Insulation Resistance testing - again!

[chrisgc]

While we are on the subject of IR test just a question about R1 R2 jump leads. What cable size do you tend to use if you have made your own?

 

[Guitarist]

All understood now As wasnt seeing all the new replies (refresh button is a great invention) - So obviously taking the line cables out of fCU and switching FCU to on will then keep circuit but bypass the neon indicator light.

Got it.

Thanks everyone.

You won't need to switch the fcu to anything. The cables will be joined outside the fcu.

 

[DaveyD]

You won't need to switch the fcu to anything. The cables will be joined outside the fcu.

I think it's refering to TigerPaul's idea - he mentioned just linking the lines outside the switch so the neutrals are still in the SFCU and therefore to include the neutrals the switch will still need to be closed.

 

[rare breed]

Kind of related to the above thread.
I am doing the 2391 practical tommorow, to speed up my testing on a rig is there a problem with doing the Insulaion testing prior to the continuity for the Periodic?

 

[malcolmsanford]

To be honest unless it as changed dramatically over the years you are advised to test in the order they are laid out in the GN 3 and the continuity test comes before the IR test, so I would do it in order.

Also isn't it an EIC test you do not a periodic, or am I at cross wires when you mentioned "periodic"

 

[topquark]

Kind of related to the above thread.
I am doing the 2391 practical tommorow, to speed up my testing on a rig is there a problem with doing the Insulaion testing prior to the continuity for the Periodic?

Yes, if you don't know that you have continuity of conductors how would you know that your IR test is testing all of the circuit?

 

[rare breed]

Its still a periodic inspection and test but you use the EICR to make the report.
I know you need to do it in order for new installations but I don't think you need a particular order for the periodic, I was just trying to figure out if I would be penalised for trying to do the IR on the motor circuit first when I connect across the switch.

 

[rare breed]

Reply past in the ether thanks for your thoughts Topquark

 

[Strima]

The sequence of tests is logically formatted so you find any faults before moving onto the next test. If you did IR before continuity you would have to do the IR again if you found a break in a circuit and rectified it, saves you doing things twice.

 

[topquark]

Its still a periodic inspection and test but you use the EICR to make the report.
I know you need to do it in order for new installations but I don't think you need a particular order for the periodic, I was just trying to figure out if I would be penalised for trying to do the IR on the motor circuit first when I connect across the switch.

Don't confuse EIC (Electrical Installation Certificate--on first install) with EICR (Electrical Installation Condition Report--subsequent test).

 

[ackbarthestar]

Generally, the hybrid nature of the 2391 test rig would mean that you do continuity before IR. However, on a real job, where you know everything is working beforehand then you would be interested in the Zs, without disconnecting all the circuits. So its justifiable to IR test and then Zs.

 

[rare breed]

Generally, the hybrid nature of the 2391 test rig would mean that you do continuity before IR. However, on a real job, where you know everything is working beforehand then you would be interested in the Zs, without disconnecting all the circuits. So its justifiable to IR test and then Zs.

Thanks for the advice. I think I will do the continuity first to be on the safe side.

 

[AndyL]

Generally, the hybrid nature of the 2391 test rig would mean that you do continuity before IR. However, on a real job, where you know everything is working beforehand then you would be interested in the Zs, without disconnecting all the circuits. So its justifiable to IR test and then Zs.

Just because its all working does not mean you have continuity of protective conductor which is what you test for.
As stated earlier, done in logical sequence so we dont have to redo earlier tests if a fault is found

 

[ackbarthestar]

Just because its all working does not mean you have continuity of protective conductor which is what you test for.
As stated earlier, done in logical sequence so we dont have to redo earlier tests if a fault is found

In most cases it does. Once you know that the MPB's are Ok then a Zs is perfectly acceptable for each circuit. (Perhaps not so with domestic installations where the Numpties roam).

I often find cpcs are cross linked to other circuit cpcs so your R1 + R2 wouldn't give you specific circuit readings, and if you did disconnect everything you would have the hassle of reconnection at each point of separation of the cpcs.

You'll be spending week on a days worth of work if you chose to undo everything just to get your R1+R2 readings.

So its often better to get a R2 reading coupled with Ze and Zs