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Posted By Topic: Correct Circuit Connections device

OctaneOutlaw
Apr 13 2019 14:13

A while ago I made a post about testing and what to use for correct circuit connection

A few people said that basically they just made there own device and that it was easy enough to do

I don't really know how to go about it or where to start, if someone that has one would be willing to share some advice on how to go about it that'd be awesome or if there is any other better way to do this

Thanks
   

ppaw1965
Apr 13 2019 15:06

Depending on what you want to test. I made up a 40A test jig to test a large pressure boiler I rebuilt. I’ve also had a test jig with a 200mA fuse. I’ve also had test jigs only relying on the supply fold back protection. What are you trying to achieve?
   

OctaneOutlaw
Apr 13 2019 15:34

Well as far as I'm aware they just looked like a device with 3 crocodile clips coming out and some different value resistor I assume connected on the other end

I'm just not sure what the best or easiest way to achieve this is

Like what's the best way to connect said crocodile clip wire to the resistors etc

To correspond with figure 3.15 and 3.16 of 3017 where resistor are connected between the phase tested and the neutral bar and the neutral tested and the neutral bar
   

pluto
Apr 13 2019 16:13

You need to also note that when using ASA/NZS 3017 fgures the final sub circuit conductors are disconnected from the neutral bar and protective device.

The resistors are connected as shoe\wn in 3017 figures 3.16 or 3.17 and using a low ohms scale on a Megger or multi-meter you are able to positively identify the final subscircuite connections without the use of a long trailing lead.
   

OctaneOutlaw
Apr 13 2019 16:24

Yeah I did see that Pluto, it's more I wanted guidance on what resistors to use and how to set them up in an easy to use device
   

pluto
Apr 13 2019 16:30

1 watt resistors as used by electronic equipment is all that is required.


I used a strip connector to connect the resistors and three single flexible tails with clips together.
   

OctaneOutlaw
Apr 13 2019 17:09

Ah, awesome that's makes complete sense and is easy as anything to do

If anyone has any further suggestions it's much appreciated
   

t92300
Apr 13 2019 19:33

This is what we were shown at block course a couple of months ago.
Get 3 1k resistors. Parallel 2 of them.
Connect an end of each of the resistors to a center clip and the 2 other ends go to a clip each.
Make the end of the 2 resistors paralleled the neutral and the single resistor phase.
Measuring between
P - E 1k ohms
P - N 1.4k ohms
N - E 500 ohms

You can use other resistors using the same principal. Using larger resistors means less confusion with the resistance of the cable, say you were to use 1 ohm resistors
   

AlecK
Apr 13 2019 19:45

All of which is really polarity rather than correct circuit connections. For which a large part of the answer is the good old IR tester.
Just read the desired outcome for correct connections; 8.3.8.1; and you'll see why the 3-resitor test for polarity is of zero use for CCC, while being very good for polarity (8.3.7.1).
   

OctaneOutlaw
Apr 13 2019 20:15

So then why is that method listed under the heading of correct circuit connections in 3017?

I mean I under the images say polarity and CCC but still under the overall heading of CCC

What do you believe are the best methods to use then?
   

AlecK
Apr 14 2019 06:15

Because "3017" isn't as good as it should be.

And because all testing is inter-related.
Not just in simple ways; like the fact that continuity of PECs is actually part of EFLI, and also part of equipotential bonding. Also in more complex ways; like unless you've already proved all the earthing continuity, your IR testing for earth faults won't be valid (because there might be an earth fault to the bit of earthing system you didn't have connected to the rest).
A bad result on any test means we can't necessarily trust the "pass" results we got earlier on other kinds of test.

----------

For individual types of test;I find it helps to look carefully at the required outcomes.

For correct circuit connections, we have to establish two very different things [3000: 8.3.8.1, repeated in "3017": 3.4.1].

The first one that PECs do not carry load current. Part of that is making sure that we haven't accidentally connected a N conductor to an E terminal of a fitting, and the PEC to a load terminal. And partly it means NOT having N-E links in DBs, because if we do the PEC of the submain will be carrying load current.\

And yes, this is directly related to polarity, so some test methods can help with both polarity and this aspect.

The 2nd kind of incorrect connections we're testing to avoid is short circuits within the circuit. We already know there's no earth fault, because we've done I.R testing. This bit is testing between actives; and the best was is a simple IR test.

Again two closely-related tests, actually but looking for different things.

Now to 8.3.8.2 / 3.4.2; and we find there's actually a third aspect, ie no interconnection between different circuits. Again IR tester is the best tool.

This may seem silly, or over-cautious; but it does happen. Just think of how often you've found an RCD tripping because one of the Ns was on the wrong bar.
There are all those times we have multiple circuits in one enclosure, eg commercial lighting switch panels, which risk of crossed connections.
And not long back there was a fatality in Oz, because of a crossed connection that meant the load side of the RCD had another feed.

A year or so back, doing a TI survey of a factory, I found a small DB where every earth was on the n bar and every N was on the E-bar. Often swapping bars doesn't matter, but this one's E-bar was bolted directly to the case of the swbd. Even good tradespeople do silly things sometimes.

"Correct circuit connections is a bit of a catch-all name; and i don't like it much. But until someone comes up with a better one, don't be fooled by it.

The heading is less important than the requirements listed under it; so if we understand those, we can work out which test method to use.

The methods in "3017" are not mandatory, but they do work. Like the requirements in"3000"; they're not standalone, but inter-related. So yes we can use other test methods (unless "3000 specified the method); but any alternative methods have to give "equally valid results". Which is why great care has to be taken when designing a test method.

Most people approach testing from the view of "proving it's right"; but that approach can get us into trouble. What we actually have to do is prove there's nothing wrong. And since there are often more ways of it being wrong than of it being right, tests have to be designed NOT around "what does 'correct' look like using this proposed method?"; but instead around "using this proposed method, what does each kind of 'wrong' look like?".

That's why the live mains polarity test published by EWRB late last year is no use. For some - in fact most - kinds of 'wrong' polarity their method will give results that are near as dammit identical to what correct polarity gives. The problem is they missed the vital step of opening the MEN link. There's a reason we have removable links, and it's about testing!