Discuss Insulation resistance test on a whole consumer unit?HELP in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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Can any one explain to me the correct method to test insulation resistance on a 3 phase consumer unit all at once as apposed to testing each final circuit individually?

Especialy circuits vulnerable to test voltage. GN3 states that you connect line and neutral together and test to eath is that all three line conductors an neutral at once or individually?
 
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G

Guest55

With the DB main switch off and all mcb's on...
test from L1 to E
L2 to E
L3 to E
N to E
test from the output side of the main switch terminals and record the lowest reading
Use 250v test voltage first if equipment may still be connected , then 500v if all clear.
 

rmc86uk

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Arms
As above but just to add also test between each phase aswell.

Sent from my GT-I9300 using Tapatalk 2
 

Jimmy Boy

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Arms
The OP doesn't state if this is a new install or a PIR type test, test method 1 for new installs, test method 2 is acceptable for existing installs if equipment can not be disconnected, in fact so is a 250 V test acceptable
J
 
G

Guest55

The OP doesn't state if this is a new install or a PIR type test, test method 1 for new installs, test method 2 is acceptable for existing installs if equipment can not be disconnected, in fact so is a 250 V test acceptable
J
If connected equiment is mentioned , i'd guess periodic
new install would be tested before equipment is connected.
usually lol.
 
  • Thread Starter Thread Starter
  • #6
Sorry should have stated, its for the insulation resistance testing part of the 2391 practical test ,our tutor mentioned this is somtimes the method you are asked to use. Not sure on the scenireo i.e initial/periodic? of install?
 

Jimmy Boy

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Arms
If connected equiment is mentioned , i'd guess periodic
new install would be tested before equipment is connected.
usually lol.
Well yes you would hope so ! but how many peeps test through the tails on a new install and push 500V through the rcbo's or RCD's ? not something I would want to do ! LMAO
J
 
jimmy would you ir circuts individually ive ir through rcbos and rcds before and had no problems what problems are you thinking you could have
 
S

SPARTYKUS

I think its a myth worrying about 500v tbh - when I did my 2391 (passed) we were told not to p**s about worrying about that.


EDIT; i meant specifically through RCDs.
 
G

Guest55

I think its a myth worrying about 500v tbh - when I did my 2391 (passed) we were told not to p**s about worrying about that.


EDIT; i meant specifically through RCDs.
I still wouldnt risk 500v between L-N though if i thought electronics were connected somewhere.
 

Rockingit

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Mentor
Arms
Esteemed
If I'm testing on the unknown, I always do the first buzz at 250v, that way you can see from a very low reading if you need to look harder. Likewise, when doing a new install I put a little flag marker on the cable of any circuits where care is needed.
 

Jimmy Boy

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Arms
jimmy would you ir circuts individually ive ir through rcbos and rcds before and had no problems what problems are you thinking you could have
Sorry for the late reply, I have had a long chat with MK technical today, and they assure me that for the purposes of the regs and the application of the regs, RCD's and RCBO's are classed as containing electronic components and should not be subjected to a 500V test, and of course any impedance in the components might skew your readings,think about the description of the test, 'Insulation resistance test' we are testing the integrity of the insulation between live conductors and Earth, we are not testing the integrity of component parts of the installation, ( although I except defects in accessories may well show as a fault) so I will continue to test them from the load side not the supply side.
J
 
O

OldskoolUpNorth

10 point test same as 'Safe Isolation'.

L's - L's
L's - Ns
L's - E's
N - E

Probably a vulnerable 3 phase motor circuit.
Tails are not to be tested as it's EICR not new install.

Plus they'll be connected to incoming supply for live tests later on.

I tested from busbar terminals of main switch, all MCB's on.
Secondary CSU main switch off.

Didn't test through RCD's or RCBO's.

Rememeber CRIPPLER and it's easy.
 
Last edited by a moderator:
O

OldskoolUpNorth

Oh yeah, forgot.

There is a small IR test rig where you have to find what sort of fail it is, dead short etc.. and on which circuit.

This is only single phase tho and the rigs are the same across all centres I think.

Never heard of cross connecting 3 phase on 2391.

But I may be wrong...
 
Word of advice, in your testing exams do not use the term "dead short" C&G are very particular about terminology. It's a short cicuit, nothing more nothing less.
 

Jimmy Boy

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Arms
Oh and I forgot to add, in GN3 , it clearly states that if test method 1 is used RCD's should be removed and not subjected to test voltage
ATB J
 
Hey all, Ive noticed alot of you are fixated and worried about pumping 500v through a consumer unit with fear of damaging elerctronic equip. In most cases for newly built electrical installations all volt sensitive equipment/IT equipment are capable and designed to withstand 500DC. If you just want to be on the safest side simply switch off mcbs that are connected to such equipment and perform your IR test as normal from output side of Main Switch.
 
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