Hi all

I have extended the ring main into a cupboard in my bathroom to power some shaver sockets. As part of the ring I need to power some 12v led strip lights.

I was planning on using a standard light switch with the following wiring
- connect the 2 neutrals from the ring to the neutral of the transformer
- connect both lives of the ring to one side of the switch
- connect the live of the transformer to the other side of the switch.
- transformer does not require earth so connect the 2 earth's of the ring together.

For some reason I think I have missed something so wanted to double check with you guys just in case.

Thanks in advance

Lee.

In article ,
wrote:
Hi all

I have extended the ring main into a cupboard in my bathroom to power
some shaver sockets. As part of the ring I need to power some 12v led
strip lights.

I was planning on using a standard light switch with the following wiring
- connect the 2 neutrals from the ring to the neutral of the transformer
- connect both lives of the ring to one side of the switch - connect the
live of the transformer to the other side of the switch. - transformer
does not require earth so connect the 2 earth's of the ring together.

For some reason I think I have missed something so wanted to double check
with you guys just in case.

This should be done through a fused spur.

--
from KT24 in Surrey, England

wrote:

For some reason I think I have missed something

You won't have any fuse between the (32A MCB?) protecting the ring and
the transformer. I'd use a switched FCU instead of a light switch,
there will be separate load L/N terminals to feed the light transformer.

Thanks both. Funny how gut feel sometimes saves us My gut said this wasn't right but couldn't see why. Glad I checked as you are spot on. Thanks.

charles wrote:

In article ,
wrote:
Hi all

I have extended the ring main into a cupboard in my bathroom to power
some shaver sockets. As part of the ring I need to power some 12v led
strip lights.

I was planning on using a standard light switch with the following wiring
- connect the 2 neutrals from the ring to the neutral of the transformer
- connect both lives of the ring to one side of the switch - connect the
live of the transformer to the other side of the switch. - transformer
does not require earth so connect the 2 earth's of the ring together.

For some reason I think I have missed something so wanted to double check
with you guys just in case.

This should be done through a fused spur.

Should not the already-fitted shaver socket have a fused switch too?
Bad style, but could not the both transformers be on the same spur if
they are adjacent?

--

Roger Hayter

In article ,
Roger Hayter wrote:
Should not the already-fitted shaver socket have a fused switch too?
Bad style, but could not the both transformers be on the same spur if
they are adjacent?

It's more usual to run a shaver socket from the lighting circuit. Cable
for that is cheaper - and often a shorter run than from a ring, which
wouldn't usually be already in the bathroom.

--
*Certain frogs can be frozen solid, then thawed, and survive *

Dave Plowman London SW
To e-mail, change noise into sound.

Unless the transformer alread has a fuse as some seem to these days. One
thing that has annoyed me though about transformers is how badly some of
them buzz, particularly when mounted on a woooden surface. Can we really not
make normal mains transformers that are silent any more. I don't like
switch mode as then they run they kick out crap and when they fail you find
they tend to go bang!
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"charles" wrote in message
...
In article ,
wrote:
Hi all

I have extended the ring main into a cupboard in my bathroom to power
some shaver sockets. As part of the ring I need to power some 12v led
strip lights.

I was planning on using a standard light switch with the following wiring
- connect the 2 neutrals from the ring to the neutral of the transformer
- connect both lives of the ring to one side of the switch - connect the
live of the transformer to the other side of the switch. - transformer
does not require earth so connect the 2 earth's of the ring together.

For some reason I think I have missed something so wanted to double check
with you guys just in case.

This should be done through a fused spur.

--
from KT24 in Surrey, England

But are the shaver outlets fused too?
Most shaver adaptors have fuses after all.(Except the one I recently bought
which is crap)
Brian

--
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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Andy Burns" wrote in message
...
wrote:

For some reason I think I have missed something

You won't have any fuse between the (32A MCB?) protecting the ring and the
transformer. I'd use a switched FCU instead of a light switch, there will
be separate load L/N terminals to feed the light transformer.

The shaver sockets are these
https://www.amazon.co.uk/GREENBROOK-...=Shaver+socket

Wired directly into the ring main with no additional fuse other than the one in the MCU

On 25/11/2017 09:23, wrote:
The shaver sockets are these
https://www.amazon.co.uk/GREENBROOK-...=Shaver+socket

Wired directly into the ring main with no additional fuse other than the one in the MCU

Maybe the transformer limits the current so a dead short won't do any
damage to the supply or itself.

--
Max Demian

Max Demian wrote:

On 25/11/2017 09:23, wrote:
The shaver sockets are these
https://www.amazon.co.uk/GREENBROOK-...-Sockets/dp/B0
04ZQFBTK/ref=sr_1_5?ie=UTF8&qid=1511601677&sr=8-5&keywords=Shaver+socket

Wired directly into the ring main with no additional fuse other than the
one in the MCU

Maybe the transformer limits the current so a dead short won't do any
damage to the supply or itself.

Unless it has an actual fuse that can safely break a current of tens of
Amps (unlikely) then it can't be relied upon to do this.

--

Roger Hayter

On 25/11/2017 13:31, Roger Hayter wrote:
Max Demian wrote:

On 25/11/2017 09:23, wrote:
The shaver sockets are these
https://www.amazon.co.uk/GREENBROOK-...-Sockets/dp/B0
04ZQFBTK/ref=sr_1_5?ie=UTF8&qid=1511601677&sr=8-5&keywords=Shaver+socket

Wired directly into the ring main with no additional fuse other than the
one in the MCU

Maybe the transformer limits the current so a dead short won't do any
damage to the supply or itself.

Unless it has an actual fuse that can safely break a current of tens of
Amps (unlikely) then it can't be relied upon to do this.

I was thinking of a transformer with low regulation (for example by
having the primary and secondary coils on different arms of the core),
so the voltage would drop as the load increased.

--
Max Demian

Max Demian wrote:

On 25/11/2017 13:31, Roger Hayter wrote:
Max Demian wrote:

On 25/11/2017 09:23, wrote:
The shaver sockets are these
https://www.amazon.co.uk/GREENBROOK-...-Sockets/dp/B0
04ZQFBTK/ref=sr_1_5?ie=UTF8&qid=1511601677&sr=8-5&keywords=Shaver+socket

Wired directly into the ring main with no additional fuse other than the
one in the MCU

Maybe the transformer limits the current so a dead short won't do any
damage to the supply or itself.

Unless it has an actual fuse that can safely break a current of tens of
Amps (unlikely) then it can't be relied upon to do this.

I was thinking of a transformer with low regulation (for example by
having the primary and secondary coils on different arms of the core),
so the voltage would drop as the load increased.

Shorted turns in the primary (common transformer fault) might dissipate
several kilowatts, to be replaced rapidly by a low resistance carbon
skeleton of the plastic parts which will continue to dissipate several
kilowatts without upsetting the 32A MCB, nor necessarily giving any
earth leakage. By the time the studs are burning it probably doesn't
help if the wires fall off.




--

Roger Hayter

Unfortunately I had to break into the ring as this also supplies a whirlpool bath in the same room

I ended up using a fused spur as suggested above

It happens that Max Demian formulated :
I was thinking of a transformer with low regulation (for example by having
the primary and secondary coils on different arms of the core), so the
voltage would drop as the load increased.

and if the primary or the supply cable develops a short?

It needs a suitable fuse before branching from the ring.

In article ,
Harry Bloomfield wrote:
It happens that Max Demian formulated :
I was thinking of a transformer with low regulation (for example by
having the primary and secondary coils on different arms of the
core), so the voltage would drop as the load increased.

and if the primary or the supply cable develops a short?

It needs a suitable fuse before branching from the ring.

I'm actually surprised the terminals in a shaver transformer are big
enough for 2 x 2.5mm.

--
*Why do overlook and oversee mean opposite things? *

Dave Plowman London SW
To e-mail, change noise into sound.

Hi All

I got a bit confused as to which transformers we are talking about the shaver socket ones or the led light one? Are you saying that both need to be fed from a fused spur? I have never noticed shaver sockets been done this way before.

Thanks

Lee.

wrote:

Hi All

I got a bit confused as to which transformers we are talking about the
shaver socket ones or the led light one? Are you saying that both need to
be fed from a fused spur? I have never noticed shaver sockets been done
this way before.

Thanks

Lee.

That's probably because they are usually supplied from the lighting
circuit, which is fused at 6 or perhaps 10 amps. I rhink they should be
on fused spur if supplied from a 32A circuit (though I am not an
electrician). Equally, if they are near together, I would supply both
transformers from the same fused spur. I thing that is, at worst, a
mild stylistic fault, especially if their combined maximum current is
well under 3A.




--

Roger Hayter

On 26/11/2017 15:36, Roger Hayter wrote:
Equally, if they are near together, I would supply both
transformers from the same fused spur.

AIUI distance doesn't come into it. Downstream of the FCU you can have
any number of accessories and any length of cable providing the total
load doesn't draw a current exceeding the fuse rating and the cable is
adequate for the current.

--
Mike Clarke

Mike Clarke wrote:

On 26/11/2017 15:36, Roger Hayter wrote:
Equally, if they are near together, I would supply both
transformers from the same fused spur.

AIUI distance doesn't come into it. Downstream of the FCU you can have
any number of accessories and any length of cable providing the total
load doesn't draw a current exceeding the fuse rating and the cable is
adequate for the current.

Isn't there something in the regs about having a convenient (in terms of
distance and not switching anything else vital off) isolation switch for
servicing purposes, or is that just good practice? Or am I thinking of
WRAS?

--

Roger Hayter

On 26/11/2017 17:56, Roger Hayter wrote:
Isn't there something in the regs about having a convenient (in terms of
distance and not switching anything else vital off) isolation switch for
servicing purposes, or is that just good practice?

I think that relates to hard wired appliances which might need to be be
serviced in situ, like ovens, boilers and extractor fans. There's hardly
any servicing you could do to the transformers other than replacing them
so from that point of view they're no different from a plug socket. If
you felt the need to be able to isolate them then use a switched FCU
instead of a plain one.

--
Mike Clarke

On 27/11/2017 11:29, Mike Clarke wrote:
On 26/11/2017 17:56, Roger Hayter wrote:
Isn't there something in the regs about having a convenient (in terms of
distance and not switching anything else vital off) isolation switch for
servicing purposes, or is that just good practice?

I think that relates to hard wired appliances which might need to be be
serviced in situ, like ovens, boilers and extractor fans.

They don't always put the sockets/fuses in a convenient place, like my
cooker hood (13A plug and socket inside the chimney) which blew a fuse
when a lamp failed and the built-in oven (13A plug and socket behind the
oven) in which the switch (which is never used) failed. I suppose it's
neater to hide everything away.

--
Max Demian

On 25/11/2017 09:10, Brian Gaff wrote:
But are the shaver outlets fused too?
Most shaver adaptors have fuses after all.(Except the one I recently bought
which is crap)

The non isolating type usually have an internal fuse. The isolation
transformer type don't usually.

There is not usually a manufacturers requirement for additional fusing
on the isolating type.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 26/11/2017 11:14, Dave Plowman (News) wrote:
In article ,
Harry Bloomfield wrote:
It happens that Max Demian formulated :
I was thinking of a transformer with low regulation (for example by
having the primary and secondary coils on different arms of the
core), so the voltage would drop as the load increased.

and if the primary or the supply cable develops a short?

It needs a suitable fuse before branching from the ring.

I'm actually surprised the terminals in a shaver transformer are big
enough for 2 x 2.5mm.

Most will do 2 x 2.5 or 1 x 4.0. Some will do more. The BG one i rated
for 3 x 2.5 and 2 x 4.0 IIRC.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 27/11/2017 22:39, John Rumm wrote:
On 25/11/2017 09:10, Brian Gaff wrote:
But are the shaver outlets fused too?
* Most shaver adaptors have fuses after all.(Except the one I recently
bought
which is crap)

The non isolating type usually have an internal fuse. The isolation
transformer type don't usually.

There is not usually a manufacturers requirement for additional fusing
on the isolating type.

What happens to the transformer in case of overload/short?

--
Max Demian

On 27/11/2017 22:56, Max Demian wrote:
On 27/11/2017 22:39, John Rumm wrote:
On 25/11/2017 09:10, Brian Gaff wrote:
But are the shaver outlets fused too?
* Most shaver adaptors have fuses after all.(Except the one I
recently bought
which is crap)

The non isolating type usually have an internal fuse. The isolation
transformer type don't usually.

There is not usually a manufacturers requirement for additional fusing
on the isolating type.

What happens to the transformer in case of overload/short?

Many transformers have an integral thermal fuse. I would be surprised if
a shaver transformer doesn't.

In article ,
John Rumm wrote:
The non isolating type usually have an internal fuse. The isolation
transformer type don't usually.

Many transformers have a fuseable link internal to the windings. I'd
expect a shaver socket would.

--
*I didn't fight my way to the top of the food chain to be a vegetarian.

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:

In article ,
John Rumm wrote:
The non isolating type usually have an internal fuse. The isolation
transformer type don't usually.

Many transformers have a fuseable link internal to the windings. I'd
expect a shaver socket would.

Would an internal fuse successfully break a 50A fault current?

--

Roger Hayter

On 27/11/2017 22:56, Max Demian wrote:
On 27/11/2017 22:39, John Rumm wrote:
On 25/11/2017 09:10, Brian Gaff wrote:
But are the shaver outlets fused too?
Most shaver adaptors have fuses after all.(Except the one I
recently bought
which is crap)

The non isolating type usually have an internal fuse. The isolation
transformer type don't usually.

There is not usually a manufacturers requirement for additional fusing
on the isolating type.

What happens to the transformer in case of overload/short?

If its on the secondary, then it will either sit there an buzz at you
(getting hot but not much bad should happen since they are normally only
30W or similar). Or it will include a thermal fuse that will open
(possibly auto resetting if you are lucky).

If its on the primary, there is no likely overload scenario, so you only
need worry about a hard short. They are presumably designed to be robust
enough to rely on the fault protection of the circuit in those cases.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 28/11/2017 00:13, Dave Plowman (News) wrote:
In article ,
John Rumm wrote:
The non isolating type usually have an internal fuse. The isolation
transformer type don't usually.

Many transformers have a fuseable link internal to the windings. I'd
expect a shaver socket would.

Yup. The non transformer type tend to have a replaceable cartridge fuse
though. The types in the transformers are often an integral part and not
a user serviceable thing.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
Roger Hayter wrote:
Dave Plowman (News) wrote:

In article ,
John Rumm wrote:
The non isolating type usually have an internal fuse. The isolation
transformer type don't usually.

Many transformers have a fuseable link internal to the windings. I'd
expect a shaver socket would.

Would an internal fuse successfully break a 50A fault current?

They're also called thermal fuses - so I'd guess would rupture before the
windings went up in smoke.

--
*What hair colour do they put on the driver's license of a bald man? *

Dave Plowman London SW
To e-mail, change noise into sound.

"Roger Hayter" wrote in message
...
Dave Plowman (News) wrote:

In article ,
John Rumm wrote:
The non isolating type usually have an internal fuse. The isolation
transformer type don't usually.

Many transformers have a fuseable link internal to the windings. I'd
expect a shaver socket would.

Would an internal fuse successfully break a 50A fault current?

You don’t get 50A fault currents with those.