Transformers + electric razors

I live in the UK and have a query regarding bathroom sockets for electric
razors: why do they always have a transformer in them?
My electric razor says it works on 240V. Given that UK mains is also 240V,
why the transformer? I have successfully used it off a normal mains socket
(via a simple 3-pin to 2-pin adapter) with no transformer.
Harrison
Reply to
Harrison Bored
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It's an isolating transformer, so the supply to your razor is floating and not tied to ground. This means that if the razor develops a fault and you come into contact with wiring in it, you can't get an electric shock which travels through your body to ground. Sockets fitted in bath/shower rooms require such isolating transformers in the UK. A shaver socket fitted somewhere else (such as in a bedroom) does not require an isolating transmforer.
Reply to
Andrew Gabriel
I am pretty sure that the motor inside is not 240v. I know that my electric shaver here in the USA motor not 120v.
Reply to
SQLit
The isolating transformer is part of the fixed socket outlet in UK bathrooms, not part of the shaver. It is only required when using the shaver in a wet room (containing a shower or bath). There's nothing stopping you fitting an isolating socket anywhere else if you want to (and sometimes people do), but normally regular non- isolating shaver sockets are used in rooms which don't contain a bath or shower.
Reply to
Andrew Gabriel
Interesting what different countries use to solve the same problem. What is the rating of the transformer? Locally fused? Recessed in wall? What if you want to plug in a heater (high Watt) in bathroom?
As you probably know, the US-NEC uses GFCIs (ground fault circuit interrupters) that trip at 5 mA ground fault currents for safety in bathrooms, kitchens, .... Doesn't the UK have a similar device?
(Hate to pick on you, but you post such great answers. Thanks.)
Bud--
Reply to
Bud
The socket has to be limited to something like 30W (I can't remember what the exact figure is). A slow acting self- resetting thermal trip is integral with the transformer. The socket is supposed to be used only for electric shavers, toothbrushes, etc.
In addition to the 240V socket, there's usually a 120V 2-prong US socket included for visitors. Since there's a transformer in there anyway, providing a 120V outlet too adds nothing to the cost. The shutters on the sockets also operate a switch which disconnects the transformer primary when there's nothing plugged in, and provide an interlock to prevent both the 120V and 240V sockets being used together (or sometimes that's done by having the two sockets partially overlap and sharing one of the prong holes).
Normally yes. They fit in our standard double width patress modules, although they require the deepest size box.
Strictly forbidden. It's not allowed to have sockets for portable appliances in bathrooms (except for the shaver socket). You can have a fixed electric heater in the bathroom, providing it was designed for the purpose -- that's quite common.
We do, but they aren't acceptable in wet rooms. I think there's a philosophy difference in that GFI's can be added to a circuit to improve safety in the UK, but are never allowed to be relied upon as the primary safety device because they don't fail-safe. The use of isolating transformers in bathrooms goes back before GFI's in any case.
GFIs are required for any sockets which might be used to supply portable appliances outdoors (even if the socket isn't outdoors). It's more common to have the GFI in the panel rather than in the socket, although socket based ones are available. One thing you have which we don't is that your GFI sockets can protect further downstream sockets (at least in some cases) -- ours never do that.
I don't mind at all.
Reply to
Andrew Gabriel
Electric razor motors come in many voltages. The early ones used a "universal" motor for 120V in the US. Some had a switch for 240V. Some recent ones use a "tuned armature" which vibrates at the line, (mains), frequency and drives the razor cutter. These are either 120V or 240V, some with a switch. I have used US made, (60 cycle), razors in the UK, at the proper voltage, and they do work on 50 cycles, but not as well.
The battery operated razors use a low voltage motor, and the batteries are charged from the line voltage. These may have an input that will work on 120/240V.
As has been stated, the UK code requires an isolating transformer in bathrooms. Many UK hotels combine this with a USA type 120V socket and a switch to choose 120 or 240 volts. I still remember the time I changed rooms in a London hotel, and forgot to set the voltage in the new bathroom! 120V motors run on 240V, but not for long.
Reply to
VWWall
| |> I live in the UK and have a query regarding bathroom sockets for electric |> razors: why do they always have a transformer in them? |> |> My electric razor says it works on 240V. Given that UK mains is also 240V, |> why the transformer? I have successfully used it off a normal mains socket |> (via a simple 3-pin to 2-pin adapter) with no transformer. | | It's an isolating transformer, so the supply to your razor is | floating and not tied to ground. This means that if the razor | develops a fault and you come into contact with wiring in it, | you can't get an electric shock which travels through your | body to ground. Sockets fitted in bath/shower rooms require | such isolating transformers in the UK. A shaver socket fitted | somewhere else (such as in a bedroom) does not require an | isolating transmforer.
You call it a "shaver socket". Is it different than the usual outlet in UK?
Reply to
phil-news-nospam
| "Harris|>I have successfully used it off a normal mains socket (via a simple 3-pin |>to 2-pin adapter) with no transformer. | | You are risky man. It would be better if you restore an isolating | transformer. It is your safety.
If he is using a socket with no isolation transformer, but it is located away from a grounded water basin, he should be relatively safe. The big risk exists in the bathroom where contact between a faulty razor and the water which is probably grounded can complete a loop to the power source perhaps with low enough impedance to get a good 5 milliamp or greater shock (46000 ohms or less).
In the USA, a similar isolation transformer that also reduces the voltage to 30 volts or less is required for lighting circuits with exposed wiring, such as track lights hanging directly on the conductors. While one could get a little ping at the low voltage (usually 12 volts) level between the conductors, at least they won't get the big whack from 120 volts (or worse in places like Russia and UK with 220 to 240 volts).
Reply to
phil-news-nospam
| |> Interesting what different countries use to solve the same problem. |> What is the rating of the transformer? |> Locally fused? | | The socket has to be limited to something like 30W (I can't | remember what the exact figure is). A slow acting self- | resetting thermal trip is integral with the transformer. | The socket is supposed to be used only for electric shavers, | toothbrushes, etc.
Obviously not hair dryers, then.
| In addition to the 240V socket, there's usually a 120V | 2-prong US socket included for visitors. Since there's a | transformer in there anyway, providing a 120V outlet too | adds nothing to the cost. The shutters on the sockets also | operate a switch which disconnects the transformer primary | when there's nothing plugged in, and provide an interlock | to prevent both the 120V and 240V sockets being used | together (or sometimes that's done by having the two sockets | partially overlap and sharing one of the prong holes).
Nice feature. Maybe I should import some for my own use in the USA. Our 60 Hz should be OK on the transformer. I'm not going to worry about the NEC 210.6(A)(2) violation since it would be just for visitors.
Reply to
phil-news-nospam
Yes. I think it's actually a very old 2-pin plug from the 1920's. It's similar but not quite identical to the 2-pin plugs used in much of Europe which fit in the Shuko and French/Belgium sockets. The shaver sockets are designed to accept all these nowadays, and the US plug and some other 2-pin plug with two diagonal blades which I've never actually seen. For some of the units, the US 2- prong plug will only go in the 120V side, but on others it will plug into the 240V side also.
I could take some pictures of a few different makes over a few days if people are interested in the different arrangements.
Reply to
Andrew Gabriel
MK (one of the higher quality brands in the UK) do actually make these with 120V mains input, presumably intended for export somewhere.
Reply to
Andrew Gabriel
Here's a link to the 120V version (part number K706)...
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It's also available in a number of other finishes (search for part number K24710 on their homepage, although they seem to have copied the description for the 240V versions and not changed the voltage).
Reply to
Andrew Gabriel
These were common (known as razor outlets) in the US at one time (required by code). They do date back before ground fault interruptors. European ones, as Gabriel has mentioned, particularly in hotels, have a center tapped secondary to provide 120/240 isolated service. Power capability is limited by the size of the isolating transformer -usually small 100-250 watts max The usual UK outlet "neutral" grounded on one side just as the usual US/Canada outlets- these just isolate one from the ground connection for safety.--
Don Kelly @shawcross.ca remove the X to answer ----------------------------
Reply to
Don Kelly
----------------------------
--------------- I think that you have brought up an important point here. UK systems tend to be much more heavily designed than North American ones with regard to safety, possibly because of the use of 240V vs 120. Compare the construction of a UK outlet, switch or lamp socket to a typical North American design. If they were outhouses, the UK ones would be made of brick.
Differences in design philosophy - possibly less emphasis on the bottom line and more on safety. Overkill - maybe, maybe not. You can make something foolproof but not damnfool proof. This used to extend to panels as well. The story is that Square D tried to start up in the UK, without success, until they resurrected old designs (cast iron, 47 bolts to hold the cover on, etc) :)
Reply to
Don Kelly
How about Phil's other question - hand held hair driers. In the US they are even common in motels.
And what is and isn't mains.
Know of any wiring-practices web sites. This and the other recent thread are really interesting.
Bud--
Reply to
Bud

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