# 110v compared to 240v, any electrician types around?



## martlewis (4 Feb 2011)

Hi,

Was working in a house the other day with a floodlight on and I managed to blow the fuse in an extension by starting up another tool  

Anyway, was wondering, if I was to use a 110v transformer rather than 240v mains is the current drain (amps or whatever) lower and hence may avoid popping more fuses? Just curious as I'm looking at investing in all new tools very soon and thinking maybe go 110v.


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## flying haggis (4 Feb 2011)

With 110V tools there is not a fuse in the yellow plug so that cant blow. but 110v tools of the same power as 240V ones will draw approx twice the current. If you go down the 110V tools route get a large capacity transformer ie 3Kw. if you are working on site, as opposed to domestic premises I dont think 240V tools are allowed for safety reasons.


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## Jonzjob (4 Feb 2011)

If you have a 100watt maching the only difference there is between 110 ans 235 volts is that the 110 kit will take a higher current from the 235 mains input. This is because the transformer is not 100% efficient and will consume some of the power just to run it.

I was talking to someone in the U.K. a short while back and he was telling me that they are going away from 110v kit. He said that it would not be necessary to have 110 kit on site in the near future. The French don't have any at all and give very strange looks to any British people who use it.


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## cambournepete (4 Feb 2011)

My 240/110 transformer used to regularly trip the circuit breaker in the house and garage.
I no longer have the tool that needed it so got rid of it...


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## Racers (4 Feb 2011)

Hi,

Remember that watts = voltage X current so as one goes down the other has to go up.


Pete


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## martlewis (4 Feb 2011)

All of the work I do is on domestic premises. Nearly everything I do is done using cordless tools. I'm thinking that plugging in battery chargers on domestic properties wouldn't require the use of 110v. Just occasionally I break out the SDS drill for cutting 100mm holes through walls. i use a 240v drill, but didn't know if I would really need to replace it? I also use a pair of floodlights on a tripod when necessary that are also 240v, and possibly a radio


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## Mcluma (4 Feb 2011)

How much amp was the fuse :idea:


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## martlewis (4 Feb 2011)

Ah now, that's a good question... I plugged into a double socket on a wall. Turns out after investigation why the power tripped and yet the CU was fine, and much cursing of my equipment, that the double socket in the wall was actually wired into a plug at the other side of the room with a 5amp fuse and 2.5mm t&e straight into the plug. Not entirely sure that's really how a ring main socket is usually wired :lol:


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## Mcluma (4 Feb 2011)

Problem solved


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## Eric The Viking (4 Feb 2011)

Also don't forget that 110V kit needs heavier cable to avoid voltage drop at the business end (tools running slow and/or losing power). It's more efficient to run 240V cable to the work area and keep the 110V cables as short as practical. Americans don't like to hear that!

I've never seen a reasoned justification for 110V site kit. It makes some sense to transformer-isolate tools, as it's then harder (but not impossible) to electrocute yourself, but 110V isn't _of itself_ all that much safer than 240V. 

In conditions where there is risk of electrocution, typically in the presence of water, frayed/damaged cables and casings or other careless operation, it could be just as dangerous as 240V mains (20mA or more continuously though the heart muscle will kill most people in most circumstances, apparently). You can only be dead, not 'very dead'. The situations where 240V will kill and 110 won't are marginal ones.

There's an argument that heavier cables, being physically stronger, are safer, but neither that, nor the use of a transformer, has got anything to do with actually running stuff at 110V instead of 240V. It applies a bit to bulbs too: the filaments are physically thicker for 110V, so there's less chance of them breaking through being knocked or vibrated. But again, these are practical not safety issues (and 12V bulbs are even more robust!).

OK, that's my twopence. I really would be interested to hear the other side though.

So why _should_ tools on site be 110V?

Regards,

E.


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## Hudson Carpentry (4 Feb 2011)

In a domestic situation I believe your only bound to to use an individual plug in RCD to run your 230v tools. I used to have 2 extension leads both with RCD plugs. These would plug into the customers sockets and my tools would only be plugged into one of these extension leads. Im quite sure 110v tools are required on for site and commercial work.

I could never understand why 110v though as its the current that kills.


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## Jonzjob (4 Feb 2011)

Current is dictated by voltage devided by resistance, so if you have 1/2 the voltage then as long as the resistance (your body) stays the same the current is also halved, therefore hopefully safer. 

There is a difference between ac anc dc too. The recognised safe ac is 110, but for dc it's 50 volts. This is because ac alternates and in doing so is reversing the polarity at a rate of 50 hertz and that has a tendancy to firstly tighten the muscles and then relax them, but with dc they tighten and stay tight. I used to be a eleky on Bristol Britannia aircraft in the R.A.F. and they have 3 different voltages, 2 of them lethal. 24v dc, 110v dc and 208v 3ø . The 110v dc is the worst one.

If you have ever had a belt off of your ingition leads on your car then you have had a VERY high voltage belt. An old car, about 9000 volts, a new one about 12000 volts. The reason that you only jump a mile and not pop yer clogs is because the coilhigh volts electronics can't produce more than a few milli amps and as has been said it's the amps that kill. I suppose that makes a nonsense of my first statement, but it doesn't because the belt you get is from a capacitor on your old car or an electronic circuit one your new one and neither is capable of producing high currents. A bit like static really, but enough static can and does kill!


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## Eric The Viking (4 Feb 2011)

I've had many electric shocks down the years, usually doing something stupid with electronics, but occasionally with mains wiring. I'm a leftie and I'm still here (it's marginally less dangerous for right-handed people).

I don't, however, mess with mains in wet conditions, nor tolerate broken or damaged appliances of any sort. And I know the "rules": no rings, one hand in pocket, rubber-soled shoes, etc., etc.

My point: 240V isn't always fatal, but had the circumstances been different, for example if parts of me had been soaking wet, or I'd got a firm grip on whatever was live (current contracts muscles, so those electrocuted by what they grab often can't let go), I wouldn't be typing now. Under those circumstances, 110V might just as easily have done it.

All 'safety' issues ultimately involve some cost-benefit trade-off. There's no such thing as absolute safety, only something that on balance is worth the extra inconvenience/cost to reduce risk. I just can't see it in the case of 110V (although isolating transformers make sense, they're not the issue - they would work better at 240V in any case and be cheaper to make).


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## doorframe (5 Feb 2011)

Hi ...

one GOOD reason for 110v on site is that the site transformers are indeed 110V output, BUT are + & - 55V in respect to EARTH, whereas 'normal' mains voltage is 240V with respect to earth. This is achieved by 'EARTH center-tapping' the secondary winding on the TX

So... if you get shocked from live to neutral or live to earth on 240V, you will have X amount of current through you and may die :| Hopefully the RCD will save your life (but ONLY if you are shocked to earth...NOT if you are shocked to neutral...then you prob WILL die if it's across your heart).

But, if you get shocked from live to earth on 110V, you will have 1/4 of the current and are expected to live, 

and... if you get shocked from live to live on 110V, you will have 1/2 of the current and are expected to live, but your hair may still go curly!! :wink: 

HTH

Roy.


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## Hudson Carpentry (5 Feb 2011)

I have been shocked by 230v, capacitors and cars. Never to earth. Non hurt but the worst was a PA system, i was soldering the speaker leads live then some twit played with the sliders.


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## chippy1970 (5 Feb 2011)

This argument has gone on for years there are the people who say you don't need 110v tools for site use and you can use 240 with a circuit breaker but at the end of the day I just bought all 110v tools regardless ever since I started so at least I have the option to work domestic or commercial. As said 110v cable is a lot more sturdy too which you need when you have people trampling all over your leads :evil: 

Also you try and get a 240v supply on one of these big building sites up in London , you wont find one easily if at all.


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## Eric The Viking (5 Feb 2011)

doorframe":39ucyvho said:


> site transformers are indeed 110V output, BUT are + & - 55V in respect to EARTH.



I'd quite forgotten the centre tap. Obviously it makes a huge difference. 55V RMS is hard to hurt yourself with: 

To get a lethal 20mA, at 55V you'd need an earth path resistance of less than 2750 Ω. 

If I lick my fingers and hold the probes, my digital multimeter (which is fairly accurate at higher resistances) shows about 1.2 MΩ. Even though that's with quite dry hands, there's still a fair margin of safety.

So it's not 110V as such, but 110V with a centre-tapped transformer that's mandatory. 

Thanks: that was the lightbulb moment!

E.


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