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Posted By JLE
We are in the process of having a new construction centre built at our college, staff are saying they would prefer 240v to be used in the new build. We are considering 110v as there are obviously safety benefits in using lower voltage. As this is a college the safety of staff and students must be paramount but we seem to be facing resistance from 'old school' lecturers.
Has anyone got any experience of this in there workplace? I am unable to find any guidance on best practice, we obviously want to get this right first time. Many thanks, Jason.
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Posted By Robert.
Why not consider a dual system?
You'll need both. One for good practise and one for common practise.
No doubt you will need 3p+N+E as well.
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Posted By Mitch
Jason,
Part of your RA will take into account the guidance given by HSE etc that you should remove/reduce the hazard 240v down to 110v is reducing the hazard, try justifying not doing it in the event of someone injuring themselves. Search HSE sire electricity at work for their advice.
Mitch
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Posted By Exdeeps
How do,
Can I take issue with the statement that reducing the voltage reduces the hazard. Most "stuff" that is plugged in to a wall socket uses electricity to do work - ultimately measured in Watts. In electrical terms the power is directly proportional to the voltage (think of it as electrical pressure) and the current (think of it as electron flow rate ie electrons per second).In order to maintain the power (Volt X Amps), if the voltage is reduced by half then the current must double and with it, by a similar factor, the current rating of the protection device fitted to the system. As we all know (don't we?) it's the current that kills not the voltage - remember putting your hand on the van Der graph generator at school to make your hair stand on end.
On a more practical note, the cost/risk balance of specifying 110 volt fixed equipment may well be prohibitive over the life time of the building,
Cheers,
Jim
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Posted By Martyn Hendrie
You do not indicate whether you are thinking of lecture rooms or practical workshops.
If lecture rooms in my opinion 240v would be the norm. In practical areas I would expect the college to train the students using the correct voltages they should use when on site (110v centre tapped to earth, or lower whenever possible)
Whether that is achieved by a fixed 110v system or transformed down from localised 240v sockets would require more information on layout, use , etc.
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Posted By GeoffB4
ExDeeps - a submariner?
I'm not completely happy with terminology such as 'reducing the hazard' because the hazard is still there, but thanks for the lesson.
Reducing the voltage from 220V to a centre tapped 110V (so in effect reducing it to 55V) certainly does reduce the risk. How can it not?
I'm told, and I don't know of any instances, that no one has been killed from contact with 110V.
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Posted By Mitch
Clarification - the risk is of electrocution 240v or 110 v either or, reducing voltage to 110v reduces the hazard! the risk is implicit. As pointed out who died from 110v?
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Posted By Exdeeps
GeoffB4,
Precisely my point - simply reducing the voltage is not the solution. The centre tapped earth is also part of the solution. A 110v device drawing 2 amps will approximately use 220W - the maximum fault energy however will be half that (again roughly). The solution is in the design and construction of the system not simply in the halving of the voltage.
Not a Submariner - an ex submariner
Jim
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Posted By Mitch
The 2 deaths on the Google search were both attributed to contact with water, is the installation being discussed in the showers or swimming pool?
Sits back and waits
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Posted By Robert.
Mitch-----they're still dead!
SBAWs
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Posted By Mitch
1st 1 deserved it IMHO sitting in wet garden watching kids splashing around in pool with an electric fan by her side!!!
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Posted By Robert.
Mitch
Are you related to Mr Goldfinger
"No Mr Bond -----etc, etc"
:)
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Posted By GeoffB4
Robert - I'm not sure now what we are discussing.
I've no problem with being corrected if we can stick to the point being discussed. How many workers have been killed in the UK from using 110V? Then compare that number with those killed by 220V. There really is no point in trying to bolster your argument by bringing in extreme examples.
ExDeeps - I can't see your point and I certainly haven't approved or reinforced yours.
Lower the voltage from 220V to centre tapped 55V reduces the risk - it's a simple truism.
I'm still not too happy with this terminology of reducing hazards. A hazard is a hazard is a hazard. We reduce risks resulting from hazards. In this case the hazard is electricity and we can reduce the risk by lowering the voltage.
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Posted By Mitch
Risk (Verb) Expose to hazard, the exposure to the hazard (electricity) is the same in the classroom/workshop whether it is 110v or 240v, therefore reduce the hazard which is the level of electricity one could become exposed to.
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Posted By GeoffB4
I don't know why I keep writing 220V when I mean 230V. Maybe the title of this thread is confusing me.
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Posted By CW
"1st 1 deserved it IMHO sitting in wet garden watching kids splashing around in pool with an electric fan by her side!!!"
Thats a little harsh mitch. Some people have no idea of safety, if they did then our profession wouldn't exist.
I know what she did was stupid, but deserving it? Behave.
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Posted By Paul Leadbetter
Mitch
You said yourself that the hazard is the same then contradict yourself in the very next line. The hazard is electricity; the risk is electrocution and that is lower at 110v, centre-tapped to earth.
Paul
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Posted By Pete48
And I always thought a hazard was the potential to cause harm:):)
Sorry I just couldn't let it pass.
On the subject of hazards, I have come across situations where systems define different levels of hazard as a means of conveying the relative significance of the potential for harm contained within the hazard and thus suggest a different level of controls required or competence required to define the risks, I guess that is where Mitch is coming from?
However, I do agree with the prime principle that a hazard is a hazard, especially when dealing with simple risk assessment theories.
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Posted By Tony Priest
Jason
Reducing the voltage to improve safety is only one aspect of your plight, educating the 'old school' people and bringing them in line with modern day practices is what also is needed here, after all if it is a colleage I would not expect young people to be trained in the old school ways!
Incidentally (IMHO) Reducing the voltage will reduce the severity rating and therefore reduce the risk, the Hazard is electricity.
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Posted By JLE
Thanks to everyone for there help, it seems to have got some very excited!!!! The reference to Ohms Law certainly took me back!! There is certainly a cultural issue here with staff that we are trying to address, lack of training, poor management etc. I will take the constructive comments from this thread and continue to liaise with the powers that be. Ps 'she deserved to be electrocuted, a little harsh' Lmao!!
Thanks, Jason.
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Posted By Mitch
Jason,
Maybe a little harsh but I take the view that someone that stupid could end up taking other people with them!! ( Ouch I keep biting my tongue when it's that far in my cheek!)
Regards
Mitch
PS pedantic semantics rule
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Posted By JLE
You are in the wrong job mate, should be on stage!! lol. Thanks for your help.
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Posted By GeoffB4
A bit charged up Jason!
OHMS - On her majesty's service - yes?
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Posted By JLE
Of course, how did you guess!!!
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Posted By mark gough2
I agree with some of other postings for lecture theatres then 230 volts is fine.
I would strongly suggest that 110 volt centre tapped to earth equipment is used in a construction type environment.
Students will be expected to use 110volt on sites
The risk of fatal electrical shock is virtually eliminated
portable equipment used by inexperienced students is likely to be miss used
students are still developing skills so may not pick up on damaged equipment
there is clear guidance that 110volt CTE supplies should be used established over the last 40 years
The idea that lowering the volts increases the amps is misleading.
Under fault conditions it is the amps that kill. The average body is about 20000 ohms the ohms law bit gives about 20mA at 110 volt cte
just over the threshold of detection (i.e you can just feel it)
and 100mA at 230 volt which is fatal in all cases.
As someone pointed out if a student was injured there would in my opinion be no defense
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Posted By mark gough2
2000 not 20 000 ohms for a body average and of course environment shock path makes a big difference
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