3.1.1 Approval. Components of the general types listed below shall be approved for the purpose and listed or labeled by a nationally recognized testing laboratory.
-Plugs, connectors, and receptacles
-Attachment cables and flexible cords
-Switches
-Overcurrent devices
-Relays and contactors
-All wire (conductors)
-Wire connections (terminations)
-Transformers and ferroresonant regulators
-Electromagnetic compatibility EMC filters
-Fuses and fuse holders
-Motors and motor protection combinations
-Tubing and sleeving
3.1.2 Installation and Use. Components shall be installed and used in accordance with any instructions included in the listing or labeling.
3.1.3 Examination. Components shall be suitable for the application and shall be examined for:
1. Mechanical strength and durability
2. Heating effects under normal and abnormal conditions.
3. Arcing effects.
4. Classification by type, size, voltage, current capacity, frequency, and specific use.
3.1.4 Mounting. Components shall be mounted in accordance with the following requirements:
1. Components shall be securely mounted.
2. Components shall be located for ease of maintenance.
3. Components requiring periodic adjustments shall be readily accessible without disassembly.
4. Components requiring adjustment, calibration, testing, or service with power on shall have external test points, insulated potentiometer extensions, etc. to minimize exposure.
5. Components shall not be mounted on hinged or removable covers or doors.
3.1.5 Shields. Shield requirements are as follows:
1. Shields shall be of sturdy construction and should be provided with holes for inserting probes.
2. Shields shall not support combustion.
3. Shields shall be easily removed and replaced by service personnel.
4. Shields shall be securely mounted independently of components, i.e., removal of a shield shall not loosen components or devices.
5. Electrical shields shall not be conductive.
6. Lacquer, enamel, sealing compounds, paper, or cotton shall not be used in place of a shield.
3.1.6 Protection. Components shall be protected so as not to exceed their maximum ampacity rating by circuit breakers, circuit protectors or fuses.
3.1.7 Temperature. Components shall not be exposed to temperatures exceeding 90% of their maximum temperature rating.
3.1.8 Marking. Component designation shall be plainly indicated.
3.1.9 Terminals. Terminals shall comply with the following:
1. There shall be no unshielded terminals having hazardous potentials or hazardous energy levels external to control enclosures, compartments, or junction boxes.
2. Terminals should be sized and used in accordance with Table 2.
3. Terminals on terminal blocks should be numbered in ascending order from top to bottom or from left to right.
4. There shall not be more than two conductors per lug and two lugs per termination.
5. Terminals shall retain conductor strands without damaging the conductor.
6. Approved terminal lugs shall be used to connect conductors to component terminals which are not equipped with wire clamps, pressure plates or equivalent means of retaining conductor strands.
3.2.1 Requirements. Terminal lugs shall:
1. Be rated for screw and conductor ampacity.
2. Have insulated barrels.
Exception: Grounding conductors larger than #8 AWG.
3. Be used on untinned, stranded wire only.
4. Be securely crimped with appropriate tool.
3.2.2 Applications. Terminal lugs shall be applied in accordance with the following:
1. Ringed tongue: Acceptable for all terminations.
2. Flat spade: NOT acceptable for terminating hazardous potentials, hazardous energy levels or for grounding.
3. Flanged spade: Not acceptable for grounding except on a captive screw.
4. Female tab: Acceptable only for terminations to fixed male tabs on components. NOT acceptable for grounding. Must be fully insulated.
3.3.1 General Requirements. Control switches shall meet the following requirements:
1. Voltage is restricted to 120 V, maximum.
2. Amperage is restricted to the maximum rating of the device.
3. Exposed parts, including mounting hardware, shall be grounded, of insulating material, or be adequately covered by insulating material.
4. Shall be labeled for their function.
5. Switch function shall comply with Sec. 10.
3.3.2 Pushbutton Type Switches. Pushbutton type switches shall meet the following requirements:
1. Pushbutton colors shall comply with Table 3.
2. Pushbutton heads shall comply with Table 3.
Examples are:
3.3.3 Lever Type Switches. Lever type switches shall meet the following requirements:
1. Snap Switch. Used for lighting control; not normally used in equipment.
2. Toggle Switch: Used for power control, 120 V or less, 15 A or less.
3. In Line Switch: Not allowed.
|
Color |
Function |
Head Type |
|
Black or Green |
Start or Power On |
Flush or Recessed |
|
Red |
Stop or Power Off |
Extended |
|
Red |
Emergency Off |
Mushroom |
|
Red |
Emergency Stop |
Mushroom |
|
Yellow |
Emergency Return |
Mushroom |
|
Black or Green |
Two Hand Control |
Mushroom |
Note: Other functions may be any color except red.
Table 3. Pushbutton Color Code
3.4 Indicating Lights and Lighted Switches
3.4.1 General Requirements. Indicating lights and lighted switches shall meet the following requirements:
1. Voltage is restricted to 120 V, maximum.
2. Shall be installed in 24 V circuits or have voltage reducing devices in the light assembly that limits the bulb voltage to 24 V maximum.
Exception: Neon lights.
3. Where multiple bulb socket assemblies are used, the bulbs shall be rated for not more than 24 V and shall be connected in parallel.
4. Two terminal lamp sockets shall be wired with the shell terminal connected to the grounded conductor.
5. Shall be labeled for their function.
6. Exposed parts, including mounting hardware, shall be grounded, of insulating material, or be adequately covered by insulating material.
7. Lens color shall comply with Table 4.
3.4.2 Lighted Switches. Lighted switches shall comply with both Table 3 and Table 4.
|
Color |
Function |
Indication |
|
Red |
Emergency or Warning (e.g., Alarm, Overload, Limit Exceeded) |
Danger, abnormal, unsafe or wrong condition |
|
Green |
Satisfactory, Ready, Go or Proceed (e.g., Power On, Cycle Complete |
Prerequisite, safe, start, test or right condition |
|
Yellow (Amber) |
Status, Interrupt, Stop (e.g., Motors On, Heaters On) |
Attention, caution, standby, alert |
|
White |
Information (e.g., AC ON, AC Off, Power Off) |
Normal conditions, other than wrong , right, or alert |
Notes:
1. Other lenses may be any color except red.
2. Green may be used when white is not available.
3. Flashing indicating lights may be used when the application requires a more compelling indication.
Table 4. Indicator Light Color Code
Notes:
1. Capacitors containing polychloronated biphenyl (PCB) shall not be used.
2. Polarized tantalum electrolytic capacitors may explode and / or ignite when reversed wired.
3.5.1 Safety Vent. Capacitor venting requirements are:
1. Capacitors greater than 1 inch in diameter, or capable of storing more than four joules, must be vented.
2. The capacitor vent must be unobstructed for a minimum of 0.2 inch.
3. Capacitors mounted horizontally must have vent hole placed in upper quadrant
(9, 12, 3 o’clock position).
3.5.2 Protection. Capacitor shielding requirements are:
1. Protection from venting or rupture must be provided by mounting or shielding capacitors so that vapors or debris will not be hazardous to personnel.
2. Terminals must be protected from shorting by tools.
3. Lacquer and sealing compounds must not be relied upon to provide protection.
3.5.3 Bleeder Resistor. Bleeder resistor requirements are:
1. A bleeder resistor must provided if operating potential exceeds 60 V or stored energy exceeds 20 joules.
2. Under no load condition, the resistor must reduce voltage to less than 60 V and stored energy to less than 20 joules in 10 seconds or less.
3.5.4 Energy Calculation. The formula for energy calculation is J = 1/2 C V^2 where:
J = energy in joules (watts-seconds)
C = capacitance in farads
V = DC voltage in volts
Inserting values in the energy formula gives the maximum allowable voltage and / or capacitance to limit the stored energy.
This section applies to transformers operating at 600 V or less and installed as field replaceable components.
3.6.1 Location. Transformers shall be accessible for inspection and service.
3.6.2 Protection. All ungrounded conductors in the INPUT (primary) and OUTPUT (secondary) shall be protected by an overcurrent device rated at not more than 125 % of the transformer full load current.
3.6.3 Selection and Use. Table 5 and Table 6 and Table 7 are provided as aids for proper selection and use of transformers and associated overcurrent protection devices.
3.6.4 Marking. Each transformer shall have a nameplate manufacturer, rating, frequency, input voltage and output voltage(s).
3.6.5 Guarding. Transformers shall be securely fastened and protected from physical damage. All exposed hazardous potentials or hazardous energy levels shall be guarded by shields or enclosures.
3.6.6 Ventilation. Ventilation shall be adequate to dissipate the transformer full load heat losses without creating an excess ambient temperature.
3.6.7 Isolation. Transformers shall provide complete isolation between input and output windings.
3.6.7.1 Auto Transformers. Autotransformers shall not be used to develop a control circuit from a power circuit because they do not provide complete electrical isolation between input and output windings. They may be used within control or power circuits with the following restrictions:
1. Control Circuits- Auto transformers may be used for varying the voltage if the output circuit has a grounded conductor that is electrically connected to the grounded conductor of the input circuit.
2. Power Circuits- Auto transformers may be used for buck / boost applications that comply with NEC Article 210-9.
3.6.7.2 Isolated Power Systems. Isolated power systems have limited use in equipment. When used, they shall meet the following requirements:
1. Purpose - To reduce noise by not referencing the output circuit to ground.
2. Labeling- The transformer and any components (devices) connected to the transformer output shall be clearly labeled to warn operators and service personnel of the ungrounded condition.
3. Grounding- All conductive metal shall be effectively bonded to the equipment grounding conductor.
4. Ground Fault Detection- Ground fault detection lights, a ground fault circuit interruptor (GFCI) or a line isolation monitor shall be installed in the output circuit to indicate an isolation fault condition.
3.6.8 Grounding.
3.6.8.1 Conductive Metal. Exposed, noncurrent-carrying metal guards, cases, etc., shall be effectively bonded to the equipment grounding conductor as specified in Sec. 5.
3.6.8.2 Output (secondary) Grounding.
The secondary(s) of transformers shall be grounded according to Figure 2 on and the following:
1. 150 V or less- The secondary of the transformer shall have one of the conductors referenced to ground, at the transformer, with a grounding conductor.
EXCEPTION: Transformers feeding rectification devices and isolated power systems.
2. Over 150 V single-phase- The phase conductors shall not be grounded.
3. Over 150 V multiphase- The phase conductors shall not be grounded. If the transformer is a "WYE" type, the center point of the secondary shall be referenced to ground, at the transformer, with a grounding conductor.
3.7 Plugs, Connectors, and Receptacles
3.7.1 Typical Uses. Typical uses for these devices are:
1. Attachment plugs and cord connectors are used on power attachment cords.
2. Connectors are used for power distribution to components and subassemblies within the equipment system.
3. Receptacles are used for :
a. Power distribution to black boxes to facilitate their replacement.
b. Convenience outlets, when required, on the equipment.
3.7.2 General Requirements. Attachment plugs, cord connectors and receptacles shall meet the following requirements:
1. Receptacles and cord connectors shall not accept an attachment plug with a different voltage or current rating.
Exception: A 20 A ‘T" slot receptacle is allowed to accept a 15 A plug of the same voltage.
2. The number of contacts shall be the same as the number of connected conductors.
3. The grounding terminal shall be used only for grounding purposes.
4. Female cord connectors shall be used only to supply power to a fixed male receptacle, eg., no extension cords.
5. Shall be designed so that grounding reliability is maintained.
6. The grounded conductors shall be terminated on the identified terminal of the device. The identified terminal shall be white or labeled "W" or "WH."
7. Shall be standard NEMA configuration. See Figure 4.
8. Special configurations shall comply with all the requirements of this section.
3.7.3 Plugs and Connectors. Plugs and connectors shall comply with the following:
1. Shall be designed so that the grounding connection is made first and broken last.
2. Shall have a nonconductive body or be internally grounded.
3. Must be of "DEAD FRONT" construction.
4. When disconnected, shall not have hazardous potentials or energy levels on exposed contacts.
5. Power and control circuits shall not be carried in the same plug or connector.
6. Input (line) and output (load) power circuits shall not be carried in the same plug or connector.
7. Shall be equipped with strain relief. See Sec. 6.8.
8. Shall be grounding type.
EXCEPTION: When supplying power to double insulated equipment.
9. Shall be rated for not less than the ampacity of the connected circuit.
10. All connectors shall be keyed or otherwise identified to prevent mismating of similar connectors in adjacent areas.
3.7.4 Receptacles. Receptacles shall comply with the following.
1. Voltage and current ratings shall not be less than that of the supply circuit.
2. When installed for convenience use, shall be rated at not less than 15 A at 125 V.
3. When installed for power distribution, shall not have a connected load exceeding 80% of rating.
4. Shall be grounding type specification grade receptacles.
5. Shall be enclosed.
6. Shall be securely mounted to a vertical surface or may be mounted to a horizontal surface with face plate down.
7. Shall be accessible to service personnel.
8. Shall be accessible without removing covers or opening doors when installed as convenience outlet for operator use.
9. Shall be protected by ground fault circuit interruptor (GFCI) when installed in a damp or wet location, e.g., hose wash down area.
10. Shall be under the control of the emergency off (EMO) circuit.
11. Faceplates shall be flush with the outer edges of the box.
12. Faceplate screws or faceplate screw holes shall not be use for receptacle mounting unless other provisions are made to counteract the plug insertion pressure.
3.7.5 Temporary Power Taps. Temporary power taps are unacceptable for installation in / on equipment.
3.7.6 Multioutlet Assemblies. Multioutlet assemblies (strips) shall comply with the following:
1. They shall be listed or labeled by a nationally recognized testing laboratory.
2. They shall contain specification grade receptacles.
3. They shall be grounded in accordance with the requirements of Section 5.
3.7.7 Boxes. Boxes shall comply with the following requirements:
1. All boxes shall be suitable for their environment. See 6.1.
2. Boxes which are accessible to nonservice personnel shall not have knockouts.
3. Boxes shall be securely mounted.
4. Box size shall be sufficient to allow free space for all enclosed conductors. See NEC, Art. 370.
5. Metal boxes shall be grounded by the main incoming grounding conductor in accordance with the requirements of Section 5.
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