• IMPORTANT: Please note that nobody on this forum should be seeking from or providing advice to those who are not competent and / or trained and qualified in their field (local laws permitting). There is a discussion thread on this global industry-wide matter HERE. This also has more information about the warning with regards to sharing electrical advice in some countries. By using this forum you do so in agreement to this.

Discuss Extraneous Parts Earth sizing in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

Reaction score
13
Customer wants to take power from an existing garage (with board) to supply a greenhouse, to be fitted with ip rated switchgear.
The greenhouse is made of aluminium.

Since this is an extraneous conductive part am i right in thinking that the aluminium frame would require a 10mm bond at least? (tncs supply)

Garage is fed with a 4mm armour (3core)

Should i still take the supply from the garage but run in a seperate 10mm earth from the house MET?
 
What's being put in the greenhouse? Maybe an IP rated outlet just outside it would allow use of garden tools etc.
 
would you like to elaborate on what yous are talking about?

you've mentioned this concrete plinth idea. (which ive never heard of)
Why would an extraneous conductive part not need earthed if sited on a concrete plinth? Wheres the logic?
Because,combined with the human body,a res of 23k would only allow a current of 10ma to flow which is considered safe.
 
Right that makes perfect sense, thanks.

But, as ive already said, (to much hilarity) the greenhouse is not on a plinth, so why would this apply?
Am i missing something here? (apart from a brain)
Because the concrete plynth may offer more insulation resistance against the path to earth, than if the metal frame was in direct contact to the earth. Just test the frame as already been mentioned if its greater than 25kohms (a safe bet value) then it would not be considered extraneous. But if you find that the tested value is very close to the minimum accepted value (22kohms) and environmental conditions might reduce this value further then its your call.
 

Reply to Extraneous Parts Earth sizing in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top