- Requirements for Specific Equipment
6.0 REQUIREMENTS FOR SPECIFIC EQUIPMENT
The electrical safety
requirements for specific equipment are determined by the following standards:
1. NFPA 70, National Electrical Code (NEC 2002)
2. 29 CFR 1910, Occupational Safety and Health Standards
3. 29 CFR 1926, Safety and Health Regulations for Construction
NFPA 70E, Standard for Electrical Safety in the Workplace
29 CFR 1910 and 1926 frequently reference other safety guidelines for design,
maintenance. Such other guidelines comprise ANSI, ASTM, and IEEE specifications and
information derived from various engineering
sources or equipment manufacturer association
standards. However, the key document is NFPA 70, the NEC; all the other documents are
to it. The NEC reflects wiring and installation requirements that provide for an installation
that is essentially free from hazard but not
necessarily efficient convenient or adequate for good
6.1 CONVEYING SYSTEMS
Conveying systems are used to move materials,
goods, etc., from one place to another.
Because of their conditions of use, they are usually classified in service applications as
6.1.1 ELECTRICAL DESIGN CRITERIA
Electrical design criteria should be closely coordinated with the architect, structural
fire protection engineer, mechanical engineer, and electrical safety engineer to ensure that all
discipline requirements are
coordinated and met.
Factory and field performance tests and control and wiring diagrams should be specified in the
or contract because they are not otherwise provided by the factory. Acceptance
tests conducted by the factory representative, qualified independent
inspector, or engineer are
recommended. Tests conducted by UL and Factory Mutual Engineering Corporation (FM) are
ANSI and CMAA standards should be carefully reviewed to ensure that all applicable safety
requirements are covered in the specifications.
The designer should specify the following requirements:
1. Available system voltage
2. Control voltage
3. The motor
is constructed for the specific application
4. Motor horsepower, service factor, insulation class, and time ratings are sufficient to meet the
Working clearances and space requirements
6. Disconnecting means and other NEC requirements
6.2 CRANES AND HOISTS
significant factor in crane and hoist safety, after structural integrity, is electrical safety.
All the referenced standards support this
fact either directly or indirectly by the amount of
definition and space provided for electrical systems' controls, operations, and maintenance.
6.2.1 NEC GENERAL REQUIREMENTS
Basic installation and wiring safety requirements for cranes and hoists are given in NEC Article
6101. Electrical designers and maintenance personnel should thoroughly understand these
requirements and their intent. Some of the more significant
requirements are the following:
1. Cranes and hoists operated in hazardous (classified) locations shall conform to NEC Article
2. When the crane is operated above readily combustible materials, the resistors must be
located in a well-ventilated cabinet constructed
of noncombustible material and constructed
so that they will not emit flames or molten metal. See the exception (and requirements) that
applies to certain cabinets made of noncombustible materials.
3. Cranes and hoists operating on electrolytic cell lines have special
requirements, as given in
a. Grounding is not required for conductive surfaces of cranes and hoists that enter the
zone of a cell line, and the parts that come in contact with an energized cell or
attachments shall be insulated from ground.
controls that may introduce hazardous conditions into the cell line working zone
shall employ one or more of the following:
and ungrounded control circuit in compliance with NEC Section 668.21(a)
(2) Nonconductive rope operator
(3) Pendant pushbutton
with either non-conductive support and surfaces or ungrounded
1 See Appendix D, Reference Matrix.
6.2.2 DISCONNECTING MEANS
The disconnecting means provided for cranes and hoists may consist of two or more lock-opentype
motor circuit switches or circuit breakers. Article 610, Part IV, of the NEC, "Disconnecting
Means," and the installation and operating plans
should be studied carefully to determine the
disconnecting means requirements and locations. The two basic disconnects to consider are:
1. The runway conductor (conductors run along a crane runway for power or control)
disconnect shall be installed in accordance with NEC 610.31.
2. The crane and hoist disconnect which shall be provided in the leads from the runway
contact conductors or other power supply in accordance
with NEC 610.32.
Figure 6-1(a). An additional control switch or a remote control switch is required if the second disconnecting means is not accessible to
Figure 6-1(b). Second disconnect not required. A monorail hoist does not require a disconnecting means in the leads to the hoist machinery
if it is controlled from the floor, if it is within view of the power supply disconnect, and if there is no work platform provided to service
the hoist machinery.
NEC grounding requirements consider the crane or hoist with all its associated equipment,
including electrical equipment, as a single piece of equipment; therefore, all the conductive
component parts shall be bonded together so
that the entire crane or hoist is grounded in
compliance with NEC Article 250, and NEC Article 610. Metal-to-metal contact is required
between all surfaces including the trolley wheels and bridge. If any such surfaces are painted or
otherwise insulated, a separate bonding
conductor is required.
The bonding of all conductive surfaces by metal-to-metal contact is not to be considered as the
conductor for the electrical equipment (motors, motor controllers, lighting
fixtures, transformers, etc.)on the crane or hoist. The equipment
ground conductors that are run
with the circuit conductors shall comply with NEC Article 250.
A limit switch
is required to prevent the load block from passing the safe upper travel limit on all
Figure 6-1(b). Second disconnect
not required. A monorail hoist does not require a
disconnecting means in the leads to the hoist machinery if it is controlled from the
floor, if it is within view of the power supply disconnect, and if there is no work
platform provided to service the hoist machinery.
In the direction of live parts, the working space clearance is 2½ feet, and doors enclosing live
that may require service or maintenance shall open at least 90 degrees or be removable.
6.2.6 OSHA AND NEC REQUIREMENTS
1910.179 and NEC Article 610, Part F, provide additional electrical requirements
derived from ANSI and other standards. Significant requirements
are the following:
1. Control circuit voltage shall not exceed 600 Vac or dc. Pendant pushbutton voltage shall not
exceed 150 Vac
or 300 Vdc.
2. Support shall be provided for pendant multiconductor cables.
3. Electrical systems for cranes and hoists shall
provide failsafe operation. When power fails,
all motors shall be automatically disconnected so that they will not resume operation when
the power comes back on. Automatic cranes shall not commence motion automatically when
the power comes on after an outage. Pendant pushbuttons
shall be returned to the off
position when pressure is released. When the signal from a remote controller fails, all motion
6.2.7 MAINTENANCE AND OPERATIONS
It is important to have a comprehensive electrical maintenance program for cranes and hoists.
Every electrical part and circuit plays a critical operational safety role and must be checked and
serviced at the frequency and in the manner
specified by OSHA, CMAA, ANSI, and the
manufacturer's manual. Required weekly, monthly, and semiannual tests and required
are contained in ANSI B-30 and CMAA documents.
The basic references for safe operation and maintenance of cranes and hoists are contained
sections of 29 CFR 1910 and 1926.
6.2.8 DOCUMENTED MAINTENANCE
Maintenance checklists and schedules in compliance with OSHA,
owner's manuals, and
manufacturer's requirements for the specific equipment shall be provided as required. Weekly,
monthly, and semiannual
inspections shall be conducted, and comments and condition of the
inspected part shall be documented and certified.
frequencies of inspections vary in accordance with application, usage, and
authority. Frequent inspection and periodic inspection are defined
by OSHA as daily to monthly
and 1 to 12 months, respectively. Typical inspection frequencies for electrical equipment of
cranes and hoists
are as follows:
The inspection records shall provide an ongoing safety assessment of the equipment and be
used to predict repair-part replacement.
All inspections shall be dated and initialed by the
6.2.9 MECHANICAL ELEVATING AND ROTATING EQUIPMENT
electrical safety concern is working in proximity to live and unguarded electrical
overhead lines by uninsulated equipment. Unless these
lines are visibly grounded at the point of
work and the owner of the lines indicates that they are deenergized, barriers or insulating
protective material shall be installed to prevent worker contact with them. The following
clearances shall be maintained between equipment
and electrical overhead lines:
1. Lines 50 kV or below: 10 ft between the lines and any part of the equipment or load
over 50 kV: 10 ft plus 0.4 in. for every 1 kV above 50 kV.
In locations and situations where it is possible that the operator may have
that these clearances are being maintained, someone shall be designated to monitor the
clearances and provide the
operator with timely warning before contact can be made. The use
of cage-type boom guards, insulating links, or a proximity sensor shall
not alter the electrical
safety requirements of 29 CFR 1910.269(p)(4) and 1926.550, even if these devices are
required. (See Figure 6-2.)
Figure 6-2. A minimum clearance of 10 ft between overhead power lines and equipment is required for 50 kV and below while a clearance
of 10 ft plus 4 in. for every kV above 50 kV is required.
6.3 ELEVATORS AND ESCALATORS
Elevators and escalators are used to move
people and elevators are also used to move
materials. Design, installation, inspection, and maintenance activities require specialized
knowledge for safe operation and use.
6.3.1 CODES AND STANDARDS
A comprehensive electrical safety program for elevators and escalators
can be achieved
through the application of the correct codes and standards. All elevators are required to be
constructed, installed, and
maintained in accordance with ANSI/ASME A17.1. Reference
standards include NFPA 70 (NEC) for the electrical equipment wiring and NFPA 101
Safety Code). These standards reflect the interrelated roles of electrical design, maintenance,
and fire protection in the electrical
6.3.2 DESIGN SPECIFICATIONS
The electrical designer shall provide for the installation requirements of Article
620 of the NEC
as well as the ANSI/ASME A17.1 requirements for signaling, automatic fire protection, and
emergency power as required.
The manufacturer shall provide the required fire service key
switches, audible alarm devices, and internal wiring up to the terminal strips
in the elevator
126.96.36.199 VOLTAGE AND CURRENT LIMITATIONS
There shall be a 300-V limitation on all operating control
and signal circuits and related
equipment, including door operators. Exceptions are permitted for 25 to 60 Hz ac if the current
29 CFR 1910.269 (p)(4), 1926.952 (b)
Figure 6-2. A minimum clearance of 10 ft between overhead power lines and
equipment is required
for 50 kV and below while a clearance of 10 ft plus 4 in. for
every kV above 50 kV is required.
cannot under any conditions exceed 8 mA, or for dc voltage if the current cannot, under any
circumstances, exceed 30 mA.
Hoistway door conductors from the door interlocks to the hoistway riser shall be flame retardant,
for a temperature of at least 200°C, and Type SF or equivalent. See NEC Table 400.4
of the NEC for approved types of elevator cables and
Note 5 to NEC Table 400.4 concerning
special requirements for traveling control and signal cables. Operating control and signal cable
conductors may be as small as #24 AWG. Traveling cable conductors must be #20 AWG or
188.8.131.52 DISCONNECTING MEANS
disconnecting means requirements for elevators and escalators are both specific and
extensive, requiring careful study of the codes and installation
plans during design, acceptance
testing, and routine inspections. Some of the basic requirements of NEC 620.51 are the
1. There shall be a single means of disconnecting all ungrounded conductors to the main
power supply of each unit.
2. A single
elevator or escalator, with multiple driving machines, shall have one disconnecting
means to disconnect the motors and control valve operating
3. When there is more than one driving machine in a machine room, the disconnecting means
shall be labeled.
disconnect shall be a fused motor circuit switch or circuit breaker capable of being
5. The disconnect shall not be provided
with a means of being operated from a remote
6. A circuit breaker disconnecting means shall not be opened automatically
by a fire alarm
system, except as allowed by NEC.
7. The within-sight rule applies to all elevator equipment disconnects. Specific
given for elevators with or without field control.
8. The disconnecting means shall be installed in a location that
is readily accessible to only
When power from more than one source is used for single- or multiple-car installations,
separate disconnect should be provided for each source. These disconnects should be in sight
of the equipment supplied, and warning
signs should be placed on or adjacent to the disconnect
to read. For example, "Warning: Parts of the control panel are not deenergized by
Lighting circuits for each elevator require a disconnect switch in the equipment room labeled for
the car it serves and
lockable in the open position.
Elevator and escalator motors are considered as intermittent duty. This allows them to be
the overcurrent protection device supplying the power for the branch circuit, which
is selected by the percentages in NEC Table 430.22 times
the full load current of the motors.
For example: What is the load for a 15-minute rated 40-hp, 460-V, three-phase motor used as a
Step 1: Finding full load current — NEC Table 430.150
40 HP = 52 A
Step 2: Finding demand factors — NEC Table 430.22 (a)
15 minute rated = 85%
Step 3: Calculating load
52 A x 85% = 44.2A
Answer: Load is 44.2 amps.
All metal raceways and cables, Types MC, Ml, or AC, shall be bonded to the metal
frame of the
car. All elevator equipment including metal enclosures for electric devices on the car shall be
grounded in accordance with
NEC Article 250.
184.108.40.206 OVERSPEED PROTECTION
Overspeed protection for overhauling and under-hauling is required, as are motor-generator
overspeed requirements that must comply with NEC 430.89, Speed Limitation. However, these
requirements are a part of the more extensive requirements
of ANSI/ASME A17.1 for electrical
safety devices, which require scrutiny by designers, maintenance personnel, and inspectors.
Emergency power requirements are governed by ANSI/ASME A17.1 Rule 211.2, which requires
that the regenerative power
of an overhauling elevator prevent the elevator from attaining the
lesser of the governor tripping speed or 125 percent of the rated speed.
If the elevator power
system cannot absorb this power, a load shall be provided on the load side of the elevator
power disconnect switch.
If an emergency power supply is designed to operate only one
elevator at a time, the energy absorption means may, if required, be located
on the line side of
the disconnect. Other building loads that may be supplied by the emergency power source may
not be considered as absorbing
regenerated energy unless they use the emergency power
source as normal power. Refer to Article 620, Part X, of the NEC, Overspeed, for the
requirements covering these requirements.
In addition to the NEC, elevator and escalator requirements,
there are numerous electrical
requirements for the facilities designer in ANSI/ASME A17.1 and A17.3. A17.1 is a required
new elevator and escalator installations and can be used by the designer in
checking submittal drawings from the manufacturer. ANSI/ASME
A17.3 provides the safety
requirements for existing elevators and escalators and shall be referenced when existing
installations are to be modified or to determine
which modifications shall be made to existing
installations and equipment to maintain optimum safety. The following lists typical key electrical
requirements from ANSI/ASME A17.1 that the designer shall control over and above those from
1. Access to elevator equipment
is to be controlled and limited to authorized persons.
2. Elevator equipment cannot share space with other building equipment except
elevator equipment is separated from other equipment, enclosed by a rigid wire fence, and
provided with a lock that is strictly
for that enclosure.
3. Only electrical wiring, including raceways and cables, used directly in connection with the
wiring for (a) signals, (b) communication with the car, (c) lighting, heating,
air conditioning, and ventilating the car, (d) fire-detecting
systems, (e) pit sump pumps, and
(f) heating and lighting the hoist way may be installed in the hoist way.
4. A minimum lighting level
of 108 lux for the equipment rooms and spaces and 541 lux on the
floor of the pit is required. The basis for the specified illumination level
should be in
accordance with the Illuminating Engineering Society (IES) lighting handbook.
5. A stop switch (emergency stop) is required
in each elevator pit at the access door to the pit.
If the pit exceeds 6 feet 7 inches, a second switch is required adjacent to the ladder.
two switches will be connected in series.
6. Car lighting shall consist of a minimum of two lamps to be supplied by a dedicated
with a lock-open disconnect in the equipment room.
7. A 115-V, 20-A receptacle shall be provided in all equipment spaces and
in the pit.
8. A phase-reversal protection shall be provided to ensure that the elevator motor cannot start
if the phase rotation
is in the wrong direction or if there is a failure of any phase.
9. Capacitors and other devices whose failure could cause unsafe elevator
prohibited; only devices specified by the NEC or the manufacturer may be installed.
6.3.5 FIRE PROTECTION
electrical designer shall coordinate with the manufacturer the design of the fire protection
systems that connect to the elevator control
panel. The system will be designed to return the car
to a designated area (normally the first floor or lobby) in the event of smoke or fire
equipment area or near the elevators. In that event, the car returns to a designated area where
passengers can safely exit the
facility. In addition to coordinating car control, the system
provides for the shutdown of the electrical elevator equipment prior to operation
of the sprinklers
and the transmission of the alarm and provides a means for the firefighters to assume manual
control of the elevator
from the designated area. The requirements for these systems are
detailed in ANSI/ASME A17.1.
6.3.6 INSPECTIONS AND RECORDS
Elevator inspections and recordkeeping are performed in accordance with the local authority
having jurisdiction. The ANSI/ASME A17.2 series of inspectors manuals provide a guide for
performing tests and inspections as well as recommended
inspection checklists. In addition to
acceptance inspections and tests, the code requires 1- and 5-year inspections for electric
and 1- and 3-year inspections for hydraulic elevators.
Elevators are required to be in compliance with the issue
of ANSI/ASME A17.1 in force the date
they were installed. If the local authority has adopted ANSI/ASME A17.3, the code for existing
they shall be in compliance with it, except they shall not be downgraded to it. When
ANSI/ASME A17.3 is in force, it becomes the minimum
standard to which installations shall
adhere, and if existing installations are upgraded in accordance with ANSI/ASME A17.1, Part
they shall also be in compliance with the more stringent requirements of A17.3.
220.127.116.11 INSPECTOR QUALIFICATIONS
meet the requirements of ANSI/ASME QEI-1 and be recognized by the local
enforcing authority. Repair and maintenance personnel should be qualified
6.4 PORTABLE AND VEHICLE-MOUNTED GENERATORS
Using portable and vehicle-mounted generators to operate electric
tools on job sites is permitted
under specific conditions.
However, OSHA inspections have disclosed a potentially serious hazard resulting
from the use
of portable generators. Both OSHA and the NEC permit the use of two-wire, single-phase
generators of not more than 5,000
W "where the circuit conductors of the generator are
insulated from the generator frame and all other grounded surfaces." Under these conditions,
neither the receptacles, cord sets, nor tools need to be protected by GFCIs or an assured
equipment grounding conductor program. This exception
from using GFCIs is granted because
with an insulated (isolated) circuit, there is no dangerous current flow from the generator-fed
to ground, structural steel, or any other grounded object. However, the use of GFCI
devices is still recommended.
If the circuit conductors
are not isolated, however, the shock hazard would be the same as with
any other electrical source and the exemption does not apply. In wet
or high humidity
environments, circuit conductors may not be suitably isolated and the exception would not
electric generators that supply 15-or 20-A, 120-V receptacles and that are in use or
are available for use on construction sites shall meet
all the following conditions or be used only
with either GFCIs or an assured equipment grounding conductor program.
1. They must be
rated not more than 5 kW.
2. They shall have only a two-wire circuit (i.e., only 120-V output).
3. They shall have both circuit conductors insulated from the frame and all other grounded
With proper ventilation
there are no special requirements for wiring and equipment installed in battery rooms per NEC 480
Figure 6-3. The ungrounded frame of a generator is acceptable as a grounding electrode if the circuit conductors are insulated from the
frame and all other grounded surfaces.
Storage batteries are considered a live source and appropriate precautions
should be taken
when working around them. Information regarding batteries and battery rooms can be found in
NESC, NFPA 70E Article 240
6.5.1 SURROUNDING SPACE
Adequate space should be provided around storage batteries for safe inspection, maintenance,
testing, and cell replacement. Space shall be left above cells to allow for operation of lifting
equipment when required, for addition of
water, and for taking measurements.
Storage batteries should be located in a protective enclosure or area accessible
only to qualified
persons. A protective enclosure can be a battery room; a control building; or a case, cage, or
fence that shall protect
the contained equipment and minimize the possibility of inadvertent
contact with energized parts.
storage area shall be ventilated by either a natural or powered ventilation system to
prevent accumulation of hydrogen. The ventilation system
shall limit hydrogen accumulation to
less than an explosive level.
Figure 6-3. The ungrounded frame of a generator is acceptable as
a grounding electrode
if the circuit conductors are insulated from the frame and all other grounded surfaces.
in NEC 250.6 and 305.6 (a),
Because the vapors given off by a storage battery are very corrosive, the wiring shall withstand
action, and special precautions are necessary as to the type of insulation used
and the protection of all metalwork. It is stated by their
respective manufacturers that conduit
made of aluminum or silicon-bronze is well suited to withstand the corrosive effects of the
in battery rooms. In contrast, if steel conduit is used, it is recommended that it be zinc-coated
and kept well painted with asphaltum paint.
6.5.5 BATTERY ROOM
There are no special requirements for the type of fixtures or other electrical equipment used in
room, with proper ventilation. (See NEC 480 and Figure 6-4)
Figure 6-4. With proper ventilation there are no special requirements for wiring and equipment installed in battery rooms per NEC 480.
6.5.6 PERSONAL PROTECTIVE EQUIPMENT
PPE capable of protecting employees from acid splashes shall be used by those working
servicing batteries. The minimum acceptable PPE shall include acid-resistant gloves, aprons,
and chemical-splash goggles. A full-face
shield may also be used; it shall not, however, be worn
in place of goggles. The design and use of PPE for wear when servicing batteries
with OSHA requirements. Safety showers and eyewash stations are also required.
Tools used for working
on batteries shall be insulated or non-sparking.
Figure 6-4. With proper ventilation there are no special requirements for wiring and
equipment installed in battery rooms per NEC 480.
6.5.8 STORAGE BATTERIES AND BATTERY BANKS
The following subsection covers rechargeable batteries used as a source of electrical
This category is not limited to batteries of a particular voltage and energy rating, since the
nature of the associated electrical
hazards is similar without regard to battery size; the severity
of the hazard increases as the battery ratings increase.
Some of the types of hazards associated with storage batteries and battery banks are listed as
grounding of one polarity of a battery bank can create a hazardous voltage
between the ungrounded polarity and ground.
shorting of the exposed terminals or cables of a battery can result in severe
electric arcing, causing burns and electric shock to nearby
3. Hydrogen gas generated during battery charging can create fire, explosion, and toxicity
4. Exposed terminals
in a battery bank present electric shock hazards.
5. Batteries, particularly sealed-cell batteries, can explode if they are shorted or
if they are
charged at excessively high rates.
6. Electrolytes can be highly corrosive and can produce severe burns to personnel on
18.104.22.168 DESIGN AND CONSTRUCTION CRITERIA
Reliable design and construction criteria for storage areas for batteries are
1. Battery installations shall conform to the requirements in the current edition of the NEC and
banks should not be grounded except as required in NEC a ground detector should
be used to indicate an accidental ground.
should be mounted to allow safe and convenient access for maintenance.
4. Lockable doors should be provided to control access to rooms
or enclosures containing
5. Approved safety showers and eyewash stations should be provided close to battery banks.
6. Appropriate ventilation for discharges of gas should be provided.
7. In areas where seismic activity is present, the installation
should be designed according to
22.214.171.124 OPERATING CRITERIA
Operating criteria are as follows:
1. Maintain battery bank connections that are clean and
tight to prevent excessive heating
because of contact resistance.
2. Do not repair battery connections when current is flowing. An
accidental opening of the
circuit could result in a hazardous arcing condition.
3. Clearly post electrical and other hazards of battery
banks and emergency first aid
information near the equipment.
4. Arrange the battery banks so that temperature stratification will
not result in over- or undercharging.
Note: The optimum storage temperature for maximum battery life is 77°F ± 2° (25°C ± 1).
1996 - 2018
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas
and reference material while performing my work as an RF system and circuit design engineer.
The Internet was still largely an unknown entity at the time and not much was available
in the form of WYSIWYG
All trademarks, copyrights, patents, and other rights of ownership to images and text
used on the RF Cafe website are hereby acknowledged.
My Hobby Website: AirplanesAndRockets.com