Voltage still detected after rcd had tripped? why could this be...

[srl-8]

Hi all,

I have install a RCD fused spur on the end of line feed to a bathroom lighting circuit. Thus protecting the bathroom with rcd.

I tested the rcd (manually via the push 'test' button) and it killed the lights and fan as expected.

I used my volt stick to confirm that the cables were dead, but to my surprise , The voltstick was telling me the there was voltage still present. How could this be?

My understanding was that with the RCD tripped, it should kill all power on the load side of the spur, .

Any ideas????

Thanks

 

[telectrix]

voltstick picking up off incoming side. use a proper tester to confirm. voltsticks are only a rough guide and don't bloody rely on them.

 

[Lucien Nunes]

Use a multimeter/ MFT rather than a voltstick to confirm what voltage is where. Voltsticks are useful but only give an indication and can be easily confused by capacitive coupling / induced voltages.

E: and again we have proof that great minds think alike, although Tel types faster

 

[srl-8]

Yes, I agree that voltstick is not a 100% guarantee, I will test what voltage is present when I go back to finish the job, just had never noticed this before.

Cable bunching can confuse a voltstick, however, the RCD (to my understanding) should break the power on both live and neutral. So there should be no current available to detect on the load side of the spur and bathroom circuits.

 

[dingledong]

What's wrong with the wet finger method

 

[Lucien Nunes]

no current available to detect on the load side of the spur

No current, indeed. But a voltstick detects... voltage. And a small amount of leakage or coupling from a live cable can cause the isolated circuit lives to float up to a voltage that the stick can detect. Readings needed.

 

[Plonker 3]

This should be in the DIY section

 

[Pete999]

You need to use the proper test equipment voltsticks have their uses but NOT to prove dead or live

 

[trev]

Forgive my bluntness but either learn the safe isolation procedure or make sure your life insurance is up to date mate.

 

[Octopus]

Hi all,

I have install a RCD fused spur on the end of line feed to a bathroom lighting circuit. Thus protecting the bathroom with rcd.

I tested the rcd (manually via the push 'test' button) and it killed the lights and fan as expected.

I used my volt stick to confirm that the cables were dead, but to my surprise , The voltstick was telling me the there was voltage still present. How could this be?

My understanding was that with the RCD tripped, it should kill all power on the load side of the spur, .

Any ideas????

Thanks

What voltage was your MFT showing at a load point after you'd tripped the RCD?

 

[Pete999]

What voltage was your MFT showing at a load point after you'd tripped the RCD?

Think he just pushed the test button, probably don't own a MFT

 

[shanky887614]

Use a multimeter/ MFT rather than a voltstick to confirm what voltage is where. Voltsticks are useful but only give an indication and can be easily confused by capacitive coupling / induced voltages.

E: and again we have proof that great minds think alike, although Tel types faster

i like to think they show potential, potential to injure yourself or generally make yourself look like a --- waving a stick with a flashing red beacon like some crazed harry potter fan

 

[Octopus]

Think he just pushed the test button, probably don't own a MFT

Give the OP a chance, how else would he have recorded the relevent details for the Cert?

 

[srl-8]

All,

I have to say, (with a few exceptions) you come across as a **** taking bunch of smart arses. You all use volt sticks, you are telling lies if you say you don't. I never said that I rely on this method to confirm voltage. It was an observation and wanted to ask other people.

With-in a few replys this forum has 'Assumed' I don't know what im doing.

I future I will think twice before I post. Ouch!

PS: Many thanks to those who offered sensible responses.

 

[Octopus]

All,

I have to say, (with a few exceptions) you come across as a **** taking bunch of smart arses. You all use volt sticks, you are telling lies if you say you don't. I never said that I rely on this method to confirm voltage. It was an observation and wanted to ask other people.

With-in a few replys this forum has 'Assumed' I don't know what im doing.

I future I will think twice before I post. Ouch!

PS: Many thanks to those who offered sensible responses.

In which case you should use the "thanks" button so we can see which ones you appreciate!

 

[telectrix]

In which case you should use the "thanks" button so we can see which ones you appreciate!

i wouldn't hold your breath.

 

[Andy78]

All,

I have to say, (with a few exceptions) you come across as a **** taking bunch of smart arses. You all use volt sticks, you are telling lies if you say you don't. I never said that I rely on this method to confirm voltage. It was an observation and wanted to ask other people.

With-in a few replys this forum has 'Assumed' I don't know what im doing.

I future I will think twice before I post. Ouch!

PS: Many thanks to those who offered sensible responses.

I'm not lying, I definitely don't use them. I have used voltsticks in the past, but in my experience they give false readings either live when dead or vice versa.
If I had used one and got a spurious reading however, my first thought would be to prove with my AVI what was going on, not ask an internet forum. That would give the impression I don't know what I'm doing or have the right tools for the job. I think that is what you have got stick for.

 

[tazz]

Quick few games to show voltsticks pick up stray and non dangerous currents.... place voltstick near tv screen... rub voltsick on your jumper, all will lite the voltstick, but non are dangerous.

 

[Deleted member 72666]

Yes, I agree that voltstick is not a 100% guarantee, I will test what voltage is present when I go back to finish the job, just had never noticed this before.
Cable bunching can confuse a voltstick,
however, the RCD (to my understanding) should break the power on both live and neutral. So there should be no current available to detect on the load side of the spur and bathroom circuits.

This can be overcome by using your finger on the end of the voltstick and slightly separating the cables as you scan.
I use a voltstick on a regular basis and it has served me well over the years in fact I would go as far as saying that it's potentially saved my life on at least a couple of occasions when I unwittingly came across a 'borrowed' neutral, that's after safe isolation was carried out, all appeared okay until I split the neutrals and one magically became live! They're also great for detecting broken neutrals in extensions.

 

[Knobhead]

I would sack any electrician that relied on a voltstick.

I gathered them all up at work and threw them in a kiln. Use recognised test methods.

 

[7029 dave]

Test Test Test, with approved tester, seperates or MFT.

 

[PEG]

Quick few games to show voltsticks pick up stray and non dangerous currents.... place voltstick near tv screen... rub voltsick on your jumper, all will lite the voltstick, but non are dangerous.

I disagree. My friend went into a pub in Liverpool,with a MCFC jumper on....and it ended badly

 

[Deleted member 72666]

I would sack any electrician that relied on a voltstick.! Too right, they should not be relied upon.

I gathered them all up at work and threw them in a kiln. Use recognised test methods.A little ott imo, unless of course they were being relied upon and then in which case dismiss the offenders and then bin the sticks.

,
......

 

[HappyHippyDad]

I think voltsticks are great! .. Wave it over something and it gives you an 'indication' of whether something is live without dismantling the switch/socket etc. If you want to touch that part or need a definite answer then you test properly with your MFT.

 

[trev]

I think voltsticks are great! .. Wave it over something and it gives you an 'indication' of whether something is live

I got one given by a rep in a wholesalers a while back. I waved it over a damp piece of wood in the rear storage yard of a pub I was working on. It indicated it was live.
I threw it away.

 

[7029 dave]

We have them on the board , BUT, they are desensitized, about £90 worth of kit and they are good.

 

[Jurassic Sparks]

You need to use the proper test equipment voltsticks have their uses but NOT to prove dead or live

actually they can save your life
recently I was asked to remove some flourescent fittings in an attic, the property had a partial rewire, new CU bonding earth electrode and a lighting circuit with CPC fitted by an aprroved electrican
(I did not want to do the work due to the distance involved)
I do the small domestic jobs for the client, so I said no probs
all the lights were off at the switch
I pop the tube out of the first one, lift the cover, and stick my test leads across R1 RN nada
but I just waved the volt stick in the area and bugger me it light up!!!
reason
the chappy doing the upgrade had not bothered to check the circuit as it was to difficult to get to ( fat lazy lump)
no CPC at all
No Neutral at all
permanent live
I ended up shutting the CU down and tracing the wiring back to a rose and it was a mess
just a looksee would have shown that up,
so the voltstick saved me bacon
ps the muppet concerned also failed to note on his report 1 burnt out and cracked socket outlet and one fractured one ? ( I took pictures for when I see him)
specsavers are fairly cheap these days???
I might be old
I might have trouble understanding modern high tech test gear
but I always like to have 2 different methods of testing

 

[Simonslimline]

actually they can save your life
recently I was asked to remove some flourescent fittings in an attic, the property had a partial rewire, new CU bonding earth electrode and a lighting circuit with CPC fitted by an aprroved electrican
(I did not want to do the work due to the distance involved)
I do the small domestic jobs for the client, so I said no probs
all the lights were off at the switch
I pop the tube out of the first one, lift the cover, and stick my test leads across R1 RN nada
but I just waved the volt stick in the area and bugger me it light up!!!
reason
the chappy doing the upgrade had not bothered to check the circuit as it was to difficult to get to ( fat lazy lump)
no CPC at all
No Neutral at all
permanent live
I ended up shutting the CU down and tracing the wiring back to a rose and it was a mess
just a looksee would have shown that up,
so the voltstick saved me bacon
ps the muppet concerned also failed to note on his report 1 burnt out and cracked socket outlet and one fractured one ? ( I took pictures for when I see him)
specsavers are fairly cheap these days???
I might be old
I might have trouble understanding modern high tech test gear
but I always like to have 2 different methods of testing

Out of interest what AVI do you use? My fluke t150 would of indicated the live wire by just putting the 1 probe on to it.

 

[Knobhead]

stantheman the electricians were employed and had a list of approved test instruments to choose from that the company would provide. The list at one time included a volt stick.

The volt sticks were taken off the list following an incident. I collected them in and threw them in a kiln. They were company property so why would it be OTT to confiscate and destroy them?

Normally if something was taken off the approved list and you had that type of meter you could take it home with you. Not so the voltsticks.

They are bloody dangerous.

 

[micknew]

Volt sticks should only be used by qualified electricians with a knowledge of electrical theory.
Previous comments by 'qualified electricians' who condemn there use are wrong.
As an aid for fast fault finding they are invaluable, ask Megger who make them.
They must not to be used for proof of safe isolation.