IET logo
 
IET
Decrease font size
Increase font size
Topic Title: porta-cabin and PME earthing
Topic Summary: connecting up a porta-cabin where supply has PME earthing
Created On: 29 January 2013 11:31 PM
Status: Post and Reply
Linear : Threading : Single : Branch
1 2 Next Last unread
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 29 January 2013 11:31 PM
User is offline View Users Profile Print this message



psychicwarrior

Posts: 220
Joined: 18 October 2010

Hello folks

A porta-cabin acting as an office at a public info. centre, to be used by staff and possibly visitors, needs connecting to mains supply at the main building on the site. Presume the porta-cabin is safe to be connected.

I have had it in my mind that a porta-cabin comes under Section 717 (I will stand corrected if needs be!)

I am particularly interested for some opinions (or even insight) on the reasoning behind Reg. 717.411.4 which seems to suggest in relation to earthing, that a PME supply is suitable if the installation is [permanently] under the control of a skilled or instructed person ( aswell as that in (ii) ) and why its particular to this special location ?

As special location regs. supplement other 'general' regs., I would presume the issues to consider regarding a separate building on a PME site (e.g outside equipotential zone issues, main bonding, using TT instead) would still be in play - though reading the above it seems to dent that view a little unless (ii) of 717.411.4 covers it. ?

Thanks in advance for any comments/replies.
Habs


Oh....As an aside, I have always struggled to understand to a degree of certainty the 'skilled or instructed person' implication. However a link by OMS ( i think) to an ECA article on RCD's helped (thank you). I was slightly surprised at this 'default position' bit:


DEFAULT POSITION
In situations where the designer is unable to ascertain
whether or not the installation will be under effective
supervision by skilled or instructed persons, such as
spec built offices, shops, factories, warehouses etc. the
default position is not to fit 30mA RCD protection to all
socket outlet circuits and all circuits having cables
concealed in walls
, unless deemed necessary by the
designers risk assessment or by the clients/developers
specification requirements, as was the case with the
16th Edition.

Edited: 30 January 2013 at 12:35 AM by psychicwarrior
 30 January 2013 08:58 AM
User is online View Users Profile Print this message


Avatar for Parsley.
Parsley

Posts: 1032
Joined: 04 November 2004

I think it's probably best to TT it, would the installation really be continuously under the supervision of a skilled or instructed person. I know some will say it's a place of work etc and EAWR requires etc.

Regards
 30 January 2013 09:24 AM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11547
Joined: 13 August 2003

I was slightly surprised at this 'default position' bit:

DEFAULT POSITION
In situations where the designer is unable to ascertain
whether or not the installation will be under effective
supervision by skilled or instructed persons, such as
spec built offices, shops, factories, warehouses etc. the
default position is not to fit 30mA RCD protection to all
socket outlet circuits and all circuits having cables
concealed in walls, unless deemed necessary by the
designers risk assessment or by the clients/developers
specification requirements, as was the case with the
16th Edition.

I think that was the original position of the IET when the 17th first came in, but it was reversed a little later - hence the Wiring Matters article: http://electrical.theiet.org/w...s/41/rcds.cfm?type=pdf - so perhaps that bit is just out-of-date, rather than deliberately contradictory.

- Andy.
 30 January 2013 10:02 AM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19747
Joined: 23 March 2004

I think we should also perhaps recognise that the views were actually expressed by different authors at different times, neither actually representing officially the IET, Andy.

Perhaps this is an opportune moment to revive the "looking back into the installation" concept and where that went with regard to RCD's and existing circuits.

It's just a shame that JPEL 64 have made such a hash of this issue (twice) particulary if you cinsider the significant input put into the draft fir public consultation of the 17th edition and the very hasty and extremely dubious change undertaken post consultation.

The regulations should have been much clearer in terms of "controlled" and "uncontrolled" installations - we already have the concept of household or similar applications - that should have been the starting point. Mandate them for domestics or similar - leave the requirement to employers and engineers wiorking under the CDM regulations with a full and proper understanding of the workplace regs and the appropriate use of risk assessments.

If ever there was a potential for a complete pigs ear it was this - all it needed was sensible industry debate - rather than the unseemly haste to botch it into the regs on the QT that really happened.

By the time we get to the 18th, I'd really hope that we end up with either a section or a seperate document that returns to being a rule book for electricians in the domestic arena - standard circuits and thou shallt type thing - leave the rest of it to competent persons to interpret and deploy for the particular application.

The hypothosis in the artice you linked to Andy is farcical - it presumes that a designer is going to make the decision to omit RCD's without documenting the risk assessment - which bit of CDM and standard risk/reward procedures do they think we don't understand. And that doesn't even begin to address employees bringing in untested kit and deploying it in a workplace environment - if they used it at home and got zapped what would be the difference ? -contributory action and probably a total breach of HASAWA anyway in that they failed to cooperate with the employer over H&S issues.

Ahh well

Regards

OMS

-------------------------
Failure is always an option
 30 January 2013 10:28 AM
User is offline View Users Profile Print this message



psychicwarrior

Posts: 220
Joined: 18 October 2010

Ooo err on the RCD issue and skilled/instructed etc!
Is it not easier to just say in any installation, that unless there is a technical reason why RCD might not be considered (unwanted tripping etc) then use them, otherwise they can be left out after due process to risk assessment by competent persons (whats competent again lol)!

Any way, please:

What are the opinions (insight) on the 717.411.4 i mentioned.

I'm curious as to the connection/relevance between the use of PME earthing and 'skilled or instructed [yadeya]', for example in the situation I provide, for this reg. to have been written ?

PME seems to come with generally raised eyebrow for supply to outbuilding in general from what one reads (without wishing to raise the debate again) and in some cases prohibited. DNO's I last talked to 'preferred it not to be used for earthing outside eqi-pot-zone' but if it was the equi-pot should be extended.

Seems easier to TT to cover most bets, but that aside, its the 717.411.4 that is puzzling me a bit??

Any views. Thanks kindly.
 30 January 2013 11:03 AM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11547
Joined: 13 August 2003

I think we should also perhaps recognise that the views were actually expressed by different authors at different times, neither actually representing officially the IET, Andy.

Although if the article is to be believed (I don't have a copy of the latest OSG to hand), its stance is meant to be co-ordinated with the On-Site-Guide, which presumably is meant to offer official guidance from the IET?

The hypothosis in the artice you linked to Andy is farcical - it presumes that a designer is going to make the decision to omit RCD's without documenting the risk assessment - which bit of CDM and standard risk/reward procedures do they think we don't understand

For bigger projects sure, but what about small jobs? I don't know much about CDM, but I guess it might not apply to adding a few extra sockets in an existing office. The "designer" is usually the local jobbing electrician and when SMEs are involved, you'd be lucky if the resulting documentation stretched any further than an EIC/MWC. Yet someone needs to make the decision on whether RCDs are needed or not - and potentially be able to justify it. You've only got to see some white vans on the road to realise that some risk/reward procedures in the trade aren't up to scratch

- Andy.
 30 January 2013 11:26 AM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19747
Joined: 23 March 2004

Originally posted by: AJJewsbury

I think we should also perhaps recognise that the views were actually expressed by different authors at different times, neither actually representing officially the IET, Andy.


Although if the article is to be believed (I don't have a copy of the latest OSG to hand), its stance is meant to be co-ordinated with the On-Site-Guide, which presumably is meant to offer official guidance from the IET?

OK - that's a good point


The hypothosis in the artice you linked to Andy is farcical - it presumes that a designer is going to make the decision to omit RCD's without documenting the risk assessment - which bit of CDM and standard risk/reward procedures do they think we don't understand


For bigger projects sure, but what about small jobs? I don't know much about CDM, but I guess it might not apply to adding a few extra sockets in an existing office. The "designer" is usually the local jobbing electrician and when SMEs are involved, you'd be lucky if the resulting documentation stretched any further than an EIC/MWC. Yet someone needs to make the decision on whether RCDs are needed or not - and potentially be able to justify it. You've only got to see some white vans on the road to realise that some risk/reward procedures in the trade aren't up to scratch

CDM applies to all construction work Andy - a few extra sockets might well not be notifiable to HSE under the regs but the duties imposed still exist. Even for jobbing works, wouldn't the EIC or MWC be the place to note the exclusion of RCD protection to socket outlets ? - as in the existing schedule with the emphasis on noting exclusin rather than inclusion.

ie in the absense of the RA, then it's a departure if not fitted ? - akin to it's a code 3 on a EICR in the absense of the RA.

Personally I think the whole thing is a total shambles and needs more robust scrutiny by JPEL 64. Given that we provide additional protection to combat carelessness how would skilled or instructed actually deal with that aspect - even skilled people may be careless.

I suggested the wording was changed to include "Where required by contract, risk assessment etc, additional protection by means of 30mA RCD's may be provided" - we have a box on the schedule to indicate that anyway.



- Andy.


Regards

OMS

-------------------------
Failure is always an option
 30 January 2013 12:02 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19747
Joined: 23 March 2004

I'm curious as to the connection/relevance between the use of PME earthing and 'skilled or instructed [yadeya]', for example in the situation I provide, for this reg. to have been written ?

PME seems to come with generally raised eyebrow for supply to outbuilding in general from what one reads (without wishing to raise the debate again) and in some cases prohibited. DNO's I last talked to 'preferred it not to be used for earthing outside eqi-pot-zone' but if it was the equi-pot should be extended.

Seems easier to TT to cover most bets, but that aside, its the 717.411.4 that is puzzling me a bit??


Basically what the reg is getting at is that, in the first instance, the cabin is connected via plug and socket - that suggests flexible conductors and thuis they are likley to be subject to greater potential damage/abuse than a fixed installation.

If it's PME and you lose a relevant conductor then you can have all sorts of problems and even in healthy conditions you may get diverted neutral currents that can raise the building MET above "earth" potential

Given that ESQCR disallows the use of a PEN conductor on the consumers side we shouldn't have any real problems. What the reg is essentially saying is that you can't use the PME earthing unless you can be sure that the PEN is intact before you make a demand on it - so a skilled person should be able to determine this and the effectiveness of the earthing is also confirmed before use - ie before you plug in the transportable unit. It may well be that earth monitoring would meet the requirement ?. Note 1b to figure 717.3 essentially tells you that the protective measures of the supply need to be effective and the Note refers you to 717.411.4 in relation to PME as an unique type of TN supply (note the prohibition isn't on TN-C-S)

It could clearly be argued that if the cabin actually has a permanent supply, then the whole of Section 717 is not applicable, you don't have a special location, and the general requirements only of BS 7671 apply. So if you use the PME earth, then all you need to address is the bonding issues if extraneous parts are present.

regards

OMS

-------------------------
Failure is always an option
 30 January 2013 12:14 PM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11547
Joined: 13 August 2003

CDM applies to all construction work Andy - a few extra sockets might well not be notifiable to HSE under the regs but the duties imposed still exist

Ah fair enough, I had "construction site" (as in 704) kind of context in mind - I now realise that CDM covers "renovation, repair, upkeep, redecoration or other maintenance" too! (I learn something new every day Xmas decs hangers beware!

Personally I think the whole thing is a total shambles and needs more robust scrutiny by JPEL 64.

I can't disagree with that - these discussions seem to prove that point.

I suggested the wording was changed to include "Where required by contract, risk assessment etc, additional protection by means of 30mA RCD's may be provided" - we have a box on the schedule to indicate that anyway.

Humm. If we have the theory that people should be no less protected at work then they are at home - where with a new domestic installation 30mA RCD protection would be expected - should the default position not be the other way around - i.e. to have RCDs unless the RA etc positively shows they're not required? As you said "if they used it at home and got zapped what would be the difference ? ".

- Andy.
 30 January 2013 12:34 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19747
Joined: 23 March 2004

The starting point is that domestic clients need 30mA RCD protection - I also disagree with that concept Andy - hence the suggestion.

I still haven't found any credible evidence to show RCD proteion of all sockets (and effectively all circuits) has brought about any increase in safety (or decrease in incidents).

You'll remember how all this emerged the first time round - and can guess at the hysterical debates that went on that resulted in the clearly rushed wording of the requirements for additional protection. I think Arbut Whatif must have been present that day.

ADS will provide disconnection in up to 0.4 seconds - even the IEC accept that's short enough for safety. The default should be that additional protection is offered where required, not should be caveated out by a few weasel words. It's a matter for the designer (and a designer of domestic installations has the duty under CDM) to decide if additional protection is required either as a matter of contract, risk assessment or second tier industry guidance.

So, no less protected at work than they are at home for sure - but not with the starting point that every domestic needs RCD protection.

Lets not forget that every designer signs the EIC - the route to investigation and potential prosecution lies in that document -

OK - perhaps the last sentence is a bit fanciful

regards

OMS

-------------------------
Failure is always an option
 30 January 2013 01:22 PM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11547
Joined: 13 August 2003

ADS will provide disconnection in up to 0.4 seconds - even the IEC accept that's short enough for safety.

But that's only guaranteed up to the end of the installation - e.g. the socket. Granted UK tradition of 13A fused plugs fed from 30/32A circuits mean we usually have a fair bit of spare Zs to cover appliance leads etc, but even then it's easy to find situations where 0.4s won't necessarily be achieved for class 1 appliance faults - e.g. faults internal to appliances (part way along element or winding to case) or at the end of long extension leads. The (apparently) growing trend for feeding sockets from 16A or 20A radials, could reduce the "spare" Zs to negligible levels too, exacerbating the problem. Maybe after the socket isn't strictly speaking a BS 7671 issue, but it's part of the bigger picture all the same.

For sure, the numbers are so low, that it'll be a long while before the statistical significance of the body count shows up clearly.

- Andy.
 30 January 2013 01:53 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19747
Joined: 23 March 2004

Don't we already account for that in circuit design (although it's hidden) in the sense of limiting Zs accounting for the rise in conductor temperature under fault - something like 20 - 25%.

Reference that to the 13A fuse and it would be difficult to imagine a class 1 appliance fault that was dangerous to the user not operating the CPD.

I may have misundertsood you Andy, but wouldn't the lower fault current required to operate 16A or 20A devices over realistic circuit lengths actually be better - in the sense it allows for more Z in the flex and appliance ?

I've no problem with RCD protection becoming the default in UK homes - just that the regulations try to say that, without saying it - and that confusion spills over into non domestic installations and causes chaos.

Isn't it time we now had a house bashers rule book based on say the definitions of dwelling, house, flat, room for residential purposes etc in the building regulations. It wouldn't be difficult to write, it would assist domestic installers and I suspect would become default for people like NHBC, Zurich etc. It would become a favourite with specifiers and probably be useful to BCO's and the approval bodies would love it.

Two tier system? - yes, for sure - we need it

Regards

OMS

-------------------------
Failure is always an option
 30 January 2013 02:15 PM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11547
Joined: 13 August 2003

I may have misundertsood you Andy, but wouldn't the lower fault current required to operate 16A or 20A devices over realistic circuit lengths actually be better - in the sense it allows for more Z in the flex and appliance ?

What I meant was that Zs at the socket supplied by a a 32A B-type MCB needs to be <=1.44 Ohms, and a 13A BS 1362 is good for 0.4s disconnection up to 2.42 Ohms - so we've got nearly an Ohm "spare". But a socket fed by a 20A B-type could legitimately be up to 2.3 Ohms at the socket - leaving barely one tenth of an Ohm spare - likewise a B16 could be up to 2.87 Ohms - effectively making the 13A fuse redundant as far as ADS is concerned. As 20A and 16A circuits tend to be radials, much of the extra Zs allowed at the point would tend to be used.

Don't we already account for that in circuit design (although it's hidden) in the sense of limiting Zs accounting for the rise in conductor temperature under fault - something like 20 - 25%.

Isn't that adjustment for conductor operating temperature vs temperature at which it's tested - e.g. 20 degrees room temp to 70 degrees operating temp - at 0.004 per degree C = 20%. And there's no guarantee the conductors won't be fully loaded immediately prior to the fault (OK, not overly likely in a domestic, but a possibility we can't write off). For sure the conductors will get hotter during the fault - and that's taken into account internally in the tables/device standards, but presumably we'll be using that margin up anyway as we'll have fault current flowing.

- Andy.
 30 January 2013 03:16 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19747
Joined: 23 March 2004

Originally posted by: AJJewsbury

I may have misundertsood you Andy, but wouldn't the lower fault current required to operate 16A or 20A devices over realistic circuit lengths actually be better - in the sense it allows for more Z in the flex and appliance ?


What I meant was that Zs at the socket supplied by a a 32A B-type MCB needs to be <=1.44 Ohms, and a 13A BS 1362 is good for 0.4s disconnection up to 2.42 Ohms - so we've got nearly an Ohm "spare". But a socket fed by a 20A B-type could legitimately be up to 2.3 Ohms at the socket - leaving barely one tenth of an Ohm spare - likewise a B16 could be up to 2.87 Ohms - effectively making the 13A fuse redundant as far as ADS is concerned. As 20A and 16A circuits tend to be radials, much of the extra Zs allowed at the point would tend to be used.

OK - with you now - although 60m long 20A radials in a domestic setting would be unusual - standard conventional circuits would be limited to about 50% of that by volt drop constraints (on the assumption the loads at the end)


Don't we already account for that in circuit design (although it's hidden) in the sense of limiting Zs accounting for the rise in conductor temperature under fault - something like 20 - 25%.


Isn't that adjustment for conductor operating temperature vs temperature at which it's tested - e.g. 20 degrees room temp to 70 degrees operating temp - at 0.004 per degree C = 20%.

That's the purpose of it Andy - I was thinking more of the note to the limiting Zs tables intended to account for operating temperature and reg 434.5.2.

And there's no guarantee the conductors won't be fully loaded immediately prior to the fault (OK, not overly likely in a domestic, but a possibility we can't write off).

Mmmm - a function of design though Andy - any circuit with Zs approaching specified limits in normal operation should still have margin for temperature increase under fault.

For sure the conductors will get hotter during the fault - and that's taken into account internally in the tables/device standards, but presumably we'll be using that margin up anyway as we'll have fault current flowing.

But won't the fault current be lower and thus the heating effect lower if the fault is now in the appliance flex - ie the bit we are concerned about given the circuit is already protected (and should be handling the temperature rise of close up faults anyway - so we already have margin "back" as it were.

You'll be advocating 16A socket circuits next, non polarised plug and no fuse - now there's an idea

- Andy.


regards

OMS

-------------------------
Failure is always an option
 30 January 2013 03:42 PM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11547
Joined: 13 August 2003

But won't the fault current be lower and thus the heating effect lower if the fault is now in the appliance flex

But disconnection time longer (and so energy let-through higher) if we're counting on the 13A fuse. What that'll do to the temperature on the (usually larger) installation conductors is beyond my ready reckoning - but I suspect it'd be 6 of one and 5.9 of another, but I'm not sure which way around.

You'll be advocating 16A socket circuits next, non polarised plug and no fuse - now there's an idea

Certainly not! (at least not without going for a 115-0-115V system with slightly oversized c.p.c.s)

It's probably fair to bear in mind that most of the contributors to CENELEC HD 60364 probably are more familiar with such systems than with ours though.

- Andy.
 30 January 2013 04:22 PM
User is offline View Users Profile Print this message



psychicwarrior

Posts: 220
Joined: 18 October 2010

@OMS

thank you for the response on the reg.

my brief interpretation of your views on the reg.: the plug-socket-flexible cable arrangement is seen as more prone to damage and is key in this reg. - so where skilled or instructed persons are not in control then use another method, as they most likely cant, or do not have the means, to prove the effectiveness of the earth path before hook-up .

Where as, a permanent supply (e.g SWA distrib circuit suitably terminated to box and isolator etc - ie 'permanent') is not at the same same risks (well, not as much), so on assessment under those circumstances then it may be OK to use the PME (subject to bonding requirements etc) - and you go further postulating that 717 clearly could be argued to not apply?

Interesting - i'll have to have another think about it all.

By the way you mention TNC-S not prohibited. Any reason why that would be ?
To me TNC(S - at the consumer side) may be more an issue if neutral lost than if it was TNC(S) with PME ?!
Or is it to do with proximity to fault points?
(Or have I just got in a twist again!)

Cheers
Habs
 30 January 2013 04:41 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19747
Joined: 23 March 2004

But disconnection time longer (and so energy let-through higher) if we're counting on the 13A fuse. What that'll do to the temperature on the (usually larger) installation conductors is beyond my ready reckoning - but I suspect it'd be 6 of one and 5.9 of another, but I'm not sure which way around.


It'll have a lesser effect on the installation conductors Andy - and keep in mind, in reality, the bigger conductors will behave non adiabatically as well.

As a reasonable assumption, the 13A fuse should account for the flex or appliance fault raising the temperature to the final limiting temp (around 160C) - sets a limit on the length of flex ?. The fault in appliance on the 2.5/1.5 shouldn't really increase the temperature from operating temperature(much) but the design will be based on 70C (or even higher at final limiting temperature) - the tails and DNO component of "Ze" won't change in reality - so ambient temp or operating temp.

If we are assuming MCB's - low fault currents won't really increase disconnection time - once you are over the set point it'll be out in 0.01 seconds (ish).

If i get a moment I'll plug in some numbers for a given 20m long 20A radial and a 13A fuse on say 6.0m of 1.0mm2 flex - lets say it's a 8A load. Load on the circuit is 13A - Ze = 0.8 ?

Regards

OMS

-------------------------
Failure is always an option
 30 January 2013 04:56 PM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11547
Joined: 13 August 2003

and you go further postulating that 717 clearly could be argued to not apply?

Not really a postulation - it's written in the second paragraph of 717.1. I suspect the logic is that if it's connected to a permanent supply then it's not really in the situation where it's expected to driven or lugged about the place, subject to all kinds of vibration and jolting and then being plugged into Lord knows what sort of supply systems (maybe foreign where the concept of a reliably earthed N or even a reliable PE at all may be a challenge).

To me TNC(S - at the consumer side) may be more an issue if neutral lost than if it was TNC(S) with PME ?!
Or is it to do with proximity to fault points?

All PME is TN-C-S, but not all TN-C-S is PME - some (according to some current standards at least) could be PNB for example. There are particular problems with PME and it's only PME, not TN-C-S in general, that might be subject to the prohibition.

- Andy.
 30 January 2013 05:20 PM
User is offline View Users Profile Print this message



psychicwarrior

Posts: 220
Joined: 18 October 2010

@AJJewsbury

without getting into a detail instruction about PME, TNCS etc, and if you have time please....what (in brief if possible) are the particular problems with PME and not with TNCS. in general as you put it and in regard to this reg. aswell ?

Just to help sanity check and see if we are not apart on the basic structure (and ignoring the separation at the consumer end):
- TNCS - neutral path all the way back to the transformer where it is earthed
- TNCS (PME) neutral path back to transformer where it is earthed AND with multiple earthing points along the way 0 - with one being before the consumer installation usually

TNCS without PME is not as robust (lets say) as TNCS, so whats the issue in this reg. ?


and yes i stand further clarified on the 717 not applying point . although i wasnt intending to give the impression i disagreed with OMS.

thanks Andy
Habs
 30 January 2013 06:33 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19747
Joined: 23 March 2004

There is very little difference in practice between TN-C-S and PME.

The former may well only have a single consumer however, the latter will be a distribution network with multiple consumers (and multiple earthing points including connection to the neutral or PEN conductor of another circuit possibly)

PME has the problem that the open PEN conductor will raise earthed metalwork at many consumers to some potential (often quite high) and obviously also results in a lost neutral which causes other problems.

This is less likley on a TN-C-S system in single ownership and short runs.

as Andy put it:

All PME is TN-C-S, but not all TN-C-S is PME


and therein lies the risk.

Regards

OMS

-------------------------
Failure is always an option
IET » Wiring and the regulations » porta-cabin and PME earthing

1 2 Next Last unread
Topic Tools Topic Tools
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.