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Topic Title: RCDs in a workshop / laboratory environment
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Created On: 05 November 2012 10:13 AM
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 05 November 2012 10:13 AM
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JeffAdams

Posts: 3
Joined: 07 February 2003

Hi All,

My company has recently moved in to a new office. We have a number of 'laboratories', which are really rooms in which projects can set out their kit - PCs, embedded systems, test rigs, hardware etc, and do a little rework on circuit boards etc.

We have been told (by the electrical contractor) that there is no requirement to have RCD protection in these rooms.

But - wait a minute - we're working on the guts of systems here, and high voltages are definately exposed.

We feel this is a bit 'dodgy'.

Could anyone comment on this situation please? I don't thik my project will approve a copy of the wiring regs somehow :-(

Kind regards

Jeff Adams
Bath
 05 November 2012 10:19 AM
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perspicacious

Posts: 7129
Joined: 18 April 2006

"But - wait a minute - we're working on the guts of systems here, and high voltages are definately exposed.
We feel this is a bit 'dodgy'."


A belated welcome Jeff

Is your risk assessment/procedure based on personel receiving an electric shock that then relies on a RCD to work to switch off the supply?

Regards

BOD
 05 November 2012 10:34 AM
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AJJewsbury

Posts: 11277
Joined: 13 August 2003

Welcome to the Forum Jeff!

We have been told (by the electrical contractor) that there is no requirement to have RCD protection in these rooms.

Yes and no. The current regulations have a general requirement for sockets (rated 20A or below) to have 30mA RCD protection - but an exception is permitted if they're only to be used under the supervision of skilled or instructed persons. There is a school of thought that says that employees - under general H&S at work legislation - are obliged to do what they're told safety-wise (hence they're instructed), so if company policies (e.g. only use tested appliances, no outdoor equipment or overly long extension leads etc) mean that safety can be achieved without relying on RCDs then, RCDs may be omitted. I think that most schemes suggest that the contractor obtains in wiring confirmation that H&S policies make RCD protections unnecessary before omitting RCDs.

we're working on the guts of systems here, and high voltages are definately exposed.

By "high voltages" I take it you mean ordinary mains (just be careful if reading regs etc - mains is usually referred to as "low voltage"!)

The regs do make the point that 30mA RCDs can't solely be relied upon for protection against direct contact with live parts. So if you've got live mains exposed you might need to be taking further or different precautions - perhaps isolating transformers (which as a side effect would defeat supply side RCD protection), or work procedures that avoided the problem.

I suspect the RCD issue might be just part of a larger problem - I guess the fashionable answer to that is an overall risk assessment.

- Andy.
 05 November 2012 11:50 AM
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JeffAdams

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Hi BOD,

The back story is that we recently did a 'safety tour' of the lab to confirm that all was in order. I spotted a test rig that had exposed 110 V ac on it.

(That must be 'quite low' then )

So we argued that - if the worst should happen, ie a trip or fall against it, or an inadvertant prod - then an RCD ought to kick in. We then looked for it, and couldn't find one, and that was confirmed by the contractor.

I take the point that an RCD does not provide a guaruntee of a safe response to touching a live conductor.

We have done the obvious thing - and that is to insulate the live conductor.

Nevertheless, it does worry me that there may be future occurences of this sort of hazard.

I guess you are right, and that I should get our safety folk to consider the whole use of the lab from scratch once more.

Any further comments are more than welcome.

Thanks

Jeff
 05 November 2012 01:38 PM
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AJJewsbury

Posts: 11277
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had exposed 110 V ac on it.

(That must be 'quite low' then )

"Reduced Low Voltage"

- Andy.
 05 November 2012 02:53 PM
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OMS

Posts: 19461
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I spotted a test rig that had exposed 110 V ac on it.


110V could actually be two 55V volt to earth supplies

Offering RCD protection at 110V RLV isn't usual, even in high risk applications (cos that's why you have a reduced voltage)

I suspect you may need to go back to the beginning on this one - ask the question, "who, am i trying to protect, and from what"

Regards

OMS

-------------------------
Failure is always an option
 05 November 2012 07:35 PM
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mikejumper

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Joined: 14 December 2006

When I worked in this environment we were all given 10mA plug in RCD's to use when connected to mains voltage. There was no other RCD protection on the circuits.
 06 November 2012 03:34 PM
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Delbot321

Posts: 77
Joined: 06 November 2012

If it is 110v between conductors - therefore a reduced low voltage system (55v single phacse or 63v three phase to earth) there is no requirement for RCDs if you can achieve the required 5 second disconnection time. (Yes - 5 seconds for 110v sockets). The HSE website states that to the best of their knowledge no on has ever been killed or significantly injured by a reduce low voltage system hence why it is used on construction sites. This type of system should be quite safe as long as you have a suitable transformer and the system is maintained appropritely and therefore there won't be exposed live conductors.

On a different note there are plenty of offices and call centres that rely on the use of instructed persons - why should a call centre employee be playing with the cables and the likes - if the items are suitably inspected and maintained then there is no problem - but as already suggested I would recorde the fact that your assessment was based on the client advising you that was their procedure.

Its worth noting that it is a requirement that the installation is installed and maintianed in-line with the requrements of BS7671. So the building is installed to the regulations, it needs to be maintained in line with them - that means an EICR (or similar eqivilant). It does not mean you need to go back retrospectively and update things. If you believe we should do this then you must also support ripping out all the cables that don't meet the current colour requirements which would mean rewiring most buildings - which is just mad. HOWEVER - it is reasonable to advise the responsible person (the duty holder) of the change in requirements and allow them to make their own judgement - thats why they are the responsible person!

If you know you have people working on 'test rigs' or similar then you should have a risk assessment to cover this. As you say it is likely that these rigs don't meet the requirement of the 'Manufacture of equipment regs' or have any similar compliance so it is up to the employer (the responsible person) to adequately assess the risk and apply suitable control measures. If you have open equipment with access to live parts then it should be a controlled area with only authorised persons allowed in - they should all be trained as to what is safe to touch and not touch. There should also be means of isolation of supply in an emergency - emergency stop buttons. Similarly you may also assess you need RCD protection or double wound 240-240 safety isolating transformer - the list of options goes on and on BUT you (the resposible person) needs to record all this in the risk assessment so their is evidence of why they made particular choices. RCDs may not be a suitable means of protection if the equipment by desing has functional earth condictor currents. It may be neccessary to employ the services of a specialist consultant to do the assessment.

You must rememeber that as the resposnible person (or if you are giving them professional advice) you may have to provide evidence and logic and reason as to why you made a particular assessment. In the original post you already identified that you had concerns but you are allowing people who may have inadequate knowledge to put themselves at risk. Again - putting someone to work with inadequate training is in itself a breach of health & safety in the work place and it is down to the resposnible person to be able to demonstrate that they did everything reasonable - and keep records showing this.

If you are the responsible person (duty holder) I would always suggest you ask yourself 'if this goes wrong and someone is injured what is my defence and would a jury consider it reasonable that I had done enough if their loved one was dead on the floor' - if you can show this then you will have met all the legeslative requirements.

Something for you to ponder on!

Edited: 06 November 2012 at 03:43 PM by Delbot321
 06 November 2012 05:14 PM
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cmatheson

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Joined: 16 January 2003

I can see no reason not to recommend RCD protection throughout. I would also ask the question - Are the staff using this area sufficiently skilled to be able to assess and mitigate the electrical risks they may encounter in their duties. An instucted person may not be sufficiently knowledgabe to do so in the the work you are describing without minute by minute supervision.

-------------------------
Chris Matheson MInstMC
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