Is it normal for a light switch to have a little spark?

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quebec

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Ultimate Geek

#260082 9-Nov-2019 21:04

It’s a 4 way light switch and the one sparking is controlling the security sensor flood lights. Was installed by a registered electrician. Only sparks little bit when you turn them switch off. I usually don’t turn it off I but noticed it today as it was dark in that area and sensor light was on for for a long time.

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#2350851 9-Nov-2019 21:10

Can't quote you for some reason, but "Was installed by a registered electrician." that means extremely little sadly. And no it should not spark, that needs to be fixed.

Tinkerisk

4227 posts

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#2350852 9-Nov-2019 21:10

Yes, having an electrical arc on mechanical switches is normal to a certain level (assuming the switch isn't overloaded beyond it's max. switching power rating). The arc depends of the load's restistance/inductivity.

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Rikkitic

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#2350858 9-Nov-2019 21:24

A small spark isn't unusual. If you hear the switch arcing, then there is a problem and it needs to be checked.

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larknz

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#2350859 9-Nov-2019 21:27

Most light switches will spark when they are operated, although it is normally not obvious. The only time to worry is if the sparkling continues after the switch has been operated. If this is happening consult an electrician.

neb

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#2350889 10-Nov-2019 00:06

+1 to all of the above, and in particular you'll notice it more in the dark as you point out. In other words it may be sparking slightly a lot of the time, but you've noticed it now because it was dark.

Bung

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#2350906 10-Nov-2019 07:03

If you pull a switch apart you can see that the contacts are designed to have a definite make or break action. They "snap" closed or open to minimise any arcing. At the beach we have a frequent ant problem. Ants get between the contacts and get zapped. The dead ants release an acid that signals intruder to other ants who swarm to heip and they also get zapped. Soon you have a paste of dead ant that stops the contact working. Time to replace the switch or socket with a spare.

SirHumphreyAppleby

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#2350912 10-Nov-2019 08:15

Technology Connections has a recent video on why switches click...

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#2350919 10-Nov-2019 09:04

Bung: If you pull a switch apart you can see that the contacts are designed to have a definite make or break action. They "snap" closed or open to minimise any arcing.

It's possible the quick make/break action can fail. Personally I haven't seen it. The switch would feel and sound very different in failure.

gzt

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#2350920 10-Nov-2019 09:12

quebec: It’s a 4 way light switch and the one sparking is controlling the security sensor flood lights.

Incandescent or LED with transformers?

quebec

852 posts

Ultimate Geek

#2350995 10-Nov-2019 11:08

gzt:
quebec: It’s a 4 way light switch and the one sparking is controlling the security sensor flood lights.

Incandescent or LED with transformers?

Incandescent Philips 120W 2 bulbs on a philips sensor light. Switch is PDL 600 series. Other 3 switches don’t spark. Two LED wall lights, 1 philips hue downlight, 2 9W standard LED bulbs controlled by each of them.

Rikkitic

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#2351085 10-Nov-2019 11:26

Filament bulbs draw a lot more power than LEDs. The bigger the current flow, the bigger the spark when the circuit is broken. Still nothing wrong with it. The switches are designed to handle it.

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sir1963

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#2351113 10-Nov-2019 12:23

quebec:
gzt:
quebec: It’s a 4 way light switch and the one sparking is controlling the security sensor flood lights.

Incandescent or LED with transformers?

Incandescent Philips 120W 2 bulbs on a philips sensor light. Switch is PDL 600 series. Other 3 switches don’t spark. Two LED wall lights, 1 philips hue downlight, 2 9W standard LED bulbs controlled by each of them.

When incandescent lamps are cold their resistance is MUCH lower.

So two 120W lamps = 240W which is close to 1A when running.

At turn on time they can draw up to 8-10 times the run current (in this case about 10A) depending on what part of the AC cycle they come on at.

Switches all bounce when they are turned on, not much, but enough to draw a small arc.

However, here is the thing. If you are concerned, replace the switch , they are cheap enough. If it is going to bring you peace of mind for the price of about 2 cups of coffee then what the hell, do it.

mattwnz

20155 posts

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#2351138 10-Nov-2019 13:55

Can you get LED bulbs to replace them with as they should draw a lot less power? At some stage incandescents will likely be phased out. Labour tried to do it when they were last in governemet under HC, but were voted out before it came in, so I suspect that will occur again.

Tracer

343 posts

Ultimate Geek

#2351816 11-Nov-2019 18:25

Rikkitic:

Filament bulbs draw a lot more power than LEDs. The bigger the current flow, the bigger the spark when the circuit is broken. Still nothing wrong with it. The switches are designed to handle it.

Actually resistive loads are the best case. Inductive loads (flourescent lamp ballasts, LED power supplies, etc.) draw much larger arcs. The inductor opposes the change in current, and can cause quite high voltages across the arc gap, prolonging the arc.

Rikkitic

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#2351833 11-Nov-2019 19:02

Tracer:

Actually resistive loads are the best case. Inductive loads (flourescent lamp ballasts, LED power supplies, etc.) draw much larger arcs. The inductor opposes the change in current, and can cause quite high voltages across the arc gap, prolonging the arc.

As I said, the bigger the current flow, the bigger the spark when the circuit is broken.

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