Main bondage

[ultinator]

Does main bonding in every circumstance always need to be under 0.05. main bonding in a house where the main water was moved has 10mm cable but resistance of 0.25 ohms!!>>

 

[Geoffsd]

THIS IS ONE OF THE MOST FAILED QUESTIONS IN TEST AND INSPECTION EXAMS when the question has been asked state the maximum value of resistance of a main protective bonding conductor...................I REST MY CASE END OF FINISH

I presume that students are advised and probably instructed to read GN3 in which case that would very reasonably be viewed as a trick question.

Furthermore, why would such a question be asked if there is no maximum resistance value?

Getting the question wrong would only result in an installation being 'safer'?

 

[Chr!s]

The figure 0.05 is just a means of confirming a connection say between a RSJ joint, simple, that's lt.

Main Bonding lust needs to be sized correctly, the length Is irrelevant.

The op, he needs to ensure his test equipment is calibrated and correctly connected.

The resistance needs to relate to the length and csa.

If it doesn't he needs to identify why and remedy.

 

[netblindpaul]

I can't believe that this is still going on.
A competent electrician should KNOW this without asking.

 

[Silly Sausage]

The figure 0.05 is just a means of confirming a connection say between a RSJ joint, simple, that's lt.

Main Bonding lust (haha...back to the thread title) needs to be sized correctly, the length Is irrelevant.

The op, he needs to ensure his test equipment is calibrated and correctly connected.

The resistance needs to relate to the length and csa.

If it doesn't he needs to identify why and remedy.

Exactly!
If the length is irrelevant and some like to say there is no upper resistance specified, you may as well use 1mm[SUP]2[/SUP].

So therefore, the resistance of the cable must have some significance.

 

[Guest55]

Exactly!
If the length is irrelevant and some like to say there is no upper resistance specified, you may as well use 1mm[SUP]2[/SUP].

So therefore, the resistance of the cable must have some significance.

well thats not quite right is it ?
a minimum sized bond conductor is specified , but no upper resistance value needs to be complied with for that conductor if its the correct csa.

 

[Chr!s]

Exactly!
If the length is irrelevant and some like to say there is no upper resistance specified, you may as well use 1mm[SUP]2[/SUP].

So therefore, the resistance of the cable must have some significance.

Archy, 1mm would be fine, when calculating touch voltage you assume little or no current in the conductor.

The min 6mm is for mechanical strength.

 

[Chr!s]

Archy, 1mm would be fine, when calculating touch voltage you assume little or no current in the conductor.

The min 6mm is for mechanical strength.

Forgot to say, Bar pme broken pen where current may flow, this is dealt with within the reg, but still only correct size required.

 

[onions1066]

I know how to put this one to bed........................ Who thinks we should use TT system to an outhouse?

 

[Silly Sausage]

well thats not quite right is it ?
a minimum sized bond conductor is specified , but no upper resistance value needs to be complied with for that conductor if its the correct csa.

That's what the regs say, half the Main E C, and no resistance value specified.
But why?


edit...


I'm sure I vaguely remember when I did my 2391 10 years ago, they said, 'If you're meter reads zero when testing bonding conductors, write down 0.01!

 

[Guest55]

That's what the regs say, half the Main E C, and no resistance value specified.
But why?

if bs7671 gave a maximum resistance value for any given bond conductor it would restrict its length.
no resistance limit = unlimited length.

 

[Silly Sausage]

I'm going dizzy now

 

[KAS1]

Personally I think it's because water pipes gas pipes and the like can introduce additional earth paths into the electrical installation and to be comparable with the resistivity of steel pipe or the old lead and copper pipe an excepted copper cable has been estimated to achieve an excepted resistive value between these services is 10mm in most cases , mainly due to the fact that most domestic situations the bonding conductor is usually a short length of cable. Having said all that who knows .................On it goes lol

That's what the regs say, half the Main E C, and no resistance value specified.
But why?


edit...


I'm sure I vaguely remember when I did my 2391 10 years ago, they said, 'If you're meter reads zero when testing bonding conductors, write down 0.01!

 

[KAS1]

second thoughts what a load of tosh lol

 

[Guest55]

second thoughts what a load of tosh lol

my explanation was way better lol.
;-)

 

[Geordie Spark]

I'm going dizzy now

Aye .......... being on this thread is like being on the magic roundabout innit.