N.B. this 16th question ... answer? ... +another one for u

[steveg1957]

Question asked a few days ago...
Which one of the following is an extraneous conductive part?

a)The metal case of a gas cooker
b)The metal case of an electric cooker
c)The steel housing of a transformer
d)The metal frame of an electric fire

Which is correct and why?

ANSWER .. the gas cooker ... the lecturer forgot to mention it had no mains connection !! Therefore it is not part of the electrical installation making it an extraneous conductive part.

NOW ANOTHER !!
When using an RCD the product of the operating current (presumably 30mA) and the earth fault loop impedance should not be greater than
a/ 2 b/ 10 c/ 40 d/ 50

Cant find any direct reference to this in regs or guide.
to get the smallest answer '2' the impedance could be 66 ohms!! (that cant be right can it.

Any input welcome

 

[Spark123]

This is in the regs and is to do with touch voltages on eebads systems.
(Since 25v is not an answer, it can't be in one of the two special locations with a max 25v touch voltage.)

 

[ban-all-sheds]

Question asked a few days ago...

ANSWER .. the gas cooker ... the lecturer forgot to mention it had no mains connection !! Therefore it is not part of the electrical installation making it an extraneous conductive part.

Only if the gas pipe is metal. It often isn't with cookers.

//www.diynot.com/forums/viewtopic.php?p=207990#207990

NOW ANOTHER !!...

You aren't going to learn very much on your course if you come here to get answers to questions that you don't understand, or find a bit tricky.

Use the regs. Use guides to the regs. Use your textbooks. Find the answers yourself.

If you don't understand a question, ask your lecturer, or he will think that you are perfectly OK with what he is teaching you. Believe it or not, lecturers do actually want their students to learn, not to be confused...

 

[steveg1957]

doh!!
maximum touch voltage = 50v ?

B.A.S.
I am learning plenty from the course .... the lecturer unfortunately doesn,t live at my house for immediate consultation, and just thought it would be of general interest for people to get their brains ticking !

cheers