hi got sum queys regading 2391

[bobby101]

hi guys been doing past test papers an i came across this question regarding insulation resistance find the overall resistance of all circuits and say whether or not it is acceptable. Now on one exam paper the overall result came to 1.14 Megohm but the individual circuits were all above 2 Megohm in one paper the given answer was that this was acceptable due to the fact that all the indivual circuits were above the 2 Meg ohm reading. but on another it said it was not i am a little confused as to what is the correct answer is.
Also i am not sure what value you put into the schedule of test results when doing RCD testing i have had one lecture saying it was the highest trip time an had another saying it was the lowest trip time that got inserted please help

 

[Sintra]

Circuits up to 500V must have a minimum insulation resistance of 1.0 Meg ohms when tested at 500V dc with all current using equipment disconnected. 612.3.2 so all your readings are satisfactory.

As for the RCD's you enter the highest value from 1X on both cycles and 5X on both cycles.

 

[Addlight]

The lower reading for the whole IR is because the indvidual circuit resistances are in parallel.

The total is greater than 1 MegaOhms, but less than 2 MegaOhms, so requires further investigation to look at individual circuits.

And for RCD measurements, you use the 'worst case' scenario - which is the higher values you get.