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• Protection against harmful effects• Correct functioning• Supply characteristics• Determining Maximum demand• Voltage drop limitations• Arrangement into circuits• External Factors• Protection against• Integrity of fire rated construction
• Direct contact• Indirect contact• Thermal effects• Overcurrent• Faults• Mechanical movement
• Type of structure/location & what it is used for• Number & type of circuits• Current carrying capacity of the cable• Voltage drop• Fault loop impedance• Maximum demand• Fault levels• Metering• Damp situations• Voltage levels
How it is going to be used
Local authority requirements
Cost
Time requirements
Site access
Appearance/Aesthetics
• Domestic• Multiple
domestic• Commercial• Industrial
Power requirements of each of the loads connected How the loads are used Flexibility Safety of Human Property and Livestock Not be too inconvenient if a fault occurs Be able to be easily worked on and tested Compatible with the climate Not be overloaded Not have too much voltage drop Not be affected by the Environment/Atmosphere
Constant or Intermittent
Temperature, High Humidity, Corrosive atmospheres, Mechanical damage, etc
Temperature, High Humidity, Corrosive atmospheres, Mechanical damage, etc
AS/NZS 30001.6.1
Power requirements of each of the loads connected How the loads are used Flexibility Safety of Human Property and Livestock Not be too inconvenient if a fault occurs Be able to be easily worked on and tested Compatible with the climate Not be overloaded Not have too much voltage drop Not be affected by the Environment/Atmosphere
AS/NZS 3000 and other electrical standards Local supply authority standards Building codes Fire ratings Heritage orders etc Appearance Speed of installation Cost
Concealed or Surface
Materials & Labor
Advantages Insulator, so earthing not a problem
Material relatively soft so cable damage not a major problem
Disadvantages Drilling in structural members is
limited
All service holes have to be drilled on site
Advantages
Used extensively used in office partitions
Most service holes are pre punched and de-burred/flanged
Very lightweight construction.
Disadvantages Earthing of the frame has to be
considered
Additional holes made must be de-burred
Cable Ladder/traySteel Conduit
Steel Wire ArmourSWA Cable is more Expensive than Steel Conduit so why is
more commonly used?MIMS
How many? What size?
Reduce the inconvenience in the event of a fault
Safe inspection, testing & maintenance
Unwanted nucence tripping
Fault protection.
AS/NZS 3000Clause 1.6.1
Different loads require different tripping times
AS/NZS 3000Clause 2.6.2.1 AS/NZS 3000
Clause 1.5.5.3
How many? What size?
The current required by each load
The nature & usage of each load
Economics
Flexibility of the installationThe smaller the cable the cheaper
cosVIP
To major factors that have to be considered
The power requirement of the load
How the load is used
cosVI3PIf used for more than 15 minutes it is
considered an “Extended Period”
Circuit requirements for a 4.8kW 230 Volt HWS
Maximum current = 230
4800
V
PI 20
AWill it be used for extended periods?
On its own circuit?
Or with other loads on one circuit?
Circuit requirements for two 4.8kW 230 Volt HWS
4mm2 T&E = $2.50/m
2.5mm2 T&E = $0.85/m
Cheaper to make two circuits
Commercial installation Containing 45 x 60W light fittings
45230
60
Are the lights likely to be all operating at the same time?
11.7A
Protection will eventually trip.
2 Circuits are required
Commercial installation Containing 45 x 60W light fittings
45230
60
Are the lights likely to be all operating at the same time?
11.7A
Protection will eventually trip.
2 Circuits are required
45230
60Are the lights likely to be all operating at the same time?
11.7A
Domestic installation
Would the protection trip if all the lights were on for a short
period?Would the cable be damaged if all
the lights were on for a short period?
AS/NZS 3000Clause 2.5.3.1
Do we put more than 1 double socket outlet on a single
circuit?What is the minimum size
cable that we can generally use?
AS/NZS 3000Table 3.3
AS/NZS 3000Table C8
What type of loads are in the kitchen and laundry of a
house?
Would you put all these loads on the one circuit?
The Current that is normal expected by this
type of load“Average Current”
AS/NZS 3000Clause 1.6.3
AS/NZS 3000Clause 2.2.2
Calculation Using:
Appendix C
HB 301
By:•Calculation•Assessment•Measurement•Limitation
15 minutes = “Extended Period”
Consumer & Sub-main size can be determined by sum of the individual outgoing protection devices
10A 16A 16A 20A 20A
82A
AS/NZS 3000Clause 1.6.1 (b) Must be negotiated with user