Gotta get an earth

[sarni31]

Mr Steptoe is not likely to back down...

the basis of your argument is on the RSJ becoming live under fault conditions and the bonding therefore will ensure good passage to earth allowing for ADOS.

Surely you would just way up the chance of the RSJ becoming live? :|

 

[ianmacd]

Mr Steptoe is not likely to back down...the basis of your argument is on the RSJ becoming live under fault conditions and the bonding therefore will ensure good passage to earth allowing for ADOS.

Surely you would just way up the chance of the RSJ becoming live? :|

Yes, against the possibility of an earth that isn't (e.g. on a PME system with a neutral fault). In this situation the RSJ could then be at a higher potential than the ground/true earth. Under these circumstances its possible the rcd won't trip.

Have I explained that better?

Ian.

 

[Andy™]

i dont see how the RSJ could introduce any potential, unless someone added a cable to it, like a G/Y earth cable.... its the same as the metallic windows, shock hazard isnt there until earth cable is. If the RSJ was sticking out the ground and in contact with soil, then i would agree with the bonding

 

[ianmacd]

i dont see how the RSJ could introduce any potential, unless someone added a cable to it, like a G/Y earth cable.... its the same as the metallic windows, shock hazard isnt there until earth cable is. If the RSJ was sticking out the ground and in contact with soil, then i would agree with the bonding

Wasn't there some stories about window cleaners falling off ladders after getting a shock from "bonded" windows under fault conditions?

 

[Apache]

Wasn't there some stories about window cleaners falling off ladders after getting a shock from "bonded" windows under fault conditions?

How often would we be under 'fault conditions'. I know it's talked of and what we must design the installation for BUT I hope I never use my earth wires. I'd hope the consequence of having no earth would be almost zero as so infrequently used.

Our RCD has never tripped in 18 months. (other than me testing it )

Now I'm not saying it never happens but do we not need to be realistic?

 

[Andy™]

Wasn't there some stories about window cleaners falling off ladders after getting a shock from "bonded" windows under fault conditions?

yes, it was mentioned here

 

[Andy™]

How often would we be under 'fault conditions'. I know it's talked of and what we must design the installation for BUT I hope I never use my earth wires. I'd hope the consequence of having no earth would be almost zero as so infrequently used.Our RCD has never tripped in 18 months. (other than me testing it )

Now I'm not saying it never happens but do we not need to be realistic?

Patch - If PME, metal work can be above ground voltage under normal conditions, since its shared with neutral. and this voltage is higher under fault conditions

Also, under certain conditions, your earthing can take the full fault current of a fault in a different house...

 

[Apache]

Patch - If PME, metal work can be above ground voltage under normal conditions, since its shared with neutral. and this voltage is higher under fault conditionsAlso, under certain conditions, your earthing can take the full fault current of a fault in a different house...

I understand both those point - BUT a fault should be an absolute rarity - no?

 

[Andy™]

BUT a fault should be an absolute rarity - no?

depends who installed it and how clever Mr. DIY is with his drill...

 

[ianmacd]

How often would we be under 'fault conditions'. I know it's talked of and what we must design the installation for BUT I hope I never use my earth wires. I'd hope the consequence of having no earth would be almost zero as so infrequently used.

Don't have a desktop PC then? they tend to "leak" to earth.

 

[Andy™]

Don't have a desktop PC then? they tend to "leak" to earth.

not a fault current, but still a valid point

 

[Apache]

Don't have a desktop PC then? they tend to "leak" to earth.

just 2 laptops? Do they count?

 

[Andy™]

just 2 laptops? Do they count?

laptops are class II. they havent yet figured how to use laptop technology in desktop PC's to avoid earth leakage...

 

[Apache]

laptops are class II. they havent yet figured how to use laptop technology in desktop PC's to avoid earth leakage...

Just power it through a transformer - no?

 

[Andy™]

Just power it through a transformer - no?

its something with the electronics in the PSU - there is an earth connection so they use it... laptops dont have earth connection so are designed around it....