continuity tester and proving unit also required?

[inquisitive]

Hi. We have a circuit where some of the sockets have a dangerously high earth loop impedance. This was identified by a professional electrician. I was thinking of rewiring this, as a DIY project.

For safety, I want to ensure the replacement is done to spec. Buying a multifunction tester seems an unavoidable conclusion. Especially because my Martindale EZ150 'advanced socket tester' didn't ring the alarm about the earth loop impedance—it only fluxuates between the lowest two readings.

My eye is on the Metrel MI325 or the Di-Log DL9110, because they seem like two of the cheaper multifunction testers available (and appear to be solve by reputable sellers).

The other obvious safety aspect is: I want to make sure I don't work on a live circuit. I have a non-contact voltage tester, but I read here that whilst those can be useful as a quick indicator, they cannot be relied upon, especially when they read negative.

First question. Do I need a separate continuity tester, given that the multifunction tester can test continuity? I hope this doesn't sound silly. The reason I ask is: a simple multimeter can be used the test continuity. Nonetheless, the advice seems to be not to use them for such mains safety checks, because of the possibility of misuse (e.g. rotating the dial to the wrong range).

Do you feel it is safer to have a separate continuity tester for similar reasons? Or maybe you prefer a separate continuity tester just because it is smaller?

Second question. Assuming the multifunction tester is calibrated (and the calibration hasn't expired), is a proving unit required? Or instead is it always a good idea to have a proving unit when testing for continuity, regardless of calibration?

Thanks.

 

[Deleted account]

Your profile doesn’t give details of your experience. I ask this because you really need to know how to use the test equipment and understand the results, so it may be more cost effective to spend 7 or 8 hundred quid towards a spa4ky with a tester. Possible a sparky who would be willing to include you in the works.

 

[inquisitive]

Your profile doesn’t give details of your experience. I ask this because you really need to know how to use the test equipment

That's a fair question. I have experience replacing switches and extractor fans, and rewiring plugs. And I've run low voltage (ethernet) cables before.

But I've never run high voltage cabling.

Maybe this is dangerous thinking, but when I see some of the equations used when QAing a circuit, it feels like something I could learn, as opposed to something intimidating. I understood the fundamentals well in high school physics. I don't *yet* have the knowledge required to do the job safely, but I feel I can learn it.

Possible a sparky who would be willing to include you in the works

Ordinarily, I think this would be a great suggestion, but I'm a bit hesitant because of COVID.

 

[Deleted account]

There is an awful lot to learn to be honest on a job of the scale your thinking.
Also this is notifiable work therefore if you don’t include a sparky to certify and notify to building control, you will have to contact building control yourself prior to starting works.
there are costs involved in this also.

 

[MJPD29]

That's a fair question. I have experience replacing switches and extractor fans, and rewiring plugs. And I've run low voltage (ethernet) cables before.

But I've never run high voltage cabling.

Maybe this is dangerous thinking, but when I see some of the equations used when QAing a circuit, it feels like something I could learn, as opposed to something intimidating. I understood the fundamentals well in high school physics. I don't *yet* have the knowledge required to do the job safely, but I feel I can learn it.


Ordinarily, I think this would be a great suggestion, but I'm a bit hesitant because of COVID.

I dont mean to be picky, but you will be running low voltage cables. You have ran extra low voltage cables before. Some terminology really grinds me, and that is a good example. The price of the multifunction tester and calibration may well exceed what is costs to pay for someone to do the actual work, there are plenty of people out there who will let you do the work and then they certify it. Its not something I do but I'm aware of others who do it.

 

[inquisitive]

I dont mean to be picky, but you will be running low voltage cables. You have ran extra low voltage cables before. Some terminology really grinds me, and that is a good example.

You're right. Thanks for the correction.

there are plenty of people out there who will let you do the work and then they certify it.

This is an interesting idea, if I still go down the DIY path (which I realise the other poster is advising against).

 

[inquisitive]

There is an awful lot to learn to be honest on a job of the scale your thinking.
Also this is notifiable work therefore if you don’t include a sparky to certify and notify to building control, you will have to contact building control yourself prior to starting works.
there are costs involved in this also.

I don't think it's notifiable in Scotland, because I'd be replacing an existing circuit. [1]

However, I take your point it's a huge job, which is presumably why it's notifiable in England, and maybe in other parts of the UK and the world.

Maybe as you suggest, I should get a sparky involved. At the very least for certification, but realistically sounds like you're saying for the whole job.

 

[loz2754]

While there's certainly nothing wrong with being inquisitive, it's not for no reason that many weeks of a trainee electrician's life are devoted to the subject of health and safety. When it comes to low voltage electricity, there are so many dangers involved. In fact there's a whole procedure for proving that cables are dead that involves a minimum of 12 steps. Please continue to be inquisitive but also extremely careful.

 

[inquisitive]

While there's certainly nothing wrong with being inquisitive, it's not for no reason that many weeks of a trainee electrician's life are devoted to the subject of health and safety. When it comes to low voltage electricity, there are so many dangers involved. In fact there's a whole procedure for proving that cables are dead that involves a minimum of 12 steps. Please continue to be inquisitive but also extremely careful.

Thanks. I clearly need to familiarize myself with all of the steps, before doing any more DIY electrical.

At the very least, those 12 steps answer my second question: of course a proving unit is required (edit: testing on a known supply is possible but frowned upon).

 

[DPG]

Nothing wrong with using a known live source as a reference to prove your voltage tester, but you often won't have one available. A proving unit is always available.

I admire your interest and enthusiasm. I would suggest maybe reading a decent book on inspection and test, and maybe also Guidance Note 3 from the IET.

You need to be sure of your abilities and understanding before shelling out several hundred pounds on a tester that you may not end up being able to use properly.

 

[telectrix]

Thanks. I clearly need to familiarize myself with all of the steps, before doing any more DIY electrical.

At the very least, those 12 steps answer my second question: of course a proving unit is required (edit: testing on a known supply is possible but frowned upon).

a proving unit used used to ascertain the performance of a safe isolation tool, which is basiaclly a 2 prong voltage tester.

this is totally different from a multifunction tester which,as it's name means, can perform several essential testes.

 

[DPG]

a proving unit used used to ascertain the performance of a safe isolation tool, which is basiaclly a 2 prong voltage tester.
View attachment 61832
this is totally different from a multifunction tester which,as it's name means, can perform several essential testes.
View attachment 61833

Good point. Have just re-read the OP's initial post and there does seem some confusion.

 

[Vortigern]

Oh yeh don't forget the building control or whatever it is in Scotland and the fee before you start work!

 

[littlespark]

Where in Scotland? There might be a member close by that could assist.

Scotland’s a big place, never mind what any of these haggis hating sassanachs say!

 

[telectrix]

haggis???? i'd rather chew on a michelin ZX.

 

[Ziggie]

The conversation has fired off a conversation I had some time ago.
Someone stated that it is difficult to get a qualified person to sign of the work. I can understand that they would prefer to do the work to earn the money.
As this is a “legal “ requirement for some work , the need for a must do on request and fixed pricing policy should be required by law.
An example of this is London taxi drivers who are not allowed to refuse a journey within central London and the meter is legally controlled and standardised.

 

[Ziggie]

haggis???? i'd rather chew on a michelin ZX.

It’s in the post if you record the video

 

[pc1966]

Even if you stick to doing simpler DIY electrics it is a very good idea to have a proper voltage tester. I always advise getting the simple sort that don't need a battery - they do the key job and if you come vback t it after a couple of years it is not corroded inside because you forgot to remove the battery...

Something like this, for example:
https://www.NoLinkingToThis/p/lap-ms8922b-2-pole-voltage-tester-with-rcd/669hy
https://www.cef.co.uk/catalogue/products/4527406-voltage-tester

As mentioned above, the process of "proving dead" is drilled in to trainees to make sure that it is not a medic proving them dead later on! Basically you check the tester, check all the permutations of cables that could be live (always connecting first to the most likely to be deal line, which initially would be the earth/CPC), and finally check the tester once more. Also you need to take steps to ensure it won't be accidentally switched on either!

A proving unit is handy for this as it is safe, available even when you think power is off, and usually the step up in voltage so you also see if the tester's range-indication is reasonable. For example:
https://www.cef.co.uk/catalogue/products/4457482-proving-unit

Getting a MFT is quite an investment, as said above it is hard to justify for sorting out a handful of sockets compared to what a professional electrician would charge simply to do the job.

You might find the high loop impedance is down to a handful of poor connections at the backs of sockets and simple to fix without a rewire, or you might be unlucky and find the poor connections are in hidden junction boxes.

 

[richy3333]

Fill it with quick dry cement , wrap it in some old carpet and bury in the ground...and NEVER speak about this ever again....

I don't think it's notifiable in Scotland, because I'd be replacing an existing circuit. [1]

However, I take your point it's a huge job, which is presumably why it's notifiable in England, and maybe in other parts of the UK and the world.

Maybe as you suggest, I should get a sparky involved. At the very least for certification, but realistically sounds like you're saying for the whole job.

You may need a building warrant but there isn’t enough info to comment.

No registered spark in Scotland will let you do the work and then sign it off. Protected title is going through government for a reason

 

[inquisitive]

I admire your interest and enthusiasm. I would suggest maybe reading a decent book on inspection and test, and maybe also Guidance Note 3 from the IET.

You need to be sure of your abilities and understanding before shelling out several hundred pounds on a tester that you may not end up being able to use properly.

Thanks, that's some concrete reading, for me to have a start with—which I would have to master.

You make a really sensible point about not spending large amounts of money on equipment, unless and until I do gain that understanding.

a proving unit used used to ascertain the performance of a safe isolation tool, which is basiaclly a 2 prong voltage tester.
View attachment 61832
this is totally different from a multifunction tester which,as it's name means, can perform several essential testes.
View attachment 61833

Good point. Have just re-read the OP's initial post and there does seem some confusion.

Yes, so leaving aside the proving unit, we are at the heart of my confusion.

As far as I can tell from the data sheet, that Megger MFT1721 multifunction tester, it has a mode for testing continuity. This mode displays the value of the live voltage if there is one. So why do other people who buy a multifunction tester also seem to buy a separate two prong tester, like the pictured Kewtech?

Possibly I completely misunderstand the functions of the multifunction tester. Or maybe the multifunction tester has the functionality, but people prefer having a standalong two prong voltage tester. If so, why is that? Maybe because it's smaller and lighter? Or maybe because the interface is simpler in a standalone two prong voltage tester - simple leds, and no dial that you have to set to the correct mode?