electrical testing

anchorman · Posted: Mon May 07, 2007 11:21 am Post Subject: electrical testing

what are the steps involved in carrying out an insulation resistance test on a flourescent lighing circuit from the distribution board to the circuit. i know which is the corresponding live neutral and earth conductors. been told to carry out test at 230v and if readings okay test at 500v. problem is i dont want to damage anything on this circuit, do i need to remove lamps and have switches in closed position and what readings should i be looking for. will my readings read through any control equiptment in the flourescent light fittings there are 9 in total. would love some feed back asap

Spark123 · Posted: Mon May 07, 2007 11:27 am Post Subject:

What sort of flourescent fittings, electronic ballasts? No doubt they'll have pf caps?

ricicle · Posted: Mon May 07, 2007 11:29 am Post Subject:

If it is impractical to disconnect the fittings it is acceptable to join L/N together and test to CPC.Make sure switches are in the on postion.

Test at 500V DC and look for a reading of at least 0.5 Mohms.

I'm not clear on the implications of testing with the above method on HF fittings.If they are standard fittings then the above will be fine.

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Spark123 · Posted: Mon May 07, 2007 11:30 am Post Subject:

Although 0.5Mohms is acceptable, anything less than 2Mohms should be investigated further.

anchorman · Posted: Mon May 07, 2007 1:51 pm Post Subject: electrical testing

thankyou for your advice if reading is low will that be because of branched neutrals in circuit. wiring is over 20 years old in copper single pvc double insulated singles and fittings are about 20 years old there are 9 flourescents on circuit and concerned of neutrals tapped off for other circuits. what if the reading is 3megohms or above L&N to earth is that okay or will there be something still in circuit?

Spark123 · Posted: Mon May 07, 2007 1:54 pm Post Subject:

There shouldn't be any shared neutrals between this and any other circuit, (been there, they hurt!!). If there are then it sounds like the lot wants rewired anyway.

anchorman · Posted: Mon May 07, 2007 2:28 pm Post Subject: electrical testing

if the readings are 3 megohms at 500v would you investigate the circuit or just record the results. i know they will not rewire the circuit as building being knocked down in 6 months. what would others do? would i need to disconnect every flourescent in circuit and put into connector blocks and re-test circuit to gain a more true reading.

anchorman · Posted: Mon May 07, 2007 4:05 pm Post Subject: electrical testing

need some info on experiences on carrying out insulation resistance tests i know what the readings should be between conductors on a new installation but at what value would an experienced spark investigate a low insulation reading at a circuit used 24/7 problem is i have tested a flourescent lighting circuit removed all lamps and switched all switches in on position also i have tested all 2 way switches on this circuit (l&n to earth) at 230v and also at 500v and have a reading 3.64 megohms on both scales is this right i know the regs state anythig below 2 megohms should be investigated but is it possible i am reading through something or is this down to the age of the circuit. not happy with low reading expected to have an higher reading. readings
live to earth at 230v =23.6M
neutral to earth at 230v = 3.64M
live - neutral at 230v = 3.68M
and live neutral - earth at 500v =3.64M
have i carried this out correctly it is racking my brain as i am faced with a low readings i have not encountered before. its either a clear reading or an automatic short between conductors anyone with any information i know it is bank holiday sorry to mither. thanks for any replies