Rule of thumb

[farmerian]

Im currently doing 2395 inspection and testing course and was wondering When doing rule of thumb of 0.8( correction factor) for Zs values do you apply this to all books e.g bs7671, on site guide, and guidance note 3 ? I allways believed you dont for guidance note 3 but tutor says over wise

 

[Knobhead]

The only rule of thumb you should apply during you’re studies is don’t hit it with the hammer.

 

[SirKit Breaker]

Im currently doing 2395 inspection and testing course and was wondering When doing rule of thumb of 0.8( correction factor) for Zs values do you apply this to all books e.g bs7671, on site guide, and guidance note 3 ? I allways believed you dont for guidance note 3 but tutor says over wise

You only apply the 0.8 correction factor to the tables in BS7671, this is because those tables are done for 70 degrees C operating temperature. The OSG tables have been corrected for 20 Degrees C, and do not need correcting.

Your tutor needs a lesson in basic electrical theory.

temperature increases, resistance increases, and vice versa for lower temp, remind him, before you all screw up your exams,

Cheers............Howard

 

[skydog23]

^^^ as above,
G.N. 3 and on-site guide are corrected values. For bs7671 values use the 80% rule.
Good luck in your exam buddy,
and give your tutor a lesson

 

[farmerian]

Cheers guys sometimes even the tutors get it wrong glad I asked the question

 

[Badged01]

Those who can do, do ..... those who cant teach!

OK, not entirely true, there are some very good ones out there. But you do make a valid point about some lecturers and their apparent lack of knowledge. The frighteneing thing is they are educating the next generation of "electricians" who bank everything the say!!