#148040  by harvs.nz
 Sat Jan 12, 2019 6:34 am
Hi can anyone tell me does the 12v electrical system in your motorhome require certification, ie lights, water pump etc?
 #148041  by mattn
 Sat Jan 12, 2019 6:49 am
No. Its classed as ELV (Extra Low Voltage) (and not in a medical or hazardous area) you do not need any certification or qualifications to work on it yourself. It must still be installed according to the New Zealand Electrical Regulations.
 #148067  by Sarmajor
 Sun Jan 13, 2019 6:51 am
12V (ELV) wiring does not require certification in the Electrical Safety Regulations.

If it is associated with LV (230V) wiring it must be installed according to the Electrical Safety Regulations and AS/NZS3000:2007 and AS/NZS3001:2008. (For connectable installations)

Associated is not defined in the Electricity Act or the Electrical Safety Regulations so we have to use the dictionary definition of associated which is along the lines of “joined with”.
Given that the power source for your caravan or motor home 12 volts is the vehicle batteries I would say that the 12V (ELV) wiring is not associated with 230V (LV) wiring.
 #148068  by idex
 Sun Jan 13, 2019 8:03 am
Sarmajor, what is your opinion on the situation where a 24VDC power supply is connected to the 230VAC supply via a 3 pin plug and switched outlet? The 27.5VDC output is then connected in parallel with the house batteries, providing a little top-up to the batteries whenever connected to mains power.

Is this likely to cause any serious risk in the event that a fault or internal short may develop within the power supply device? Presumably the two systems could be termed "associated" in this case? Does this fall within the EWOF system?

Would the RCD and/or overload protection on the incoming mains supply provide sufficient protection? Is there any possibility that mains voltage could anyhow become interconnected to the 24V house wiring?

Your opinion?
 #148083  by Karmann57
 Sun Jan 13, 2019 3:16 pm
idex wrote:
Sun Jan 13, 2019 8:03 am
what is your opinion on the situation where a 24VDC power supply is connected to the 230VAC supply via a 3 pin plug and switched outlet? The 27.5VDC output is then connected in parallel with the house batteries, providing a little top-up to the batteries whenever connected to mains power.
When you say "connected to 230VAC supply" I can only assume that you have a 24VDC charger plugged into the 3 pin plug outlet. There is no other logical way to connect 24VDC to 230VAC.

Therefore there is no danger associated with the 24VDC system.
 #148118  by Sarmajor
 Mon Jan 14, 2019 11:51 am
It is my belief that the reason for this rule is things like decorative lighting especially garden lighting in installations. Requiring installation in accordance with 3001 and the regulations means that the ELV garden lighting wiring should be buried 600 deep in the garden, This stops the Gardner from digging it up on a regular basis.
There would have to be several faults with a plug in charger that maintains your house batteries for it to cause the mains to appear at the 12/24 volt system. The RCD would most likely have tripped well before this could occur.

Given that most house batteries are connected to the vehicle chassis and the Mains Earth is connected to the vehicle chassis any fault that allowed excessive leakage of current will operate the RCD long before harm could occur to any person.

The ELV system of the vehicle is outside the scope of the WOEF system except for this small element.
C7.6 Segregation of ELV and LV
Connectable Installations shall pass a 500VDC insulation resistance test between the Active and each unearthed ELV circuit. The resistance shall not be less than 1Mohms. ( if your house battery negative is connected to the chassis then it is earthed and all ELV circuits are earthed and this test is not required)
 #148126  by idex
 Mon Jan 14, 2019 1:48 pm
Thanks Sarmajor and Karmann57 for your comments. I think I now have a much better understanding of these systems as a result.
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