Discuss the maximum length of cable permissible in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

B

Banburyman

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

[FONT=&quot]I found this question in "practical giude to inspection, testing and certification" book

A lighting circuit is to be wired in l mm2 twin and earth thermoplastic [/FONT]
[FONT=&quot]cable, the circuit is protected by a 5 A BS 3036 fuse. What would be the [/FONT][FONT=&quot]maximum length of cable permissible to comply with the earth fault loop impedance requirements (Zs)? (Ze, is 0.45.)[/FONT]
 
SuperlecDirect - ElectriciansForums.net Electrical Suppliers
This official sponsor may provide discounts for members
A

acat

  • Thread Starter Thread Starter
  • #2
Untitled

Hi if you follow the link that should give you the answer you need


Chris
 
B

Banburyman

  • Thread Starter Thread Starter
  • #3
it is how I did it
Zsmax for 5A 3036 is 9.58
[FONT=&quot]Ω
rule of thumb 9.58 * 0.75 = 7,17[/FONT]
[FONT=&quot]Ω
[/FONT]
[FONT=&quot]Zsmax - [/FONT][FONT=&quot]Ze[/FONT][FONT=&quot] =
7,17[/FONT]
[FONT=&quot]Ω[/FONT] - 0.45 [FONT=&quot]Ω[/FONT] = 6.72 [FONT=&quot]Ω[/FONT]
[FONT=&quot]R1+R2 = 36,20 m[/FONT]
[FONT=&quot]Ω/m

Length * (R1+R2)/1000 = 6,72
[/FONT] [FONT=&quot]Ω[/FONT][FONT=&quot]
lenght = 185 meter

I try to prepare myself to C&G2391 exam but it is very difficult as I have to use a book with so many errors.
According to Practical Guide to Inspection Testing and Certification the answer is 498meters (this is one of many errors in this book)
thanks a lot I just needed somebody to confirm my calculation
[/FONT]
 
looks like they used the max zs value of 100% of 17.7 ohms for the 5 second disconnection time .
remember the .8 rule is only to give us a safety margin, not the max zs allowed.
 
CK Tools :) The professionals choice when it comes to Electrical Tools
This official sponsor may provide discounts for members

Reply to the maximum length of cable permissible in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

SuperlecDirect - ElectriciansForums.net Electrical Suppliers
This official sponsor may provide discounts for members
Top Bottom