Proper wiring installation and protection are paramount to ensure the reliability and safety of electrical systems. Adherence to these technical guidelines is essential:
Wiring Installation Method Statement
Following are points we included one by one.
1. Raceway Systems and Supports
All wiring should be installed within raceway systems or cable trays, as specified in the contract drawings. When below-grade concrete pits, manholes, pull boxes, or wireways are used, wiring must be adequately supported and secured to cable trays or similar supports. Cable racks should be installed on manhole walls to route and support cables along the walls’ perimeter.
Cable Handling
Whenever possible, wire and cable should be fed directly from spools or reels into conduits or manholes to prevent cable damage caused by dragging it over the ground during cable pulling. If pulling the cable over the ground becomes necessary, ensure that the ground surface is smooth, free of sharp gravel, and covered with protective material to prevent damage.
2. Splices in Wiring
For wire and cable runs involving 480 volts or higher system voltages, the wiring must be continuous without any splices.
Splicing Control Wiring
Splices in 120-volt control, alarm, instrumentation, and thermocouple wires are only permitted to be made on terminals as identified on the contract drawings for that purpose.
3. Splicing in Lighting and Convenience Receptacle Circuits
Splices in lighting and convenience receptacle circuits should be made using indent-type splicing sleeves insulated with ScotchÒ 33+ tape, 3M “ScotchlokÔ” electrical spring connectors, or equivalent. These splices must be securely fastened to the wires with ScotchÒ 33+ tape and enclosed within approved enclosures to ensure accessibility and safety.
Terminal Terminations
Terminations to solenoid valves and pigtailed devices should adhere to standards. For all other switches and devices, wiring should be connected directly without intermediate terminations.
4. Neat Wiring Bundling
Field wiring installed within panels or equipment enclosures must be neatly bundled and securely fastened unless wiring ducts are provided for field wiring. Bundles should be secured by attaching cable ties to the internal structure of the enclosure or screw-attached or epoxide cable tie mounts. The use of self-adhesive cable tie mounts is not allowed.
Preparation of Type TC Multiconductor Cable
Where type TC multiconductor power and control cables, or equivalent, enter an enclosure or motor control center wireway, the outer jacket should be entirely removed within 50 mm (2 in) of entry.
5. Cable-Pulling Compound
A cable-pulling compound must be used for all cable or wire installations required for underground or long above-ground conduit pulls. The chosen compound should be certified by the cable manufacturer as harmless to the specific type of cable used, and alkaline soap compounds must not be used.
6. Treatment of Aluminum Conductors
Whenever aluminum conductors are terminated, they should be treated with a corrosion inhibitor and oxide-penetrating compound, such as “Penetrox A” manufactured by the Burndy Company.
7. Taping of Lugs and Busses
The taping of lugs and busses should only be performed upon the request of the field representative engineer. Specific taping requirements for different voltage levels and situations are provided in the specifications.
Terminal Lugs for Low Voltage AC Power
Terminal lugs for low-voltage AC power wiring, not terminated on terminal strips or under terminal screws (e.g., motor leads to field conductors in motor terminal boxes), should be insulated using 3MÒ “Motor Lead Splicing Kits” 5300 Series, sized as required. If necessary, taping may be used as an alternate method following the provided procedure and materials.
| 1st Release Layer: | Two, half-lapped layers of ScotchÒ 33+ tape, sticky side out |
| 2nd Insulation: | Three, half-lapped layers of ScotchÒ 130C tape |
| 3rd Jacket: | Two, half-lapped layers of ScotchÒ 33+ tape |
Taping of Non-Insulated Busses
Non-insulated busses of bus duct in motor control centers, switchgear, and all non-insulated motor control center (MCC)/switchgear bus splice connectors should be taped following the specified procedure and materials. Alternatively, removable molded insulating boots (Raychem type BCIC or equivalent) may be used, provided they have the suitable voltage rating and are applied to match the exact bus/cable or bus/bus configuration. Heat-shrink-type insulation systems are not acceptable.
| Low Voltage | |
| 1st Release Layer: | Two, half-lapped layers of ScotchÒ 33+ tape, sticky side out |
| 2nd Insulation: | Two, half-lapped layers of ScotchÒ 33+ tape |
| Medium Voltage, 5 to 15kv | |
| 1st Release Layer: | Two, half-lapped layers of ScotchÒ 70 tape |
| 2nd Insulation: | Three, half-lapped layers of ScotchÒ 130C tape |
| 3rd Jacket: | Two, half-lapped layers of ScotchÒ 70 tape |
8. Torquing of Bolted Connections
All low and medium voltage power cable connections to lugged connectors and bus section joints, regardless of voltage, should be torqued according to the manufacturer’s requirements. Calibrated hand torque wrenches must be used for these terminations, and they should be witnessed and signed off by the field representative. In cases where the manufacturer’s torque data is unavailable, consultation with the field representative for proper torque values is necessary.
9. Spare Wires
All spare wires and instrument pairs/triads must be neatly bundled, coiled, and labeled individually as “SPARE” along with the appropriate conduit or cable tag. These spare wires should be of sufficient length to reach any termination point within the enclosure, programmable electronic system (PES), and motor control centers lineups. Spare wires in motor control centers entering via pits should be coiled in the top horizontal wireway. Ground all 600V spare wires and conductors in multiconductor cables at both ends using split bolt connectors or equivalent. Ensure that the grounding conductor in multiconductor cable is identified with a green surface as noted in paragraph 4.4.1. The grounding of spare conductors should only be performed upon the request of the field representative.
10. Pre-Bundling of Wiring
Pre-bundling of individual AC control and power wiring in a continuously wrapped manner is prohibited to prevent overheating of the innermost wires in the pull bundles.
11 Protection of Wiring
Grommet Strip for Access Holes
When wiring passes through access holes between adjacent metal or fiberglass enclosures (e.g., the rear of motor terminal boxes for motor lead access or wire routing cut-outs between motor control center and switchgear sections), either field-cut by the contractor or provided by the equipment manufacturer, the contractor must protect the wiring from damage caused by sharp edges around the entire opening. This protection should involve the use of a poly-cushioned, nylon-coated stainless steel push-on grommet strip.