Junction Boxes : Selection , Sizing and Termination : Top 50 Question and Answers

Junction Box Philosophy: Top 50 Q&A

Junction Box Philosophy: Top 50 Interview Questions and Answers

Part 1: JB Selection and Specification (Q1 - Q15)

1. What are the three primary criteria for selecting a Junction Box (JB) material?

Key Philosophy: Material Suitability

  1. Environmental Corrosion Resistance:
    • For Offshore/Coastal/Chemical environments, 316L Stainless Steel is the standard, offering superior resistance to chlorides.
    • For General Industrial (non-corrosive) or cost-sensitive areas, painted Carbon Steel or Glass Reinforced Polyester (GRP) may be used.
  2. Hazardous Area Rating (Ex Certification):
    • The JB must possess the correct Ex rating (e.g., Ex-e, Ex-ia, Ex-d) corresponding to the area classification (Zone 1, Zone 2, etc.). Ex-e (Increased Safety) is common for general signaling JBs.
  3. Temperature and UV Resistance:
    • Operating temperature range must be suitable for the site (T-rating). For outdoor use, the material (especially GRP) must have adequate UV stabilization.

2. Explain the difference between an **Ex-e** and an **Ex-d** JB and their typical use cases.

Key Philosophy: Hazardous Area Protection Methods

  1. Ex-e (Increased Safety):
    • Principle: Prevents sparks/hot surfaces in normal operation by limiting temperature rises and providing secure terminations/clearance.
    • Construction: Typically robust stainless steel or GRP with adequate internal space and robust terminals.
    • Use Case: Most common for instrumentation and control signaling, where power is low.
  2. Ex-d (Flameproof/Explosion Proof):
    • Principle: Contains any explosion that may occur inside the enclosure, preventing propagation to the surrounding atmosphere.
    • Construction: Heavy, thick-walled cast aluminum or steel, often with flame paths on the cover.
    • Use Case: Used for higher power applications (e.g., motor starters, heaters) where sparking is inherent during normal operation.

3. What is the significance of the **IP Rating (e.g., IP66)** for a JB?

Key Philosophy: Ingress Protection

  1. Definition: IP stands for Ingress Protection, defining the degree of sealing effectiveness against foreign bodies (solids and liquids).
  2. First Digit (6 - Solid):
    • Indicates complete protection against dust ingress. This is crucial in dusty industrial environments.
  3. Second Digit (6 - Liquid):
    • Indicates protection against powerful water jets (e.g., hosing down equipment). IP66 or IP67 (immersion) are standard minimums for outdoor industrial JBs.

4. Why must JBs used in Intrinsically Safe (IS) circuits be distinctly segregated and labeled?

Key Philosophy: Intrinsic Safety Integrity

  1. Energy Limitation: IS circuits limit energy (voltage/current) to prevent ignition in a hazardous area. Cross-contamination with Non-IS circuits invalidates this protection.
  2. Segregation Requirement:
    • IS JBs must be painted Light Blue and distinctly marked.
    • IS and Non-IS cables and terminals must maintain specified clearance (typically 50mm) if run in the same area. It is best practice to use separate JBs entirely.
  3. Personnel Safety: Distinct labeling prevents untrained personnel from inadvertently connecting non-certified equipment to the IS loop.

5. What is the minimum required **spare capacity** (in terms of terminals) typically specified for a JB, and why?

Key Philosophy: Future Expansion and Maintenance

  1. Minimum Requirement: Typically, a minimum of 20% spare terminals is specified for instrument and control JBs, and sometimes higher (e.g., 25% or 30%).
  2. Purpose of Spares:
    • Future Modifications: Accommodate last-minute changes, temporary wiring, or additional instruments added during the later stages of a project or after commissioning.
    • Maintenance: Provide spare terminals for bypassing faulty terminals or testing without disturbing existing wiring.
    • Efficiency: Reduces the need to install a new JB when only a few extra connections are required.

6. When specifying a JB, what type of terminal block is preferred for long-term reliability in vibrating environments?

Key Philosophy: Termination Reliability

  1. Preferred Type: Screw Clamp Terminals with a robust, self-locking design (e.g., cage clamp) are traditionally preferred in heavy industrial applications.
  2. Alternative: Spring Clamp (Cage Clamp) terminals are also highly reliable and resistant to vibration, often preferred for signal wiring due to fast installation and self-adjusting clamping force, which reduces the need for re-torquing.
  3. Reasoning: Screw connections, when correctly torqued, maintain consistent low resistance. Spring clamps maintain pressure via a spring mechanism, compensating for temperature fluctuations and conductor relaxation better than standard screw terminals.

7. Describe the key consideration for JB selection when cable entry is required from the top and bottom.

Key Philosophy: Internal Separation and Drainage

  1. Need for Separation:
    • If a JB has entries from both top and bottom, the risk of water ingress (running down cables from the top) is higher.
  2. Best Practice (Bottom Entry): Most industrial specifications mandate bottom entry only, as it minimizes water ingress and allows the enclosure IP rating to be more reliably maintained.
  3. Glanding and Sealing: If top entry is unavoidable, ensure IP-rated shrouds or weather covers are used, and that the glanding technique is impeccable to prevent water tracking down the cable sheath into the enclosure.

8. What is the role of the **Temperature Classification (T-rating)** on a hazardous area JB?

Key Philosophy: Auto-ignition Prevention

  1. Definition: The T-rating (e.g., T3, T4, T6) specifies the maximum surface temperature the JB can reach under the worst-case operating conditions.
  2. Critical Safety Check: The maximum surface temperature of the JB must always be lower than the auto-ignition temperature of the flammable gas or vapor present in the classified area.
  3. Common Ratings:
    • T4 (135°C max) is often a minimum requirement.
    • T6 (85°C max) is the safest and is required for highly volatile substances like Carbon Disulphide.

9. When are GRP (Glass Reinforced Polyester) JBs preferred over Stainless Steel JBs?

Key Philosophy: Non-metallic Advantages

  1. Weight: GRP JBs are significantly lighter, making installation easier, especially at height.
  2. Corrosion: GRP is completely immune to galvanic and general corrosion, which is a key advantage over metallic JBs, even stainless steel, in extremely aggressive chemical environments.
  3. Radio/EM Interference: GRP does not interfere with radio frequency (RF) signals and acts as an insulator, reducing the risk of accidental contact with live components inside.
  4. Cost: GRP enclosures are typically a more economical solution than stainless steel.

10. What information is crucial to include on the **JB Tag/Nameplate**?

Key Philosophy: Identification and Safety

  1. Unique Identification: The JB Tag Number (e.g., EJB-001, IJB-102) matching the instrumentation or electrical index.
  2. Ex Certification Details: The full ATEX/IECEx certification markings, including Ex type, protection level, and T-rating.
  3. Voltage/Current Rating: The maximum operating voltage/current of the JB circuits.
  4. Warning: A standard warning (e.g., "IS Circuit - Do Not Open When Energized" or "Hazardous Voltage").

11. How do you select the **gland material** based on the JB material (e.g., brass vs. stainless steel)?

Key Philosophy: Galvanic Corrosion Prevention

  1. Prevent Galvanic Corrosion: The primary rule is to avoid dissimilar metals coming into contact, especially in damp or corrosive environments.
  2. Metal JB Rule: For Stainless Steel JBs, Stainless Steel Glands (316L) should be used. Using brass glands on SS JBs without suitable interfacing washers can lead to galvanic corrosion.
  3. GRP JB Rule: For GRP JBs, Nickel-Plated Brass Glands are often used, as GRP is non-metallic, eliminating the galvanic corrosion risk at the enclosure interface.
  4. Earthing Integrity: Metallic JBs require metallic glands for armored cables to ensure armored earth continuity.

12. What specific features are required for a JB housing a **fiber optic cable**?

Key Philosophy: Fiber Management

  1. Strain Relief: Adequate strain relief mechanisms to prevent tension on the delicate fiber.
  2. Splice/Patch Tray: Internal provision for fiber optic splice trays or patch panels to manage and protect the fusion splices or connectors.
  3. Bending Radius: Sufficient internal space and radius controls to ensure the fiber bending radius is not violated, which can cause signal loss (attenuation).

13. In a high-vibration application (e.g., near a large compressor), what JB mounting accessory must be specified?

Key Philosophy: Vibration Mitigation

  1. Accessory: Anti-vibration mountings or damping pads (rubber/elastomeric isolators).
  2. Function: These absorb the mechanical vibrations from the machinery before they are transmitted directly into the JB structure.
  3. Internal Impact: Vibration can cause:
    • Screw terminals to loosen, leading to intermittent connection faults.
    • Internal components to fail prematurely (e.g., relay contacts).

14. What determines the selection of **terminal size (cross-sectional area)** for a JB?

Key Philosophy: Conductor Capacity and Current Rating

  1. Conductor Size: The terminal must be sized to accept the largest conductor feeding into it (e.g., if the main cable is $2.5mm^2$, the terminal must accept it).
  2. Current Rating: The terminal's continuous current rating must be equal to or greater than the maximum expected current in the circuit, even if the wire size is smaller.
  3. Standardization: Projects often standardize on a few sizes (e.g., $4mm^2$ for control signals, $10mm^2$ for power) to simplify procurement and installation, even if a smaller terminal would suffice for current rating alone.

15. Why is a **drain/breather plug** sometimes required on a JB, and where is it installed?

Key Philosophy: Condensation Management

  1. Condensation Build-up: In environments with high temperature and humidity cycles, moisture can condense inside the JB, even with a high IP rating.
  2. Drain Plug Function: The drain plug allows condensed water to be expelled. It is typically installed at the lowest point of the enclosure.
  3. Breather Function: The breather allows the enclosure to 'breathe' and equalize internal pressure without compromising the Ex or IP rating, preventing seal damage.

Part 2: JB Sizing and Design (Q16 - Q30)

16. Outline the steps for calculating the required **minimum physical size** of an electrical JB.

Key Philosophy: Space and Accessibility

  1. Terminal Count: Calculate the total number of terminals needed (Input + Output + Earth + Spares, typically $1.2 \times$ cable count).
  2. Gland Plate Area: Calculate the minimum area required for all cable glands, ensuring adequate pitch (spacing) between them for safe installation and tool access (typically $1.5 \times$ the gland diameter).
  3. Minimum Clearances: Ensure specified internal clearances between terminals, metallic walls, and Ex-e requirements (to prevent flashover).
  4. Cable Bending Radius: The JB depth must accommodate the minimum bending radius of the largest incoming cable (especially for large power or fiber optic cables).

17. Explain the necessity of **gland plate earthing** in a metallic JB.

Key Philosophy: Bonding and Safety

  1. Protective Earth Continuity: The gland plate must be effectively bonded to the JB body (protective earth circuit). This ensures that in the event of a fault, the entire JB enclosure is maintained at earth potential.
  2. Armored Cable Earth: For Steel Wire Armored (SWA) or Screened cables, the gland itself provides the earth termination for the cable armor/screen. If the gland plate is isolated, this critical earth path is lost.
  3. Standard Requirement: Industry codes mandate that all metallic components capable of carrying fault current must be bonded to earth.

18. What is the rule for mixing **different voltage levels** (e.g., 24V DC and 230V AC) within the same JB?

Key Philosophy: Electrical Separation

  1. Prohibition: The general rule is to prohibit mixing different voltage classes in the same JB to prevent fatal cross-wiring.
  2. Exception (with Segregation): If mixing is unavoidable and approved by the design (e.g., for space constraints), strict segregation must be maintained:
    • Use of separate, clearly marked terminal rails.
    • Physical separation using insulating barriers.
    • Maintaining mandatory clearance distances between the voltage groups.

19. How is the **number of gland holes** determined, including provision for spares?

Key Philosophy: Cable Routing and Density

  1. Calculate Required Glands: Sum the total number of cables entering the box (Input + Output).
  2. Add Spares: Add a minimum percentage of spare glands (typically 10% to 20%). These should be protected by blanking plugs rated for the same IP and Ex classification as the JB.
  3. Gland Hole Pitch: Verify that the total number of required and spare glands can fit on the gland plate while maintaining the minimum specified spacing (pitch) between gland bodies.

20. What consideration must be given to **cable weight and bending moment** when sizing large JBs?

Key Philosophy: Structural Integrity

  1. Gland Plate Reinforcement: Large power cables exert significant stress on the gland plate. The plate may need to be thicker or internally reinforced to prevent deflection.
  2. Cable Support: External cable supports (e.g., cleats) must be specified to take the weight of the cable before it enters the JB, ensuring the stress is relieved from the gland and the JB itself.
  3. Mounting: The JB's mounting arrangement must be robust enough to handle the combined weight of the box, terminals, and the cables.

21. What is a **diode-equipped terminal block**, and when is it used?

Key Philosophy: Circuit Protection

  1. Function: A diode terminal block contains a diode integrated within the terminal, allowing current flow in only one direction.
  2. Use Case:
    • Signal Summing: Combining signals from multiple sources (e.g., alarm contacts) to a single input without back-feeding other circuits.
    • Reverse Polarity Protection: Preventing damage to sensitive electronic instruments due to incorrect wiring polarity.

22. Describe the importance of a **JB Schedule/Index** in the design phase.

Key Philosophy: Documentation Control

  1. Centralized Data: The JB Schedule is a master document listing every JB on the project.
  2. Key Information Contained:
    • JB Tag No. and Location (Area/Unit).
    • Manufacturer and Model No.
    • IP Rating, Ex Rating, and Material.
    • Total Terminals Required (utilized, spare, earth).
    • List of cables entering the JB.
  3. Procurement and Engineering Basis: It serves as the single reference for ordering the correct JBs and for cable/core management.

23. How does **diversity factor** influence the current rating and sizing of power JBs?

Key Philosophy: Thermal Management and Derating

  1. Definition: Diversity factor is the ratio of the sum of the maximum demands of the individual loads to the maximum demand of the entire group.
  2. Impact on Current: In JBs where many cables carry load, the terminals' continuous current capacity must be derated due to heat build-up inside the enclosed space.
  3. Sizing Rule: The total terminal block rail current rating (and the busbar, if present) must be selected based on the calculated maximum combined load, applying an appropriate derating factor (often based on terminal proximity and enclosure temperature).

24. What are **blanking plugs**, and how should they be specified for Ex-rated JBs?

Key Philosophy: Maintaining Rating Integrity

  1. Function: Blanking plugs are used to seal unused cable entry holes.
  2. Critical Specification: They must carry the exact same Ex-certification and IP rating as the JB enclosure itself. An uncertified blanking plug immediately invalidates the entire JB's certification.
  3. Installation: They must be installed and torqued using the manufacturer's specified method to maintain the seal.

25. Why must the **JB mounting location** be approved by the site HSE/Operations team?

Key Philosophy: Accessibility and Safety

  1. Accessibility for Maintenance: The JB must be mounted at an ergonomic height (typically 1.2m to 1.5m) and not above process lines or in areas requiring scaffolding for access.
  2. Escape Routes: JBs must not obstruct emergency escape routes or fire-fighting equipment.
  3. Vibration and Heat: Must be located away from excessive heat sources (e.g., exhaust stacks) or areas of high mechanical vibration.

Part 3: Termination and Installation (Q31 - Q50)

31. What is the single most critical tool used during the termination of screw-type terminals in a JB, and why?

Key Philosophy: Connection Integrity

  1. Tool: A Calibrated Torque Wrench or Screwdriver.
  2. Why it is Critical:
    • Under-Torque: Leads to a loose connection, high resistance, heat build-up, power loss, and potential fire/failure.
    • Over-Torque: Can damage the wire strands, strip the terminal thread, or crack the terminal block housing, leading to failure.
    • Terminals must be torqued to the manufacturer’s specification (e.g., $0.5 Nm$) and documented.

32. How is **armored cable earthing** achieved at the JB gland?

Key Philosophy: Armored Earth Continuity

  1. The Gland: A metal cable gland (e.g., brass or stainless steel) is used. The steel wire armor (SWA) is clamped between the gland’s cone and rear seal.
  2. Bonding to JB: The gland body then physically screws into the gland plate, creating a low-resistance path from the armor to the gland plate.
  3. Final Earth: The gland plate is already bonded to the main JB earth bar, completing the circuit from the armor to the protective earth system.

33. What is the process for terminating a shielded/screened instrument cable in a JB?

Key Philosophy: Shield Grounding Protocol

  1. Signal Integrity: The shield (screen) must be grounded to prevent electromagnetic interference (EMI) from corrupting the signal.
  2. Single-Point Grounding: The most common method is to ground the shield at only one end (typically the control room or marshalling cabinet end).
  3. JB Termination: At the JB (field end), the shield is trimmed back, insulated with heat shrink, and **left floating** (not connected to the earth bar). The drain wire is left disconnected and tucked away.
  4. **Note:** Grounding at both ends creates a ground loop, which severely increases noise.

34. Why should **ferrules** or **crimp lugs** always be used on stranded conductors before termination in a JB?

Key Philosophy: Preventing Strand Damage and Cold Flow

  1. Strand Protection: The terminal screw pressure can damage or sever individual wire strands if a lug is not used.
  2. Containment and Conductivity: Ferrules ensure all strands are contained, providing a robust, controlled metal surface for the screw to clamp onto, maximizing the contact area and minimizing resistance.
  3. Preventing Cold Flow: Without proper termination, the soft copper strands can deform ("cold flow") over time, leading to a loose connection requiring frequent re-torquing.

35. What is the required **minimum length of spare cable core** inside a JB, and why?

Key Philosophy: Re-termination Allowance

  1. Allowance: Typically, a minimum of 150mm to 300mm (6 to 12 inches) of slack is required inside the JB.
  2. Purpose: This slack allows cores to be re-terminated multiple times due to:
    • Termination mistakes or damage during installation.
    • Future maintenance, such as changing a damaged terminal block.
  3. Dressing: This slack must be neatly dressed and tied off, allowing easy access without obstructing the terminals.

36. What is the final pre-commissioning test performed on all the terminals in a JB?

Key Philosophy: Wiring Validation

  1. Test: Point-to-Point Continuity Check (and Insulation Resistance Check).
  2. Procedure: Using a multimeter/megger:
    • Continuity: Verify the resistance is near zero between the terminal in the JB and the corresponding terminal in the other connected panel/instrument. This confirms correct wiring and termination.
    • IR Check: Verify high insulation resistance (typically $>1M\Omega$) between the core and earth, and core to core, to ensure no shorts.

37. Describe the safety protocol for **opening an Ex-e JB** in a hazardous area.

Key Philosophy: Hot Work Permit and Isolation

  1. Permit: A Hot Work Permit (or equivalent site permit) is generally required, as opening the enclosure is considered breaking containment.
  2. Gas Check: A gas test must be performed to confirm the atmosphere is non-flammable (LFL below the safe limit).
  3. De-Energization: If possible, the circuits within the JB should be de-energized and verified 'dead' using LOTO (Lockout/Tagout) and a proximity voltage test.
  4. Re-sealing: Upon closing, the enclosure seal (gasket) must be inspected, cleaned, and properly seated, and the cover bolts torqued to specification to maintain the IP and Ex ratings.

38. What is the risk of using **aluminum terminals** in a JB with copper conductors?

Key Philosophy: Thermal and Galvanic Issues

  1. Galvanic Corrosion: Copper and Aluminum have different electrochemical potentials. In the presence of moisture (electrolyte), severe corrosion can occur at the contact point, increasing resistance.
  2. Thermal Expansion: Aluminum and Copper expand and contract at different rates. This thermal cycling can cause the connection to loosen ("cold flow" or "creep") over time, requiring frequent re-torquing.
  3. **Mitigation:** If copper-to-aluminum termination is unavoidable, specialized bi-metallic lugs or terminals containing a barrier material must be used.

39. When installing cable glands, why is the **gland sealing ring compression** critical?

Key Philosophy: IP and Ex Seal Integrity

  1. IP Rating: The sealing ring provides the critical barrier against dust and moisture ingress, maintaining the JB's IP rating.
  2. Ex Rating (Ex-d): In flameproof applications, the seal prevents the ingress of the explosive atmosphere into the box.
  3. Tool Usage: Over-tightening can crush the cable sheath or distort the seal, leading to failure. Under-tightening results in a breach of the IP/Ex rating. A final **torque check** is mandatory.

40. What is the function of **terminal markers (ferrules)**, and how must they be installed?

Key Philosophy: Traceability

  1. Traceability: Markers (e.g., printed sleeves or ferrules) provide the unique core number (e.g., L1, N, 24V+) that corresponds to the project wiring diagram.
  2. Installation Requirement:
    • Markers must be durable and non-fading (UV resistant).
    • They must be installed close to the termination point, facing the installer, and must not slip or cover the conductor insulation.
    • The marker number must match the terminal number on the terminal strip.

41. What is the procedure for ensuring **drainage** when installing a JB on vertical piping?

Key Philosophy: Vertical Glanding

  1. Bottom Entry Mandate: All cable entries (glands) must be located at the bottom face of the JB.
  2. Prevent Water Tracking: Positioning the glands downward prevents water from pooling on the gland plate and tracking down the cable into the enclosure.
  3. Orientation: If the JB itself is mounted vertically, the side with the glands must face down towards the ground.

42. How do you verify the **correct polarity** for DC circuits within a JB?

Key Philosophy: Color Coding and Cross-Check

  1. Color Code Compliance: Verification starts by checking that the wiring follows the project standard (e.g., Blue for negative, Red/Brown for positive for 24V DC).
  2. End-to-End Test: A continuity test is performed between the JB terminal and the source/destination terminal, checking that:
    • The $L+$ core connects to the $L+$ terminal.
    • The $L-$ core connects to the $L-$ terminal.
  3. Final Power-Up: The final verification is often done during the loop check by measuring the voltage across the field device to confirm the correct positive and negative voltages appear.

43. What is the danger of double termination (two cores under one clamp) in a JB?

Key Philosophy: Unreliable Connection and Overheating

  1. Uneven Pressure: It is impossible to guarantee even clamping pressure on both cores, leading to one core potentially being loose and creating high resistance/heat.
  2. Code Violation: Most international electrical codes and terminal block manufacturer specifications strictly prohibit double termination.
  3. **Solution:** Use a terminal block designed for multiple connections, or use a bridge/link to connect two terminals together, ensuring each core has its own individual clamping point.

44. Why must all internal wiring within an Ex-e JB be neatly dressed and securely tied?

Key Philosophy: Maintaining Creepage and Clearance

  1. Creepage/Clearance: The internal clearances required for the Ex-e rating (distance between conductors, and conductors and earth) must be maintained. Loose cores could sag and violate these critical distances.
  2. Inspection: Neat dressing facilitates easy inspection, troubleshooting, and maintenance, ensuring all terminal markers are visible.
  3. Safety: Prevents cores from fouling on the cover seal or hinge mechanism when the JB is opened or closed.

45. What is the standard **JB mounting height** for field instruments, and why?

Key Philosophy: Ergonomics and Visibility

  1. Standard Range: Typically between 1.2 meters and 1.5 meters (4 to 5 feet) from the platform or floor.
  2. Ergonomic Access: This height allows personnel (operators, technicians) to easily open the JB, read the labels, and perform terminations or voltage checks without bending over or using a step ladder.
  3. **Note:** Deviations are allowed only in specialized areas (e.g., low-level JBs for vibration sensors or high-level JBs for overhead lighting).

46. What must be checked before a JB cover is permanently closed and signed off?

Key Philosophy: Final Inspection and Sealing

  1. Termination Integrity: Final torque checks are completed and documented.
  2. Tidiness and FME: Internal cores are neatly dressed, and a **Foreign Material Exclusion (FME)** check is done to ensure no tools, wire offcuts, or debris are left inside.
  3. Gasket and Seal: The cover gasket is clean, lubricated (if necessary), correctly seated, and undamaged.
  4. Documentation: The installation/termination sheet is signed off by the supervisor and client inspector.

47. Define the concept of a **Marshalling JB** and its design intent.

Key Philosophy: Consolidation and Interface

  1. **Definition:** A Marshalling JB (or cabinet) is a large JB designed to terminate multiple smaller, multi-pair field cables (from local JBs or instruments) and consolidate them into a few large, high-core-count multi-pair cables running back to the control room.
  2. **Design Intent:**
    • Reduces Cost: Reduces the number of long, expensive home-run cables back to the control building.
    • Facilitates Maintenance: Provides a clear demarcation point between field cabling and home-run cabling.

48. Why is it essential to use **Ex-rated cable glands** with certified JBs?

Key Philosophy: Component Certification

  1. **System Integrity:** The safety rating (Ex-e or Ex-d) is for the entire system, not just the box. The gland is a critical component that maintains the enclosure's integrity.
  2. **Certification Loss:** Using a non-certified gland on an Ex-rated JB immediately invalidates the JB's Ex-certification, rendering the entire installation unsafe and non-compliant.
  3. **Gland Requirements:** Ex glands are specifically designed to restrict the flow of hot gases/flames (Ex-d) or provide enhanced sealing/strain relief (Ex-e).

49. What is the purpose of applying a small amount of **grease or anti-seize** to JB cover bolts?

Key Philosophy: Maintenance and Corrosion Prevention

  1. **Prevent Seizing (Galling):** Especially critical for stainless steel bolts and enclosures, which are highly susceptible to galling (threads locking up) in corrosive outdoor environments.
  2. **Ensure Correct Torque:** Lubrication ensures that the applied torque is used to stretch the bolt and provide clamping force, rather than overcoming friction. This guarantees the correct pressure on the gasket/seal.
  3. **Accessibility:** Makes it possible for maintenance teams to easily open the JB years after installation.

50. What is the required practice for handling **unused cores** inside a JB?

Key Philosophy: Safety and Clarity

  1. Trim and Insulate: Unused cores must be trimmed to the same length as the terminated cores.
  2. Insulation: Each unused core must be individually terminated with an insulated ferrule or cap and/or covered with heat-shrink tubing.
  3. Tuck Away: The insulated ends must be neatly bundled, identified as "SPARE," and secured away from the live terminals to prevent accidental contact or short circuits.
  4. **NEVER** leave a spare core stripped or untrimmed, as this creates a major short circuit hazard.

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