Why does an isolating transformer in a shaver socket prevent shock?

[Adz]

I was told that a shaver socket has an inbuilt isolating transformer to prevent electric shock. But surely if someone touched Live and Neutral at the same time, at the socket outlet, they would get a shock? Can someone explain... thanks..

 

[montoyas7940]

Receptacles located in bathrooms, such as a shaver might be plugged into, should have GFCI capability. You might see a push to test and reset button on the receptacle. Or the breaker supplying the receptacle might be GFCI. GFCI means ground fault circuit interrupting. If the GFCI device detects current leaking to ground it opens the circuit stopping the current flow.
You could still kill yourself getting between the two legs of the supply. But if current were flowing through you to ground the GFCI would trip.

 

[Danger]

I believe that Adz is referring to the original 'razor only' sockets which were the only ones allowed in bathrooms up until a couple of decades ago. A quick Google brought up this explanation.
jkogel
Active Poster


Location: Sooke, BC
Posts: 177
Re: Razor only outlets
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Quote:
Originally Posted by Mark Nicholet
Thanks, I think it would be good idea to recommend replacement with GFI. But, how does this 'razor only' low volt transformer outlet prevent a shock hazard by being isolated from ground? I would think it would increase shock hazard if there is no ground.

Mark, the isolation transformer consists of 2 coils insulated from each other. 120 volts from the household circuit running thru 1 coil produces 120 volts in the secondary coil. You could still shock yourself by touching both of the output terminals. But there is no electrical potential between one of the output terminals and ground, as there is with conventional wiring because it is a little isolated mini-circuit. Drop it in the tub, theoretically no shock!

As for the lack of ground, most razors and hair dryers are 2-prong devices anyways, no ground wire to the chassis, but the plastic body provides insulation.

I'm not sure if it's legitimate to quote someone from another forum without permission, so this might get deleted.

 

[montoyas7940]

Cool, thanks. I have never seen one.

 

[Adz]

cheers thats, that's exactly what i was thinking.

 

[stewartcs]

I was told that a shaver socket has an inbuilt isolating transformer to prevent electric shock. But surely if someone touched Live and Neutral at the same time, at the socket outlet, they would get a shock? Can someone explain... thanks..

The isolation transformer electrically decouples the circuit. Essentially, the ground that the utility company provides (at the pole or pad transformer) does not get passed across the transformer (hence the name). Thus one cannot receive an electrical shock from touching only the hot wire will grounded to the earth. However, if one completes the circuit by touching the hot and the return wire then one will indeed receive an electrical shock.

CS