RCD testing - 180V line A to load N

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JamieP
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RCD testing - 180V line A to load N

Post by JamieP »

When testing RCDs I am pressing the test button.

I confirm 230V on line side A and N

I confirm 0V on load side A and N

I confirm 0V on load side A and line side N

But I am getting 180V when testing line side A and load side N

Shouldn't this be 0V as well? Is this caused by internal components?

EC testing was completed with N disconnected and IR testing was completed confirming A-E and N-E @<500MOhm
AlecK
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Re: RCD testing - 180V line A to load N

Post by AlecK »

yes Line A to Load N should be 0V; because Load N should have been disconnected from installation N.
That's exactly what the test is supposed to confirm; that ALL poles have been disconnected
(which is something that none of the fancy operation-time-measuring devices can check for).
This reading is likely a symptom of a partial path between load N and installation N.

With voltage-independent RCDs required in NZ (by ESR 24); there are no internal components that can do this.
Tripping is not dependent on having 230V on the RCD, it's done entirely by the small current imbalance sensed by the toriod.
The test button circuit is from load A, through resistor, to line N. Works the other way also of course, but if A is taken from line side, then pressing the button livens load N. So there's generally auxilliary contacts so that even if you get line / load wrong; keeping the button pressed doesn't keep the load side live.
In tripped position (ie main & aux contacts open), there's no path through the RCD at all (easy to test for).
And to get that voltage, you must have a path.
Perhaps via a capacitor, so passing a.c. but not d.c..
Satobsat
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Re: RCD testing - 180V line A to load N

Post by Satobsat »

I have noticed this too and various different brands of RCCBs and RCBOs, all showing different voltages depending on what brand.
When I test I use a pair of analogue duspoles, when both motors are engaged the voltage drops to zero and the motors do not operate.
I always thought the voltage was due to something in the test circuitry as AlecK mentions.
I also check load side to earth to ensure that the voltage is zero on both A and N when the device is tripped.
JamieP
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Re: RCD testing - 180V line A to load N

Post by JamieP »

Very weird.

Downstream was 6 socket outlets, nothing plugged in. 2 general purpose, 4 for lights

Upstream was inlet. This was in two identical transportable installations.
AlecK
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Re: RCD testing - 180V line A to load N

Post by AlecK »

Begins to look like "phantom" voltage; perhaps some capacitive coupling?
Though wouldn't have thought that likely given the short cable runs in a CI.
Satobsat
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Re: RCD testing - 180V line A to load N

Post by Satobsat »

Jamie, are you using a different test instrument to what you usually use?
Line testers will pick up on transients where as other instruments I have will not show anything.
I have found this to be the case on pretty much all brands of RCCBs and RCBOs.
Next time I am going to reverse the line and load side of how I normally connect them and see if the phenomenon still presents.
Very few RCD units define a load and line side theses days but some do show a preference and some do state that there is one side that you must never IR test connected circuits.
I will also make sure that I am not charging a circuit up with my IR tester before connecting it.
JamieP
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Re: RCD testing - 180V line A to load N

Post by JamieP »

Ah, in this case I used a Fluke T6

It wasn't mine but a coleuges
AlecK
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Re: RCD testing - 180V line A to load N

Post by AlecK »

Quote from "3017: 2022"

2.2.2 Requirements for specific types of test equipment
2.2.2.1 Voltage indicator
Voltage indicators are required to perform the following functions to —
(a) confirm that no hazardous voltage is present; and
(b) confirm the presence of voltage.

Non-contact and single-contact voltage indicators shall not be relied on for proving that no hazardous voltage is present, and that the wiring or fittings have been de-energized and/or isolated to a safe state. A dual-contact voltage indicator is required for this function.
NOTE When using a voltage meter, low-impedance meters are preferred as they draw current from the circuit under test, reducing the effects from circuit anomalies, for example, those due to capacitive effects or external mutual inducted current. Analogue voltmeters are a low-impedance device, and some digital meters have a selectable low input impedance function.


Partly repeated in App A; which includes detailed advice on test gear:
A.2.2.1 Voltage indicators
Non-contact and single-contact voltage devices are indicators only. They cannot be not relied on for proving that no hazardous voltage is present, and that the wiring or fittings have been de-energized or isolated to a safe state.


Accordingly use of a non-contact type voltage tester is not compliant with the Standard for taking voltage readings.
While it's true that the test methods of "3017" are not mandated by Section 8 of "3000"; any alternative methods must produce "equally valid results". Which a non-contact or single-contact voltage indicator simply cannot do.
And therefore using such instruments for Section 8 testing is non-compliant with Section 8,
and any CoC based on results of the testing is a false declaration.
JamieP
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Re: RCD testing - 180V line A to load N

Post by JamieP »

Sorry, I should have specified although I used a T6 voltage measurements were taken with the two leads attached and not via the clamp thing.

But appreciate the info Alec
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