What fault can turn a TT into a TNCS and disable the RCD?

[sparkytim]

So here is another interesting Fault situation.

Testing Zs on a TT system socket and gets 1.2 ohms.

Ra known to be 64 ohms

On testing RCD it fails to trip at 1x, 5x and even with a 25 Amp Loop test, but operates on Test button.

What was the fault causing this and why?

 

[steptoe]

do you want the answer, or is this aimed at the students?

 

[Manator]

do you want the answer, or is this aimed at the students?

Aimed at students steptoe so do not answer

---------- Post Auto-Merged at 20:52 ---------- Previous post was made at 20:52 ----------

:yawn :innocentut the kettle on

 

[steptoe]

yes boss :Salute

 

[sparkytim]

Thanks for holding back Steps, just as an aside this is one Dangerous condition that CAN occur with TT.

 

[steptoe]

tim, I hadnt looked at the forum,

so I didnt know if it was a fault or a fault scenario.

my bad. :|

it can, but under those conditions then there is another massive change that takes place to negate the effect the fault has in situations of direct/indirect contact.

 

[Jono Pashley]

Steps knocked his rod through the incoming Neutral conductor :slap

 

[steptoe]

I wondered what that bang and little puff of smoke was, :C

 

[Manator]

It could be some time before you get a decent reply, hang on for the inrush of students, they will all be out on the town tonight.

 

[sparkytim]

Reminds me, once I segregated a Garage from a TNCS, banged a stake in and got a 1 ohm Ra.

Only sliced the outer sheath on the Swa and picked up the Armour CPC again! :innocent

That is NOT the answer to this one by the way

 

[steptoe]

and who exactly buried the SWA?

and what about the bit where you check for underground services before digging?

or banging rods in!!!!

 

[gavindrummond]

I must be the only student who ain't out getting drunk from the lack of replies by students lol

 

[sparkytim]

and who exactly buried the SWA?and what about the bit where you check for underground services before digging?

or banging rods in!!!!

Pre existing SWA, didn't have me CAT handy.

 

[steptoe]

I must be the only student who ain't out getting drunk from the lack of replies by students lol

your just old and worn like the rest of us, this is our pub, we sit in here and get drunk.

---------- Post Auto-Merged at 21:50 ---------- Previous post was made at 21:48 ----------

Pre existing SWA, didn't have me CAT handy.

another 1" and you wouldnt have need it,

bad day explode

:slap

 

[Sidewinder]

Steps, get us another can of lager when you go out to the fridge will you please, my glass is empty.

 

[Manator]

Pre existing SWA, didn't have me CAT handy.

Animal testing as well eh?

When will this ever end?

 

[steptoe]

Guinness

:Salute

---------- Post Auto-Merged at 21:53 ---------- Previous post was made at 21:52 ----------

I think Apache told him to hammer the earth rod in using a cat and it would save any problems.

 

[sparkytim]

My ears are still ringing:slap

Disclamer NO PETS were harmed in this activity

 

[steptoe]

And some bread well buttered please :slap

do you want a sleeping bag with your vino?????????

 

[remustered]

Ok I'll have a bash...

TT to TNCS needs connection between cpc and N.

As RCD is balanced ,then a cross wire to keep both conductors balanced would disable it....my answer either short or crossed wiring on RCD circuit ?