The rating on materials is maximum allowed fuse size upstream and continuous load. All materials are tested and approved according to some standard for me uknown to comform FEL and NEK.

When it comes to the definition of "materiell" in technical norwegian, compare it to words like hardware or component. Not just "material" used in english.

So yes, that includes hardware such as switches, outlets, junction boxes etc.

A good rule to follow is for the fuse or circuit breaker always being the weakest link (with its I2 value) compared to the rated current on the components used. You want to cut the power before the current gets out of hand and exceeds the rated current. But you said: "If so then that seems to imply you can not make a 16A circuit with socket outlets, light switches, etc. All the CEE 7/3 'Schukos', light switches, etc I see are rated at 16A, but you would need higher (I2) on a 16A In circuit." No, you're misinterpreting it. (... )- vernets høyeste prøvestrøm I2 ikke overstiger (...)

It states that you cannot exceed (overstige) the rated currents on the components or the cables with the nominal current (I2) on the fuse/breaker. Everything at or below 16A if all components are rated for that current: OK.

If any of them is for instance, rated at 10A, then you cannot secure the circuit with anything more than 10A. As this will be the new benchmark on what the whole circuit can handle. There are a few exceptions though with fixed loads with fixed connections (never with outlets). For example. It would be okay on a 16A circuit to connect an 8A fixed load behind a 10A switch on things such as water heaters etc. In cases where the amount of load are fully controlled/will never change. The danger of overload is not present anymore.In this case the 10A switch will not risk being overloaded. It will never see more than 8A.

These exceptions never applies when you use plugs and outlets as the interface between the load and the power supply though. As you, being the electrican, have no control over what people might consider plugging into it. So in that case you have to go for worst case; which is making sure that every link in the chain can handle the currents up until the fuse/breaker trips.

Thanks for the replies, but sorry I dont fully understand yet.

Forgive me if I'm wrong, but what you describe sounds just like the 'normal' practice I am used to of IEC 60364 (or UK national version BS7671) and not this specific Norwegian deviation described in the Norwegian regulations and NEK 400-8.

If I use an example maybe I can be more clear. I believe terminology is the same in IEC and NEK so it should make sense hopefully.

In Europe/UK we can use the design rule Ib <= In <= Iz (433.1 in NEK also)

Where Ib = circuit design current, In = protective device nominal rated current, Iz = cable continuous capacity

So for example I could make a circuit protected by a B16 RCBO (JFA), cable with capacity Iz of 16A or greater (2.5 or even 1.5 depending on method), and some 16A rated CEE 7/3 outlets.

But Norway takes a more conservative approach and says I2 <= Iz (in 823.433.1 and the regulations I quoted).

I2 is the current guaranteed to trip the protective device in conventional time (1-2 hours), and for standard MCB/RCBO (JFA) that can be up to 1.45 x In.

So in Norway a circuit with B16 JFA will need cable with capacity Iz of 16 x 1.45 = 23.2A with a standard device (which means method B/C or 4mm2 cable), or if I use the special Norwegian JFA (eg Schneider Electric with I2 value of 1.2 x In for B16) the Iz can be 19.2 A (which just allows 2.5mm2 cable for this circuit even with method A - possibly the reason these JFAs exist! :) ).

That seems clear to me for the cable - have I got it right?

But for the 'materiell' - switches, socket outlets etc I'm still confused. It seems in Norway this example circuit with a B16 JFA needs switches, sockets also rated at I2 (vernets høyeste prøvestrøm I2 ikke overstiger høyeste prøvestrøm som er benyttet for materiell i kretsen) which we see is 19.2 or 23.2A depending on the I2 value of the JFA. But as far as I'm aware outlets, switches etc are all rated 16A.

Does this mean a circuit with sockets, switches etc rated at 16A must in Norway be protected by a device with I2 < 16A, which would mean a In around 11A, meaning a B10 (with I2= 14.5A)? Seems very impractical - surely can't be true. Hence I wonder if I am reading wrong!

Tusen takk!

Bare hyggelig.

I'm sorry. I must have completely misread that the norm was refering to the I2 value and not the In.Missing the whole point altogether.I'll try again.

"- vernets høyeste prøvestrøm I2 ikke overstiger kabelens maksimale strømføringsevne IZ."

Yes, this one is pretty straight forward. You got it right. Making sure you use a suitable cable with Iz higher than the I2. We used In here instead before. Just like the rest of europe/UK.

"- vernets høyeste prøvestrøm I2 ikke overstiger høyeste prøvestrøm som er benyttet for materiell i kretsen."

It says highest test current (prøvestrøm). I think this is where the confusion lies. This is not the normal rated current of the unit, judging from the second sentence (Merkestrøm. which would normally be 16A). This implies that it is okay as long as the manufacturer has tested the unit with a higher current than I2. Which actually makes some sense. They're always testing their products with far higher currents in order to get a good safety margin and to allow some overload for the protective device to trip. So our job would then be to make sure that the components are tested at higher currents than I2. Which sounds a bit drastic in my opinion. But this should in that case be stated in the manufacturers documentation.

It's been a while since I was in the business. I left before NEK400:2010 and its changes came into effect, but this is how I would interpret it.I'm sorry if I use other terminologies than you are familiar with. My technical english is not that good, but you taught me a few of them. Thanks for that.

You could also ask for a clarification directly from the NK64 committee behind NEK.

nek@nek.no

I don't think they mind writing in english.

Hi Liam.

You make an excellent point and the wording really makes you wonder. But the question has been raised before and DSB answer with highlighting the OR between the two sentences. In DSB's magazine Elsikkerhet no 55 you can read the full explaination:

http://assets.elsikkerhetsportalen.no/Documents/DLE/Elsikkerhet%2055-84.pdf

Page 6!

Btw, impressive that you're that up to speed on the regulations; and you're not even from Norway.

Tusen takk for the detailed replies! Much appreciated :)

Glad to know this is even a little confusing for you guys too! I did notice the 'eller' so I guess I dont have to worry about the second point if I comply with the first point for cables which is easy, but it is still nice to understand the reason. Hmmm I wonder if 16A CEE stuff sold in Norway is tested up to potential I2 values??

Your technical English is excellent Preple. Mats - I'm an electrical engineer with some experience as an installer of LV installations and in UK was approved as an electrician by my local authority. I'm hoping to apply to DSB/my DEL for dispensation just to work on my own home in Norway, although I think I will probably be rejected! :( Whatever the outcome it is still nice to know the national regulations.

Right I've got one more question about strange Norwegian rules - will start another thread...

Thanks again