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Posted By Ian Stone
We have a new construction tutor here at the Xollege and he says that you dont have to use 110v tools as long as you have RCD protection on building sites. Other staff are disputing this so they want written proof either way
can anyone help??
Thanks
Ian
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Posted By Paul Leadbetter
Ian
110v equipment is less likely to 'wander'.
Paul
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Posted By Martin Daly
110 is banned in every country in Europe except UK and Ireland.
240 is much safey if used with RCL and protected cables.
110 might have been best in the past But no longer and should be consigned to history.
Martin Daly
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Posted By Tom Clark
Ian
I'm not fully into construction rules and regs etc. you can only know so such, but I agree with Paul less likely to go walkabout, but also look at the obvious advantages which you are know doubt aware of:
Lower voltage and less risk.
Everybody I know in construction is geared up for 110 so why mix the site? This could be dangerous even fatal.
Have a look at this site:
www.hse.gov.uk/pubns/indg231.pdf
Also the old chestnut of Risk Assessments comes into play.
If you have access to a library with the HSE's book Electrical Safety on Construction Sites, check in there I would also like to know the outcome.
Regards
Tom
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Posted By steve e ashton
Your college lecturer would have problems passing the CSCS passport test for working on construction sites - the question book is very definitely looking for 110V portable electrics. If he is teaching your students that 240V is OK, then it is likely they will fail the CSCS test and be unable to get work on a great many sites. What are you training the students for?
HSE guidance HS(G) 141 (1995) strongly advises use of 110V (or lower where practicable). 'A reduced voltage system, which delivers 110V to the equipment, designed so that the maximum voltage to earth is only 55V in a single phase system (65V in a 3 phase system) is safer than using 230V'
Not sure why anyone would advocate a return to 240V when 110V centre tapped is inherently safer. (RCDs fail to danger...)
Not an electrician, so open to persuasion, but for the time being I will go with the HSE advice.
Steve
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Posted By Peter MacDonald
Martin
Can you expand on your argument please?
Peter
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Posted By Bob Baynes
As I understand it RCD's only detect current leakage to earth, so if you manage to connect youself across live and neutral, the RCD will not necessarily operate. If it doesn't. neither will you, unless you are very lucky. The RCD's I've seen all have a test switch and instructions to test regularly. There is presumably a foreseeable risk they will fail, in which case you are not protected. Why use 240 volts and an RCD in preference to centre-tapped 110 volts with its maximum 55 volts? This starts from an intrinsically safer basis.
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Posted By Mark Bywater
Also interested to hear more from Martin and the "banned" 110v in Europe.
Where does this info come from Martin?
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Posted By Rob T
S'funny - how does the banning of 110v work in countries where the main power is 110v?
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Posted By Tom Clark
Maybe they're banning the use of 110 abroad because people keep nicking the gear!!
Great - no need to take all those little adapters.
Tom
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Posted By Merv Newman
Most of europe works on 220v
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Posted By Ian Stone
Thanks for all your responses, Im meeting the section leader later today to try and sort this issue out
Once again thanks
Ian
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Posted By Martin Daly
The main reasons I think 230 is safey are.
You can not get an electric shock if there is an RCL in the circuit.
Its the current that kills. With 110v you have a very high current.
Because of the high current you cannot use protected cables as extention leads.
Because of the high current you get voltage drop which causes tools to burn out.
There may have been a time when 110v was safey but that was in the past. Today it is just an urban myth.
Martin Daly
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Posted By Chris Black
Wind-up? Yes?
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Posted By Paul Costelloe
Could I respectfully ask what "safey" means. This can't be a typo as its used several times by the same author. Also, what's an RCL ?
Actually, thinking about it, it probably IS a wind-up !
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Posted By Keith Archer.
Possibly a “mega” wind up
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Posted By Terry Smyth
All in all some "Shocking" repiles
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Posted By peter gotch
Hi Martin
I think you have got a job on your hands to persuade your local regulators. Quote from their website
http://www.hsa.ie/publis...aID=1081&nID=369&pID=109
"Voltage
All portable electric tools used on construction sites must be rated at 110V."
Most of these tools are double insulated, so that an RCD would not work anyway, as their is no earth wire to enable the RCD to detect leakage.
As other commentators have pointed out, also
1. RCDs fail to danger which is why you should test them regularly e.g. each time you need their protection.
2. In the relatively rare event of fault between live and neutral, RCD will provide zero protection.
Should of course usually provide an RCD on the supply side of centre tapped to earth [CTE] transformer
Regards, Peter
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Posted By JJ
To clarify Peter's response above:
RCDs work on the principle of detecting a current imbalance between phase and neutral and therefore do not require an earth wire to detect leakage to earth.
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Posted By Jack
'Its the current that kills. With 110v you have a very high current'.
I think your grasp of electrical safety is not yet sufficient for you to comment accurately on this.
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Posted By Kevin Walker
What you may find is that with 110v systems the amperage (or current) is a lot higher than 230-240 v systems in the domestic situation.
Most household 240 sytems have a rating of 13 amps for most appliances, 110v systems can load up to 50 amps making then inherently more dangerous.
Electricity in any form is dangerous but the real problem is the amps running through the sytem. High voltage low amps is much the same as low voltage high amps. Just to add to the amp story.
kevin
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Posted By Jack
It was Mr Ohm who pointed out to us all that current is proportial to voltage. So halving the voltage will mean double the current (for the same load). But the point is that the current through the human body is also dependent on the voltage applied across it, hence why 110v is safer in terms of electric shock (even more so if there is a centre tap to earth, so the actual potential is 55v).
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Posted By Laurie
Can't really comment on the current/voltage question as I'm not a qualified lectrishun, but I do know that if you get a belt from the ignition system on a car it is something like 25,000v, but the current is so low that you would be unlucky if it killed you
Laurie
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Posted By Jack
But that current is limited by other factors and not the internal resistance of the human body. I'm sure you wouldn't assume that an overhead line operating at 25kv would be so forgiving?
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Posted By Charles Robinson Tech SP
The current magnetude is mainly dependant upon body impedance
about 50% of the population have an impedance of around 1500 ohms
I = v/r
240/1500 gives .16 amp 160 mA
110/1500 gives .073amp 73mA
55/1500 gives .036 amp 36mA
the lower the voltage the less current that can flow, car batteries can deliver huge currents but will not give an electric shock.
rcd`s do not fail to safety as they are mechanically operated and should only be used as a secondary protection against electric shock. They also require regular testing using the trip button and should be periodicaly tested using appropriate test equipment.
110 volt reduced voltage transformers offer greater protection centre tapped ie. 55v to earth.
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Posted By Simone Plaut
further to the excellent response posted by one of the earlier contributors
think about wet conditions.......body impedence drops due to water on clothing, hands etc.......current shoots up
if lower voltage.....fatal shock is less likely
risk assessment has the day as usual
I=v/R if resistance drops due to wet hands....current shoots up
RIP
seems pretty obvious to me
cheers
Simone Plaut
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Posted By steve e ashton
If an RCD fails to operate when a fault current passes - the current will continue to pass. This is fail to danger. That is why they need testing so frequently. And still they fail.
110V centre tapped is inherently safer than 240V protected by RCD.
Steve
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