Trick Question

[kai]

Consider an immersion circuit, feeding a 3kw Immersion Element.

It is wired in seven metres run of 1.5.mm.sq.cable clipped direct to the surface.

The Circuit protection is a B32 breaker. There is NOT a 13amp fuse-connection unit inline.
The ZS at the immersion was measured to be Twelve Ohms exactly.

This is clearly over the disconnection time requirement for the B32 breaker.

I would personally Code One it as a faulty circuit.

Would others agree with me that it's a Code One fault??

I have heard some people just ignore it, as OH, but the Immersion will never overload the cable, stuff the High ZS attitude, who cares!!....

 

[bhm1712]

Is this really a trick question?

 

[Iggifer]

Is the circuit RCD protected?

What is the supply Ze?

 

[EFLImpudence]

The faulty earth may be a code.

 

[bhm1712]

For me it's a code one fault. The installation does not have adequate protection and as you have already pointed out - the EFLI is contrary to the permitted values and will mean the breaker cannot function as intended. There is an immediate risk of danger and injury (fire) if the element becomes faulty.

 

[EFLImpudence]

What is 'OH'?

 

[Echo the husky]

if the element becomes faulty.

Doesn't that make it code 2, potentially dangerous? There is no immediate danger right this minute.

 

[securespark]

Is it a TT supply?

 

[kai]

It is a TN-S supply, external loop impedance is half an ohm measured at the incoming terminals of the main switch in the CU, and the Earth Bar, with all other bonding disconnected for the duration of the testing. There is a 30mA RCD for each half of the 17th edition board (All Steel Cased).

 

[bhm1712]

if the element becomes faulty.

Doesn't that make it code 2, potentially dangerous? There is no immediate danger right this minute.

I don't think so, because you cannot say at what time an appliance or piece of equipment will (or if) become faulty and so therefore for me it's still a 1. If you could define at what points or under what conditions it becomes faulty then I would agree that it's code 2

 

[bhm1712]

I can see your point though. Personally I would hate to code 2 it and then leave the premises and find out that a couple of hours later it set fire to the building and somebody was trapped and died because it went faulty and that I knowingly said it wasn't immediate danger and that I knew the protection wasn't adequate.

 

[Iggifer]

It is a TN-S supply, external loop impedance is half an ohm measured at the incoming terminals of the main switch in the CU, and the Earth Bar, with all other bonding disconnected for the duration of the testing. There is a 30mA RCD for each half of the 17th edition board (All Steel Cased).

Then, TECHNICALLY, the Zs is not an issue. Clearly there's a fault with the cable/terminations but it's allowed. I think C2 also.
And lets face it, C2 also means the EICR would be unsatisfactory.

 

[EFLImpudence]

What is the L-N loop value?

 

[securespark]

Gotta be a poor connection somewhere.

 

[ban-all-sheds]

Then, TECHNICALLY, the Zs is not an issue.

YES IT IS.

With a TN supply, and RCD is NOT, repeat NOT a sticking plaster for a too-high Zs.