rcd trips when lamp blows

[sparkwright]

before everyone gets upset with me please be aware that all i have done on this thread is ask a question which i was interested in the answer. look through the posts and be aware of what has happened to this thread since a certain person decided to attack rather than answer. RMS as i have stated in a previous post i am aware that you don't want to get involved. , but surely you can see who is bullying who! can we please get back on topic as this had the beginnings of a decent & informative discussion!

I think it's a very relevent question you have asked, and am disappointed by the bad response you have received.

Another point about RCDs/RCBOs is that some have an earth lead and others don't.

 

[RMS]

Another point about RCDs/RCBOs is that some have an earth lead and others don't.

Do you mean a functional earth lead?

Would that make difference in the circumstance described in the original post?

 

[JohnW2]

Another point about RCDs/RCBOs is that some have an earth lead and others don't.

An RCD with an earth lead??

As for RCBOs, they do often/usually have 'functional earth' leads, but I don't think that helps to answer the initial question.

I would have thought that the most likley answer to the original question is that both RCDs and RCBOs appear to contain 'electronics' which operate the 'RCD mode' tripping, and electronics of any sort are at risk of being susceptible to the effects of 'spikes' such as one can get when a lamp blows.

Kind Regards, John.

 

[Adam_151]

bernards answer was an angle i'd not really considered it from... not really sure how much inductance the coils in an RCD have... I'd have thought it would be 'not much' ?

I was lead to beleieve that when the filament first startered to break, it would be a fleeting contact and impose high frequencys over the wave form, these would drive much more current into the capacatance of the cable than the normal 50hz AC mains frequency would and in some cases trip the RCD

 

[JohnW2]

bernards answer was an angle i'd not really considered it from... not really sure how much inductance the coils in an RCD have... I'd have thought it would be 'not much' ?

I'm sure that's right, but Bernard was talking about the coil of an MCB, which I imagine has appreciably higher inductance. However, even if that is one possible mechanism, it would only apply if an MCB operated first, causing the RCD to trip - and I don't think that's the situation we're discussing, is it?

bernards I was lead to beleieve that when the filament first startered to break, it would be a fleeting contact and impose high frequencys over the wave form, these would drive much more current into the capacatance of the cable than the normal 50hz AC mains frequency would and in some cases trip the RCD

Again, a possible mechanism. However, without doing the sums I suspect that it would have to be a pretty high frequency to get 30mA through the small capacitance of the cable. However, it's certainly another possibility.

I'm also wondering how common this is. In the days when I had incandesecnt lamps, with some circuits fairly highly loaded, it was very common for MCBs to operate when one of those bulbs died (usually at switch-on), but I haven't experienced that with CFLs and, more to to the point, I can't recall ever having had an RCD operate when a lamp of any sort died, despite having a very large number of lamps in my house. Am I just lucky?

Kind Regards, John.

 

[elrobbo82]

i have come across it a couple of times with main switch rcd's thus isolating the full installation.

thanks for all the comments they are very helpful. didn't think there would be a "simple" answer as someone stated.

thanks

 

[RMS]

elrobbo,

Main RCD covering the full installation. tt system?

You will learn in this trade that nothings evers a simple as it first appears.

Glad to see the mods have finally recognized starspark and removed him from the forum. Bullying should never be condoned

 

[elrobbo82]

elrobbo,

Main RCD covering the full installation. tt system?

You will learn in this trade that nothings evers a simple as it first appears.

Glad to see the mods have finally recognized starspark and removed him from the forum. Bullying should never be condoned

haven't worked on many tt systems, i was just talking about cu's with rcd main switch.

don't mind a bit of banter but most posts should be relevant to the topic. hence the reason some people aren't allowed to post any more.

 

[krieghammer]

After reading the thread...... Still confused.

 

[elrobbo82]

i think what is being said is that at the point of the filament failure there is a voltage spike and a high current created through the line coductor and through capacitance in the cable leaks around 30 mA onto the cpc causing the imbalance needed to trip the RCD if sensitive enough.

is this roughly what is happening?

bit of a head scratcher this one!!!

 

[ban-all-sheds]

Glad to see the mods have finally recognized starspark and removed him from the forum. Bullying should never be condoned

Proportionately he's had over 10 times as many posts removed as I have.

 

[elrobbo82]

Proportionately he's had over 10 times as many posts removed as I have.

Geez

 

[securespark]

Another point about RCDs/RCBOs is that some have an earth lead and others don't.

An RCD with an earth lead??

Yup! Like MEM's A80HE, it has a connection to earth so it can sense the DC element:

http://www.thefusecompany.com/fuse.php?cPath=68&products_id=850&sid=u9se7riopt6h2st9j161b7ohr5

 

[JohnW2]

An RCD with an earth lead??

Yup! Like MEM's A80HE, it has a connection to earth so it can sense the DC element:

Thanks .... I just knew that someone would find one to wave at me I somewhat doubt that many DIYers, or even residential installations, have ever seen these - a bit like all the fancy RCDs that ericmark is often talking about!

Kind Regards, John.