Fig. 5 System 1850 MI cable termination
8 of 22 Tyco Thermal Controls www.tycothermal.com (800) 545-6258 H57573 12/05
Fire Alarm Circuits
Roof
n th floor
9 th floor
8 th floor
7 th floor
6 th floor
5 th floor
4 th floor
Data-gathering panels Other devices 3 rd floor
2 nd floor
1 st floor
Bas CPU First device on each floor Ground
em (Pull station, horn, speaker, strobe)
ent
Basement
Fire-rated
cable Transfer Emergency Security console
switch splitter (Central alarm control facility)
Fig. 6 Typical fire alarm system
Installation Guidelines
These installation guidelines apply to Pyrotenax System 1850 MI and Raychem CI polymeric
cables only. When installing a system, refer to the requirements in the UL/ULC Fire Resis-
tance Directory and the appropriate System 1850 or Raychem CI data sheets and installation
instructions (available via the Tyco Thermal Controls web site at www.tycothermal.com).
SUPPORTING FIRE ALARM CABLE
It is important that all support components are made of appropriate materials, such as copper,
steel, stainless steel, and concrete. Materials such as aluminum, brass, plastic, lead, wood,
etc. are not acceptable.
Raychem CI polymeric cable
In fire alarm applications, Raychem CI may be installed without conduit protection, pro-
vided that it is mounted on noncombustible surfaces such as concrete or masonry, or
supported by steel hangers from these surfaces. It may also be installed in 1/2" minimum
EMT, with steel set-screw fittings, or 1/2" RMC. Conduit supports must be spaced 48" on
center.
System 1850 MI cable
System 1850 MI cables may be directly mounted on noncombustible surfaces such as
concrete or masonry, or supported by steel rod and channel (trapeze) systems.
Tyco Thermal Controls and UL/ULC listing requirements for fire-rated cables stipulate
support spacing at certain intervals; refer to the installation instructions shipped with the
product and available via the Tyco Thermal Controls web site, www.tycothermal.com.
H57573 12/05 (800) 545-6258 www.tycothermal.com Tyco Thermal Controls 9 of 22
FIRE-RATED FIRE ALARM AND POWER CABLES
Trapeze Method Direct Mounting Method
Steel
rod
Twisted pair
cables
Noncombustible
Twisted pair material
cables
Steel
channel
Fig. 7 Typical fire alarm installations for System 1850 MI cable
SEISMIC CONSIDERATIONS
In areas where the risk of seismic activity is high, precautions must be taken where Tyco
Thermal Controls fire-rated cables cross expansion joints and at termination points.
For more information, see Appendix D.
TERMINATING FIRE ALARM CABLE
Raychem CI polymeric cable
Raychem CI cables are terminated in the same manner as conventional cable and do not
require special terminations. When terminating shielded cable, the shield is exposed by
stripping back the outer jacket, then removed and discarded. The shield drain wire is in
direct contact with the shield throughout the cable, and is used to preserve shield conti-
nuity at termination and splice points. The drain wire is joined at intermediate splice
points, but not bonded to ground; single point grounding dictates that it be bonded to
ground only at one end of a complete circuit.
Pyrotenax System 1850 MI cable
Details on terminating Pyrotenax System 1850 MI cables can be found in the installation
instructions provided with each System 1850 MI fire alarm cable termination kit. Factory
preterminated System 1850 MI cable sets are available. For details on preterminated
cable sets, contact your Tyco Thermal Controls representative or phone Tyco
Thermal Controls at (800) 545-6258.
CONNECTING FIRE ALARM CABLE
Raychem CI polymeric cable
For Raychem CI cable installed in EMT, use only steel set-screw connectors or an all-steel
compression bushing for coupling the EMT, and for the EMT connection to the enclosure.
Zinc or other materials are not acceptable.
Pyrotenax System 1850 MI cable
For Pyrotenax System 1850 MI cables, the termination gland is a brass fitting available in
1/2" and 3/4" NPT sizes, depending on the cable diameter.
Fig. 8 Brass gland
10 of 22 Tyco Thermal Controls www.tycothermal.com (800) 545-6258 H57573 12/05
Critical Power Circuits
Gland size information for each specific cable is available from the product data sheets in the
Technical Data section. When tightened with the recommended torque, this gland simulta-
neously seals the enclosure and grips the cable through a brass compression sleeve. This
connection, when installed according to the installation instructions, provides the following
benefits:
• Hydrostatic withstand pressure up to 6000 lbs/sq in (4.22 kg/sq mm)
• Pull-off force, when tightened to torque settings, as shown in Table 1
Table 1 Pull-Off Force for Torque Settings
Gland size (NPT) (in) Recommended torque (lbs-ft) Pull-off force (lbs)
1/2 25 175
3/4 42 200
Critical Power Circuits
Critical power circuits utilize Pyrotenax and Raychem cables. The following general
guidelines relate to the design and installation of critical power circuits specific to both
technologies.
Circuit Design Considerations – Pyrotenax System 1850
Critical power circuit systems should only be designed by professionals familiar with gener-
ally accepted design practices. The information provided below relates specifically to designs
using Pyrotenax power cables and must be followed, along with all relevant local codes and
standards, to ensure that the systems are designed properly. For further information, contact
your Tyco Thermal Controls representative or phone Tyco Thermal Controls at (800) 545-6258.
CABLE SIZING
System 1850 MI cable size is based on circuit breaker size, which in turn is based on load
calculations. Special rules apply for motors, including fire pumps, where cable size is based
on 125% of full load current. Use the ampacity tables specified in the electrical code to
determine the cable size. If the calculated voltage drop exceeds the specified limits, a larger
cable size must be chosen.
Multiconductor MI cables have the same ampacity ratings as multiconductor polymeric cable
types. However, the NEC allows full “free air” ampacity for unjacketed single conductor MI
cables configured according to Fig. 9 as long as a space of 2.15 cable diameters is
maintained between bundles.
In Canada, cable size is determined in accordance with Sections 4 and 8 of the CEC.
H57573 12/05 (800) 545-6258 www.tycothermal.com Tyco Thermal Controls 11 of 22
FIRE-RATED FIRE ALARM AND POWER CABLES
Spacing (S) between
multiphase paralleled
single conductor cables
(see Fig. 1.16)
Multiconductor
MI cable
(S)
Single
(S)
conductor
MI cables
Fig. 9 Spacing of bundled conductors
Although unjacketed single conductor MI cable is unaffected by any temperature increase
resulting under the installation conditions shown in Fig. 9, the termination may need to be
“sized-up” to keep it within its temperature limits in accordance with electrical code require-
ments. Refer to the installation instructions shipped with the product for details on sizing
terminations.
VOLTAGE DROP
Voltage drop calculations are based on calculated load, not circuit breaker rating.
For conventional cables, simple formulas are used to determine if the cable size listed in the
ampacity tables meets the required voltage drop limits. While these formulas can be applied
to System 1850 MI cable, voltage drop values specific to the characteristics of MI cable can
be calculated using any of the following:
• An equation based on the run length, the conductor current, and the circuit voltage is
provided in Appendix B
• A quick voltage drop calculator is available via the Tyco Thermal Controls web site,
www.tycothermal.com
• Pyrosizer™ MI cable sizing software is available via the Tyco Thermal Controls web site,
www.tycothermal.com, or through your Tyco Thermal Controls representative
EQUIPMENT BONDING
The copper sheath of System 1850 MI cables meets North American code requirements for
the equipment grounding conductor. The brass gland completes the grounding path from the
cable sheath to the equipment. For single conductor cables, the ground path includes a non-
ferrous brass plate, as shown in Fig. 10 (in Canada, brass plates are required only for ampac-
ities over 200 A).
12 of 22 Tyco Thermal Controls www.tycothermal.com (800) 545-6258 H57573 12/05
Critical Power Circuits
.
Single conductor Multiconductor
MI cables MI cable
Brass plate Brass gland
Lock washers
Enclosure wall
Lock washer
Lock washer
Steel enclosure cutout
(steel must be removed)
Details of brass plate
Fig. 10 Equipment bonding using brass plate
SHORT CIRCUIT CAPABILITY
The following graphs give the maximum allowable short circuit currents for System 1850 MI
cables. The first is based on the cable only. The cable will survive if the short circuit currents
shown are not exceeded; however, the terminations could be damaged. The second graph
provides the maximum short circuit current to avoid damage to terminations. The cable
system will tolerate short circuit currents up to this magnitude and survive undamaged.
1000 1000
Maximum short circuit currents Maximum short circuit currents
for Pyrotenax MI cables 1 cycle for Pyrotenax MI cables
excluding terminations 2 cycles to avoid damage to terminations 1 cycle
4 cycles 2 cycles
8 cycles 4 cycles
Conductor Current – Thousands of Amps
Conductor Current – Thousands of Amps
16 cycles 8 cycles
100 100
30 cycles 16 cycles
60 cycles 30 cycles
90 cycles 60 cycles
90 cycles
10 10
1 1
0.1 0.1
18
16
14
12
10
8
6
4
3
2
1
1/0
2/0
3/0
4/0
250 kcmil
350 kcmil
500 kcmil
18
16
14
12
10
8
6
4
3
2
1
1/0
2/0
3/0
4/0
250 kcmil
350 kcmil
500 kcmil
Conductor Size Conductor Size
Fig. 11 Short circuit currents
H57573 12/05 (800) 545-6258 www.tycothermal.com Tyco Thermal Controls 13 of 22
FIRE-RATED FIRE ALARM AND POWER CABLES
EXPANSION AND VIBRATION
In certain circumstances it may be necessary to take precautions to prevent mechanical
damage to System 1850 MI cable. See Appendix D for details.
CORROSION AND MI CABLE
In most applications, System 1850 MI cables can be used without any additional protection
against corrosion. However, in applications where the cable may be exposed to corrosives,
such as when the cable is directly buried or embedded in concrete, additional protection in
the form of a polymer jacket is required. Refer to Appendix E for more information on corro-
sion and MI cable.
CABLE TERMINATION AND SPLICES
System 1850 MI cables are approved as a complete system only when used with the appro-
priate Pyrotenax termination and splice kits. The use of nonapproved components will com-
promise the reliability of the system and will invalidate approvals and warranties.
Two types of termination kits are available: Pyropak™ kits for all single and multiconductor
cables, and Quickterm™ kits for #6 AWG and larger single conductor cables. The Quickterm
kits include a special connector to splice the solid MI conductor to a flexible tail (flexible tail
not supplied).
Factory preterminated System 1850 MI cable sets are available in a range of sizes and lengths.
For details on preterminated cable sets, contact your Tyco Thermal Controls representative
or phone Tyco Thermal Controls at (800) 545-6258.
Pyropak™ Quickterm™
Cap and
sleeve
Self-sealing
assemblies
tape
Brass
glands
Brass
pots
Brass
glands
Sealing
compound Heat-shrinkable
Crimp sleeving
connectors
Fig. 12 Terminations for System 1850 MI cable
In cases where the manufactured length is shorter than the required run length, a splice is
used to join individual lengths of cable. Two options for splicing System 1850 MI cable are
available:
Factory fire-rated splice: A UL/ULC 2-hour fire-rated, all-welded joint is installed at the
factory.
Field-installed fire-rated splice: A field-installed fire-rated splice, consisting of a splice kit
and a separate field fire protection kit, is used to extend cable length.
14 of 22 Tyco Thermal Controls www.tycothermal.com (800) 545-6258 H57573 12/05
Critical Power Circuits
Field-installed splice
Factory splice
Fig. 13 Splices for System 1850 MI cable
TYPICAL SYSTEM INSTALLATION
A typical critical power circuit installation utilizing System 1850 MI cable is shown in Fig. 14.
Additionally, components and accessories available for single and multiconductor MI cables
are shown in Table 2. For further information on components and accessories, see the prod-
uct data sheet in the Technical Data section.
Emergency
splitter
Splice
Brass
Transfer plate
switch
Quickterm
Transfer Clamp Flexible
switch tails
Gear
clamp
Main G
electrical Fire System 1850 fire-rated MI cable
switchgear pump Emergency
Generator splitter
Fig. 14 Typical System 1850 power circuit system
Table 2 Component and Accessory Availability
Catalog number Single conductor MI Multiconductor MI
Pyropak • •
Quickterm •
Field and factory splices • •
Brass plates •
H57573 12/05 (800) 545-6258 www.tycothermal.com Tyco Thermal Controls 15 of 22
FIRE-RATED FIRE ALARM AND POWER CABLES
Installation Guidelines
These installation guidelines apply to System 1850 MI cables only. When installing a system,
refer to the requirements in the UL/ ULC Fire Resistance Directory and appropriate System
1850 data manuals and installation instructions shipped with the product, and available via
the Tyco Thermal Controls web site at www.tycothermal.com. Refer to national and local
electrical codes for additional details. For further information, contact your Tyco Thermal
Controls representative or phone Tyco Thermal Controls at (800) 545-6258.
SUPPORTING SYSTEM 1850 MI CABLE
It is important that all support components are made of appropriate materials, such as copper,
steel, stainless steel, and concrete. Materials such as aluminum, brass, plastic, lead, wood,
etc. are not acceptable.
System 1850 MI cable may be directly mounted on noncombustible surfaces such as
concrete or masonry, or supported by steel rod and channel (trapeze) systems. To achieve
free air rating, spacing must be maintained between the cable bundles and also between the
bundles and the mounting surface; refer to Fig. 15. Tyco Thermal Controls and UL/ULC
listing requirements for fire-rated cables stipulate support spacing at certain intervals; refer
to the installation instructions shipped with the product and available via the Tyco Thermal
Controls web site, www.tycothermal.com.
System 1850 MI cable should not be installed in conduit, other than when transitioning
through a wall, floor, or ceiling,
Free air rated installation Free air rated installation Non-free air rated installation
Steel
rod
1-1/2" channel
(to maintain NEC Single
free air rating) conductor
Multiconductor cables
cable
Single
Noncombustible Noncombustible
conductor
material material
cables Steel
channel
Fig. 15 Supporting System 1850 MI cable
It is important to keep the overall loading on the rod and channel system within limits.
Table 3 shows the recommended loading guidelines based on the minimum channel depth
of 1-1/2 inch. Note that the cable load calculations as shown in Table 3 take into account
only the load represented by the MI cable.
Table 3 Loading Guidelines
Cable load* Support method
Up to 150 lbs 3/8" threaded rod
Between 150 lbs and 200 lbs 1/2" threaded rod
Between 200 lbs and 300 lbs 1/2" threaded rod, double channel
* Cable load = lbs/ft cable x total number of runs x 4
Note: Maximum width of 1-1/2" channel: 36"
16 of 22 Tyco Thermal Controls www.tycothermal.com (800) 545-6258 H57573 12/05
Critical Power Circuits
SEISMIC CONSIDERATIONS
In areas where the risk of seismic activity is high, precautions must be taken where the cable
crosses expansion joints and at termination points. For more information, see Appendix D.
CABLE LAYOUT
In multiconductor cables, the magnetic effects of the phase conductors cancel each other
out, allowing for cable installation in any configuration. However, single conductor cables
should be bundled in groups containing one conductor from each phase to minimize the
resulting magnetic field in each grouping. The grouped single conductor cables are then
fastened tightly together, ensuring that the gland connectors at each end of the cable run are
connected to the metal enclosure, either directly or through a brass plate. Typical single
conductor cable configurations are shown in Fig. 16. The neutral conductor may be located
within or outside the cable group.
Single Phase 3 Phase • 3 Wire 3 Phase • 4 Wire
Single circuit N A AN
(preferred)
AB BC BC
Single circuit
(alternative) ABN ABC ABCN
Two cables in
N S N A S A AN S AN
parallel per phase
(preferred) AB BA BC BC BC BC
Two cables in S
parallel per phase
(alternative)
ABNNBA ABC ABC ABCNNCBA
Three or more cables
N S N S N A S A S A AN S AN S AN
in parallel per phase
(preferred) AB AB AB BC BC BC BC BC BC
Three or more cables S S S S S S
in parallel per phase
(alternative) ABN ABN ABN ABC ABC ABC ABCN ABCN ABCN
Note: The spacing “S” between bundles, not including neutral, should be a minimum of 2.15 cable diameters in the U.S. (NEC), or 2 cable diameters in Canada (CEC).
Neutral may be located as shown, or outside groups in the most convenient location.
Fig. 16 Recommended installation configurations
Electrical codes generally limit paralleling cable configurations to cable sizes 1/0 AWG and
larger. The codes address the balancing of resistance by stipulating:
• All conductors must be the same length
• All conductors must be the same size and the same material
• All conductors must have the same type of insulation
• All conductors must be terminated in the same manner
A current measurement should be taken immediately after the cables begin to carry load.
Load imbalances between conductors of up to 10% are tolerable and expected. Deviations
above 10% must be investigated and corrected.
When installing single conductor cables through a ferrous enclosure, precautions must be
taken to prevent induction heating in the steel. This is accomplished by removing a section of
the enclosure and installing a nonferrous brass plate (in Canada, this is only required above
200 amperes). Brass plates with pretapped holes are available for the gland connectors.
H57573 12/05 (800) 545-6258 www.tycothermal.com Tyco Thermal Controls 17 of 22
FIRE-RATED FIRE ALARM AND POWER CABLES
Brass
plate
Fig. 17 Enclosure with cutout and brass plate
TERMINATING SYSTEM 1850 MI CABLE
Details on terminating System 1850 MI cables can be found in the installation instructions
provided with each System 1850 MI cable termination kit.
Factory preterminated System 1850 MI cable sets are available in a range of sizes and lengths.
For details on preterminated cable sets, contact your Tyco Thermal Controls representative
or phone Tyco Thermal Controls at (800) 545-6258.
Fig. 18 Preterminated cable set
CONNECTING SYSTEM 1850 MI CABLE
The termination gland is a brass fitting available in standard NPT sizes. The glands are sup-
plied in 1/2", 3/4", 1", or 1-1/4" sizes, depending on the cable diameter.
Fig. 19 Brass gland
Gland size information for each MI cable is available from the product data sheets in the
Technical Data section. When tightened with the recommended torque, this gland simulta-
neously seals the enclosure and grips the cable through a brass compression sleeve. This
connection, when installed according to the installation instructions, provides the following
benefits:
18 of 22 Tyco Thermal Controls www.tycothermal.com (800) 545-6258 H57573 12/05
Critical Power Circuits
• Hydrostatic withstand pressure up to 6000 lbs/sq in (4.22 kg/sq mm)
• Pull-off force when tightened to torque settings as shown in Table 4
Table 4 Pull-Off Force for Torque Settings
Gland size (NPT) (in) Recommended torque (lbs-ft) Pull-off force (lbs)
1/2 25 175
3/4 42 200
1 58 250
1-1/4 75 300
Note: Terminations are not required to be fire-rated since the emergency equipment they
serve is in a fire-rated room.
Circuit Design Considerations – Raychem RHW and MC cables
Critical power circuit systems should only be designed by professionals familiar with
generally accepted design practices. The information provided below relates specifically to
designs using Raychem RHW and MC power cables and must be followed, along with all
relevant local codes and standards, to ensure that the systems are designed properly. For
further information, contact your Tyco Thermal Controls representative or phone Tyco
Thermal Controls at (800) 545-6258.
CABLE SIZING
Cable size is based on circuit breaker size, which in turn is based on load calculations.
Special rules apply for motors, including fire pumps, where cable size is based on 125% of
full load current. Use the ampacity tables specified in the electrical code to determine the
cable size. If the calculated voltage drop exceeds the specified limits, a larger cable size must
be chosen.
Ampacity for Raychem RHW cables is based on cable in conduit rules in the NEC and CEC.
Higher ampacity is allowed for single conductor Raychem MC, in accordance with NEC Table
310.20, when bundled and configured for free air as shown in Fig.1.15 as long as a space of
2.15 cable diameters is maintained between bundles.
VOLTAGE DROP
Standard voltage drop calculations apply to Raychem RHW and MC cables.
EQUIPMENT BONDING
Normal equipment bonding rules apply to Raychem RHW in conduit; a properly sized equip-
ment grounding conductor is required. For further information on Raychem fire-rated
grounding conductors, contact your Tyco Thermal Controls representative or phone Tyco
Thermal Controls at (800) 545-6258.
Raychem MC cables are designed so that the copper sheath meets the NEC requirement for
an equipment grounding conductor; no separate grounding conductor is required. For single
conductor cables, the ground path includes a nonferrous (brass) plate.
CABLE TERMINATION AND PULL BOXES
Raychem RHW cables are terminated in the same manner as conventional cable in conduit
and do not require special terminations. Pullboxes are approved for use with Raychem RHW.
Raychem MC is terminated using readily available brass fittings and simple tools. Details of
terminating procedures can be found in the installation instructions provided with each cable
shipment.
H57573 12/05 (800) 545-6258 www.tycothermal.com Tyco Thermal Controls 19 of 22
FIRE-RATED FIRE ALARM AND POWER CABLES
Installation Guidelines
These installation guidelines apply to Raychem fire-rated cables only. When installing a
system, refer to the requirements in the UL/ ULC Fire Resistance Directory and appropriate
Raychem RHW or Raychem MC installation instructions shipped with the product and
available via the Tyco Thermal Controls web site at www.tycothermal.com. Refer to national
and local electrical codes for additional details. For further information, contact your Tyco
Thermal Controls representative or phone Tyco Thermal Controls at (800) 545-6258.
SUPPORTING RAYCHEM FIRE-RATED CABLES
It is important that all support components are made of appropriate materials, such as
copper, steel, stainless steel, and concrete. Materials such as aluminum, brass, plastic, lead,
wood, etc. are not acceptable.
SUPPORTING RAYCHEM RHW
Raychem RHW fire-rated cable in conduit may be mounted in any environment suitable for
conventional RHW cable in conduit. The conduit may be directly mounted on noncombusti-
ble surfaces such as concrete or masonry, or supported by steel rod and channel (trapeze)
systems. In a vertical run, the conductors must be supported inside the conduit in the rec-
ommended manner described in the installation instructions shipped with the product and
available via the Tyco Thermal Controls web site at www.tycothermal.com.
Trapeze support Two piece clamp
Clamp
Clamp
Conduit Conduit
Steel
Wall or floor channel
assembly
(noncombustible
material)
Steel channel
Fig. 20 Supporting Raychem RHW cable
It is important to keep the overall loading on the rod and channel system within limits.
Following are the recommended loading guidelines based on a minimum channel depth of
1-1/2 inch.
Table 5 Loading Guidelines
Cable load* Support method
Up to 150 lbs 3/8" threaded rod
Between 150 lbs and 200 lbs 1/2" threaded rod
Between 200 lbs and 300 lbs 1/2" threaded rod, double channel
* Cable load = (lbs/ft of conduit x total number of conduits + lbs/ft cable x total number of runs) x 5
Note: Maximum width of 1-1/2" channel: 36"
20 of 22 Tyco Thermal Controls www.tycothermal.com (800) 545-6258 H57573 12/05
Critical Power Circuits
TERMINATING RAYCHEM RHW
In critical circuits, Tyco Thermal Controls requires installation of an intermediate box to
prevent ingress of gases into critical equipment enclosures, as described in the installation
instructions shipped with the product, and available via the Tyco Thermal Controls web site
at www.tycothermal.com.
CONNECTING RAYCHEM RHW
No special accessories or tools are required for connecting Raychem RHW.
SUPPORTING RAYCHEM MC
Raychem MC may be directly mounted on noncombustible surfaces such as concrete or
masonry, or supported by steel rod and channel (trapeze) systems (see Figure 1.21). Free air
rating may be achieved when using bundled single conductor cables providing the proper
spacing is maintained between bundles and also between bundles and the mounting surface;
refer to Fig. 1.15. Tyco Thermal Controls and UL/ULC listing requirements for fire-rated
cables stipulate support spacing at certain intervals; refer to the installation instructions
shipped with the product and available via the Tyco Thermal Controls web site,
www.tycothermal.com.
Trapeze support Kindorf clamp Two piece clamp
Clamp Clamp
Clamp
Steel
Steel
Armor channel
channel
Armor Armor
Steel channel Wall or floor Wall or floor
assembly assembly
(noncombustible (noncombustible
material) material)
Fig. 21 Supporting Raychem MC cable
It is important to keep the overall loading on the rod and channel system within limits.
Following are the recommended loading guidelines based on a minimum channel depth of
1-1/2 inch. Note that the cable load calculations as shown in Table 6 take into account only
the load represented by the MI cable.
Table 6 Loading Guidelines
Cable load* Support method
Up to 150 lbs 3/8" threaded rod
Between 150 lbs and 200 lbs 1/2" threaded rod
Between 200 lbs and 300 lbs 1/2" threaded rod, double channel
* Cable load = lbs/ft cable x total number of runs x 4
Note: Maximum width of 1-1/2" channel: 36"
TERMINATING RAYCHEM MC
In critical circuits, Tyco Thermal Controls requires installation of an intermediate box to
prevent ingress of gases into critical equipment enclosures, as described in the installation
instructions shipped with the product, and available via the Tyco Thermal Controls web site
at www.tycothermal.com.
H57573 12/05 (800) 545-6258 www.tycothermal.com Tyco Thermal Controls 21 of 22
FIRE-RATED FIRE ALARM AND POWER CABLES
CONNECTING RAYCHEM MC
Removal of the copper sheath and insulation from the conductors is accomplished with stan-
dard tools in a few simple steps. For details, refer to the installation instructions shipped with
the product, and available via the Tyco Thermal Controls web site at www.tycothermal.com.
SEISMIC CONSIDERATIONS
In areas where the risk of seismic activity is high, precautions must be taken where the cable
crosses expansion joints and at termination points. For more information, see Appendix D.
CABLE LAYOUT
In multiconductor cables, the magnetic effects of the phase conductors cancel each other
out, allowing for cable installation in any configuration. However, single conductor cables
should be bundled in groups containing one conductor from each phase to minimize the
resulting magnetic field in each grouping. The grouped single conductor cables are then
fastened tightly together, ensuring that the gland connectors at each end of the cable run are
connected to the metal enclosure, either directly or through a brass plate. Typical single
conductor cable configurations are shown in Fig. 22. The neutral conductor may be located
within or outside the cable group.
Single Phase 3 Phase • 3 Wire 3 Phase • 4 Wire
Single circuit N A AN
(preferred)
AB BC BC
Single circuit
(alternative) ABN ABC ABCN
Two cables in
N S N A S A AN S AN
parallel per phase
(preferred) AB BA BC BC BC BC
Two cables in S
parallel per phase
(alternative)
ABNNBA ABC ABC ABCNNCBA
Three or more cables
N S N S N A S A S A AN S AN S AN
in parallel per phase
(preferred) AB AB AB BC BC BC BC BC BC
Three or more cables S S S S S S
in parallel per phase
(alternative) ABN ABN ABN ABC ABC ABC ABCN ABCN ABCN
Note: The spacing “S” between bundles, not including neutral, should be a minimum of 2.15 cable diameters in the U.S. (NEC), or 2 cable diameters in Canada (CEC).
Neutral may be located as shown, or outside groups in the most convenient location.
Fig. 22 Recommended installation configurations
Electrical codes generally limit paralleling cable configurations to cable sizes 1/0 AWG and
larger. The codes address the balancing of resistance by stipulating:
• All conductors must be the same length
• All conductors must be the same size and the same material
• All conductors must have the same type of insulation
• All conductors must be terminated in the same manner
A current measurement should be taken immediately after the cables begin to carry load.
Load imbalances between conductors of up to 10% are tolerable and expected. Deviations
above 10% must be investigated and corrected.
When installing single conductor cables through a ferrous enclosure, precautions must be
taken to prevent induction heating in the steel. This is accomplished by removing a section of
the enclosure and installing a brass plate, or by cutting slots in the enclosure between the
cable entries.
22 of 22 Tyco Thermal Controls www.tycothermal.com (800) 545-6258 H57573 12/05