110V UK site transformer - Why?

[MetalMonkey]

Right and wrong.

No, he's right. Most shocks will be line to earth.

Correct, it won’t trip if an idiot touches live and neutral.

Not necessarily. If somebody touches a live conductor, unless they are perfectly insulated, they will still leak a certain amount of current to earth, which if sufficient will trip the RCD. Even if the majority of the current passes between the line conductors, some will still flow to earth.

It isn't foolproof or to be relied upon as there are scenarios whereby someone might well be sufficiently insulated from ground to not trip the RCD, but yes it may well trip just from touching L and N.

I assume you mean 240v.
24 won't do much....

 

[ajlelectronics]

(if the Brits and Aussie folks would drive on the right, like much of the rest of the world, we would have a greater choice of vehicles).

But you would then have to wield your sword in your left hand, whereas most people are right handed.

 

[skotl]

@Agroshield​

List of Countries Who Drive on the Left​

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United Kingdom
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Left is Right!

 

[Jack Ryan]

Incorrect because there is a risk of someone receiving a 24V electric shock. The use of a 55 - 55 Volt transformer will avoid that risk completely.

Except if someone touches the two lines - then they get a 110V boot.

Statistically, electric shocks are line to Earth and in that case, an RCD will trip. I assume that an RCD is required with a transformer supply so the transformer is really only there to supply the historically obtained 110V tools.

Jack

 

[Maker]

As someone who's been shocked by bother, but 110v multiple times, i'd take 110v any day of the week

And 240 is still preferable to however many DC volts are in a photographic flash.

 

[brightspark]

If you were a hire firm would you trust the rcd of a customer to protect the customer, and yourself from a claim for death? Even an rcd trip event is likely to be painful....

yea verry ive had about 10 good belts of rcd protected circuits 240v and have tripped them at 240v after a second or 2 they still dont stop you getting electrocuted if you touch the live and the neutral you just end up being the circuit in between so 110 on site is far safer . it dont matter 2 much on the voltage up to 415 its the amps that kill

 

[ajlelectronics]

And 240 is still preferable to however many DC volts are in a photographic flash.

'Tis the volts that jolts, but the mills that kills!

 

[dobbslc]

Except if someone touches the two lines - then they get a 110V boot.

Statistically, electric shocks are line to Earth and in that case, an RCD will trip. I assume that an RCD is required with a transformer supply so the transformer is really only there to supply the historically obtained 110V tools.

Jack

The site transformers all have rcd protection on the supply side, typically 300ma but that doesn't protect to outgoing RLV side of the transformer, you can short out the live to earth all day long on the 110v side and it won't trip the supply side.

 

[Agrismith]

OK, thanks for the replies. I didn't realise it was a version of "split-phase".

Are there specific regulations that govern the use of 110V on work sites?

Are the tools identical to American tools?

I guess I'm a sceptic, but did the safety justification come first or was it the cheap 110V tools?

I don't think I have ever seen a 110V transformer used here (except, rarely, to operate imported American equipment in workshops etc) and, of course, no cords at all for a long time.

Jack

Whilst there is no law stipulating the use of 110v it should be noted that that it is in the HSE code of best practice.
Which basically means if anything happens and you aren't using 110v then you are going to have a very hard time. Essentially if not following codes of best practice you should be doing better than the code.

 

[brightspark]

110 its mainly on sitework factorys workshops and harsh enviroments. in housing school dt rooms etc 240v tools and gear are ok to use provided its rcd protected

 

[Erie Fred]

Left is Right!

Are we to call them......."Leftist's" ?

 

[sparkysy]

Also 1 thing that has been missed it that it's a transformer, two coils not directly connected to each other. So safely isolating you from full current should you become part of the isolated side of the transformer circuit, this significantly reduces the current passing through you!

 

[ajlelectronics]

Also 1 thing that has been missed it that it's a transformer, two coils not directly connected to each other. So safely isolating you from full current should you become part of the isolated side of the transformer circuit, this significantly reduces the current passing through you!

Can you elucidate please? I can't see what you are saying.

 

[Maker]

Also 1 thing that has been missed it that it's a transformer, two coils not directly connected to each other. So safely isolating you from full current should you become part of the isolated side of the transformer circuit, this significantly reduces the current passing through you!

I thought the centre tap was actually connected to earth, so you're not getting the benefit of galvanic isolation like you do with a shaver socket in a bathroom.

 

[sparkysy]

The secondary of these transformers is 110V with the center tap earthed. That center-tap is the only point on the secondary which is earthed, so there can be no short-circuit. The two outer of the secondary winding connect to the two current-carrying pins on the 110V sockets.

You then have 110V for portable power tools, but each side of the circuit is only at 55V with respect to earth. This reduced voltage to earth lowers the shock risk.

Hope that makes sense.

 

[sparkysy]

This might help explain what I mean.
Lifted off the net to save me drawing and photographing it, on a Friday night

 

[JOEPRO]