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Murdoch,No cu change required
Are you sure you were a spark
Be nice to new members, right or wrong, there ways to interact with people that are polite, and this is not one of them.
Murdoch,No cu change required
Are you sure you were a spark
Murdoch,
Be nice to new members, right or wrong, there ways to interact with people that are polite, and this is not one of them.
Again though, give me a reason why this is bad practice, other than you don't like it. I agree, made off badly it would look a mess. None of my work ever looked a mess, it was always exceptionally neat. Why is a direct connection to an earth block worse than going through several connections to get there? It is neither electrically, or in the case of being inside a plastic enclosure, entering from the rear, aesthetically worse than the official method of termination? Remember I'm only advocating this in the case of small cables in plastic enclosures in a residential situation where the official method isn't practical, or would aesthetically look a mess. Using this method, it can be done exceptionally neatly.
Sure ................ but clamp down on the chancers ................................................but you NEVER do
You state you are talking about small cables in residential situations. So I am assuming this CU you are terminating into, as it is plastic, and I guess other cables are standard PVC T&E? is not actually installed in an area at risk of high impact, or other serious external influences? As such the SWA could easily have been terminated somewhere more suitable externally and the final length of cable brought into the CU as PVC. As a small PVC cable will always be easier to dress and terminate into a small residential board and a single copper CPC will be far easier to work with in a confined space than multiple twisted steel strands of armour butchered into an earth bar. Other than a bit of laziness and possible speed to get away from the job ASAP on the installers side, there is no advantage to your method. Obviously if you can link a manufactures guidance where this method of terminating a SWA is considered acceptable then I am open to correction. But until such times there is no practical benefit to your solution. Additionally when it comes to periodic inspection and testing or any fault finding work where you may need to open up your twisted armour termination, it will be far more time consuming than a standard copper conductor. Your earlier comment statement about multiple connections being less safe due to HR joints etc. is irrelevant. Excluding the most basic of final circuits, you will always have multiple joints, or shall we limit light circuits to single luminaires just in-case we get a HR joint in the circuit? This is one of the key reasons we do dead testing before energising a modified circuit. Any competent person will be able to correctly terminate all cable types and ensure an electrically and mechanically sound joint in accordance with manufactures and industry standard guidance. It all pivots back to the "good workmanship and proper materials" guidance.
Doc H.
@ Sidewinder,
Just looked up most of those regs, pretty subjective stuff to be honest...
Some are, some are cut and dried, remember, in the event of an issue then there would be an investigation, and witnesses would be called, and you would need to find a professional who was willing to back you in your method, I suspect that most would not.
OK, how were you restraining the cable entry to ensure that there could be no undue mechanical strain on the terminations?I suspect you are correct, but I don't see how the way I did this would cause any sort of danger. I accept it's considered bad practice by many and it may not have complied with all relevant regulations at the time. If I were practicing today, I'd certainly not do it, but I've still yet to hear a valid argument as to why it might actually be electrically unsafe in the use cases I've suggested.
so youve acknowledged that its not the correct way but its fine because youre retired?
I acknowledge it's not the accepted norm & today, due to the far more stringent regime, part P etc. I'd not consider doing it, but back in the day, yes I did it when the situation seemed appropriate. Maybe it was incorrect, but I don't see how, and no one has yet come up with a valid reason as to why, in the situations I've described, it could be considered unsafe.
I think a lot of people just blindly follow rules, or do things a certain way because that's what they were taught. Sometimes thinking outside the box and using common sense is appropriate.
OK, how were you restraining the cable entry to ensure that there could be no undue mechanical strain on the terminations?
When you split the armour into multiple connections, how did you calculate the distribution of the fault current?
How did you ensure that the fault current could not have EM effects on the armour such that iw would not become displaced in fault scenario, and cause other issues, i.e. come onto contact with other parts etc.?
Which is all well and good but it needs to be recorded in departures on the certs and you will be expected to show sound engineering reason as to why you have made the departure and the assurance that it isn't less safe. At the end of the day its your signature on the cert and you in court if it goes wrong and if you cannot prove that it isn't less safe than following the regulations then the usual defence of EAWR reg 29 will not apply and you will be hung out to dry.
But going by that flawed logic we would still be using Screwits to make connections, which moved onto terminal block and now we have moved onto Wagos, all our screwdrivers would still have tape insulation or if you are posh pyro sleeve, we would still be doing daft things like trying to Earth window frames.I acknowledge it's not the accepted norm & today, due to the far more stringent regime, part P etc. I'd not consider doing it, but back in the day, yes I did it when the situation seemed appropriate. Maybe it was incorrect, but I don't see how, and no one has yet come up with a valid reason as to why, in the situations I've described, it could be considered unsafe.
I think a lot of people just blindly follow rules, or do things a certain way because that's what they were taught. Sometimes thinking outside the box and using common sense is appropriate.
Good points,
I'd only do this were mechanical strain wasn't an issue, ie, cable was fully cleated to the location on the other side of a wall high up with no realistic chance of the cable being pulled.
Armour would be split into 2 equal bundles, twisted, sleeved, run and terminated next to each other in the CU earth block, fault current would behave exactly as in a conventional termination except the CSA of the final earth connection is bigger than it would be with the usual tail from an earth ring/nut.
Quite rigid steel armour twisted and run directly together, we're only talking protection by 20A/32A MCB's at most here, your suggestion is absurd. In any case it was all sleeved, any slight movement that may have occurred would have had no detrimental effect on surrounding components in the CU.
But going by that flawed logic we would still be using Screwits to make connections, which moved onto terminal block and now we have moved onto Wagos, all our screwdrivers would still have tape insulation or if you are posh pyro sleeve, we would still be doing daft things like trying to Earth window frames.
Things move on, standards get better (mostly), and hopefully as we get older and more experienced our own standards get better.
OK, a few very common misconceptions in your answers.
If the cable is not terminated at the entry to the enclosure, it is not adequately terminated to prevent mechanical strain, thus it must have a gland. No gland, inadequate termination.
Fault current does not beehave like "normal" current, the di/dt is such that there are phenomenon that are not normally observed, and area, length, bend radius, route, proximity to other materials all have an effect upon the current flow.
My suggestion is NOT absurd, the protective device has zero bearing on the potential fault current, and it is only the energy let through which limits the "harm" to downstream equipment.
How do you know that the movement would be slight, you are suggesting that this was a long time ago, but now you are suggesting 20/32A MCB's, would it not be more likely that we would be dealing with fuses, and 1 or 5s disconnection times.
What were the potential fault currents at the origins of the supply, 3kA, 4.5kA, 6kA, 10kA, higher?
Was this only domestic, or industrial/commercial?
OK, in order,
In the use cases I've stated, in reality, barring a violent attack on the enclosure, this would not be an issue, in such an attack, I'd firstly be more worried about the T&E's that have no such strain prevention.
Fault current, fair enough, but I find it hard to believe there would be a problem there, and is so, what about the tail from an standard gland installation?
I was using MCB's back in 1994.
Domestic only, plastic consumer unit only.
Good points,
I'd only do this were mechanical strain wasn't an issue, ie, cable was fully cleated to the location on the other side of a wall high up with no realistic chance of the cable being pulled.
Armour would be split into 2 equal bundles, twisted, sleeved, run and terminated next to each other in the CU earth block, fault current would behave exactly as in a conventional termination except the CSA of the final earth connection is bigger than it would be with the usual tail from an earth ring/nut.
Quite rigid steel armour twisted and run directly together, we're only talking protection by 20A/32A MCB's at most here, your suggestion is absurd. In any case it was all sleeved, any slight movement that may have occurred would have had no detrimental effect on surrounding components in the CU.
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