Is it acceptable to enter low IR on MWC

[FreeLec]

When doing minor works on a circuit, which may take a very short time to complete and it requires a MWC the IR test between L-N and E may be zero due to other electronic items.
You can end up spending 10 times longer looking for and disconnecting them just to get a good IR reading.

The company I work for has a policy of entering the low reading with an explanation of why and then arranging extra time at another time and charging to diagnose and rectify, even if it just means tracing electronic items, disconnecting and re-testing.

This is acceptable to the establishments they are working for.

However, it does not seem correct to enter what is effectively a fault on a certificate that is supposed to show the circuit as tested and okay, just as with an EIC. It's not a EICR so I would have thought this wrong.

However, what other way of doing it is there short of saying to the customer that before any work is done the circuit has to be tested as to fitness and any faults rectified but it's done the other way round with this lot ending up with a fault on the MWC. Only when the fault is cleared (or found that it is just electronic items) is the MWC changed.
The one with the fault is still given to the client until the updated one is done.

There are times, though, when no one has gone back to re-test as the client has given no further instruction, so the client has ended up with a MWC with an IR fault.

Any thoughts?

 

[Midwest]

Midwest

I only mentioned RCBOs as an example of a device that causes a problem on IR to earth. (However, I have seen sparks test with both L and N still in terminals and then fail the circuit).
I test from the DB with both L and N disconnected from the MCB/RCBO/Neutral bar.

The minor works I have explained just above. (This problem I am having is only with this particular job. On other jobs I am doing one thing at a time and can properly test the circuit, but on this it's a nightmare. Working where there are schoolkids you have to take so many precautions and this adds more time. Then there are access problems. It once took me all day to do a 2 hour job there because I had to have access to 3 rooms and 2 corridors. When I could get into one I then couldn't get into the other. I needed to go from one to the other and back. Worked on occupied offices before but it's the first time I've had to work like this.)

I only do small domestic work, so can't comment on what you and Lucien were chatting about.

As you know, you can't do an IR test with rcbo still connected, as it will effect the result, unless you make allowances for the rcbo resistances.


Tin hat on, some might say, that should you be carrying out all the tests prescribed by BS7671, when replacing luminaires for example, hence my question of type of work being done. I also suppose it will depend on what said in the spec for the job you are doing here, as its in a school. Council might specify exactly what it wants done in terms of testing, which your employer has quoted for. Can't see any point doing IR tests, if the circuit in question has not be isolated from accessories that will effect the results of the test.

Have you been given guidance by your employer, and spoke to them of your concerns. If they are telling you to something in a particular way, you'll have to follow their instructions. If your uncomfortable with that, you'll need to find a new employer.

 

[FreeLec]

Aahh! This forum drives me mad. It logs you out while you are typing a reply.

Anyway

The guidance is test Zs to make sure there is and earth. Report IR result as is. This gets reported to the client. The client orders remedials that may involve finding and rectifying a fault or just disconnecting equipment to get an acceptable IR. That's it. Sometimes I hear nothing further and nothing further happens but that is the client and my employers responsibility, not mine.
Personally I think it's not right to give a completion certificate with faults.
I don't have a problem if they want to work that way. It's by pre-arrangement with the client due to the nature of the establishment.
I just posted this to see what others think.
By doing that it led on to what others and Lucian has said causing me to look further and deeper into the types of equipment.
Whenever there is low IR every electrician I have worked with has run around unplugging everything but according to Lucian this may be going over the top. So although not part of the original post about MWC it is still sort of related and very relevant.

 

[HappyHippyDad]

Thanks Lucian.


Here is a comment from someone who replied to the same issue on another forum.
"Nearly every circuit I test has low IR, that is until I unplug the surge protection extension. Another useless invention causing problems".

.

I have just had the same problem testing L/N - E on an IR test, I cant remember the reading but I know it was quite abit <1MΩ (I think around 0.2 or even 0.02MΩ) but this was tested at 500V, tested at 250V it was approx 200MΩ? My mind is a little hazy so results may not be accurate but I'm sure it was something along these lines. This was on a surge protected extension lead.

 

[FreeLec]

That makes complete sense as to the way the surge protector works.

Now that, without a doubt, is due to the component dealing with the surge. At 250V it would not conduct but at 500V it would.
I have found that some surge protectors only have components between L and N so 500V will have no problem with them.

The issue is more to do with other equipment.

 

[Octopus]

DAVESPARKS

I have just noticed your stupid and ignorant comment.

If I was not competent I would not know that something was not right.
I already said that I did not feel happy about the way I am being asked to work.
I am being told to work that way.
I am installing about 50 bulkhead emergency lights next to existing failed integrated fittings.
It is in a school where I have to drag tools, materials, rubble bags, vacuum cleaner, etc between 14 different buildings and back to the same ones as different rooms are being used at different times.
I have to get each one done as quickly as possible within the allocated time.
I have not been given time to disconnect any item of equipment not allowing an acceptable IR result.
I've been told to put a failed IR on the MWC with a comment about why the result is likely + further investigation required.

Maybe you should think it bit more and read the post properly before you make nasty comments.

I also see you thanked Murdoch for making the sarcastic comment of money making con.
If both you and he read the post properly you would both have seen that I said this is pre-arranged with the client. How can it be a money making con if the client has agreed that if something can't be done within an allocated time then a return visit has to be arranged and the initial charge is only for the first allocated time period. They have agreed this.

But it is a money making con..... your company provide a quote to do a job, your company provide an unsatisfactory IR reading on a MWC, so you go back and charge more...... rather than quote to do it properly the first time round...

 

[ipf]

But it is a money making con..... your company provide a quote to do a job, your company provide an unsatisfactory IR reading on a MWC, so you go back and charge more...... rather than quote to do it properly the first time round...

First con I've ever come across where it's agreed with the client to con him..:wink5:

 

[FreeLec]

Murdoch

I can't see what you don't understand about this.

The client is quoted for the job with the understanding that it will take a set amount of time to complete.
The quote takes no account of any other remiedials that may need to be done.
If the remedials take a short time they are done then and there with no extra charge.
If the remedials will involve more than has been quoted for they are informed of such.
They then order those remedials to be done fully expecting to be charged for the extra time.
This has already be pre-arranged with these particular clients. I'm not saying this is the case will all clients but because of the nature of the establishment and the disruption it causes this is what they have agreed and arranged.

Now, where is the con in that?

 

[Plonker 3]

There should be no remedials, the job should be surveyed and priced accordingly before hand. Filling out a EIC with unacceptable results isnt something that should be done on a job. Any discrepancies should should be sorted before any works are carried out.

Besides you are potentially leaving a install that doesnt comply with the BYB. Just because the customer agrees it is acceptable doesnt men that it is OK does it? What if you Zs values were to high but the customer said thats fine sort it out later would you think thats acceptable?

 

[FreeLec]

Dillib

I absolutely agree with what you are saying.
That's why I am trying to sort out the issue with what sort of items cause problems with IR testing rather than end up going to everything and disconnecting etc. This takes up so much time causing comments like "why is it taking so long" and "why have you only done so few" etc.
I presume you have read the whole post and seen the conversation with Lucian.
If I can get an IR result of at least 1 Meg then officially I can continue. However, this is still far too low and leaves no room for further deterioration of IR and still needs to be investigated. I don't know why I have been getting results below 1 Meg. All I know is to get an acceptable result I have to disconnect everything so something isn't right, but not with the wiring. That's why I'm going to be investigating what's going on but it will take a while. Hopefully, I will be able to do that withing this week.

As I've said I don't like working like this but nothing is surveyed beforehand. It is done there and then at the time when the job is going to be done.

I don't install if there is a problem.

For example, on Friday, when identifying the circuit that an integrated emergnecy light is on, I found that the switch line feed was from 3L3 and the permanent feed was from 6L3.
I reported it, then moved on to the next one.

I have had comments from other forums and from sparks I work with that you only need to test the part of the circuit that you are extending but I have already said that I don't agree with this and it should be the whole circuit. This shows the pressure put on sparks to get the job done.

However, the fact that I have posted this in the first place surely shows that I am not happy with the current situation and I am trying to do something about it.

 

[TJ Anderson]

Hi Freelec. Very interesting points and I understand where you are coming from regarding time restraints in real world sparking. A sensible approach would be to write in the Limitations Box "IR of new wiring only". Before someone shoots me down, don't bother. You are the qualified spark, you can put whatever limitations you want on your cert as long as client agrees (I do).

 

[FreeLec]

I'm not sure you can just agree with the client what is acceptable in the cert. After all, it's not a condition report. It is supposed to be saying that everything that has been involved in the minor works is inspected, tested and safe. Therefore the circuit that the new works is involved in must be safe to add to or alter.
So many different views on this.

But at least you can see where I'm coming from.

 

[TJ Anderson]

It is not ideal, but what else can you do if you are not testing prior to extending circuit. As you know, you should not if you cannot confirm circuit is compliant to extend from. If do anything else but limitation of IR you would be leaving yourself wide open. A limitation would not render cert non compliant. An IR <1 meg would.

 

[FreeLec]

When I did put LIM on the cert my boss said to still test and put the result even if it was 0.00 Meg.

The only problem is that you can't put LIM somewhere where there is no genuine reason for limitation.
I'm sure the IEE or NICEIC would not accept LIM because of time constraints on the job.
A genuine reason would be LIM between L and N and that's what's put down. Your not expected to disconnect everything.
Now, I've just realised what I've just typed. If that's the case between L and N then why should it not be the same with L-N and E. There's a contradiction there.

I'm going to have to have a think about that. LIM is allowed for L to N on existing circuits as you're not expected to remove every item of equipment. Why should it not be the same for IR test to E?
Of course. Because there could be a fault to earth and by not testing and removing any item of equipment causing it you won't know that there is an actual fault on the circuit itself. Mind you, the same could still be said of a L to N fault. It seems acceptable to have a possible L to N fault but not a L or N to E fault.

Am I missing something or does this seem contradictory.

Or is it because it's 12:00 at night and I'm about to fall asleep in front of the PC.
Time for bed. I have to get up at 04:30

 

[TJ Anderson]

There should be no remedials, the job should be surveyed and priced accordingly before hand. Filling out a EIC with unacceptable results isnt something that should be done on a job. Any discrepancies should should be sorted before any works are carried out.

That is not in anyway helpful or telling the OP anything he does not know. He is well aware of this, hence his post.

 

[Richard Burns]

Just remember that the result you are putting down is not (in most cases) a non compliance with BS7671 it is just a result that has been obtained inaccurately.
If disconnecting connected loads gives the circuit an IR value that is within the limits then the circuit was compliant.
The problem you have is that you are unable to state whether or not the circuit is compliant at the time of install because of the method of testing.

You state that you feel you should test the entire circuit and this is a good approach even if it is not required as your work is the changing of a fitting and (presumably) you are doing this part in compliance with BS7671.

A minor works certificate states that the installation work does not impair the safety of the installation, if it is done correctly then your work will not impair the safety of the installation.
The installation may already be unsafe, but outside of your control.

The certificate should not be issued with false results but should be issued with the proviso that the measured IR on the existing circuit was outside of the limits of BS7671 and the situation should be investigated, then you have issued a valid certificate but raised the issue of the possible non compliance with the existing installation.