Minor Electrical Installation Cert

[Ste69]

These are now going to be used within my job (lighting maintenance) the client want these for adding to circuits and also for changing like for like i.e light fitting for new light fitting, socket for socket etc.

My issue is with insulation resistance testing on lighting circuits incorporating control ballasts, transformers etc.

Say you have a circuit of lights incorporating the above where it is not possible to disconnect ballasts or remove lamps or switch off locally. how would you do the insulation resistance test?

i know you can lower the volatge for the test for sensitive equipment to not cause damage BUT that wouldnt help with getting funny reading from the ballasts would it?

Any help welcome!

cheers

 

[Baker1988]

I agree with the minor works for adding to a existing corcuit but why do you need a mwc for a like for like replacement?

Also could you not connect l and n and ir test to earth

 

[Ste69]

I agree with the minor works for adding to a existing corcuit but why do you need a mwc for a like for like replacement?


Also could you not connect l and n and ir test to earth

In the regs it says Minor works certs can be used for replacement, the client has obviously taken it to the extreme and gone down this route.

I though about the LN to earth test but in some cases it is not going to be possible to disconnect from ballasts.

 

[Ste69]

Limitations on minor works cert........

Can you leave out the insulation resistance test on an addition to an existing lighting circuit? and explain your reasoning in limitations? e.g could not perform insulation resistance test because sensitive equipment could not be disconnected as it was not accessible.

Cheers

 

[Richard Burns]

Limitations only apply to EICRs they do not apply to installation certificates.

The work you do must be fully tested and compliant, however if you are adding a light to an existing circuit then the work you do is the new cable and light fitting, the rest of the circuit is existing. You could IR your new cables, perform a Zs at the point from where you extended the circuit, do an R1+R2 for your cable, test any RCD (if required), check and upgrade if necessary earthing and bonding and ensure that the existing circuit is safe for you to extend and you would have just about complied with the regulations.

I would say that this is the very bare minimum and would recommend that testing is extended to the entire circuit wherever possible, most equipment will not suffer damage from an insulation resistance test of line and neutral connected together to earth. You could test at 250V first to see if the readings are poor and not proceed to 500V if they are suspect.

 

[Ste69]

Thank you for your reply Richard.

On the certificates my company has given us there is a section for limitations to the testing......it is a NICEIC certificate.

Cheers for the help, i will definitely do as you have said.......unfortunately i work in old commercial buildings riddled with asbestos and unacesible circuits, so testing the whole installation would not be allowed from the client......

Richard maybe you could help me with my original post please...as below.
also would you be able to test a circuit of lights with controll ballasts connected on 250 volts? without causing damage? or would i need to disconnect them?

again thanks

 

[Richard Burns]

I just had a look at the NICEIC certificate, the limitations box is there, even though I did not think it possible they have gone down even further in my opinion.
I really cannot believe they put that in there.

Anyway there is no provision in BS7671 for limitations on inspection and testing of a new circuit, though there are from the NICEIC!


Even though I cannot be absolutely certain for all cases, testing of any equipment that is supplied with 230Vac in normal use should not be damaged by the application of 250Vdc to the circuit since the circuit is subjected to a peak voltage of 325V from the ac source.
The use of line and neutral connected together and tested to earth means that the functional parts of the circuit are not subjected to the test voltage, only the live conductors to earth are subjected to the test voltage. Where there are smoothing circuits that can bleed power to earth these may be damaged by the 500V test (but only in certain circuits, generally this will not cause harm).

Therefore I would be of the opinion that testing line and neutral connected together to earth at 250Vdc would not cause any harm to any properly functional item of 230Vac equipment.
Testing each conductor separately at 250Vdc should not cause any harm but may give false readings where the functional circuit is involved.

 

[Ste69]

Thanks again mate! much appreciated............if for some unknown reason i did the insulation test and it did cause damage i would be sacked lol, the amount of money damage could be in the 10s of thousands lol....so ill stay clear just in case..........i will do the full tests on the parts i install/replace and use the limitations section to explain why i didnt test the existing part of the circuit.......

also thanks for explaining the reason for connecting live and neutral as i have been wondering about that myself.........