Does anyone use a 110v transformer at home?

[p0689109]

Thank you piman(alec) for that info. You are correct in that I do not truly understand the fundamentals of electricity (after all it is black magic!).

 

[marlinspike]

Thanks for the comments and explanations, guys. I don't understand electricity either, but it's a bit clearer now. Sounds like the 110v thing and a transformer is certainly worth looking into.

I do very little buying on ebay and have never bought electrical items, but must admit the idea of the stuff being stolen has put me off in the past.

 

[Kayos]

I used to use a lot of 110 gear on sites, but as my work type changed I went 99% battery, now everything is battery except I keep a couple of mains sds drills and grinders just in case, last transformer went with the last of the 110 stuff I sold. I buy new as a rule, because I like new shiney stuff, and I'd hate to buy something someone bought new then some scumbag stole it

 

[Bill Edwards]

Safety of 110v transformers

The reason that 110v "site transformers" are safe(r) is because they are isolating transformers, not because of their 55v centre tap or 110v output.
As stated earlier in the thread, it's not the voltage but the current that will kill you - as little as 75ma (source).

However, any electrical force is dangerous only when it uses you to complete a circuit. With UK electrical mains, the physical ground is the return path for the electrical current so if you stick your finger on the live pin while standing in your garage then the electricity flows through your hand, up your arm, down your chest (unfortunately, traversing your heart) down your legs, into the ground and back to the substation - you have become a piece of electrical cable*.

Site transformers are isolating transformers, which means that they present a live and neutral (return) on the other side of the transformer which are not connected to the physical earth. So if you touch the live conductor the electricity has no path across your body to the return (unless you are dumb enough to also be touching the neutral with your other hand!).

This is why many sites demand 110v kit - there is a far higher risk of equipment or cable damage on a busy site and the isolation massively reduces the risk of someone receiving an electric shock.

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(*This is why RCDs are essential - they detect an uneven leak to earth, probably caused by you sticking your finger in a 240v socket, and disconnect the supply rapidly. Most RCDs are designed to trigger at 35ma or less)

So presumably anybody using 240v tools and worrying about their safety (such as when working in wet areas, or if cables get damaged) could simply use a 240v isolating transformer and be far safer?

 

[brightspark]

if your working with 240v leads and gear just run it through a 30 ma rcd thats suficient protection

 

[roofman]

Touch voltage (the level at which it will penetrate your skin) is 50V on dry skin (less if your soaking wet...prob closer to 25V) because of that...a 55V shock is far less likely to do you serious harm than a 240v shock (I've had a 240 belt more than once...last one off a badly put together fusebox...that hurt badly) Seemingly USA 120V is more likely to kill you though as they run 60Hz which is more likely to cause your heart to fibrillate (or so I was told)

I was doing a shingled roof in California and went to hang my jacket on the overhead in-coming mains cable from the wall bracket...i can confirm i am still alive but at the time it instantly dried my mouth up and i was throwing up all morning....nasty but not fatal in my instance

 

[Bill Edwards]

On that basis, why don't sites allow 240v gear on the condition that 30 ma rcd's are used?

 

[brightspark]

On that basis, why don't sites allow 240v gear on the condition that 30 ma rcd's are used?

some will allow but most wont and if they dont want u to use them on there site its there choice

 

[Bill Edwards]

But, although you can't change the rules, would it be accurate to say that in practical terms there isn't much to be gained using 110v through a transformer than ordinary, non isolated 240v with a 30ma rcd?
I.e the sites with 110v only rules simply don't understand?

 

[Pete.]

Four times the potential and a very high chance of equipment getting wet and leads getting damaged means that the risk of electrocution is much higher.

 

[brightspark]

http://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=38480

 

[Bill Edwards]

I seem to be none the wiser after following that link, is it that the rcd's need frequent tests whereas if the sites are 110v only it's easy?

 

[brightspark]

personaly i use mostly 110v tools apart from a few bits of gear in peoples private residences dry enviroment .on sites 110v all the way wether 240v is allowed with an rcd or not

 

[Pete.]

I can think of many instances over the years where I could have been seriously hurt by electricity if I were using a 240v power tool on site. You can still get a tasty belt off 110v (even at 55v potential to earth) if you're working anywhere near sea water for instance as it conducts very well. Put a 240v tool near it and you're talking life-taking jolts or you could use a RCD in which case you won't worry about getting a jolt, or even doing any work because it'll trip at the first sniff of getting damp.

 

[brightspark]

I can think of many instances over the years where I could have been seriously hurt by electricity if I were using a 240v power tool on site. You can still get a tasty belt off 110v (even at 55v potential to earth) if you're working anywhere near sea water for instance as it conducts very well. Put a 240v tool near it and you're talking life-taking jolts or you could use a RCD in which case you won't worry about getting a jolt, or even doing any work because it'll trip at the first sniff of getting damp.

i wouldnt bank on that. ive had hold of a few live cables and stood on damp ground fortunately there was rcd fitted but u still get a hell of a shock before it trips and it hurts and u wouldnt want another

 

[Pete.]

It was just to illustrate a point that if you add high potential and RCD you'll be constantly frustrated by the supply - which might be several floors away - tripping out in poor weather.

When I do projects like THIS it's quite common for us to get shocks through the handle on the small tools as the sea water forms a conductive path from the switch through the join in the plastic, even on double-insulated stuff. 'Intelligent' switches such as in Hilti stuff that detect a fault refuse to allow the soft-start to work so the tool soon become lifeless. We keep a drum of clean water on hand and a small jetwash and give it a good flush-through with tap water then leave it to dry out a bit so we can start using it again.

If any of those tools were 240v I wouldn't even take them along. The 415V plant we shut the genny down before un-plugging if the plugs are wet, even though they are all RCD-protected.