Electrical Wiring Systems

Electrical Wiring Systems

• These systems deliver power from the source to all electrical equipment
• This includes socket outlets, lighting, electrical plant, plus data, voice, fire protection, and security devices
• Wiring systems comprise cables, supports, protection, conductors, connections, and joints
• They refer to cable type, installation method, and combinations of cables, conductors, supports, and enclosures

Types of wiring systems

• Wiring systems are categorized into enclosed and unenclosed types
• Enclosed systems use a protective structure separate from the cable like conduits or trunking, and can be within control panels or switchboards
• Unenclosed systems expose cables, such as TPS cable on a cable tray
• Installations can combine both types, like older homes with metal conduit or wooden cap casing for original wiring and newer TPS cable additions
• Sheathed cables, like TPS, are the most commonly used wiring system
• Unsheathed insulated cables require installation within an appropriate enclosure
• See AS/NZS 3000 3.10.1 for exceptions

Wiring Enclosures

• AS/NZS 3000 3.10.2.1 lists conduits and cable trunking systems as wiring enclosures
• All wiring enclosures provide mechanical protection
• Damage to cables depends on usage and location
• Mechanical damage includes abrasion, compression, torsion, and excessive bending
• Tension from pulling cables during installation or between supports can cause damage
• Failure of cable joints/terminals can also cause damage
• Cables may be further affected negatively by other factors like: mechanical damage, fire/explosion/temperature, vandalism and corrosion

Conduit as enclosures

• Wiring systems needing mechanical damage protection require adequate protection, complying with AS/NZS 3000 3.3.2.6 and 3.9.4.2 to 3.9.4.4
• Enclosures offer extra mechanical protection for both sheathed and unsheathed cables
• An example is using PVC conduit to support and protect sheathed cables in areas prone to bumps.
• Steel conduit provides heavy-duty mechanical protection in tough environments, like industrial or public areas prone to vandalism
• AS/NZS 3000 Table 3.5 shows enclosures for use with underground cables
• Cables must be protected against mechanical damage, positioned to avoid damage from floors or fixings, and protected from sharp bending

Cable bending rules

• Research how to calculate the minimum bending radius, as per AS/NZS 3000 3.10.3.4 and 3.9.6
• AS/NZS 3000 Appendix H5 features a Mechanical Protection Classification guide for info on mechanical and fire protection for electrical circuits
• AS/NZS 3000 3.9.7.2 covers an exception to mechanical protection

Cable support systems

• Support systems protect and keep cables in place
• Select different fixings, fastenings, and supports based on the cable's operating conditions
• Use methods protecting against mechanical/electrical failure under ordinary use, including wear and tear
• AS/NZS 3000 3.9.1 details ordinary use expectations
• Wiring system selection and installation are outlined in AS/NZS 3000 Section 3 of 3.1.2 within the Wiring Rules

Maintenance

• When maintaining, installing, or operating cables, minimise damage to connections, sheathing, & insulation
• Refer to AS/NZS 3000 3.3.2.8 to minimize damage
• Minimize damage using continuous supports at suitable intervals
• Use proper fixings to hold cables in place
• Cables must be secured with connections reducing joint termination strain (mechanical)
• Follow minimum cable bending radius
• Tension and movement stresses should be accommodated through flexibility

Cable Fixing

• External factors and material of the wiring system must be considered for their affect on cable fixings, per AS/NZS 3000 3.9.3.1
• AS/NZS 3000 3.9.3 applies here
• Support systems summary
• Wiring enclosures and supports are summarized in two tables, covering use and location

Wiring Enclosure options

• Conduit enables convenient, efficient cable support for general use and to install sheathed cable for extra protection
• Trunking is for tidy cable installation in commercial settings
• Slotted trunking separates cables in switchboards and control panels
• Heavy-duty underground conduit is for underground wiring systems

Support Options

• Cable clips secure sheathed cables out of sight, such as in ceilings or floors
• Cable ties attach sheathed cables to structures, typically with cable trays and ladders used to tie cable groups
• Cable trays and ladders support large or grouped cables in basements, commercial and industrial sites, and high-rises
• Catenary support suspends cables above ceilings; ensure cables are sun-exposure-rated for outdoor use

Cable Current

• Ensure cables have necessary current-carrying capacity to derate cables
• Electrical demands differ between residential and commercial buildings; wiring must manage the expected load
• New constructions allow wiring design flexibility; renovations require working with structures and possible limitations
• Spaces with exposed ceilings may be suitable for more industrial wiring, however, concealed wiring provides a cleaner look

Environmental Wiring

• Extreme temperatures can affect wire insulation and current-carrying capacity, and cables with appropriate temp ratings may be necessary
• Construction sites or industrial areas may have hazards; Robust conduit or cabling with strong jackets is recommended
• Moisture, chemicals, or UV exposure can damage wiring; Choose appropriate cable materials/corrosion-resistant components

Wiring Cost

• Seek cost-effective balance between initial costs with long-term durability
• Electrical installation info comes from job specs, cable schedules, floor/site plans, and client consultation
• Plan installation: job specs, cable schedule, number, type, fixing and protection are key
• Identify installation environment
• Note the ease, or difficulty, of wiring system and its supports
• Plan for installation H&S such as height and space available
• Assess support available and the structural preparation
• Plan for using materials efficiently
• Identify possible conflicts as per AS/NZS 3000 3.9.8
• Consider the hole sizes and / positions allowable in timber framed buildings
• Remember compliance with AS/NZS 3000 3.9 – 16 for the installation

Conduit Specifics

• Conduit protects cables and it's the most common enclosure and must comply with AS/NZS 2053 and AS/NZS 61386 standards
• Cable and Conduit is manufactured to specific standard and data/ standard is found in on the cable drum, or printed directly on the cable or conduit
• Rigid steel conduits, flexible metal conduit, insulating rigid/flexible conduit, and insulating corrugated conduit are types of conduits
• AS/NZS 3000 3.10.2.1 covers this
• AS/NZS 3000 H4.4 gives impact strength, and conduit impact rating can be VLD, LD, MD, HD or VHD
• Read AS/NZS 3000 H5 for conduit impact ratings for different situations
• Consider the low and upper temp ratings and follow AS/NZS 3000 3.10.1.1

Reasons to choose conduit

• These include fixing cables in difficult surfaces or spanning across possible sagging areas
• Conduit also gives mechanical protection plus sunlight and allows cables in concrete
• Conduit can be used to protect consumer mains and provide barriers as per AS/NZS 3000 figures 3.8 and 3.9

Number of conduit cables

• Careful planning must occur for the amount of cables to avoid damage if conduits or other wiring enclosures are used

• Use the below equation to assess the number of conduits:

    Number of cables = (Internal cross sectional area of enclosure/ cross sectional area of cable)  x  space factor
  

• Space factor acknowledges space reduction

• Space factor reductions, conduit cable numbers and common conduit/ cable types is in the wiring notes

• Ensure temperature rise, de-rating factors or voltage drop are made with AS/NZS 3008

• Number depends on run vs obstruction free conduit

Installing conduit

• Rigid rolls may also be used, however PVC comes in rigid/flexible rolls and UV resilience plus differing strengths is a factor
• Bends and joints need to occur and PVC glue should be used and joints should be watertights
• Saddles and clips fasten the pipe
• Electrical joints can be made and conduit accessories may help with diameter/ direction
• Metal with PVC can offer greater flexibility/ strength but needs to be threaded to screw fittings

Conduit installations

• Flexible wiring can be hard but bends add cost and prefer metallic bending tools
• Applying a heat gun to rigid PVC and use bending springs is key and allows protection
• While heating PVC: avoid burning items, burn others, set fire or overhead plus burn
• Do not kink or meet AS/NZS 3000 3.10.3.4 if a severe bend happens
• Use something round for a curve and the bend can be pulled after the bend occurred
• Bend must be tighter than a 6 X radius
• Look at AS/NZS 3000 3.10.3.4

Conduit fixing for wires

• Supports, that do not harm cables, are key per AS/NZS 3000 3.10.3.1
• Connects through saddles or clips and ensure that they are correctly supported
• Manufacturer ensures connections close to one metre apart and avoid sag or sideways work

Anchoring + sunlight

• Anchoring is key using glue, clips and retainers per AS/NZS 3000 3.10.3
• Conduit needs to install per ASS/NZS conduit 3000 3.10.3.7
• Light- coloured acrylic paint is key or choose an item made for sunlight
• Check for the T letter to ensure suitability
• Solar use can disintegrate, and unsafe and unsound if non-solar rated
• Allow around .1mm longer for 10 degrees based on AS/NZS 3000 3.10.3.8
• Watch for heat damage, and ensure extra cabling for installation

Water Ingress

• Install wiring enclosures that prevent water from entering inside the electrical equipment, see AS/NZS 3000 3.10.2.3
• AS/NZS 3000 6.6.4.2 covers cold ratings or refrigerated rooms
• Ensure moisture is not accumulating and follow AS/NZS 3000 3.3.2.3 for drainage
• Condensation will happen with different installation and humidity
• Conduit can also let it get in, so ensure appropriate levels

Conduit Water

• Use IP66s which have valves plus drill to allow water to drip
• Follow AS/NZS 3000 3.10.2.3 and ensure cabling is on the top or sides/ or under
• This can also seal against the spread of the fire AS/NZS 3000 2.9.7
• Steel conducts + better than PVC when needing greater force, while prewar cables are steel now
• Electrical + mechanical joins are KEY as per AS/NZS 3000 3.10.3.3
• Use wires per AS/NZS 3000 5.3.2.3 for earthing and the correct tightness for fittings as per of AS/NZS 3000 2.9.7
• Wiring as per AS/NZS 3000 5.3.2.3

Cable supports

• Cable supports provide cable trunking and trays
• The cable must meet any electrical protection standards or 3.9.9.3 fire
• Ducting uses 75mm- or enclosed cables that are used on sides/ back made of aluminum, steel/ PVC

Sheath and compartment

• Trays + cables can be run inside per AS/NZS 4296; with an easy cable lid that AS/NZS 3000 3.9.8.3 to 3.9.8.4 with and AS/NZS 3000 7.2.8.2

Slotted trunking

• Used on sides of a square and there must be no burs/ breaks
• Keep min radius for safe cabling as AS/NZS 3000 3.10.3.9 states

Cable trough

• Bigger, tough, with the heavy lids and made of concrete
• Lay cables and have the right grounding

Cables

• Cable trays are made of steal or aluminum and are very safe while crossing large lengths with the curves per a wide variety
• These must meet the cantilever/ or bar support standards
• There are solids sides or holes + the material can have a rating

Cable support systems

• Support systems typically are custom made to a 6 lengths
• The ladder is 6 lengths, where the flat are 3, and do keep smooth sides per AS/NZS 3000 3.10.3.5