Around-Oz: Living the Dream!


Australian Cable Rules 2005
By Collyn Rivers - A Must Read!


Historically, electrical regulators laid down what must be used, where and how. Increasingly however the obligatory use of safety devices such as circuit breakers (that limit excess current) and RCDs (residual current devices that disconnect electrical supply in event of certain faults) enables a shift from prescriptive requirement. Now, there is a global move to allowing alternative approaches proven to be safe. This is reflected in the new joint Australian/New Zealand Standard AS/NZS 3001:2001 - Electrical installations - relocatable premises (including caravans and tents) and their site installations. This Standard also covers campervans, motorhomes and annexes. The changes that affect motorhome users mostly relate to supply cables, but there are many other requirements that installers and repairers need urgently to study. Preparing this article required close and ongoing consultation with Standards Australia and also an Energy Safety Authority. The former required that any comment be published as provided. I regret that some parts of this feature may not be fully clear to people lacking a technical background in this area. It will however be understood by licensed electricians and I have provided the necessary references to enable them to locate the further information they will need. Because these regulations are both recent and very comprehensive, members are likely to find that not all licensed electricians are yet aware of the implications (and some I fear are not even aware that the regulations have changed). In light of this I strongly recommend that Members likely to need electrical work retain or copy this article and show it to the electrical contractor concerned.

Supply Outlets
Australian caravan parks that provide mains electricity have, for some years, been legally required to install safety-protected 15-amp outlets. It is now permissible to use an outlet of another rating or configuration . for specific anticipated types of relocatable premises 1 . In practice however caravan parks will continue to provide service pillar mounted 15-amp outlet sockets, circuit breakers, and residual current devices.

Supply Cables
It is now permissible, subject to the requirements and restrictions set out below, to use a 10-amp supply cable up to 25 metres long. This is a welcome change as it also enables a vehicle to be plugged into a 10-amp outlet socket. "The simplest way to connect a motorhome or similar to a 10 amp outlet of any kind is to arrange for the appliance inlet on the motorhome to be a 10 amp appliance inlet (rather than the usual 15 amp unit) and for the load limiting device on the motorhome to similarly be 10 amps" 2. The latter requirement (load limiting) is described below .

Table 1 in this article sets out the maximum and minimum supply cable lengths, and the minimum cable conductor sizes 3. The longer the cables, the heavier that conductor must be, but it is both sensible and legal to use heavier cable for the shorter lengths. It is also permittable to fit approved 10-amp plugs and sockets to '15-amp' cable (such cables are already on sale). Existing (approved) 15-amp, 30-metre leads may still be used. Only one cable may now be used: you must not interconnect supply cables to extend reach. 4

Minimum Cross Sectional Area of Lead Conductors (sq. mm)
Maximum Length of Lead (m)
1.0
10
1.5
25
2.5
30
4.0
40

Table 1. Maximum permissible supply cable lengths and required (minimum) conductor sizes.
This is Table 5.1 in AS/NZS 3001:2001.

Limiting the Supply Current
The ability to use a 10-amp plugged cable is welcome, but this change, if applied alone, would allow 15 amps being drawable via a cable and/or plug designed for only 10 amps. To preclude this, the eminently sensible requirement is that if the supply plug is rated at 10 amps, then there must be automatic provision to prevent more than 10 amps being drawn. Replacing the vehicle's existing 15-amp circuit breaker by a 10-amp device is one obvious and acceptable solution.

Inlet Provisions
It is now legal to have the vehicle inlet also 10-amp rated provided the inlet socket rating (ampere) meets the maximum demand (ampere current rating) of the vehicle. That inlet must have not lower than IP24 protection (electricians know what this means) 5 . Currently the only approved 10-amp inlets appear to be surface-mounting IP56 rated, but no doubt conventional flush mounted units will become available.

A workable and legal alternative is to do away with the inlet socket altogether by having the supply cable (of any size or length that complies with (our) Table 1 permanently connected at the vehicle end and housed within the vehicle in an enclosure of specified form when not in use 6 .

Ten Amp Plug/Cable - Fifteen Amp Inlet
It is also now possible to retain the 15-amp inlet and 15-amp supply capability but to use a special cable that limits supply to 10 amps (see below) when it is required to make a power connection where only a 10-amp outlet is available. The normal approved 15-amp cable is then used at all other times.

The Energy Safety Directorate (of the WA Department of Consumer and Employment Protection) advises that whilst a flexible cord with a 15-ampere socket outlet and a 10-ampere plug top is not recommended:

If the cable is protected by an external 10-ampere overload device with combined RCD and maximum demand does not exceed 10 ampere then this arrangement would be acceptable.

In other words the cable assembly automatically limits current to 10 amps and thus provides its own protection. Where the full 15-amp circuit capacity is required an approved 15-amp cable must be used. This 'self-limiting cable' is thus used only when circumstances dictate 7.

Standards Australia notes that: "such a device might be available as a ready-built unit (including units designed for use as outlet boxes on show and carnival sites and complying with AS/NZS 3002:2003". It also advises that such a device might be constructed from proprietary components by a licensed electrician "who will ensure that the rating of the components and the enclosure are appropriate for the circumstances in which it will be used and comply with electrical principles . . . [the electrician] will also decide if consultation with the State electrical safety authority is appropriate." 8 .

In other words, the 10-amp cable has a special plug or socket that incorporates a built-in 10-amp circuit breaker (and perhaps an RCD). These devices are commercially available (from electrical wholesalers - but not hardware stores) but they must be assembled as a cable by a licensed electrician. Their maximum length must be 25 metres. No alternative enables a 10-amp supply cable or outlet to supply a 15-amp circuit load. And nor it should - it cannot safely be otherwise! Fortunately this unfulfillable 'need' will only normally arise in either of two situations:

1. In homes with only 10-amp outlets. The only solutions are to have a licensed electrician install a 15-amp circuit and supply outlet; or to use the special 10-amp current-limiting cable described above.

2. At caravan parks that only have 10-amp outlets. You should move on, or forgo mains power as it's odds on that obligatory safety devices are not installed either. This leaves users at risk as these safety devices are now relied upon to provide safety protection in otherwise potentially lethal fault conditions.

The recent changes have removed some anomalies but have increased complexity. It is now even more necessary to stress that caravans and motorhomes are more potentially dangerous electrical environments than are houses. Further, there are many differences in their wiring, circuit breakers, RCDs, switches and power points. You must have work done by an electrician licensed by the State in which that work is being done. It is still legal for a competent person to make up basic supply cables for their own use only 9 , (but not the specialised self-limiting cable described above). However, electricity authorities, the CMCA Safety Committee, and the author, strongly recommend you have a licensed electrician do it for you - or at least check your work for compliance and safety.

New Zealand-built Vehicles
Whilst there is now a combined Australia/New Zealand Standard, there are a few but profound differences between our electrical practices. If using an RV made in one country but used in the other it is vital to have a licensed electrician check the wiring for compliance. Most vehicles will require one absolutely essential change. For New Zealand vehicles used in Australia, there may be others. (Show the electrician the note re this at the end of this article).

Connecting Generators
The new regulations only partially address the connection of generators that are supplied with 10-amp outlet sockets (that cannot be changed to 15 amps without invalidating warranty). A 10-amp cable may now be used subject to the vehicle being limited to 10 amps draw, or to use a 10/15 amp self-limiting cable as described above. This is probably not a serious restriction. Most users requiring a 15-amp service will have a 15-amp generator. If you don't, then change the inlet etc.

About Standards
Australian 'Standards' are only 'Recommendations' until and if adopted by State Regulators: " Australian Standards only become law if a relevant body says so," note s Standards Australia . There is thus a lag between a Standard being published and becoming law. This made it impracticable to publish this article until all States had adopted the new rules because, until then, the existing Standard applied - hence my sometimes-guarded responses to recent enquirers. Some of the implications are only surfacing now and because of their newness, scale and complexity not all electricians may yet be fully aware of all of the implications.

Essential Disclaimer
The author thanks Australian Standards, the Energy Safety Directorate of Western Australia, and CMCA Member Ian Bond for assistance in preparing this feature. This article reflects my own current understanding based on a close study of the relevant Standards, and direct correspondence to and from Ian Bond and myself with the above authorities. I must emphasise that whilst I have taken considerable care to ensure the accuracy of this article and have an extensive background in research and electrical engineering, I am neither a licensed electrician nor a professional electrical engineer. This article is limited to an overview of what seems to be possible. I do not accept any responsibility for its accuracy excepting that the relevant authorities have provided the credited quotations with their knowledge that they would be published herein. Those professionally concerned with this matter should study the AS/NZS 3001:2001, and AS/NZS 3000:2000 (plus recent Amendments). Any decision or work relevant to this matter should be made and/or done by a licensed electrician.

Electricians Note
NZ practice is for Earth and Neutral to be bonded within the vehicle - as with normal domestic practice, but not RV practice, in Australia. This link must be removed if the vehicle is used in Australia otherwise reversed polarity will impose 240 volts on the chassis etc of the vehicle. Australian RVs also use double-pole circuit breakers, RCD, and switching throughout.

References
1. AS/NZS 30001:2001 Section 2.3.2.4.2
2. Direct communication from Standards Australia.
3. This is Table 5.1 in AS/NZS 3001:2001
4. Section 5.1.1 of the above
5. Section 3.2.1 (iv) of the above
6. Section 3.2.2 of the above
7. Direct communication from Energy Safety Directorate (WA) 22 December 2003.
8. Direct communication from Standards Australia
9. As (6) above, and also confirmed by Standards Australia

Collyn Rivers W 8054 (copyright 2005)


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