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?

 

[Octopus]

Define low reading.......

 

[FreeLec]

Anything under 1 meg but usually 0.01 or 0.00 as even one piece of equipment can cause that

 

[Andy78]

Are the correct procedures for testing of IR with electronic equipment connected followed ?

 

[FreeLec]

L-N connected together. N removed from N bar. 250V, not 500V.

 

[Lucien Nunes]

L-N connected together. N removed from N bar. 250V, not 500V.

and

0.01 or 0.00 as even one piece of equipment can cause that

...do not tally. I don't know of any normal piece of equipment that has just tens of kΩ or lower IR to earth. What sort of equipment are we talking about here? The only time I see this kind of result on a 250V test is where US-spec 120V equipment containing surge arrestors designed for 120V supplies is supplied via an auto-transformer from 230V. Because the transformer passes the DC test voltage direct to the load, the VDRs can start to conduct and throw the reading off.

What specifics can you think of on these sites that would be causing this?

 

[FreeLec]

Have to go out. I will respond in about an hour or two.

 

[Octopus]

Do your employers charge for the 2nd visit?

 

[FreeLec]

Yes.
They charge for the time taken to investigate whatever the problem may be. If it's a matter or taking something out of circuit to re-test or a fault that needs rectifying it is chargeable. If the fault is major then that may even involve arranging a further visit to allow time to rectify. All chargeable.
This is something that is arranged with the clients as they are educational establishments where disruption can be an issue.

 

[Pete999]

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?

Link L&N and test IR to Earth and note on the cert, sorry forgot set test voltages to 250v

 

[FreeLec]

Pete999

Look at comments 4 and 5 above.

 

[Pete999]

Pete999

Look at comments 4 and 5 above.

Point taken must read the whole thread

 

[FreeLec]

LUCIEN NUNES

Sorry! Completely forgot to look at your comment when I got back as someone else left one and I got distracted by that.

I don't understand why you would think that the two comments would not tally. Some electronic equipment have functional earths so there will be a current flow, all be it very small, between L-N and earth. One well known example right at the start of the circuit is an RCBO with an earth tail. Even the simplest circuit with nothing connected, e.g: radial to one socket outlet with nothing plugged in, will show 0.01 Mohm between L-N and E unless you either disconnect the earth tail from the earth bar or you remove both L and N from the RCBO.

 

[davesparks]

Why is this only becoming apparent at the testing stage?
Any faults in the existing should be identified before you start work, not after.

 

[Octopus]

Hum.... so you quote for a job, don't isolate everything, issue a cert stating extra investigation is required, then go back for a 2nd chargeable visit.

Sounds like a dodgy money making exercise to me.

 

[FreeLec]

davesparks
Agreed. However, in reality I would never get anything done.
A spark I work with said he thinks it only refers to anything that has been added.
I agree with you, if a circuit has a fault by rights it should not have any modifications until the fault is rectified. I test for Zs as this is quick. If there is a problem I don't start work on it, report it, move on to the next thing.
However, IR can involve a lot longer process and I would never get anything done if I ended up fully testing the circuit with disconnecting every piece of electronic item that has functional earths etc, just to make sure the circuit IR is OK before I start anything.

Also, you may be modifying in a way that you are adding nothing but removing and re-routing.
Same issue.

Murdoch
NO! That's not what I said.
Re read the response I gave to you (no 9)
Read the last sentence.


Remember, I work for a company, not myself. I already said that I'm not comfortable with this and this is not the only work being done. Other work does not have these issues.

 

[FreeLec]

Something's wrong with this. I keep loosing the message I post.

 

[FreeLec]

Something's wrong with this. I keep loosing the message I post.

 

[Lucien Nunes]

I don't understand why you would think that the two comments would not tally

Because I design, build and test a wide variety of electronic equipment and find that very few devices in general usage today deliberately have such a low resistance L+N->E. Functional earthing yes, capacitive leakage current yes, all understood, but 10kΩ DC resistance? Typically the lowest I encounter for an SMPSU is around 7MΩ. We know about RCBOs but I didn't count them as connected equipment and you are in a position to disconnect them.

OK, I understand that you might be coming across a lot of faulty circuits and your original question still applies to those, but I would be keen to know what current-using devices, other than faulty ones, are complicating your testing to the extent that it requires callbacks.

 

[FreeLec]

Regarding circuits that have faults, until I am 100% certain that all equipment is disconnected I cannot say for certain that there is a fault in the circuit.
Many is the time that I have tested a ring or radial and have got low IR until I find something hidden out of the way or not expected to be on the circuit being tested. Unplug it and finally the reading will go up to >999. This can also include active RCD sockets.
Lighting can have something somewhere in the dropped ceiling that can take an age to find. Controllers for DALI, DSI, 1 to 10V etc.
As to exactly what the equipment is; I don't keep a note so I cannot tell you what exactly they are.
My intention now is to directly test various equipment disconnected from the supply, between L-N and E on the supply lead and see what type of equipment cause the problem.
When you are testing you don't take notice of exactly what the item is. You see something and disconnect it or unplug it.
I don't know how long this will take until I get a decent list of items but when I do I'll post it under an obvious title for you and others to see.
However, I don't understand why you think that there should not be an issue. You accept that RCBOs have that issue so why not other types of equipment?

Here are links to another post I put up. Look at the response from others who replied with an explanation showing that there is an issue. I was trying to understand what it is that causes this. I have a basic understanding of electronics but when it gets to deep I get lost in the explanation.

IET Forums - Electronic Equipment and IR testing

Electronic Equipment and IR testing. What component causes low reading to earth? | Screwfix Community Forum

The callbacks are agreed with the client in the sense that we have been told not to spend time doing something that has not been factored into the original quote. Account has not been taken of any problems. No one is being conned. The client wants it this way as there are sometimes limited time slots to get the work done and has to be tightly scheduled. Drives me mad. It's frustrating to work that way.

 

[Lucien Nunes]

Look at the response from others who replied with an explanation showing that there is an issue.

Some relevant comments there but also a lot of errors. I'm not picking this apart to be awkward, I was genuinely surprised by your original comment and it set me thinking about the possibilities. But I could not find any valid ones, and neither did these other threads. Let's look at the key points raised:

Capacitor charging current. Yes, true, but only for a few seconds unless your IR tester is faulty. Capacitors wired L+N->E are never very large in value, to limit AC leakage and because of the job they do (RF suppression for EMC). I often test equipment with quite high capacitance to earth and it only takes seconds for the reading to settle with a normal tester.

Capacitor leakage. I don't know how many capacitors these guys test but at a guess I've tested many tens of thousands in my life, of all kinds, sizes and ages. Any of the types of capacitor that are used L+N->E (normally class Y construction) that test under tens or hundreds of megohms, are faulty. But I've never found any that are not also physically destroyed, because they are designed specifically to have high integrity against developing leakage. Other kinds of capacitors do develop significant leakage, e.g. wax-impregnated papers in vintage radios over 60 years of age; if the radio works today most likely they have been changed already and they weren't usually used L+N->E anyway. 'Aluminium foil jobby' is not a kind of capacitor I recognise but if it means aluminium electrolytic, they do have high leakage but are never used L+N->E for a bunch of reasons.

Bleeder resistors. Exist, often across X-caps (L-N) which are typically much larger, but not commonly class Y capacitors. The numerical example given contains errors: The initial voltage of interest is Vpk not Vrms, 325V for 230V AC, 50/325=15% so 2RC<5s and R<=250MΩ. A resistor that high is expensive and potentially unstable, so practical designs use lower resistors on the rare occasion they are fitted at all. I mentioned 7MΩ - that's a favourite of Sony that one still sees occasionally, more often its >99MΩ. If we take your '0.01' reading as 20kΩ, as it could well be, it would still need 7000/20 = 350 pieces of Sony equipment of these specific models on the circuit to cause it.

Inductors and zener diodes. Since when were inductors ever connected L+N->E in appliances? Nonsense. Zener diodes / VDRs can be present as surge protection and I did mention these as a typical special case where rated for 120V mains only. But testing at 250V should not cause 230V-rated surge arrestors to conduct significantly, or else they would try to clamp the 325Vpk of normal mains. Therefore they will not badly affect the reading at 250V (They can ruin it at 500V though).

Filters. Well these are where the said class Y caps are usually located, usually with some inductors, often built into the IEC inlet etc as a power entry module. They are no more and no less than the components inside them. All reputable filter makers will permit insulation tests, many filters are tested to >2kV in the factory (although repeated, prolonged tests at this voltage will cause damage). Even the cheap nasty unknown brand ones survive 250V just fine, or they wouldn't last on the mains at all.

There are other errors in posts in those threads (e.g. confusing different types of capacitors and their functions) but they are not so relevant to my point. Which is, that ordinary non-faulty equipment that might be connected to ordinary circuits (I am not talking about multi-megawatt induction furnaces or electrode boilers!) will not under normal conditions present a DC resistance of tens of kilohms to a 250V IR test L+N->E. Unless you can find real-world examples.

E2A OK, OK, I've thought of one - old sheathed heating elements that have not been used recently. Leave a Baby Belling from the 80's plugged in but switched off only in the line, and you'll get a low reading due to moisture absorption in the mineral insulant. They used to fail PAT IR tests regularly, although not often at 10k . Run them for a few hours, at first the value falls as the moisture condenses at the cold tails, and then they will usually come up fine once it's evaporated again. But they are pretty easy to spot and unplug.

 

[FreeLec]

Thanks Lucian.

I'm glad I started this thread.
I really appreciate the info you've posted. So the info on the posts I directed to you is misleading. I would never have known.
I understand electronics to a point but some things go to deep to get a grasp of without an underlying understanding.

So from what you are saying, no equipment connected to a circuit, be it power or lighting should pass enough current at 250V so as to get a low IR between L-N and E.

One problem though.

It does.

Many's the time I have had to go and search for an item plugged in that when I eventually find it, the difference is the change from 0.00 or 0.01 to >999 Mohm.
Now I accept that a faulty item can cause this but this happens far too often. All those items causing this can't all be faulty.

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".

There are some circuits that have N-E faults but that would not be the case if the reading changed when removing the item from the circuit. The fault would still be there.

Normally, under the pressure to get the job done quickly, I don't stop and think about what I've just taken out of circuit. Next time I will keep a record of what the item is and also do a test on it between L-N and E. That will identify what's going on.

You have really got me thinking now. Your information and what I experience on site are conflicting. Normally, my reaction would have been to say you must be wrong but you seem to know what you are talking about. You can usually tell the difference when someone is guessing or knows what they're talking about.

Like I say, I will post the results of what I find but this may take some time. Unfortunately, I don't have the time to check that out at the moment as I have to record what I find and move on to the next one.
Even when we are doing EICR it's the same thing. If you can't find what the problem is in 5 mins record the result and move on. At the moment I am starting at 06:00 to get the quite time in the morning to get as much done as possible. Normally I start at 08:00 so I still get in at 07:00 to avoid the traffic. I can get in at 06:00 and test a few circuits for a few hours each morning for a while and see what it is exactly that is causing the problem rather than just unplug everything.

Until now I was always sure that it is the circuitry in electronic equipment that is causing the problem but now you have got me wondering.

The thing about the MI insulated heating element. I had a coffee maker that I didn't use for a year. When I went to use it it started smoking from the element then went pop.
I called the manufacturer who explained that if it's not used for a while moisture can get into the end of the element. I was very surprised by this. That would mean from the time of manufacture all items containing MI elements must be used soon after and never put into storage for too long.
That seems a bit strange to me. Personally, I think he was fobbing me off and the item was faulty. All MI elements are totally sealed from what I can see, so moisture should not be able to get in unless there is a fault.

 

[Lucien Nunes]

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'm not ruling out that there might be some oddball surge protectors that come in on the low side at 250V. I would be interested to hear about them if you find them. My experience of commercially available units with type 3 MOVs is that they normally read >10MΩ and oftern >99MΩ at 250V between any pair of conductors. The clamping voltage is often around 400V so the results on a 500V test are unpredictable, often between 0.1 and 1 MΩ though. I have probably PATed 100 different types and brands and they normally pass fine at 250V, so I am wondering whether the poster of that comment is testing at the higher voltage? The most common reason we find for failure is that they rattle when shaken, due to physically disintegrating inside.

You have a point about active RCD sockets; USB-equipped sockets are another installed electronic nuisance, often substandard and non-compliant, impossible to isolate for general testing. My work doesn't normally involve general purpose socket-outlet circuits so thankfully rarely encounter them.

I agree about your coffee maker - I think he found a peg to hang his faulty appliance on. Sheathed elements used to be un-sealed and moisture did get in even when new, it was a known and significant problem for testing but it did not normally cause the elements to go bang. You could run them to dry out, if they were really low they might trip an RCD but this didn't indicate they were irredeemable. Back when PAT was a new thing and we were still trying to devise test regimes, I had dialogue with element makers trying to pitch the test criteria so that testers could pass damp-but-sound elements that otherwise would be considered failures. We got to know their foibles in more detail than we cared to!

Thanks again for expanding on this in detail.

 

[davesparks]

davesparks
Agreed. However, in reality I would never get anything done.
[

Then perhaps you should stand aside and let someone who is competent to do the job take your place.

 

[PEG]

Bit harsh Dave,Landrover swivel hubs leaking again? :smile5:

 

[davesparks]

Bit harsh Dave,Landrover swivel hubs leaking again? :smile5:

Nope, just the wonderful nhs has bolloxed up my prescription again

 

[Midwest]

OP, ain't making no comment on what you and Lucien have been talking about, but as regards RCBO's, can't see that they should be an issue. If the circuit your testing has been disconnected, they won't factor into the test?

Which end of the circuit are you conducting your tests from?

What sort of minor works are you doing for your employer?

 

[bigspark17]

Then perhaps you should stand aside and let someone who is competent to do the job take your place.

NOT NICE TO SEE COMMENTS LIKE THIS!!! As it says by moderators if your reply cant help the OP then dont reply, that is just rude to a person who obvious is concerned and reaching out for help over something he has concern for!

 

[FreeLec]

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.

 

[FreeLec]

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'm going to have the same problem tomorrow where I am working in one room but the lighting circuit feeds another room that's being used. Not looking forward to it. I just hope it's nice an bright with the sun shining so they won't need lighting on.

 

[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.

 

[davesparks]

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

Really? It's going on every day in commercial work.
People in offices taking backhanders to sign off on unnecessary extra works.
In this case it's a school which may very well mean it is ultimately us taxpayers who are financing this little racket.

 

[davesparks]

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.

So quit and go get a job elsewhere, if you are indeed a competent electrician then you'll have no trouble getting another job.
'I was told to do it that way' will not stand up as a defence in law, as a competent person you are responsible for what you do.

So get something with wheels on it to move your gear around the different rooms, it's hardly rocket science!

If you have allotted time for a job why do you have to get it done as quickly as possible? The whole point of having an allotted unit of time is that you have that whole unit of time available.

On that subject, how much time have you been allotted to complete each light?

 

[davesparks]

NOT NICE TO SEE COMMENTS LIKE THIS!!! As it says by moderators if your reply cant help the OP then dont reply, that is just rude to a person who obvious is concerned and reaching out for help over something he has concern for!

I agree it isn't nice to see comments like that, but what would you call someone who comes onto the forum and tells us that they are carrying out testing incorrectly? Are they competent or incompetent?

 

[YoungBart]

I wouldn't feel comfortable putting either LIM or a low IR reading down on a test cert of any type. Especially If I can't verify the wiring, I appreciate to remove all emergency lights or other loads is a pain But if I got a low IR I'd be trying to get it to an acceptable result however long it takes. Afterall It could be a potentially dangerous fault. I wouldn't be happy if my name was on the cert if a potential fault was not found.

 

[Risteard]

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.

Other than during school holidays, most (although admittedly not all) of the work in schools that I have done has been nightshift to avoid these sorts of problems.