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Old 2nd April 2014, 11:26 AM   #1
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Default Mains Switch

Here I would like to post a probably silly question, but I couldn't find any info about it.

Could the toggle of a mains switch, being metal, endanger safety matters under any circumstances?

I am talking about an earthed metal box using such a switch. There are other switch types including plastic toggles as well (I have also seen them mentioned as levers). Could these be considered safer?

My guess is that for an earthed metal box, a metal toggle could not be dangerous if it makes immediate contact with the chassis, which should rest at earth potential. And if the contact/toggle insulation fails, the automatic switch of the house will go down - and nobody gets killed.

In that manner, I assume that plastic toggles are used in Class 2 appliances, where no earth potential is present, to isolate the user from mains completely.

Are the above correct? Has anyone ever heard about any exceptions?
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Old 2nd April 2014, 11:41 AM   #2
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The switch is made such that the contacts are completely insulated from any metal parts of the switch body.

Under extreme circumstances it "might" be possible for the switch contacts to vapourise and cause a carbon film to build up inside the switch. Class 2 appliances would use entirely plastic switches to prevent this causing injury. Metal enclosures MUST have their chassis connected to mains safety earth for the same protection.
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Old 2nd April 2014, 11:56 AM   #3
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Quote:
Originally Posted by KatieandDad View Post
MUST have their chassis connected to mains safety earth for the same protection.
Which should always guarantee safety then, right?
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Old 2nd April 2014, 12:30 PM   #4
DF96 is offline DF96  England
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Provided the earthing of the metal box is done properly and the mains supply is properly fused it should be safe.
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