Non-motoring > Mains electrical quirk Miscellaneous
Thread Author: bathtub tom Replies: 15
View Threaded 

New Sun 17 Mar 24 19:38 
 Mains electrical quirk - bathtub tom
I was moving a socket in the garage of this place I've bought, it's on a spur. There's separate isolating switches for the power and lights, so I used a neon to check it was live and again to check it was dead after switching the isolator. When I cut the cable, it tripped the the RCD in the house!
Anyone explain why please?
Reply to this message | Report message
       
New Sun 17 Mar 24 19:51 
 Mains electrical quirk - tyrednemotional
...if you've isolated only the live feed (via a single-pole switch), subsequently shorting across earth and neutral (which it sounds like you might have in cutting) is likely to trip any RCD in the circuit.
Reply to this message | Report message
       
New Sun 17 Mar 24 20:30 
 Mains electrical quirk - Runfer D'Hills
No, it’ll be the pixies.
;-)
Reply to this message | Report message
       
New Sun 17 Mar 24 20:39 
 Mains electrical quirk - tyrednemotional
...yeah. It's obviously what he ↑ said.

(I've been on the magic mushrooms! 8-( )
Reply to this message | Report message
       
New Sun 17 Mar 24 20:53 
 Mains electrical quirk - Runfer D'Hills
I prefer whisky myself, but each to their own etc.
;-)
Reply to this message | Report message
       
New Sun 17 Mar 24 20:54 
 Mains electrical quirk - tyrednemotional
...that would explain the pixies..
Reply to this message | Report message
       
New Sun 17 Mar 24 22:09 
 Mains electrical quirk - tyrednemotional
www.youtube.com/watch?v=uRNoIUqfaqA
Reply to this message | Report message
       
New Sun 17 Mar 24 22:07 
 Mains electrical quirk - bathtub tom
>> ...if you've isolated only the live feed (via a single-pole switch), subsequently shorting across earth
>> and neutral (which it sounds like you might have in cutting) is likely to trip
>> any RCD in the circuit.

That's a relief, I thought it could be shonky electrics.
Reply to this message | Report message
       
New Sun 17 Mar 24 22:09 
 Mains electrical quirk - tyrednemotional
...or pixies...?
Reply to this message | Report message
       
New Mon 18 Mar 24 07:31 
 Mains electrical quirk - sherlock47
Measure the voltage N-E. You may find a surprising voltage that will be dependent on load on both your premises and possible other premises connected . Dependent on the configuration of your supply. Suggest that you get it checked fully as you may have other problems with earthing and earth bonding.

Certainly do not rely on neon screwdrivers!
Reply to this message | Report message
       
New Mon 18 Mar 24 08:47 
 Mains electrical quirk - Fursty Ferret
www.toolstation.com/tis-voltage-tester/p11032

Less than £20.

As sherlock said there should be no N-E voltage under normal circumstances. Having said that there is obviously some bonding given that the RCD tripped so it might just be capacitative coupling but probably worth investigating.

Solar inverters can induce significant N-E voltages. Mine measured at about 120V N-E when first installed and ended up needing an extra bond that was only made under specific conditions to avoid tripping other RCDs.
Last edited by: Fursty Ferret on Mon 18 Mar 24 at 08:47
Reply to this message | Report message
       
New Mon 18 Mar 24 09:09 
 Mains electrical quirk - bathtub tom
When I replaced a porch light, I found it connected across switched live and earth! I guess there could be other anomalies.
Reply to this message | Report message
       
New Mon 18 Mar 24 11:16 
 Mains electrical quirk - Manatee
Have you got one of those plug in outlet testers? Is the "polarity" correct?

It will work perfectly well if the live and neutral are reversed but a single pole isolator switch could leave full mains voltage on the "neutral" even if switched off. It would also mean parts of your appliance could be live even if the plug fuse blew.

www.amazon.co.uk/QUILLE-Socket-Display-Neutral-Testing/dp/B07GNPKHQ9/ref=asc_df_B07GNPKHQ9
Reply to this message | Report message
       
New Mon 18 Mar 24 12:02 
 Mains electrical quirk - Bromptonaut
>> Have you got one of those plug in outlet testers? Is the "polarity" correct?

Keep one in the caravan as French electrics can be odd re L/N
Reply to this message | Report message
       
New Mon 18 Mar 24 13:27 
 Mains electrical quirk - Zero
Yeah got one in the caravan tool kit, even UK service posts can be suspect.
Reply to this message | Report message
       
New Mon 18 Mar 24 17:18 
 Mains electrical quirk - bathtub tom
>>Have you got one of those plug in outlet testers? Is the "polarity" correct?

The red tested live with the neon and the black didn't.
Reply to this message | Report message
       
Latest Forum Posts