Shaver sockets - how safe?

[davetheglitz]

I've been asked to add shaver sockets to a classy holiday let in two bathrooms. Wired to the 16th edition. Would like classy bright chrome fittings.

Thoughts - backed up by NAPIT inspector - insulated shaver socket - no problem - transformer isolated. Metal faced - into RCBO / supplementary territory. Bit dodgy However - suspect both fittings are to the same British Standard (but don't know for sure).

I've been thinking about the failure modes of a transformer. If the primary and secondary are isolated then by nature the Line and Neutral currents will be balanced. However if there is a short on the line side between primary and secondary - which would be feasible - then there would be no protection for the customer unless the circuit was on RCB.

Even if the circuit was RCB protected, If there was a fault on the appliance making the secondary live connect to the metal blades, the RCB would never trip as the currents are balanced with respect to the primary. Could this deliver a fatal shock with respect to earth?

Is it right to add a shaver socket without an RCB/RCBO upgrade - or is it right to add a shaver socket at all!

Any opinions?

 

[Apache]

Does anyone actually use a shaver socket?

 

[batty]

Does anyone actually use a shaver socket?

Yes Paddy to plug electric toothbrush into.

Batty

 

[SPECIAL LOCATION]

Does anyone actually use a shaver socket?

Yes...

I know loads of people, our house included...

to plug in the charger for the electric toothbrush!

 

[SPECIAL LOCATION]

Yes Paddy to plug electric toothbrush into.Batty

PUSHY SHOVEY!!!

that'll be the red wine effecting me fingers!!!

p.s.

may not be able to make tea and cake tomorrow if the weather is a bit snowey...

may have to leave it till next week..

double portions of cake though!!! :^O :^O:^O

 

[Apache]

Ok - I have electric toothbrush but use an adapter in a normal socket

 

[batty]

PUSHY SHOVEY!!!that'll be the red wine effecting me fingers!!!

p.s.

may not be able to make tea and cake tomorrow if the weather is a bit snowey...

may have to leave it till next week..

double portions of cake though!!! :^O :^O:^O

No tea making tomorrow working local for a couple of weeks. Handy with weather as it is.

Batty

 

[batty]

Ok - I have electric toothbrush but use an adapter in a normal socket

Better in bathroom though.

 

[SPECIAL LOCATION]

I've been asked to add shaver sockets to a classy holiday let in two bathrooms. Wired to the 16th edition. Would like classy bright chrome fittings.Thoughts - backed up by NAPIT inspector - insulated shaver socket - no problem - transformer isolated. Metal faced - into RCBO / supplementary territory. Bit dodgy However - suspect both fittings are to the same British Standard (but don't know for sure).

I've been thinking about the failure modes of a transformer. If the primary and secondary are isolated then by nature the Line and Neutral currents will be balanced. However if there is a short on the line side between primary and secondary - which would be feasible - then there would be no protection for the customer unless the circuit was on RCB.

Even if the circuit was RCB protected, If there was a fault on the appliance making the secondary live connect to the metal blades, the RCB would never trip as the currents are balanced with respect to the primary. Could this deliver a fatal shock with respect to earth?

Is it right to add a shaver socket without an RCB/RCBO upgrade - or is it right to add a shaver socket at all!

Any opinions?

Short between primary & secondary without involving the chunky metal core causing some fuse blowing short circuit potential?

or magically becoming an autotransformer not an isolating transformer..

unlikely? IMHO

The secondary windings are not part of the earth fault loop path..

Magnetically isolated.

Current only flows in secondary when secondary loop circuit complete,

potential difference only relative between the two ends of the secondary winding.

Could be consider similar to a genertor....

output has no relative potential to earth, only to its own output terminals.

can't see how symptoms you suggest could realistically happen? ?:|

 

[SPECIAL LOCATION]

Ok - I have electric toothbrush but use an adapter in a normal socket

Can you make it run backwards though!? ]B-)

 

[Apache]

Can you make it run backwards though!? ]B-)

no - but would make no difference!

 

[davetheglitz]

Short between primary & secondary without involving the chunky metal core causing some fuse blowing short circuit potential?or magically becoming an autotransformer not an isolating transformer..

unlikely? IMHO

Not so sure about that. With a conventional mains stepdown transformer traditionally the primary would be wound first, then the secondary.

For 1:1 transformers for isolation the primary and secondary are often wound together - either in layers or in a lump. If that is the case then the short is a possibility. Perhaps this technique isn't used for mains transformers - only audio types.

By the way I meant RCD/RCBO not RCB/RCBO - red wine again!

The secondary windings are not part of the earth fault loop path..Magnetically isolated.

Current only flows in secondary when secondary loop circuit complete,

potential difference only relative between the two ends of the secondary winding.

Could be consider similar to a genertor....

output has no relative potential to earth, only to its own output terminals.

can't see how symptoms you suggest could realistically happen?

Yep - another moment of clarity from SL! Should have thought this through myself! Even more red wine!

 

[Evans Electric]

As said above, the secondary is isolated from the mains so there is no earth reference and is deemed safe for bathroom use. Its an induced voltage isolated from earth, your test lamps would not read between the shaver plug and the plate. The chrome plate , in my experience, is connected to the earth of the primary feed cable. Under the 16th/ 17th editions you have to RCD the supply anyway as its a bathroom, so you you should be good to trot with it.

Deke

 

[nemesis]

Just been on the 2382 course and it was said that for an isolating transformer the primary and secondary windings are isolated from each other physically, so there should be no short between the primary and secondary windings.