Testing for MWC

[sparky1508]

Hi all,
I have recently finished a job and need to do the necessary tests to fill out the MWC. Can I do the earth fault loop impedance test with all lights on as this is in an office environment and switching all lights off is not practical. Also doing the insulation resistance test is not possible as it's not possible to disconnect all the lights in the circuit. Would this go down as a limitation. Might see if the client will allow me to go in and do it on a Sunday so I can isolate the circuit and not disrupt anything. Thoughts please.
Thanks

 

[Pete999]

What work have you actually carried out, is it an alteration or a new circuit, if it's the later (a new circuit) the a MNW certificate isn't applicable you would need an EIC to record your test results.

Your client is not being very helpful he or she requires a certificate for insurance purposes, by not allowing you access is, to be honest plain stupidity. those are my thoughts anyway.

 

[HandySparks]

In this sort of situation I would IR test the new work I had done, not necessarily the whole of the existing circuit.

Yes you can do a Zs test with loads connected, but some loads might cause so much electrical noise that the meter may fail to complete the test. Fluorescent lights may be an example of such a load.

 

[sparky1508]

What work have you actually carried out, is it an alteration or a new circuit, if it's the later (a new circuit) the a MNW certificate isn't applicable you would need an EIC to record your test results.

Your client is not being very helpful he or she requires a certificate for insurance purposes, by not allowing you access is, to be honest plain stupidity. those are my thoughts anyway.

It is an addition to the lighting circuit where I have added an extractor fan to dissipate heat from the server room so MWC it is.

 

[sparky1508]

In this sort of situation I would IR test the new work I had done, not necessarily the whole of the existing circuit.

Yes you can do a Zs test with loads connected, but some loads might cause so much electrical noise that the meter may fail to complete the test. Fluorescent lights may be an example of such a load.

So I would need to IR test from where I connected to the existing to the SFCU that I installed and then from SFCU to appliance. It is all fluorescent lights in the suspended ceiling tile type and lots of them.
Thanks for the replies.

 

[HandySparks]

So I would need to IR test from where I connected to the existing to the SFCU that I installed and then from SFCU to appliance.

Er, yes. But why not just leave the SFCU switched on and IR test the whole of the new wiring in one go?

Anyway, how did you connect to the existing wiring if you couldn't isolate the circuit (and turn off the lights)?

And surely you did an IR test before connecting and energising the new wiring?

 

[sparky1508]

Er, yes. But why not just leave the SFCU switched on and IR test the whole of the new wiring in one go?

Anyway, how did you connect to the existing wiring if you couldn't isolate the circuit (and turn off the lights)?

And surely you did an IR test before connecting and energising the new wiring?

I did isolate the light circuit which was looped in the switch so easy one to connect to buy no didn't do IR test before switching it back on as all the lamps are still connected. Or do you mean just the new bit? If so then no I didn't!!! Will remember that in future. Lots of people had to work in the dark for a little bit.

 

[HandySparks]

Or do you mean just the new bit?

Yes.

You'll find that it's often easier to do the dead testing as work progresses rather than as a separate task at the end of the installation.

 

[7029 dave]

I find that a bit strange, before connecting to the existing circuit,surely you would conduct your dead testing before energising the new additional circuitry anyway.?

 

[sparky1508]

I find that a bit strange, before connecting to the existing circuit,surely you would conduct your dead testing before energising the new additional circuitry anyway.?

Yes I realise this now. Still a bit fresh but will learn more as I go and only get better.

 

[7029 dave]

Yes I realise this now. Still a bit fresh but will learn more as I go and only get better.

Yes indeed, everyday is a school day for all of us.  I give you a manual like.

 

[sparky1508]

Yes indeed, everyday is a school day for all of us.  I give you a manual like.

Thanks