TT system main bonding CSA?

[Engineer54]

problem with your solution Dave is that most terraced streets built pre war dont have the available space to space road 10' apart. the advice i have always worked to is anything over 200 ohms should be deeemed not safe and regs state 1667 ohms

So working to that daft philosophy a value of 199 ohms is safe!! It actually says nothing of the sort it refers to an arbitrary figure relating to an earth electrodes stability.... Being happy with a 3 figure Ra value is a basic nonsense!! Oh, and what happens when that 30mA 1667 ohm RCD device you are totally relying on, fails to operate??

Nothing stopping you installing 2 or 3 5/8'' rods coupled together in the one location though is there?? Many of the older DNO supplies supplying TT installations have been PME'd. So the first course i'd be making, is contacting the local DNO to find out if this is the case in the area you will be working...

 

[D Skelton]

So working to that daft philosophy a value of 199 ohms is safe!! It actually says nothing of the sort it refers to an arbitrary figure relating to an earth electrodes stability.... Being happy with a 3 figure Ra value is a basic nonsense!! Oh, and what happens when that 30mA 1667 ohm RCD device you are totally relying on, fails to operate??

Replying to this comment only, not taking into account anything else that has been said in this thread; with that logic, being happy with a two figure Ra value is just as much a basic nonsense, as is relying on a high single figure Ra value. Exactly the same thing is going to happen when that 30mA RCD fails... Sod all. This is why we fit an s-type up front, or, we rod an installation in order to obtain TN values and rely on them.

Nothing stopping you installing 2 or 3 5/8'' rods coupled together in the one location though is there?? Many of the older DNO supplies supplying TT installations have been PME'd. So the first course i'd be making, is contacting the local DNO to find out if this is the case in the area you will be working...

Totally agree.

 

[richy3333]

All ok then

Ha ha

 

[richy3333]

You wish ....No-ones spanking my butt laddie, but i can give your butt a bloody good spanking if you like!!

Sorry mate, but bum bandits just ain't my bag

 

[Engineer54]

Replying to this comment only, not taking into account anything else that has been said in this thread; with that logic, being happy with a two figure Ra value is just as much a basic nonsense, as is relying on a high single figure Ra value. Exactly the same thing is going to happen when that 30mA RCD fails... Sod all. This is why we fit an s-type up front, or, we rod an installation in order to obtain TN values and rely on them.



Totally agree.

I was basically referring to the crap stated in BS7671 and NICEIC propaganda and the OP's statement of misinterpreting BS7671. I was also trying to get him to Think past/further than painting by numbers so to speak.... I didn't want to go through the same old tooing and throwing seen in similar previous posts...

I think by now everyone here knows my views on UK TT systems and what's needed to make them as safe as you can realistically achieve...

 

[Engineer54]

Sorry mate, but bum bandits just ain't my bag

You don't need to be a bum bandit to have it thrashed!!

 

[D Skelton]

I was basically referring to the crap stated in BS7671 and NICEIC propaganda and the OP's statement of misinterpreting BS7671. I was also trying to get him to Think past/further than painting by numbers so to speak.... I didn't want to go through the same old tooing and throwing seen in similar previous posts...

I think by now everyone here knows my views on UK TT systems and what's needed to make them as safe as you can realistically achieve...

Dammit!

No bite

 

[Deleted member 9648]

Replying to this comment only, not taking into account anything else that has been said in this thread; with that logic, being happy with a two figure Ra value is just as much a basic nonsense, as is relying on a high single figure Ra value. Exactly the same thing is going to happen when that 30mA RCD fails... Sod all. This is why we fit an s-type up front, or, we rod an installation in order to obtain TN values and rely on them.

What a complete load of utter common sense!

 

[D Skelton]

What a complete load of utter common sense!

I do my best ;-)

 

[Engineer54]

What a complete load of utter common sense!

Say's the man that can't be arsed to even TRY to construct a half decent TT system!! But there you go!!

 

[GB.Kayak]

Rewiring an older TT terraced property. There is currently 6mm earthing from the rod, and also as main bonding to gas and water. I (was!) confident that 6mm main bonding met the requirements of BS7671, but a fellow Part P installer insists that I need to upgrade the main bonding to 10mm, but that 6mm for the earth rod is satisfactory.

So, please could someone tell me the minimum CSA for the main bonding, and, if it is meant to be 10mm, how come the earth rod only needs 6mm? A reference or page number to the big book would also be helpful.

Many thanks

Falcon Flyer

Here is one that members of this forum prepared earlier to coin a well known phrase from a famous childrens' TV programme ... http://www.electriciansforums.co.uk...cal-regulations/70322-adiabatic-equation.html

 

[Knobhead]

Is the >200Ω being regarded as unstable in the new version of the IET joke book?
I suppose it would be too much to hope they would have taken the trouble to add a clarification of the value and point out it is not the acceptable minimum value.

 

[Deleted member 9648]

Dammit!

No bite

Say's the man that can't be arsed to even TRY to construct a half decent TT system!! But there you go!!

There's always a bite if you wait long enough,just need the right bait!

 

[Deleted member 9648]

Is the >200Ω being regarded as unstable in the new version of the IET joke book?
I suppose it would be too much to hope they would have taken the trouble to add a clarification of the value and point out it is not the acceptable minimum value.

Not got a copy yet.....but would seem unlikely anything will change.

 

[Anthony S]

Is the >200Ω being regarded as unstable in the new version of the IET joke book?

Yes it is