Printable Version of Topic

Posted by: gel Aug 5 2012, 11:15 AM

3 pin electrical sockets:
Safe as they are!



Came across this www (below) which may be of interest to those with tiny tots at home.
These socket covers increasingly seen at public places eg hotel lobbies I note too:
no doubt under some Health & Safety guidance...which it seems is flawed.

http://www.fatallyflawed.org.uk

Posted by: Timbo Aug 5 2012, 11:24 AM

Particularly bored this Sunday?

Never did understand putting fake socket covers in. Always made less sense to me than when you just leave them alone.. Kind of a case of spoiling the broth by messing around with it..

Posted by: Nothing Much Aug 5 2012, 01:41 PM

Interestingly... or not. I had an outside socket installed by an electrician.
It failed after a few years. It was meant to be safe in the garden for power tools.

I dismantled it and found a failed spring. I complained and as I had only sent a partial component
I was given a brush off.

So I bought another(cheaper alternative)
Blow me down 10 months later I got a new unit in the post. I still have not installed it yet.Yes I am lazy.
No comment in the covering note.

I expect where children's fingers are concerned one would try harder.
ce

Posted by: Exhausted Aug 5 2012, 04:10 PM

'A few years', tell me you really didn't really bother to get a replacement under warranty for an object that only cost a couple of quid after you spent time taking it apart. You really do lead an exciting life.

I have always maintained that those socket blanks are dangerous. What is more dangerous however are people who overload sockets and damage them and then do not get them replaced.

Posted by: Nothing Much Aug 5 2012, 04:41 PM

Fair comment the original was £ 150.00 The alternative was about £90.00. My kids are bigger than me. Only use it for music.
No fingers are involved
The chap who takes care of the garden has a proper cable as well with stuff.. So he is safe.
it had all sorts of funny electrical blockings . I really should put it back. RCDs I think.I like my chainsaw so perhaps a job for the summer! When that happens.
ce

Posted by: user23 Aug 5 2012, 05:43 PM

I'm not sure people should be giving electrical advice unless they're qualified to do so.

Posted by: Nothing Much Aug 5 2012, 06:23 PM

Probably why it has been in a jiffy bag for a few years.
ce

Posted by: massifheed Aug 6 2012, 08:35 AM

It's the information on the website that seems to be flawed to me. Their arguments against socket covers seem to be that many covers can be easily removed by children, and also that UK sockets don't need any extra protection as they have safety built in.

I have kids and do indeed use socket covers at home. The main reason for this is because (even though the website suggests it's very difficult) it's actually increadibly easy to defeat the earth pin 'safety' feature they are banging on about with a lot of items that kids may be able to get their hands on. I tried it with the lid of a biro and, sure enough, it's possible to get the pen lid to stay in the socket therefore exposing the live and neutral parts. With a decent socket cover this can't happen.

As far as socket covers being easily removable goes, I'm sure common sense on the part of the adult installing them would solve this perceived problem. If you install a socket cover and it's loose, remove it and get one that fits!

Posted by: On the edge Aug 6 2012, 09:05 AM

Perhaps we ought to start thinking about lower and therefore safer voltages. Quite feasible and experiments seem to be ongoing. Maybe new build initially.

Posted by: Biker1 Aug 6 2012, 09:09 AM

I presume you are thinking of 110V?

The cost of this would be phenomenal and may be logistically almost impossible.
You would have to change the whole of the UK electricity distribution system and, at the same time, change every electrical appliance, right down to the last light bulb.
You would also probably have to re-wire most, if not all premises, as lower voltage appliances take more current and would therefore need more heavy duty wiring.
All at the same time!!

Posted by: dannyboy Aug 6 2012, 10:01 AM

You can easily run a 240v appliance on 110v supply. It just does not work as fast.

Don't do it the other way round though....

Posted by: On the edge Aug 6 2012, 10:42 AM

Now take that one stage further. Most electronic appliances run on about 50v DC - which means they need transformers to use 'mains' voltages. That means TVs, computers, radios etc etc. all 'waste' energy converting. LED lights work LV DC as well. So, you could have an internal wiring at 12v DC - just right for micro generation....

May be just a dream but distinct possibilities and far far safer! Of course, the big stuff (washers / cookers) would need a bigger oomph - but that's just how they do it in the States. Ovens there are often 3 phase.

Posted by: JeffG Aug 6 2012, 10:42 AM

So the only effect on a TV set would be that everything is in slow motion, right? Yes, my comment is just as silly as your statement.

Posted by: dannyboy Aug 6 2012, 11:05 AM

Certain applicances. Such as a 240v drill. I have done it.

If you under volt an electric lamp, ie stick a 240v 100w lamp in a 110v circuit it will last far far longer than if in a 240v circuit. It won't give off as much light mind....

Posted by: Biker1 Aug 6 2012, 11:45 AM

--

Posted by: Biker1 Aug 6 2012, 11:45 AM

If you plugged 240V appliances with high current drain such as washing machines, dishwashers, electric fires etc. into 110V the current drain would be so high it would blow all the circuit breakers in your house!
It is HIGHLY DANGEROUS to plug an appliance matched to a certain voltage into a different voltage supply be it higher or lower voltage.
Always match the appliance to the supply voltage!

Posted by: dannyboy Aug 6 2012, 11:47 AM

LOL, I didn't say it wasn't without danger......see them cables glow.....

Posted by: Biker1 Aug 6 2012, 11:47 AM

Posted by: On the edge Aug 6 2012, 12:25 PM

Can do you a nice re chargeable electric drill - but you'd get one cheaper at B&Q!

On the voltage difference front, we can get lulled into a sense of false security as many small appliances are dual voltage - particularly the 'travel ' stuff. My reasonably new Philishave is just plug and go.

Posted by: JeffG Aug 6 2012, 02:15 PM

Sorry, but that is absolute nonsense. I suggest you need to revise http://www.kpsec.freeuk.com/ohmslaw.htm

Posted by: Biker1 Aug 6 2012, 02:34 PM

I understand what you are getting at Jeff and it seems you are correct for a 240V appliance plugged into 110V.
However, you would get half the power out of it.
To get the same POWER out of an appliance you need more current the less voltage so my theory that you would need a re-wire for 110V appliances still applies.
See http://www.kpsec.freeuk.com/power.htm from the same site.

Posted by: dannyboy Aug 6 2012, 02:36 PM

you would get half the power out of it
exactly.

Posted by: gel Aug 6 2012, 03:26 PM

We're on overhead supply lines and get occasional cuts, sometimes for several hours;
sometimes before it happens voltage drops to around half of normal, and some domestic appliances such as fridges/freezers make a most peculiar noise at this below par voltage.
SSE always recommend you switch them off to prevent damage.

Posted by: Andy Capp Aug 6 2012, 03:45 PM

I read this with some interest. It seems different apparatus will react differently. Lower voltage could result in higher current, and therefore burned out motors.

http://en.wikipedia.org/wiki/Brownout_%28electricity%29

Posted by: Biker1 Aug 6 2012, 04:14 PM

That's basically what I said and I was advised to re-check Ohm's Law!

Posted by: Exhausted Aug 6 2012, 05:18 PM

Ohm's law works for DC resistance and voltage. It does not take into account calculations for AC voltage and impedance, the AC version of resistance. It also doesn't take into account induction motors which will require more current as the speed drops with a drop in AC voltage. So, you don't need to check that law as with AC circuits, it doesn't apply.
Canada seems to operate dual voltage in their domestic properties as far as I can make out from Holmes on Homes. That said, their hardware, sockets etc seem to be poorly designed.

The best bet for safety is to have a new mains board installed by a qualified electrician with built in RCD's which are now standard and will trip at the slightest imbalance.

The current regulations are very strict and for good reason. The message is, don't take chances, your life may depend upon it.

Posted by: JeffG Aug 6 2012, 07:09 PM

No, assuming an electric fire, which is a resistive load, you would get a quarter of the power out of it. Or more accurately, (110/240) squared, which is 21%.

I have just spotted Exhausted's post, and Ohm's law does apply for resistive loads (an electric fire was one of your examples). AC voltages are quoted as RMS values (not peak), which means you can directly apply Ohm's law.

Power (watts) is voltage (volts) times current (amps). If you halve the voltage, you halve the current too, which is why it's a square law. Put another way, Power is voltage squared divided by resistance.

This all comes from Ohm's law.

Obviously, if you want to run an electric fire to give the same power output on half the voltage, it needs to have a quarter of the resistance, and the current will be doubled. But it's not the same appliance!

Posted by: Exhausted Aug 6 2012, 08:18 PM

Yes, I agree simplified....

A 2kw electric fire has an approx resistance of 29ohms
With 240v RMS applied it will draw 8.4amps = 2016 watts
With 110v RMS applied it will draw 3.8amps = 418 watts


I was careful to apply the word impedance to the AC circuit when using inductive loads.Transformers, motors, flourescent lights etc as that does confuse ohms law. (Power factor).

Posted by: dannyboy Aug 6 2012, 08:21 PM

fact remains you can plug in 240v equipment to a 110v supply and get it to 'function'. ( not that I'm suggesting anyone should on a regular basis ).

Posted by: Exhausted Aug 6 2012, 08:47 PM

Yes, I guess the family could all huddle around the electric fire with a quarter the heat output so what's the point. If you are talking about personal safety, the killing effect of 110v to earth is not that much different from 240v unless you use an isolating transformer. On the mains system, the Neutral line is at the same potential as the earth line but a low current connection from the phase line to earth through a body will be detected by an RCD trip as an imbalance and will instantly trip out. A shock but not a death. So, you pay your money you take your choice. I know that my trips work and protect me and my family from death by electrocution, not bits of plastic plugged into the sockets.

Posted by: Exhausted Aug 6 2012, 08:56 PM

Just one last item which will put the low voltage system into perspective.

If I use a 3Kw microwave (that's 3kw input not microwave output) it will draw from the 240 volt mains 12.5 amps. Lowish current andwill use basic 3 core cable. If I want to use an equivalent microwave on 24volts it would draw 125 amps for the same output. That would be car starter cable to carry that current

Posted by: JeffG Aug 6 2012, 09:15 PM

As I understand it, the US system uses a centre-tapped earth, so that live (or neutral) to earth is only 55v, whereas 240v mains gives you the full whack*. That's only what I vaguely recall, in case I am wrong!

* And it is a whack. As a youngster I remember having an argument with a light socket, and it was though I had been kicked by a mule in the armpit. (No RCDs in those days!)

Edit: I just looked this up, and apparently these days in the US, appliance voltage is 120V, not 110V, delivered as two out of phase 120V 'hot' wires with centre-tapped earth. This gives the possibility of 240V where required. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/hsehld.html

Posted by: dannyboy Aug 6 2012, 09:20 PM

It works best with incandescent lamps. Undervolting by just 5% will more than double the life of the lamp. So, to make old fashioned GLS lamps last longer they should have been rated at say 300v. You'd have to stick a pretty big lamp in to get the same light as a 60w 240v lamp though.

Posted by: On the edge Aug 6 2012, 09:24 PM

Wholly agree. House wriring would necessarily become more complex. However, arguably the big watts are generally in a few locations and not that portable. To make 'green' work without reverting to hair shirts does mean some fundamental rethinks/redesigns. These can work far better than the originals if got right - Dyson airblade hand drier a good example..

Posted by: Simon Kirby Aug 6 2012, 09:44 PM

Rather than lowering the voltage, increasing the mains frequency would also be safer. I have a feeling that 500 Hz is quite a bit less lethal than 50 Hz but you still have the advantages of both low current and AC, and at 500 Hz AC components tend to be smaller and more efficient. Some existing equipment would still work, though not all, particularly not induction motors.

Posted by: On the edge Aug 7 2012, 04:49 AM

All compromise as ever! Birmingham took some time to move from 25Hz simply down to needs of motors. North East staying on 40Hz - delaying its connection to the grid. Time perhaps for some deep thought at least.