EICR - Do I Need to TT the Earth in This Installation?
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- Опубликовано: 16 май 2024
- In this video we look at the benefits of fitting a type 2 SPD (surge protection device) and what type of items it can protect. It is now very common to fit a type 2 SPD in a domestic consumer unit to protect circuits from transient over voltages caused by switching inductive loads and atmospheric conditions.
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== 🕐 Time Stamps - Cut to the action 🕕 ==
00:00 - TT stake required?
00:17 - Extraneous conductive part
00:32 - TN-C-S
01:03 - RCD protection
01:38 - C3?
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I would prefer to TT it but another option could be to add a supplementary earth rod to the TNCS to keep touch voltages within safer limits. You could do this at the exported CU in the container. Then you’d have some migrating factor against PME faults also general live earth faults to the frame metal work bonding this to the MET with the ground connection. TT with separate Earthing is the ideal solution the second is pragmatic.
Another option again add PME fault protection in the main building before the TNCS is exported. Other measures after the EICR write a safety note to the client
And Give it a C2 because you want the client to act on the EICR.
Another option again insulate the floor and walls inside to to above 22k ohms so you reduce the shock hazard and bond and services 🥶 ( still with a rod keeping the frame safe )
Agree if the shell of the container becomes live, a supplementary earth rod in the ground right next to the container is going to keep the touch voltage to a minimum.
If you are stood on the outside with your feet on the ground and touching the container, what touch potential would you be exposed to? If it is less than 50V, then you are okay, if it is more, then you may need to ad an earth stake. However, it looks like the container is close to other metal structures, so if you can touch those metal structures at the same time, then the touch potentials for that scenario also need to be assessed.
I think Marcus' instinct to make it TT is correct. Any guidance I have found on this subject (eg NAPIT On-site Solutions book 2nd ed page 208) acknowledges concerns related to exporting PME earth (I'm assuming the SWA distributor to the container DB is 3-core as I can't see a separate protective conductor) and recommends making the outbuilding TT. I would say the code should be C2.
There is a danger that, in completing an EICR, the person doing the testing is solely focussed on the installation under test but there are broader issues here and they cannot be ignored. The most obvious concern is the hazard presented in the immediate vicinity of the container under test during a PEN fault on the DNO supply. However, from what little we can see of the environment, I would say that are also hazards with transfer potential (adjacent containers look to be touching - maybe, maybe not - we don't know for sure) and touch potential with regard to the fencing.
I would suggest that there is a duty of care on the tester under EaW regs to bring these hazards to the attention of the person(s) controlling the site, even though they may not be the party commissioning the EICR. Failing that, an email to the DNO at least. Is that just covering your backside? You may think so but, all things considered, you'll be glad you put something in writing when the police or HSE come knocking on your door post-incident.
It was Napit that told him to code it a C3 🤦🏻♂️
@@GSHElectrical to be fair to NAPIT, the guidance I quoted wasn't addressing EICR codes as such. I know they publish a 'codebreakers' guidance book too but I don't have a copy so it may well be that the guidance in _that_ document is consistent with the conversation Marcus had with (presumably) their technical help line.
On a completely unrelated matter - does the description section for this vid need an edit? 🤔😊
I do these container installations all the time but I’m never there for the whole n site installation to it’s main source of power.
If this was being ran of a generator (building site etc.) The genny would more than likely be a tt? And there for if the test results are ok it’s good to go?
was the container bonded?
Just by way of a thought experiment. I think the risks of connecting a container to PME are similar to having an exposed neutral bar. Or having a cross polarity neutral and earth connection. Or having a broken cpc connection to a metal light fitting. None of these conditions will hurt someone unless the conditions are right. But in each case only one thing needs to happen to cause a danger. So I think it’s potentially dangerous.
I would TT it.
My concern would be what would happen if the neutral went open-circuit? There's a reason petrol stations and caravan parks are not allowed to use TNC-S!
Good morning, please I want to buy multi functional tester, the one you often use in your videos. What is the brand name and which model is the best. Can you also recommended any online shop I can order it.
Thanks
TIS is made in Britain 🇬🇧Test instruments solutions, Megger , Fluke , Kewtech or kyoritsu KTW 4148 model recommended for loop testing but start searching with 1 st TIS 👍
We come across this a lot and it is clear in Section 717 that the PME ‘shall’ not be used.
When we look at why we think faulty PEN conductors and the hazards they import.
For me it is a toss up between a C2 or a C3 and having the fuse board within may tilt me towards a C2 as if there were a PEN fault people may look to go in the container to check breakers.
Don’t fall out with either code tbh.
It's a metal shed surely that happens to be a 20ft container - I'm not sure that makes it either a 'mobile or transportable unit' so I wouldn't have thought 717 applies? I mean - it's tethered to the ground by at least a SWA! 😆
how is this 141K ??!?
It is not as simple as simply sticking an earth electrode in the ground. Conisderation needs to be given to the distances of underground metal work connected to the local PME supply since open pen fault voltages may be transferred to the earth electrode. the latest COP for EV vehicles suggests 10m separation from such metal work. I would argue that section 717 applies to the container and as such the use of PME earthing is prohibitied and I would argue a C2 is required. Other methods of protection may be more suitable than earth electriode such as an isolating transformer but the absence of further informaiton would mean that I could not decide what the most cost effective solution would be.
It's a metal shed surely that happens to be a 20ft container - I'm not sure that makes it either a 'mobile or transportable unit' so I wouldn't have thought 717 applies? And there is a real risk of shock in a domestic (say kitchen setting) with open PEN currents and nobody codes everybody's installation a C3 or even a C2 consequently?
😊😊😊
So what if theres an RCD? An RCD offers no protection whatsoever in the event of a PEN fault, as it still sees balance between L+N - this is clearly a C2 - potentially dangerous, though the danger is dependent upon network conditions rather than installation conditions - however, if an EVC only attracts a C3 if not PEN fault protection is provided, that container will have to be a C3 also, though I disagree with it. I'm very surprised you've mentioned the benefit of an RCD without mentioning that it's useless during PEN faults, enabling the container to liven up unchecked.
Good to see the issue of RCD effectiveness mentioned in this scenario, however wouldn't the failure to operate be due to the lack of a neutral which is needed along with the live to power the electronics in the RCD? How common is a PEN fault in view of this danger possible in every installation (apart from three phase delta)?
No reason not to put an earth rod in alongside the pme. Often done in Ireland for example. C2 for me. Pen fault light the thing up
@@alanb4789 allegedly 400 in the UK annually - so not many and I'm not sure there are attributable deaths? I agree though that PEN fault risk of shock is apparent in a domestic setting too - it's only that the risk of shock is increased outdoors - but it's ever-present indoors too -- In a kitchen setting you're highly likely to have access to metal attached (bonded) to the MET and have a reasonable connection to earth too - unless you habitually wear rubber slippers!