Gotta get an earth

[steptoe]

structural metal work that is bolted to the floor and forms the main structure of the building yes.... because its bolted/embedded to the floor and therefore in contact with earth...rsj's, steel windowframes, metal sinks, baths.... no

Of course... I could be wrong Guiness Drink

are no longer considered structural,

unlike the 15th,!!!!

 

[steptoe]

Arn't garages made out out of bricks, giving very high resistance to earth..therefore no potential and no need to bond the rsj .. ?:|

your house is made out of bricks, your water comes in in plastic, you still have to earth it,

for electrical terms the general mass of earth is considered to be anything that would normally be at 0 volts potential, on TT systems this can vary greatly from the house to the outbuilding.

IMHO the garage itself I would consider to be at earth potential, therefore I would consider any metalwork in contact with it to be extraneous.

you may well interpet the regs on TT systems differently.

 

[sarni31]

MMmm not sure now....

Why would you bond differently depending on the earthing arrangements ?:|

the whole plastic pipe thing is an entirely different argument ...

in simple terms (thinking out aloud) you need a potential difference between an exposed conductive part and an extranious conductive part for it to be a hazard ....

if you bond an RSJ (between two supporting walls) you have put it at earth potential and therefore introduced a hazard.. ?:| ? :| ?:|

Guiness Drink

 

[Jono Pashley]

At college we were told to bond if the steelwork went through the DPM.

 

[Janice]

I hope Janice doesn't see that.

She did! Grrr...

J.

 

[a1]

She did! Grrr...J.

Run Man, Run for the hills.

 

[steptoe]

the whole purpose of earthing is to ensure anything that is not intended to have a potential across it will activate your overcurrent device should a fault occur.

therefore if you dont bond your RSJ, thus failing to ensure it is at 0v (theoretically), you could have (under fault conditions) a piece of exposed metalwork sitting at 230v that will not operate your protective device until something (you touching it) draws it to earth potential.

 

[batty]

the whole purpose of earthing is to ensure anything that is not intended to have a potential across it will activate your overcurrent device should a fault occur.therefore if you dont bond your RSJ, thus failing to ensure it is at 0v (theoretically), you could have (under fault conditions) a piece of exposed metalwork sitting at 230v that will not operate your protective device until something (you touching it) draws it to earth potential.

My thoughts to steps but if there are no cables running near it is unlikely but you don't know what people will do in the future so a bit of 10mm g/y won't break the bank.

Batty

 

[kingsway47]

Guidance note 8 (earthing) from the IET is worth looking at if you borrow one, I would not buy one at the moment because it hasnt been reprinted for the 17th.

As far as exporting an earth as you rightly say no problem with TT, the more paths to earth the better

If the swa to the garage has no earth protection at the moment then it must be brought up to date with either its own RCD or RCBO as it is a seperate circuit

Now as soon as you alter or add something you become responsible for the whole gambit which means as someone already said poor access to the house DB is not acceptable, when you sign the installation cert you sign for all your work or anything you have added to or altered being up to the current regs which includes access

 

[Jono Pashley]

Guidance note 8 (earthing) from the IET is worth looking at if you borrow one, I would not buy one at the moment because it hasnt been reprinted for the 17th.As far as exporting an earth as you rightly say no problem with TT, the more paths to earth the better

If the swa to the garage has no earth protection at the moment then it must be brought up to date with either its own RCD or RCBO as it is a seperate circuit

Now as soon as you alter or add something you become responsible for the whole gambit which means as someone already said poor access to the house DB is not acceptable, when you sign the installation cert you sign for all your work or anything you have added to or altered being up to the current regs which includes access

Wouldnt this come under the making it no worse than it originally was clause.

 

[sarni31]

the whole purpose of earthing is to ensure anything that is not intended to have a potential across it will activate your overcurrent device should a fault occur.therefore if you dont bond your RSJ, thus failing to ensure it is at 0v (theoretically), you could have (under fault conditions) a piece of exposed metalwork sitting at 230v that will not operate your protective device until something (you touching it) draws it to earth potential.

I take your point about the "under fault conditions"

but where do you stop?..

if its a large garage/building with multiple RSJs (none in direct contact with earth through DCM)

do you bond them all?

"TO BOND OR NOT TO BOND" That is the question! :| :|Guiness Drink

 

[ianmacd]

the whole purpose of earthing is to ensure anything that is not intended to have a potential across it will activate your overcurrent device should a fault occur.therefore if you dont bond your RSJ, thus failing to ensure it is at 0v (theoretically), you could have (under fault conditions) a piece of exposed metalwork sitting at 230v that will not operate your protective device until something (you touching it) draws it to earth potential.

What if someone/thing introduces an earth fault? Suddenly your bonded RSJ's are at a different potential to earth and may not cause an RCD/RCBO to trip when someone bridges them.

Ian.

 

[steptoe]

What if someone/thing introduces an earth fault? Suddenly your bonded RSJ's are at a different potential to earth and may not cause an RCD/RCBO to trip when someone bridges them.Ian.

I really dont get your point ian.

that is exactly why you should bond, to have the metalwork at the same potential as earth.

or am I missing something here?

 

[Jono Pashley]

If the RSJ has no potential to earth and you bond it are you not creating a shock hazard as it would otherwise not be able to complete the circuit?

 

[steptoe]

If the RSJ has no potential to earth and you bond it are you not creating a shock hazard as it would otherwise not be able to complete the circuit?

but it would have a potential to earth if you were to touch it.

that is the basic principal of bonding, to ensure extraneous parts are at earth potential, ie, 0v.

 

[Jono Pashley]

The principle of bonding is to reduce shock magnitude. Bonding is to stop the item rising above 50v for the duration it takes the protective device to operate. An Item sited directly on dry concrete and isnt piercing the DPM or gaining earth potential from another location doesnt meet the criteria for extraneous or exposed.

 

[steptoe]

The principle of bonding is to reduce shock magnitude. Bonding is to stop the item rising above 50v for the duration it takes the protective device to operate. An Item sited directly on dry concrete and isnt piercing the DPM or gaining earth potential from another location doesnt meet the criteria for extraneous or exposed.

so you are stating that the general mass of earth doesnt include the dwelling?

my, thats a sweeping statement, I hope you put that in your deviations box of you certs.

or have you a reg to back that up?

 

[Jono Pashley]

At which point did i state that it cant be a source of potential? In Most cases if an item doesnt penetrate the damp proof course it wont be introducing potential. However this should always be confirmed, and the item would also be bonded if the surface had the potential to become damp.

 

[sarni31]

I just started to read the exported earth thread.... interesting reading ... well the first few pages, then goes off on several tangents:z

I wonder what Markysparky is doing now......Guiness Drink

 

[Jono Pashley]

Probably what we should be doing and sleeping?