Minor Works Certificate for DIY’ers.

[ericmark]

This follows on from the post Lack of Minor Works Certificate with DIY’ers? but from the other angle. Can we produce a lets call it a check list which if followed will result in DIY’ers doing most of the tests and inspections done by electricians with full test sets?

I am looking at the old red book BS7671:2008 Part 1 simple although of course departures may be hard for DIY guy to know about so miss out number 4.

Part 2 no reason to have anything more than TN or TT as the EZ150 can’t show if 0.35 or 0.8 ohm incomer.

Method of fault protection can be left out as we all enter EEBADS or ADS

So just protective device for modified circuit. Type and Rating.

So in essence just Part 3 essential tests.

Insulation resistance is a problem as one needs at least 250 volt and normally 500 volt to test with. However using the highest ohm range of a multi-meter is better than nothing.

The earth fault loop impedance would need to be better 1.7Ω (TN) or 200Ω (TT) as that is the limit of EZ150 tester.

Polarity is shown by plug in tester.

RCD only real test is to push button and see if it trips.

However the minor works certificate seems to have missed out many tests. I would always test all three wires in a ring final to show continuity. I would also test to find out is it a radial, ring or spur and with the latter is there a fuse. I would also test wires to see what size. 1/0.044, 1/0.064, 3/0.029, 3/0.036, 7/0.029, 7/0.036, 7/0.044 or with metric 1.5, 2.5, 4, or 6 mm².

As to if any DIY person can work out sizes I don’t know. But unless they can, then hard to identify faults.

So can we produce a check list instead of a MWC so the DIY person can in the main ensure the work they do is reasonably safe?

 

[ban-all-sheds]

However using the highest ohm range of a multi-meter is better than nothing.

Hmmmm.

 

[JohnW2]

However using the highest ohm range of a multi-meter is better than nothing.

Hmmmm.

Hmmmm indeed - it's probably actually 'worse than nothing', since it could give false confidence. If a multimeter using a 1.5V, 3V or 9V battery did show up an IR problem, then that would be fine. However, if it failed to show any problem, it would be wrong and potentially dangerous to draw any conclusions from that.

Having said that, in terms of eric's quest to define a minimum set of tests that would be 'reasonable' (although clearly not ideal) for a DIYer to use to indicate that work they had done was probably reasonably safe, I would suggest that IR tests are probably not all that important - certainly far less important than some other tests.

Kind Regards, John

 

[JohnW2]

The earth fault loop impedance would need to be better 1.7Ω (TN) or 200Ω (TT) as that is the limit of EZ150 tester.

Do you know how the EZ150 (or similar) behaves? ... if the EFLI is, say, 1.69Ω, does that result in the "1.7Ω" or the "0Ω" light coming on? ... and what about 1.71Ω - does that display as "1.7Ω" or "5Ω"? .... or does it perhaps 'round' - i.e. anything between 0.85Ω and 3.35Ω results in the "1.7Ω" light coming on?

Kind Regards, John

 

[JohnW2]

Duplicate post! ... so that still happens

 

[ericmark]

The video shows it flashing the 0 ~ 1.7Ω (green) lamp and the three lights at the bottom and on the three lamps flash green as if it is doing a sequence of tests then showing results. It says in the specs:-
Mains Supply
230V (50Hz)
Earth Loop Impedance Span
0 - 1.7Ω, 1.7 - 5Ω, 5 to 10Ω, 10 to 100Ω, 100 to 200Ω, 200 to 500Ω
Earth Loop Impedance
+/- 10%, +0.3Ω
Voltage Low Indication
<195V
Voltage High Indication
>270V
Open Earth Indication
>500Ω
Power Consumption
<1.6W
Overvoltage
CAT II, 300V
Housing
Flame retardant ABS
Dimensions
65 x 65 x 50mm
Weight
64g approx
To my mind at under £50 it seems to have a reasonable spec. At 1.6W that's 6mA as to if 6 mA is really enough to test earth loop impedance is the same as asking is 9 volt enough to test insulation clearly not ideal.

I will admit I tested a compressor motor with my multi-meter showing 2MΩ but testing with my insulation tester it was showing short circuit so yes the multi-meter can fail to show some faults. However my son was telling me how he visited a house after a CU replacement had blown the main DNO fuse to find both line and neutral in the same henley block and clearly it would show that type of fault.

The

other testers seem only to have three lights "Good", "Check" and "Urgent Check" and I can't find what the limits are. Jumping to three times the price the Socket&See PDL234Plus still only gives lights to show better than 1, 2, 20, 200 or worse than 200Ω. It shows voltage less than 207 OK or more than 253 but in real terms not much better than the Martindale at a 1/3 of the price.

Even the Minor works certificate does not ask one to test for ring continuity and really to my mind does not prompt the tester to do what I would consider essential tests. I would never dream of extending a final circuit without finding out where it was supplied from. For all I know it could be the lighting circuit.

The point is we all tell the DIY guy he should test but even if he had a full test set the tests required for a minor works are really not good enough. The Wiki how to extend a ring final circuit shows just 3 stages. To my mind first stage should be to test it is a ring and by extending the volt drop will not be exceeded, that is not tested, and last stage should be to plug in a tester again nothing.

So we in the forum are showing how simple it is to extend a ring. Where in real terms no way as easy as shown. I have argued many times about where to test if ring is intact. I have seen where a wire has popped out as the socket is replaced so personally would do final ring test using the earth loop impedance tester both line ~ neutral and line ~ earth and would also have done same test before starting. Although in theroy you could still have a open ring in practice any open ring would show a high loop impedance.

But the DIY guy has no loop impedance reading so any error like a wire popped out he would be unaware of. He could of course test in the consumer unit. But I would not be happy telling an apprentice to go into a consumer unit without being there to watch never mind a DIY guy.

I have gone into the Wiki many times to find if there is an instruction set and I am sure there were more. I would have expected the Wiki how to extend a ring final circuit would have had a link to Inspection and Testing but it does not exist. However on clicking on Ring Final Circuit Testing it states:-
This Article Does Not Exist Yet
You are unable to add articles to the Wiki. Sorry!

So back to nitty gritty what is the point in talking about testing and inspection when we are offering so little advice on how to do it?

 

[JohnW2]

Earth Loop Impedance Span; 0 - 1.7Ω, 1.7 - 5Ω, 5 to 10Ω, 10 to 100Ω, 100 to 200Ω, 200 to 500Ω

OK, thanks. So, in answer to my question, I presume that 1.69Ω would show as "0-1.7Ω", and 1.71Ω would show as "1.7-5Ω".

Kind Regards, John

 

[ericmark]

It would seem that way but never used one. I like I am sure yourself have a full test set so would not consider buying one.

 

[ban-all-sheds]

If you are a heavy sleeper, then a Socket+See plus a plug-in timer makes an excellent alarm clock if you use a socket you can't reach from the bed.

 

[ericmark]

I am guessing it has a buzzer of some type.

However I would still like to see some instruction set for a DIY man to use with minimal tools to ensure the work he does is reasonably safe.

Some things I suppose we can forget for example volt drop. And some tests we are taught to do I question anyway like looking for figure of 8 with ring. But although minor works certificate is completed from tests done after installation is complete in real terms testing starts before we do the work.

The mind map method is likely the best and a expansion for each section. So for a simple job of say fitting an extra socket what are the recommended order of events? I will give an example so it can be expanded.
1) Plug in some item to show if socket is live buzzing socket tester is ideal.
2) Switch off breakers one at a time until correct one found including RCD's noting which RCD and which breaker and what size they are.
At this point we start to split as under 20A will have different instruction to over 20A and no RCD will have different instruction to RCD (30mA) fitted.
So with RCD fitted and under 20A MCB then the addition could go ahead assuming the plug in tester showed all OK before starting.
On completion then simply using the plug in tester would likely be good enough.

If of course over 20A then we start to look at inspecting cables more carefully to see if 4mm or 2.5mm and if the latter we need to do a lot more testing to see if a ring still exists or a FCU fitted etc before continuing.

We do these tests without really thinking about it only when we try and write it out do we realise how much we test. I remember at school having to write out instructions to a robot to make tea and I don't think any one in the class did it with out missing something. Forget to turn tap off for example.

So between us can we write a testing instruction set for something like fitting an extra socket?

 

[JohnW2]

It would seem that way but never used one. I like I am sure yourself have a full test set so would not consider buying one.

It might be worth considering - after all, an MFT would not fit in one's pocket! One issue, of course, is that without adaptation (or adaptors!) these plug-in testers cannot be used directly for testing anything other than sockets circuits - whereas I would guess that the most common DIY electrical work (certainly judging by questions here!) relates to lighting circuits.

Kind Regards, John

 

[JohnW2]

Some things I suppose we can forget for example volt drop. And some tests we are taught to do I question anyway like looking for figure of 8 with ring.

As often discussed, I personally think that, at least in a domestic environment, VD is simply not an issue, certainly not a safety issue.

Your interest appears to be in advising DIYers what tests they should do to give a reasonable indication that the work they have done has probably not made the installation any less safe than it was. If that is literally true then there is presumably scope for discussing whether they need to undertake tests (as an electrician would do) to identify pre-existing and persisting problems (not of their doing) - which would have been present and persisting even had no DIY work been done.

Kind Regards, John

 

[ban-all-sheds]

132.16

 

[JohnW2]

132.16

Yes, we know that, but what I wrote to eric was in relation to:

Your interest appears to be in advising DIYers what tests they should do to give a reasonable indication that the work they have done has probably not made the installation any less safe than it was.

In other words, I (and presumably eric) was not talking about full compliance with BS7671, but a desire to assist DIYers in not making things any less safe than they would have been had they not done any DIY work.

I realise that you would not be happy with anything less that "full compliance with BS7671" but, in the real world in which 'not fully BS7671-compliant' DIY work is going to continue to be done, despite your views, to attempt to assist a DIYer not to make things any less safe than they were is, in most people's minds (even if not yours) a desirable goal.

Kind Regards, John

 

[ban-all-sheds]

It is a desirable goal.

What is undesirable is the route to it being "let's encourage the OP to do things he doesn't understand".