To me accessible has everything to do with it, as it relates to risk of some one shock the person has to actually be there and be in contact. Hence skeleton live bus bars in a locked substation are a lot less icky than the same thing would be if it was left in the open. Perhaps the room or the building void is the enclosure…
Further, to get a shock off LV at 50 and 60Hz you need to be in contact with both sides, so L and E or L and N. Notwithstanding Tom and Jerry electrocutions in films, it does not leap out and get you with one point of contact only, unless we are talking RF, when body capacitance will complete the path.
I'm a lot less worried about the letter of the regs than some on here, in my view they are sometimes neither necessary nor sufficient (sometimes even both at once) to guarantee proper electrical safety, and can be also far too intolerant of properly engineered alternatives, while having gaping bind spots in other areas.
Consider the humble batten lamp holder, as seen around mirrors in theatre dressing rooms since the year dot, or on kids bedside tables. Clearly not as safe as the same holder on a drop cord from a ceiling rose, but regs wise, ignored, while an insulated but not sheathed wire 8 feet up is always a disaster waiting to happen ..
Mike.
In this case, where do you stand on protection against fire?
There is an assumption in the regulations that electrical fires can only come from electrical overheating, in the same way, that electric shocks can only come from direct contact with some things at different potentials. This may be a live point and real earth, or both a live and neutral conductor) ignoring 3 phases for the moment. Insulated but not sheathed conductors are not unsafe to touch, they are only dangerous if also damaged, maybe in the touching or a previous incident.
It, therefore, follows that insulated conductors that are not damaged are only dangerous if they can be damaged, so those hidden from contact by position cannot be dangerous. It is also implicit that containment (cable sheath, plastic conduit, accessory boxes) does not need to be conductive to provide mechanical protection where contact is likely.
Electrical fires can only occur if there is serious overheating, and there is inflammable material present and close enough to burn. Overheating is almost always due to poor resistive connections, or faulty appliances such as a toaster that fails to “pop-up”. A cooker fire from the chip pan is not an electrical fire. We protect cables etc. from serious overheating with the CPD, and the design. Whether an AFD can protect against poor connections is far from clear, so this must be the primary cause.
Unsheathed cables themselves are not really “potentially dangerous” but could become so if there is a mechanical incident, but the same could just as well happen if a plastic accessory is smashed. We do not code plastic accessories as C2, and therefore the exposed cables should receive the same treatment and require improvement, C3.
There is a serious logical inconsistency in many of these codings from the books, they do not reflect the danger correctly, and many are a case of “I don't like the look of that”. The fact that a situation does not exactly reflect the regulations does not mean that it must be dangerous, even if a potential danger can be found by imagining some very unlikely scenario. In that way all of life is dangerous, even being in bed. Most people die in bed, does that mean beds are inherently dangerous and should be banned? It certainly means that all kinds of transport should be banned, particularly horses, riding is one of the most dangerous kinds of transport.
There is an assumption in the regulations that electrical fires can only come from electrical overheating, in the same way, that electric shocks can only come from direct contact with some things at different potentials. This may be a live point and real earth, or both a live and neutral conductor) ignoring 3 phases for the moment. Insulated but not sheathed conductors are not unsafe to touch, they are only dangerous if also damaged, maybe in the touching or a previous incident.
In that case, the requirement to provide suitable containment (or sheathing) is nonsense in the first place?
Of course it is a necessary requirement … but why?
It, therefore, follows that insulated conductors that are not damaged are only dangerous if they can be damaged, so those hidden from contact by position cannot be dangerous. It is also implicit that containment (cable sheath, plastic conduit, accessory boxes) does not need to be conductive to provide mechanical protection where contact is likely.
Electrical fires can only occur if there is serious overheating, and there is inflammable material present and close enough to burn. Overheating is almost always due to poor resistive connections, or faulty appliances such as a toaster that fails to “pop-up”. A cooker fire from the chip pan is not an electrical fire. We protect cables etc. from serious overheating with the CPD, and the design. Whether an AFD can protect against poor connections is far from clear, so this must be the primary cause.
Unsheathed cables themselves are not really “potentially dangerous” but could become so if there is a mechanical incident, but the same could just as well happen if a plastic accessory is smashed. We do not code plastic accessories as C2, and therefore the exposed cables should receive the same treatment and require improvement, C3.
External influences such as damage by rodents can lead to such a situation. Far more likely to go unaddressed where it can't be seen. Shouldn't be “C3” because this can be left forever without correction. “Out of sight, out of mind". Potentially dangerous - C2.
There is a serious logical inconsistency in many of these codings from the books, they do not reflect the danger correctly, and many are a case of “I don't like the look of that”. The fact that a situation does not exactly reflect the regulations does not mean that it must be dangerous, even if a potential danger can be found by imagining some very unlikely scenario. In that way all of life is dangerous, even being in bed. Most people die in bed, does that mean beds are inherently dangerous and should be banned? It certainly means that all kinds of transport should be banned, particularly horses, riding is one of the most dangerous kinds of transport.
Clearly mechanical protection is needed here, otherwise SWA wouldn't have been chosen. However, is it immediately dangerous (the criteria for C1)?
Well, in this case, it could be if there's water (particularly salty water) present …
As DZ alluded to in an earlier post, it's OK having “coding rules” but sometimes the particular circumstances do need to be taken into account.
For example, if the above picture were outdoors in a position accessible to children in a primary school within a few hundred yards of the coast, I'm sure we might be seriously thinking about a more stringent coding. But C2 leads to unsatisfactory anyway …
What is the gland made of? It does not look like brass. If the sheath is the CPC, it has been lost so that's C2 plain and simple.
The risk of conductors becoming detached is high. If that is on the load side of the box, and everything came out, no problem; but if one of them is the CPC, that's back to C2. If the conductors are TPN, the consequences of one becoming detached depends upon what is at the other end.
What is the gland made of? It does not look like brass. If the sheath is the CPC, it has been lost so that's C2 plain and simple.
The risk of conductors becoming detached is high. If that is on the load side of the box, and everything came out, no problem; but if one of them is the CPC, that's back to C2. If the conductors are TPN, the consequences of one becoming detached depends upon what is at the other end.
There doesn't look to be a protective conductor connected to the gland, although that in itself may or may not be an issue - it might be earthed at the other end.
Is it a mains cable or a control cable operating PELV (although the latter would still require an earthed armour if the cable is buried).
davezawadi (David Stone): . The fact that a situation does not exactly reflect the regulations does not mean that it must be dangerous, even if a potential danger can be found by imagining some very unlikely scenario.
1. If an installation confirms to the regulations it can be regarded as safe.
2. If it does not confirm it might or might not be safe Only engineering judgement can tell.
But a lot of electricians (perhaps lacking engineering judgement) think that if it does not confirm it is, ipso facto, dangerous
I believe it’s a control cable operating solenoids. Interesting discussion alot of factors to consider. I doubt there would be a presence of salty water and being industrial mostly operational staff on sites so from what you’re saying a C2 would be relevant. However if full of rain water would this then become a C1?
