insulation resistance testing rcbos

[kevc]

hi people, hope yous can help?

testing domestic houses, all the circuits are protected by rcbos! main switch off,individual rcbos off. disconnected neutral and earth flying leads and tested at out going terminals of the rcbos at the consumer unit- getting a low reading of 0.35 mega ohms? is this because of the rcbo? im not testing thru it tho e.g at the busbar ends so dont understand? need to disconnect each live and neutral conductors at the rcbo which are a pain !but get the correct results! so anybody got any ideas? better to test at the end of the circuit? help!!!!!!!!!!!!!!!

 

[ianmacd]

Testing between L & N? Could it be something plugged in still. You should disconnect the leads from the rcbo's.

 

[Lurch]

testing domestic houses, all the circuits are protected by rcbos! main switch off,individual rcbos off. disconnected neutral and earth flying leads and tested at out going terminals of the rcbos at the consumer unit- getting a low reading of 0.35 mega ohms? is this because of the rcbo? im not testing thru it tho e.g at the busbar ends so dont understand? need to disconnect each live and neutral conductors at the rcbo which are a pain !but get the correct results! so anybody got any ideas? better to test at the end of the circuit? help!!!!!!!!!!!!!!!

.35M on all circuits? Sounds a bit unlikely, if so then something is still connected.

 

[kevc]

no empty houses nothing plugged in, spurs , light switches off

 

[kme]

Sounds like you`re reading the RCBo`s. Test one circuit with one circuit conductor removed; and see what your readings are....

HTH

KME

 

[kevc]

even a basic shower circuit, same result, just wired! very strange! the flying leads - i just disconnect from neutral bar and earth bars making sure they are not touching anything!

 

[Lurch]

no empty houses nothing plugged in, spurs , light switches off

I was meaning to the RCBO's, just in case that reply was to mine, which it may or may not have been. Every circuit same reading regardless?

 

[kevc]

yeah more or less! will give that a try just a pain cause of the size of consumer units and connecting and reconnecting 10mm for showers etc

 

[Lurch]

yeah more or less! will give that a try just a pain cause of the size of consumer units and connecting and reconnecting 10mm for showers etc

I know what you mean, something's connected somewhere though.

 

[kevc]

can u disconnect the flying leads from the rcbo or do u mean from the neutral and earth bars?

 

[Lurch]

can u disconnect the flying leads from the rcbo or do u mean from the neutral and earth bars?

From the neutral and earth bars. I'd try taking all cables out of an RCBO and testing directly on the ends of the circuit cables, should knwo for sure then.

Push the quote button under the post you are referring to when replying, makes following the thread easier.

 

[kevc]

From the neutral and earth bars. I'd try taking all cables out of an RCBO and testing directly on the ends of the circuit cables, should knwo for sure then.Push the quote button under the post you are referring to when replying, makes following the thread easier.

yeah its fine when i do that! so have been doing that but just dont understand why its bringing the reults down when i do it the other way. i know you cant test thru the rcbos ( at the dead side of main switch and switching all the rcbos on) but thot it would be fine doing it thru the outgoing ends?

 

[Lurch]

yeah its fine when i do that! so have been doing that but just dont understand why its bringing the reults down when i do it the other way. i know you cant test thru the rcbos ( at the dead side of main switch and switching all the rcbos on) but thot it would be fine doing it thru the outgoing ends?

Ah, I see. Thought you said you were disconnecting one of the outgoing live conductors, if you are leaving both connected then you will be testing through the RCBO, whether it is up or downstream of the testing point, you are still testing the RCBO internals, or parts of them, if it is still connected.

 

[kevc]

Ah, I see. Thought you said you were disconnecting one of the outgoing live conductors, if you are leaving both connected then you will be testing through the RCBO, whether it is up or downstream of the testing point, you are still testing the RCBO internals, or parts of them, if it is still connected.

so what if i leave the neutrals connected in the rcbo and diconnect the live ends then test, would that be okay?

 

[Lurch]

so what if i leave the neutrals connected in the rcbo and diconnect the live ends then test, would that be okay?

Yes, assuming you have also disconnected the relevant earth and neutral tails from the busbars.

I usually find it easier to disconnect both live conductors from the RCBO to test, nothing else needs disconnecting then and no digging about in the back of the board.

 

[kevc]

Yes, assuming you have also disconnected the relevant earth and neutral tails from the busbars.

yeah them too will give that a try, at least i can leave the neutrals which are the worst to disconnect and reconnect cause you cant see the terminals!

 

[kme]

I usually find it easier to disconnect both live conductors from the RCBO to test, nothing else needs disconnecting then and no digging about in the back of the board.

Must agree Lurchio - I do the same thing. Wylex & Hager RCBo`s seem to be the worst for re-connecting; Won`t put ring rain cables into those anymore, since spending 2 hours ( on assessment last year), trying too find loss of phase continuity on the ring. One cable hadn`t bitten down the deep well for the phase connection. Grrrrrrr