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Posted By Topic: Caravan Earthing

markcraven
Oct 03 2016 16:33

Hi

Doing a complete new install on an old Caravan. Had a casual chat to an Inspector who told me I needed a 4mm2 minimum Protective Earthing Conductor.

Looking at Table 5.1 3001 for a 15/16A supply cable the maximum conductor size would be 4mm2. Then checking Table 5.1 3000 that would give a minimum Earthing conductor size of 2.5mm2 not 4mm2. Is this right?

Also from 3001 3.5.1.1 it states that The Protective Earthing conductor needs to be connected to the earth contact of the appliance inlet. Does this mean you cannot use the DB earth bar for this purpose?

   

ShaneR
Oct 03 2016 17:56

"Looking at Table 5.1 3001 for a 15/16A supply cable the maximum conductor size would be 4mm2. Then checking Table 5.1 3000 that would give a minimum Earthing conductor size of 2.5mm2 not 4mm2. Is this right?"



AS/NZS 3001 1.2

...shall be carried out in accordance with AS/NZS 3000 except where AS/NZS 3001 specifies otherwise.......
   

ShaneR
Oct 03 2016 18:01

"Also from 3001 3.5.1.1 it states that The Protective Earthing conductor needs to be connected to the earth contact of the appliance inlet. Does this mean you cannot use the DB earth bar for this purpose?"


3.5.1.1 is under the heading of 3.5.1 which is taking about the "Detachable connection"

Just checking...........
   

markcraven
Oct 03 2016 18:15

Hi ShakeR

This is a detachable install so both 3000 and 3001 apply. Any thoughts?
   

markcraven
Oct 03 2016 18:19

Sorry ShaneR not ShakeR for the typo.


   

ShaneR
Oct 03 2016 19:20

"This is a detachable install so both 3000 and 3001 apply. Any thoughts?"


My understanding is 3001 is defined in the "Scope" AS/NZS 3001 1.1

If the installation fits into the 3001 scope then 1.2 applies.
   

Sarmajor
Oct 03 2016 20:13

A caravan main earthing conductor is contained in the supply lead and will generally be the same size as the phase and neutral conductor. For a caravan with a permanently connected supply lead the earthing conductor will be connected directly to the earth bar.
For a caravan with an appliance inlet the main earthing conductor will run from the earth pin of the appliance inlet to the earth bar.

The bonding conductor that is connected from the earth bar to the chassis of the vehicle is generally 6mm green earth wire. I can't find any reference in 3001 for this so it comes from 3000 and I think it comes from section 5.6.3.2 where the minimum size is 4mm.

I suspect that 6mm is used in most caravans that I see because it is just that bit bigger and stronger and more likely to survive at the connection point to the chassis of the vehicle.
   

daniel2
Oct 03 2016 21:25

I've been picked up on this by an electrical inspector. Even though that everything in the caravan is wired in 1.5 mm2 2 c + E TPS (multi-stranded - 7 strands) and the incoming supply is a normal caravan inlet, the size of the earth bond to the chassis and frame is 6 mm2. Its a bit strange but that's what's stated in the Standards, barked the inspector.
   

AlecK
Oct 04 2016 09:21

"that's what's stated in the Standards, barked the inspector."

Another "inspector" who doesn't know what he's talking about.

Sarmajor is correct about the rule for the chassis bond. Same as any EQP bond, minimum 4 mm2. Anyone who says it must be 6 mm2 is ignorant at best.

Other than the requirement for all conductors to be minimum 7 strands and minimum 1.5 mm2 [3.4.1]; and the length vs size of the lead [Table 5.1]; "3001" is silent on conductor sizes.

A connectable installation doesn't have an MEC, only PECs and EQP bonds; and the sizing is as per Section 5 of "3000". And for that to lead to a PEC of 6 mm2 would mean it had actives (& neutrals) at least 16 mm2 - that's either a waste of cable or a bloody big caravan with likely 63 A rated supply.

ShaneR is correct that 3.5.1.1 is part of 3.5.1 talking about the detachable connection; so the effect is that one end of this PEC for the incoming supply is connected to the appliance inlet. There is no rule about where you put the other end, except it can't be connected to an earth electrode; and all inlets must have their PECs connected together.

Then 3.5.1.2 tells you all the things that have to be connected to the incoming supply PEC. it doesn't tell you how to do that, just that it has to be done. Which leaves it open any of the methiods listed in "3000" for connecting items that must be earthed to an installation's MEC. Including use of an earth bar in a DB.