insulation resistance question FICA

[DM Elec]

Hi yesterday I sat my FICA test and during the insulation resistance test I’m not sure if I made a mistake

I measured it doing individual circuits I had the main switch at db on but forgot to turn on the mcbs

I measured between Line at MCB and earth and Neutral bar to MCB then neutral bar to earth but not sure if this is giving incorrect readings as i never turned on the MCBs for the circuits?

 

[telectrix]

i'd like to see anyone do an IR test with the circuit/s energised.

 

[Richard Burns]

Measuring from the top of the MCB to the earth bar and also to the neutral cable (should not be in the neutral bar or you measure against all the other neutrals as well) and measuring from the neutral wire to the earth bar should be OK for individual circuits.

You would only have the MCBs on when doing a global test of the entire installation. Otherwise the MCBs being on (with main switch off) would link all the line conductors via the busbar.

 

[telectrix]

but OP says he had main switch ON.......

 

[MFS Electrical]

Hi yesterday I sat my FICA test and during the insulation resistance test I’m not sure if I made a mistake

I measured it doing individual circuits I had the main switch at db on but forgot to turn on the mcbs

I measured between Line at MCB and earth and Neutral bar to MCB then neutral bar to earth but not sure if this is giving incorrect readings as i never turned on the MCBs for the circuits?

Did you pass? Apologies if you don’t find out on the day or if your heading back to do the Questions etc mine was that long ago so I can’t really remember. but it Seems to me like you forgot to do it like it says in the OSG? I made a boo boo on my trade test pinched a cable against the backbox in the remote motor control part of the circuit (that patricular wire wasn’t in circuit for IR tests because the contactor was in the open state)which went boom when the assessor tried to start the motor Still passed though, he said you’ve got 5 mins to find it and fix it or you Fail, opened it up and it became immediately apparent that’s what happened cut and remade the wire took extra care fitting the faceplate on and hey presto PASSED so don’t be too worried if you made a mistake you could still Pass

 

[DM Elec]

Basically it was the full installation I was to test but I done it through individual circuits so didn’t think I would need to remove the neutrals from the neutral bar but I never turned on any of the MCBs just the mainswitch was on but the power was isolated

 

[DM Elec]

I was getting readings greater that 500 mega ohms in fluke meter but when switching the 2 way switch it wasn’t changing and also the motor circuit was giving a reading without pressing the contractor but I had the motor control switched on

 

[Highresdis]

I'd be surprised if you were getting >500Mohms neutral to earth with the main switch on, unless you had the dp RCCB off...

 

[DM Elec]

They were offf