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.
 
I'm surprised you're not aware, but if the metalwork tests at >22kOhms to earth then it isn't extraneous.
 
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)
 
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

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock