Consumer unit wiring for 10.8kW shower

[Seb101]

I haven't got the results on me at the moment, will supply later.

The shower is connected by plastic piping from the cold supply to the bath (which is earth bonded). The metal water inlet section of the shower is bonded to the shower radial CPC. No additional bonding is required as far as I am aware?

'clamped the circuit breaker to the busbar' - of course yes! Or did you mean the DIN bar?

R1+R2 at the shower terminal is 0.345 Ω
L-E IR is 3.723 MΩ

 

[Iggifer]

L-E IR is 3.7MΩ? Is that right?

 

[Taylortwocities]

If its new wiring you have a problem. The IR reading should be much, much better than that.

 

[JohnW2]

If its new wiring you have a problem. The IR reading should be much, much better than that.

Indeed - unless, I suppose, a neon in the shower isolator was in-circuit (and the neutral not isolated at the CU end).

Kind Regards, John

 

[flameport]

R1+R2 at the shower terminal is 0.345 Ω

For a new circuit of 10mm T&E, that is either wrong or you used in excess of 50m of cable.

 

[ban-all-sheds]

Indeed - unless, I suppose, a neon in the shower isolator was in-circuit

In circuit between L & E?

 

[JohnW2]

Indeed - unless, I suppose, a neon in the shower isolator was in-circuit

In circuit between L & E?

You omitted the (crucial) rest of my quote, namely "... (and the neutral not isolated at the CU end)".

If the neon were between L & N and the neutral supply to the circuit were still connected at the CU end (hence providing a N-E route {most obviously with TN-C-S, but also true with any other supply}) then, yes, the neon (plus associated resistor) would be be 'seen' by a L-E IR test, wouldn't it?

Kind Regards, John

 

[PBC_1966]

And if you're testing insulation resistance you want to disconnect N anyway so that you can include it in the test to earth.

 

[JohnW2]

And if you're testing insulation resistance you want to disconnect N anyway so that you can include it in the test to earth.

Yes, but since the OP referred to "L-E insulation resistance", I rather suspected that the neutral might still have been connected.

Kind Regards, John

 

[PBC_1966]

Yes, but since the OP referred to "L-E insulation resistance", I rather suspected that the neutral might still have been connected.

Certainly sounds like a possibility. And is that 3.7 meg measured including the shower heating element or not?

 

[JohnW2]

Certainly sounds like a possibility. And is that 3.7 meg measured including the shower heating element or not?

If the element were across L-N (with neutral still connected at CU), the measured L-E IR would obviously be dramatically less than 3.7MΩ. If the element were somehow in series with the IR test path, its effect would be far too small to notice.

Kind Regards, John

 

[PBC_1966]

If the element were across L-N (with neutral still connected at CU), the measured L-E IR would obviously be dramatically less than 3.7MΩ.

Unless, perhaps, it was disconnected from N at the shower during the testing, although I admit that would be odd if L were still connected through. I think we need some clarification on how the tests were conducted.

 

[JohnW2]

Unless, perhaps, it was disconnected from N at the shower during the testing, although I admit that would be odd if L were still connected through. I think we need some clarification on how the tests were conducted.

As you say, we need more details of how the measurements were made - otherwise the speculation about pretty unlikely scenarios will carry on!

Kind Regards, John

 

[ban-all-sheds]

I can't decide whether to deprecate this:

I haven't got the results on me at the moment, will supply later.

Yeah, right.....

or to express great puzzlement at the apparent dichotomy between someone who owns and knows how to use an IR tester and low-ohm meter and someone who asks "If I disconnect the white cables from all three alarms, is there a quick multimeter test I can do to see if the white cables are connected to Earth or not?"