Neon / Ring Final Circuit Tests

[OnOff]

Hi, I have a 20A DP switch on a 2.5mm ring that feeds a single, unswitched socket under a worktop via a single 2.5mm cable. The DP switch has a built in neon. My question is this: For carrying out the ring final circuit tests at the CU how do I "allow" for the neon? Obviously I have to switch the DP switch on when dead testing to bring the single socket in circuit for testing but I don't want the resistance of the neon bridging line and neutral while I test.

We covered this at college as far as them saying ""Make sure there's no neons in circuit......" but that's as far as it went. Ideally I would remove the neon but it's pretty much integral to the DP switch. It looks like I could take the back off of the DP switch plate by 4 screws but I'm thinking lots of springs and bits to fall apart!

Am I missing something here, is there an easy way. Going to dig out my Scadden book on Inspection & Testing and have a read!

Thanks in advance.

 

[Revved Up Sparky]

The neon will not make any difference to the ring final circuit tests as it will be on the load side. However when doing insulation resistance testing I would leave the switch off, excluding that neon, the short piece of 2.5mm T&E and the socket and thus record that part of the circuit down on the certificate as a limitation.

 

[sparkytim]

And if you do want to include the spur via the neon just short L to N and test between these and earth.

 

[PC Electrics]

It is quite legimate to carry out IR testing L&N to E, see GN3.

As suggested, leave the switch 'off' and IR L to N, then switch on and IR L&N to E.

Another tip: always IR a fresh reel of cable before you start using it.

 

[NozSpark]

For initial testing you should reallly be removing the neon from the circuit and also be testing the entire circuit, so you could remove the DP switch and temporarily connect all parts of circuit using terminal strip or just stick the load wires in the supply terminals...just for the dead testing that is....and refit the switch afterwards.

 

[PC Electrics]

Ooo! This might be considered controversial, but I'm gonna have to disagree with that Noz. Testing is about verifying the completed circuit. This includes all the connections and accessories. If we go dismantling the circuit after building it then we are not testing the completed circuit. Also after reassembly we would need to test again (how do you know you haven't put it back wrong polarity or the accessory has an IR fault in the fitted condition). I believe it's legitimate here to use the L&N to E method because circumstances dictate. The only exception to this that comes to mind is shorting out a dimmer to carry out R1+R2, necessary because it is impossible to carry out the test otherwise.

Another example is central heating control wiring, where you would IR at 250V so not to fry anything and only carry out R2 tests to all cpc connections because, again, it's impossible to carry out R1+R2 due to relays in the system.

Just to expand on my earlier reply: switch off, test IR in usual way for the whole circuit minus the output side of the switch. Then switch back on and retest using L&N to earth method which now includes the output side

(or leave off and test the output side 'backwards' from the socket it feeds)

Of course, limitations to testing should be noted on any certs.

 

[OnOff]

I did think about stripping the switch to remove the neon, then putting it back together (minus the neon) and testing. BUT I can see that to refit the neon would mean interfering with a TESTED circuit! I'd theoretically then have to test it again in case I'd made a faux pas in reassembling it. As the L&N method complies with Guidance Note 3 then taking from the above, if I:

"switch off, test IR in usual way for the whole circuit minus the output side of the switch. Then switch back on and retest using L&N to earth method which now includes the output side."

Then there won't be any limitations to note?

Thanks by the way for all the input, much appreciated.