Insulation resistance test

tim west said:
Lectrician said:
tim west said:
Lectrician, i'm not questioning your abilities just trying to clarify the issue, take a look here:

http://www.rsc-northwest.ac.uk/curr...tion/myweb3/insulation_resistance.htm[/QUOTE]

Look at what exactly?

Have you ever tested before or are you simply talking the test?

Several chokes will inevitably give you a low reading to earth - I am not saying a fail type reading, but a low reading.

The above link I wasnt going to read an entire page telling me how to test to please you - What exactly ON THE PAGE.

Of course as an Electrician myself, talking not sure what you mean? This line doesn't make much sence either.

Depends on what your definition of "shocking readings" were, if not failure readings then what was the problem you were trying to get at?
If the "low reading" was within the stated limits and passed then no problem. I beleve my original wording was "surprising", but not too sure. If you can visually see wiring and then get low readings you could be fooled into thinking there is a problem unless you are aware that a quantity of chokes in parallel could give misleading values.
 
Sponsored Links
Lectrician said:
I wasnt going to read an entire page telling me how to test to please you - What exactly ON THE PAGE.
You don't need to read the whole page even though there isn't that much to read. It will pay you to read it anyway to get the whole thing into context, whether you read it or not won't pleasure me?? It's just how can you make an opinion on what I wrote previously unless you look? Just hope you are more bothered to read when it comes to the regs book!

Lectrician said:
Have you ever tested before or are you simply talking the test?
Talking the test, I don't understand what you are trying to get at here?? Yes as an electrician I have tested before, the question now is have you tested before Properly?

Lectrician said:
I beleve my original wording was "surprising", but not too sure.
This is what you wrote:

Lectrician said:
Thats what I would do - although you may get shocking readings due to the inductors - they are never great.


Lectrician said:
If you can visually see wiring and then get low readings you could be fooled into thinking there is a problem unless you are aware that a quantity of chokes in parallel could give misleading values
You mention "low readings" again but I explained earlier if your definition of "low" is within the stated pass level then it doesn't matter. Where do the chokes come into it? If you did what i said and remove the starter switches then unless the chokes are faulty with unacceptable insulation to earth, they should pass along with the rest of the circuit, if it doesn't pass the test then there is a problem. Why do I have to keep repeating this fact?
 
If you remove the starter, the choke is still connected to the live of the circuit. FACT.

By the very nature of construction, and by having several in a circuit, you will find a choke does not have infinate insulation resistance. The more fittings, the lower the reading is going to be.

I have never said it will below 0.5M, nor 2M, but could certainly still give you a reading where you think "ehh - these are new cables by the look of things".

Thanks for your concern, I do test regularly, and due to the size of my company have to endure a 2 day inspection with the NIC - 1 day concentrating purely on periodics. This year is scaled down to a single day, with the afternoon being periodics. I am happy to say there is no problem with my testing - perhaps this is why I was asked to teach at the college, and also why I get calls from other sparks who need tuition before their inspection - I get paid as spark to teach a spark. Still, makes money for my boss.

Perhaps you have never gone in and tested a factory with a huge long row of flourescents or lowbays of some description? If you had, you would be aware of what results you may find.

I dont want to argue, but I don't want someone questioning my ability either, especially when it seems to be them that is lacking in on site knowledge.

Oh, and yes, I do read the regs, when required. I am not one of those pricks who thinks they know the regs in side out - Even the best chefs still follow a recipe.
 
Sponsored Links
I did previously state that I wasn't questioning your ability but as this thread progressed I needed to question parts of what you had stated previously, please don't let this thread degenerate into getting personal.

Yes I know that the Live is still connected to the choke, what point are you trying to make?

If you are a teacher you should know better the points I raised, I told you I am a sparks, have been for more than thirty years so I have a "little" experience of going into factories,office blocks etc and testing.

You seem to have totally missed the point I was telling you, that electricity is not discriminate, that is why tests are carried out, and yes I have tested many flourescent circuits in my time and those that came back with failure results were due to failing components in equipment, which once replaced allowed a pass result on next testing it.

The attitude of not testing fully and avoiding a part of any test because you believe it will fail is dangerous in the extreme, you may as well not bother testing at all.
You MUST carry out all tests in accordance with the regs regardless of whether you think they may produce a failed result (Sensitive equipment must be tested accordingly), if they pass but are "low readings" then there is no harm in adding this to a test report advising that the equipment may need replacing in the not too distant future (of course this will depend on anymore degredation in insulation resistance readings on the next test date.

You say you were never stating a result that would be a failed one so what are you making such a fuss about? I know what you are trying to say about many parallel resistances and of course you will eventually be able to get a failure result if too many are in circuit but as stated before then you may have to look at modifying the circuit.

Design of a circuit should, if carried out according to the regs be safely within tolerances, if badly designed, so that it was on the borderline and now through ageing of components has now fallen below these tolerances then the act of testing shows this up and it's up to the tester to advise the customer accordingly.

If a new and badly designed circuit on which test results have always failed has been put into service, then both the designing engineer and the commissioning tester need to be seriously looking for new jobs.

If you had read my previous posts you will see I have already stated parts of this before.
 
This is fine. However, I didn't say do not do the test, I just said expect poor results, shocking results, suprising....whatever. What you do with the results is up to you.
 
Lectrician said:
This is fine. However, I didn't say do not do the test, I just said expect poor results, shocking results, suprising....whatever. What you do with the results is up to you.
Ok I accept that I may have assumed that you wouldn't do an IR test between L+N because you only mentioned L and N to Earth. So are you now saying you would do an IR test between L + N on a starter switch flourescent circuit?
 
Yes, but not if inaccessible which is what this thread was about.
 
That's where the tower comes in, mind you if any of the fittings are totally inaccessible due to maybe an alteration to the building, then my advice to the customer would be to replace them with more accessible ones say wall fitted as you should have proper access to electrical equipment for maintenance purposes and test purposes.
 
Not always practicle. Would customers (who more than likely are being forced for the PIR) want to pay for moving lights, or pay for a tower/picker or indeed allow you to interupt production while you push your tower around?

Ok, yes, if I had the time, and it was in the scope of the PIR, and it was in a warehouse or similar......do the full test. But there are times - many times - when this simply is not practicle or cost effective.

A test from L and N to E is more than likely going to show if you have a problem, and this test is better than non at all.

It is a widely accepted fact that the insulation test is obviosuly desireable, and has been documented that this test is certainly not the most important test to carry out - An overcurrent device, if correctly selected, is there to protect in the instance of a dangerous fault.

The most important test to carry out is the EFL to ensure that if the insulation resistance did indeed show a fault, that the overcurrent device would operate with in the required time.

Above and beond all this, the most important part of the PIR is the inspection - and it is this that most sparks seem to spend the shortest amount of time on, and miss things.
 
Which takes us back to the test itself, How can you do a visual if you cannot gain access? If the test shows a failure then the customer has to make a choice, continue working with dangerous uncertificated equipment leaving them liable to either future failure and disruption of production and possible prosecution or shut down parts of production and if possible work around safely whilst the remedial work is being done. You say part doing a test is acceptable, I disagree and say then you may as well not bother at all.

The last thing you need is a customer dictating how a test should be carried out, they must be educated as to the importance of what you have to do in order to give certification to the installation.
This may sound a bit "jobs worth" to your customer but they need to be made aware that their attitude is the wrong one.

If they feel like getting someone else in who is willing to bypass their obligations purely for the money then so be it, it is they and the tester taking the risk, I have come across these types of customer before and a short injection of the "fear of god" usually changes their attitude, instructing them of the pitfalls both from using unscrupilous tradesmen to the fear that they may one day walk in to find they have no factory anymore as it has burnt to the ground tends to get the point across.

The ones who didnt care were not worth my time and effort and for no money would i have scrimped on testing and put myself at risk of prosecution putting my name to a certificate I know is not valid.

In general I have found customers to want peace of mind.

The main point I have been trying to get over all through this thread is there is no compromise with testing. One must not allow part of a test to be avoided, the word practible is often left open to interpretation "It would cost too much in lost production" or "The expense of getting towers built" etc do not excuse the Mandatory aspects of Health and Safety Law.
The Regs are not Mandatory I hear you say but they guide you towards complying with the Mandatory parts of the Health and Safety Act which is Law.
 
Hence the importance of agreeing and recording the extent and limitations of the inspection.
Are you saying if you did a PIR in a factory you'd want to disconnect every piece of current using equipment to do IR testing?
 
Spark123 said:
Hence the importance of agreeing and recording the extent and limitations of the inspection.
Are you saying if you did a PIR in a factory you'd want to disconnect every piece of current using equipment to do IR testing?
The previous discussion was regarding flourescent lighting and ways of disconnecting them, I gave a solution if a particular type, there was disagreement over whether the chokes would cause problems or not.
Obviously you work out how you will go about testing and split it up accordingly but no complete circuit under test should be compromised by only carrying out part of a test.

Lighting is difficult in that it can be hard wired and you still need to test the switchlines up to the fitting, this is where removal of incandescent lamps, flourescent starter switches, local fusing etc comes in (you may have to rig temporary lighting up whilst doing so).

As for All current carrying equipment, each circuit has to be tested on its merits and if possible isolated from the equipment pulling local fuses if necessary(negotiation must be carried out first to determine what implications are involved).
Parts of an installation that don't get tested cannot be included in any certification so I leave it up to you to decide, personally I would let the customer know what i was unable to test and for what reason and another visit may be in order but to sign off an installation i would only be happy once all circuits had been completely tested.

One final thing i'd like to add is don't take on more than you can chew would be my advice to the OP if a big complex installation it may be better to leave it to a specialist firm and have enough labour not to cause too much disruption.

Easy enough to test in domestic premises but more complex with factories, office blocks etc.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top