Hi All,
I am only a newbie, with not much experience at all, but anyway, i will just jump in with my observations!!!
First off, it seems to me that the original "source" of all this, [the bloke that has his name in the big red or green book] is a nitpicking know it all, trying to "show off" how superior his vast knowledge is compared to everyone else's.
Now, if i install a circuit, be it an extension to an existing one, or an entirely new one, or in the case of you lot rewiring houses, [i have never done this] a whole group of circuits I ALWAYS do an IR check on the bit i have installed [each individual circuit i have fiddled about with] BEFORE connecting ANY of it to the existing circuit or DB [or CU in the case of you lot doing the houses]
I do this to check out the new cable i have installed, [faulty cables do exist] and all the other bits i have installed too, for two reasons;
1, Just for my own piece of mind.
2, When filling in the certs, you are asked to record IR values for EACH INDIVIDUAL circuit. How you going to do that unless you test "your" circuit "on its own" before connecting it all up??? As an asides, although there is a column for this on the certs, i cannot find ANY reg that requires you to test each individual circuit.
Next, i will connect it all up. AFTER doing this, i will do a GLOBAL IR on the entire installation. This fullfills 3 objectives.
1, You are testing the installation "as installed" this is VERY important, as, if you just test the individual circuits [with or without their cpc's connected] you could introduce faults when you finally assemble the rest of it.
2, If, when you do the global, you then find a low reading, you then only have to disconnect "your bit" and re- test, to find out if the fault was already there, or if there is a problem with "your bit" after all.
3, To do a global is a [the only??] REQUIREMENT OF THE REGS.
Here is what the regulations concerned ACTUALLY say;
612.3 Insulation resistance.....
612.3.1
"The insulation resistance shall be measured between the live conductors and between the live conductors and the protective conductor connected to the earthing arrangement. Where appropriate during this measurement, line and neutral conductors may be connected together"
[Note how there is absolutely NO reference to testing INDIVIDUAL circuits here at all, cpc's connected or not, so we can only assume that it relates to a global, in which case, of course the cpc's will already be connected, especially as the ONLY figures given in the regs for minimum IR, are given in table 61, which SPECIFICALLY refers, by operation of reg 612.3.2, to global testing...
Let us look then, at the following paragraph [which is presumably intended to be read in conjunction with the one above]......
612.3.2
The insulation resistance measured with the test voltages indicated in table 61 shall be considered satisfactory if the main switchboard and each distribution circuit tested separately, with all its final circuits connected but with current using equipment disconnected has an insulation resistance not less than the appropriate value given in table 61.
This obviously refers SPECIFICALLY to a global, when the cpc's will obviously all be connected, and likewise, the figures given in the table to which this paragraph refers obviously relate to the test done globally, in which case the cpc's are obviously already connected to the earthing arrangement.
NOTE IN PARTICULAR HOW THERE ARE NO FIGURES GIVEN FOR VALUES FOR INDIVIDUAL CIRCUITS AT ALL just for "each distribution circuit tested separately, with all its final circuits connected but with current using equipment disconnected"
So, by merely doing a global, [which is all the regs require] you are automatically "testing with cpc's connected" Which is what the nit picking "know it all" concerned is refering to.
So.....unless 99 percent of electricians do not do a global on completed installations, 99 percent of "experts" do not know what they are on about....................
You all do globals [or at least i hope you do!!] so you are all doing it to the regs, and you are all doing it right!!!!
So, you all just keep on doing what you are doing, actually DOING the work, and not merely talking clever about it... Good for you lot!!!!!
john....
I am only a newbie, with not much experience at all, but anyway, i will just jump in with my observations!!!
First off, it seems to me that the original "source" of all this, [the bloke that has his name in the big red or green book] is a nitpicking know it all, trying to "show off" how superior his vast knowledge is compared to everyone else's.
Now, if i install a circuit, be it an extension to an existing one, or an entirely new one, or in the case of you lot rewiring houses, [i have never done this] a whole group of circuits I ALWAYS do an IR check on the bit i have installed [each individual circuit i have fiddled about with] BEFORE connecting ANY of it to the existing circuit or DB [or CU in the case of you lot doing the houses]
I do this to check out the new cable i have installed, [faulty cables do exist] and all the other bits i have installed too, for two reasons;
1, Just for my own piece of mind.
2, When filling in the certs, you are asked to record IR values for EACH INDIVIDUAL circuit. How you going to do that unless you test "your" circuit "on its own" before connecting it all up??? As an asides, although there is a column for this on the certs, i cannot find ANY reg that requires you to test each individual circuit.
Next, i will connect it all up. AFTER doing this, i will do a GLOBAL IR on the entire installation. This fullfills 3 objectives.
1, You are testing the installation "as installed" this is VERY important, as, if you just test the individual circuits [with or without their cpc's connected] you could introduce faults when you finally assemble the rest of it.
2, If, when you do the global, you then find a low reading, you then only have to disconnect "your bit" and re- test, to find out if the fault was already there, or if there is a problem with "your bit" after all.
3, To do a global is a [the only??] REQUIREMENT OF THE REGS.
Here is what the regulations concerned ACTUALLY say;
612.3 Insulation resistance.....
612.3.1
"The insulation resistance shall be measured between the live conductors and between the live conductors and the protective conductor connected to the earthing arrangement. Where appropriate during this measurement, line and neutral conductors may be connected together"
[Note how there is absolutely NO reference to testing INDIVIDUAL circuits here at all, cpc's connected or not, so we can only assume that it relates to a global, in which case, of course the cpc's will already be connected, especially as the ONLY figures given in the regs for minimum IR, are given in table 61, which SPECIFICALLY refers, by operation of reg 612.3.2, to global testing...
Let us look then, at the following paragraph [which is presumably intended to be read in conjunction with the one above]......
612.3.2
The insulation resistance measured with the test voltages indicated in table 61 shall be considered satisfactory if the main switchboard and each distribution circuit tested separately, with all its final circuits connected but with current using equipment disconnected has an insulation resistance not less than the appropriate value given in table 61.
This obviously refers SPECIFICALLY to a global, when the cpc's will obviously all be connected, and likewise, the figures given in the table to which this paragraph refers obviously relate to the test done globally, in which case the cpc's are obviously already connected to the earthing arrangement.
NOTE IN PARTICULAR HOW THERE ARE NO FIGURES GIVEN FOR VALUES FOR INDIVIDUAL CIRCUITS AT ALL just for "each distribution circuit tested separately, with all its final circuits connected but with current using equipment disconnected"
So, by merely doing a global, [which is all the regs require] you are automatically "testing with cpc's connected" Which is what the nit picking "know it all" concerned is refering to.
So.....unless 99 percent of electricians do not do a global on completed installations, 99 percent of "experts" do not know what they are on about....................
You all do globals [or at least i hope you do!!] so you are all doing it to the regs, and you are all doing it right!!!!
So, you all just keep on doing what you are doing, actually DOING the work, and not merely talking clever about it... Good for you lot!!!!!
john....
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