Arching

[nedhed]

Hi all new to this forum so please be steady on me,

After a fault we had at work where a main switch was burnt out because of arching (according to the electrician).

Now i know what the smell is like and obviously what sounds to look out for but i was just wondering if it is more likely to happen if the current is bigger on for example a shower circuit and less likely to happen on something with lower current like some lights.

 

[mikhailfaradayski]

Thats quite probably true.

There may be other factors that affect the amount of arcing aswell.
e.g. inductive or capacative loads, frequency of switching, contamination of switch contacts, etc...

 

[nedhed]

Thanks for the reply to be honest the reason i'm asking is because me and the missus overly worry about things, At the moment my young lad lives above are kitchen, which has itself got a load of gu10 downlights installed in it.

Now i obviously don't want the house going up anyway but if for example i were to change these GU10's for LED 12 volt bulbs would this then eradicate the possibility of arching completley because obviously the current would be alot lower.

 

[mikhailfaradayski]

It might make a subtle difference, but seems a bit pointless. Effectively, Its the current, not the voltage that causes heat/fire. The switch at the wall would still be at 240v and the current would proabably be similar.

If you are worried, i might suggest get a spark in to give the place a check over (s/he would know what to look for, ask for an EICR) for safety sake.

WRT to downlights with a room above, i would always advise using the fire rated type. You spark should be able to tell you whether they are or not

 

[nedhed]

I was refering to acrhing at the lights as opposed to the switch, and was wondering whether it would be possible for this to happen if the bulbs were LED.

Like the idea of an EICR any idea how much roughly that'll cost.

 

[mikhailfaradayski]

Arcing happens where a switch makes and breaks a circuit. If you have arcing at a light fitting, call a sparky, pronto. Generally, its only a switch that arcs.

EICR costs can vary with the type/size of house. Do not bother with a very low price, get 3 quotes and decide. You (hopefully) get what you pay for and its your safety at stake.

 

[nedhed]

Oh ok i was under the impresion from the sparky at work that arching was the cause of a lose connection and therefore could happen anywhere a connection is made i.e. at light fittings not only at switches.

 

[riveralt]

Oh ok i was under the impresion from the sparky at work that arching was the cause of a lose connection and therefore could happen anywhere a connection is made i.e. at light fittings not only at switches.

Arcing in action:
http://www.youtube.com/watch?v=_2LpCdhuOyQ

 

[nedhed]

Arcing happens where a switch makes and breaks a circuit. If you have arcing at a light fitting, call a sparky, pronto. Generally, its only a switch that arcs.

EICR costs can vary with the type/size of house. Do not bother with a very low price, get 3 quotes and decide. You (hopefully) get what you pay for and its your safety at stake.

Sorry after reading your post again i understand what you mean, fortunatly there is no arcing at my lights. I was just asking in case there ever was would putting LED's in lower the risk o fire because they are pulling less current?

 

[viewer]

Yes but not because of arcing, simply, as you say, they use less current so less energy goes into heat and more into light compared to say, halogen.
Your first check should be the smoke alarm upstairs - is it loud enough to wake him? Have you rehearsed an escape procedure? Where is the torch?
You don't sound to have a problem - you're normal parents - but, as said an electrician will soon check to set your mind at rest.

 

[nedhed]

So what your saying is if there was a loose connection at some point then it wouldn't matter if the bulbs were halogen or LED' as the amount of arcing would be the same? And yes we definitely have smoke alarms fitted and not just the battery type we've got the mains powered battery back up.

Sorry to keep going on.

 

[TonOfSand]

Arcing occurs when the voltage is high enough and the gap is small enough for current to flow through the air. The Jacob's Ladders etc. you see in Frankenstein films is an example and operate at 10s of thousands of volts but draw little current because of the use of induction transformers. But, domestically for example, if you operate a switch, as the gap gets smaller eventually it will be small enough to arc at 230V. Of course this happens so quickly that it's not a problem and you rarely notice it but you can sometimes see the effect if you turn on a switch in a dark room. The higher the voltage the easier it is for current to flow as an arc. So for 230V the variables are switch gap (negligible) and current draw. A larger load i.e. lower resistance/higher current, will make arcing easier, as the overall resistance is lower. Take for example an arc welder. Varieties operate between 50-120 volts, but it's easier to strike an arc when the current is set higher. Inductance loads (fluorescents/sodium/MVL lights) require a high start up current until it stabilises and therefore a higher rating switch than their rated working current. If your light connections are secure there should be no arcing.

 

[ricicle]

You could, if you feel confident, isolate the supply to the lights (at the mains) and then carefully inspect each light for signs of overheating (blackenned wires/connectors, brittle wires, discoloured wires/connectors, blistered paint or melted plastic)

 

[wotan]

Oh ok i was under the impresion from the sparky at work that arching was the cause of a lose connection and therefore could happen anywhere a connection is made i.e. at light fittings not only at switches.

ffs it's arcing not arching!