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.