European Equivalent to AWG

[PetrosA]

Actually there are are lots of tables in BS7671. In fact the section on current ratings for conductors is is over 60 pages long. Different installation methods, different numbers of conductors, temperature correction factors, DC, AC type of overcurrent protection etc.......very detailed stuff.

I was possibly a bit too vague, but that's what I meant. Our tables are very simple compared to what most EU countries use.

 

[Besoeker]

I was possibly a bit too vague, but that's what I meant. Our tables are very simple compared to what most EU countries use.

Possible true - I don't have a copy of your code.
I don't know what other EU countries (we all oght to be the same although my experience suggests otherwise) but here in UK we use BS7671, commonly known as "The Regs".

Taking 25mm² as an example:
From table 4D1A which is for single core 70C pvc non-armoured and 30C ambient, we get current ratings of
80, 73, 101, 89, 114, 104, 126, 112, 146, 130, and 110

The 73A rating is for 3-phase in conduit in a thermally insulating wall.
For free air, horizontal, flat spaced you get 146A.

Take the ambient up to 40C for this type of cable and you have to apply a 0.94 correction factor.
Use a semi-enclosed fuse (who does these days?) and you have to apply I_n/(0.725*C_a*C_r)
Stick it in a trench with as many different geometric layouts as a Rubic's Cube could generate....

Table 4D2A, multicore pvc non-armoured gives you a different set of values.
Make it multi-core armoured and another lot of readings.
Then there is single-core (non-magnetic) armoured.

Make it XLPE and you get another set of tables.
With mineral unsulated (MI), a whole different bunch of stuff.

Repeat for Al instead of Cu.....

I think it sounds a lot more complicated than it is in practice - it covers all possible eventualities.
In reality, aluminium conductors are rarely use. We never do. So, to all intents and purposes, that takes out half the bumf at a stroke.
MI is used for fire alarms and maybe some other specialist applications. Another whole chunk out of the way. For us.

It's probably easier to say what we commonly use.
For our panels, the control wiring is mostly 1.0mm² in various colours depending on function. They are run in open slot PVC trunking to keep it neat.
Signal wires (encoders etc) are screened. Comms Cat5.
Power cables are single core and in free air. Or copper bar for high current.

Externally, everything is run in multi-core steel wire armoured.

 

[Smart $]

If you are trying to specify a supply conductor size for this equipment why not just specify a minimum ampacity instead of a specific size? Not sure but I get the feeling that is what you are trying to do here.

I agree, considering wiring methods and conditions will vary. My main concern with this approach is differences in determining the minimum current rating...

 

[GeorgeB]

...

If I convert #8AWG into 8.37mm^2, ...

If it is the SIZE conversions you want, AWG=17-4.27*ln(mm^2)

I'm kinda stupid and cannot remember even the common sizes. In electro-hydraulics, I often have to review a vendors documentation to support my request for larger wire than the electrician "knows" is ok ... #16 AWG is NOT good for 5 amps at 100 feet _AT 24VDC_ ... about 0.8 ohms ... 4 volts ... 15% drop ...

so I have this in my smartphone spreadsheet now.

Area Size
mm^2 AWG

0.25 22.9
0.35 21.5
0.5 20.0
0.75 18.2
1 17.0
1.5 15.3
2.5 13.1
4 11.1
6 9.3
10 7.2
16 5.2
25 3.3
35 1.8

 

[mbrooke]

Actually there are are lots of tables in BS7671. In fact the section on current ratings for conductors is is over 60 pages long. Different installation methods, different numbers of conductors, temperature correction factors, DC, AC type of overcurrent protection etc.......very detailed stuff.

Do you happen o have a link to the tables? Im curious

 

[mbrooke]

For what its worth I have heard than in the EU the ampacity of the lower gauge wires has changed. Also wire in insulation is rated lower and wire such as Twin and earth stapled over open joists is rated higher where as the NEC dictates the current rating be the same in residential and commercial regardless ie, 14 will always be 15 amps no matter if its conduit, in insulation ect.

 

[Besoeker]

Do you happen o have a link to the tables? Im curious

I'm sorry, I don't.
They are part of BS7671, Requirements for Electrical Installations.
More commonly known as "The Regs"
It's an A4 sized 300 page book.
I don't think you can download it. Not free anyway.

 

[kwired]

For what its worth I have heard than in the EU the ampacity of the lower gauge wires has changed. Also wire in insulation is rated lower and wire such as Twin and earth stapled over open joists is rated higher where as the NEC dictates the current rating be the same in residential and commercial regardless ie, 14 will always be 15 amps no matter if its conduit, in insulation ect.

But the same size conductor in an NEC application will have adjustment factors if over three current carrying conductors are in the cable. They probably could have made it more complex by having different adjustment factors for every current carrying conductor, but for some reason decided up to three was acceptable to be at one level, 4-6 at another level 7-9 at a level and over 9 takes a bigger jump in adjustment factor but also a bigger jump in number of conductors before changing the adjustment factor again.

The ampacities they did choose as well as adjustment factors I believe do have a lot of room for error or other "just in case" factor built into them. You can run a 14 AWG at much more than 15 amps without any significant insulation damage, even in a bundle of 10 all carrying same current. Over time though you may notice degrading of that insulation.

 

[mbrooke]

But the same size conductor in an NEC application will have adjustment factors if over three current carrying conductors are in the cable. They probably could have made it more complex by having different adjustment factors for every current carrying conductor, but for some reason decided up to three was acceptable to be at one level, 4-6 at another level 7-9 at a level and over 9 takes a bigger jump in adjustment factor but also a bigger jump in number of conductors before changing the adjustment factor again.

The ampacities they did choose as well as adjustment factors I believe do have a lot of room for error or other "just in case" factor built into them. You can run a 14 AWG at much more than 15 amps without any significant insulation damage, even in a bundle of 10 all carrying same current. Over time though you may notice degrading of that insulation.

I agree. Insulation when new is forgiving however constant over temperatures degrade the insulation prematurely.

 

[fifty60]

Is there a document that is accepted across the EU that I can refer to when directing the customer to size supply wires and ground? Is BS7671 only a british regulation, or has it been adopted by the EU? It sounds like it would almost be impossible for me to do, and would have to be done by the individual installing the machine.

Can anyone think of any situations where sizing the fuses and conductors according to the NEC would be less than what I would need following the European standard?

It seems like the NEC calculations will always be the worse case scenario...

 

[PetrosA]

I can't think of any situation where the NEC would specify a smaller conductor that what British Standards or any of the the other European standards would dictate. My experience in Poland and Germany is that a much higher operating temperature is acceptable there than it is here, mostly because wiring is typically embedded in plaster so the risk of combustion is miniscule compared to what we deal with. Wooden homes have much stricter wiring guidelines in Poland than other buildings do, but I don't think the wire size is affected greatly. If you spec NEC standards for wire sizes, they will most likely be ignored as ridiculously oversized. I wired my coffee house in Poland as close to NEC wire sizes as I could and the inspector shook his head in amazement that we use such large conductors.

 

[GoldDigger]

I can't think of any situation where the NEC would specify a smaller conductor that what British Standards or any of the the other European standards would dictate. My experience in Poland and Germany is that a much higher operating temperature is acceptable there than it is here, mostly because wiring is typically embedded in plaster so the risk of combustion is miniscule compared to what we deal with. Wooden homes have much stricter wiring guidelines in Poland than other buildings do, but I don't think the wire size is affected greatly. If you spec NEC standards for wire sizes, they will most likely be ignored as ridiculously oversized. I wired my coffee house in Poland as close to NEC wire sizes as I could and the inspector shook his head in amazement that we use such large conductors.

One possible factor that affects the wire sizing, in residential anyway, is that with a voltage of 120V the wire size for a given current will be larger for the same percent voltage drop as for 220V. Voltage drop is not what NEC rules deal with, of course, but it tends to provide an additional motivation for larger wire sizes in the US.

 

[PetrosA]

One possible factor that affects the wire sizing, in residential anyway, is that with a voltage of 120V the wire size for a given current will be larger for the same percent voltage drop as for 220V. Voltage drop is not what NEC rules deal with, of course, but it tends to provide an additional motivation for larger wire sizes in the US.

I still suspect it has more to do with operating temp than anything else, and it's probably a leftover from the days of rubber insulation. We have blanket ratings for 14 and 12 AWG that have nothing to do with the amperage the conductors can safely carry. 14 AWG in free air is rated for 35A in the NEC, and at 90C it's rated for 25A but we're only allowed to fuse it at 15A max.

I found some tables with standards from Europe, but I need some time to translate them. Not gonna happen tonight

 

[broadgage]

Yes, cables are allowed to carry significantly greater currents under UK regulations than would allowed by the NEC.
I am not aware of any circumstances in which UK regs would require larger wire sizes than the NEC, and if any such circumstances DO exist, they would be very rare, specialialist, unusual situations, not a typical house wiring job.

For large or complex installations, calculations should be done regarding cable sizes.
However for domestic or similar work, rules of thumb are usually applied.

Lighting-------------------------1.0 or 1.5 mm cable on a 5 amp or 6 amp circuit
Larger lighting circuits--------------1.5mm cable on a 10 amp circuit
Outlets-----------------------------2,5mm cable on a 20 amp circuit, or
Outlets 2.5mm cable in a ring on a 32 amp circuit.

That would cover most simple domestic installations.

My personal view is that UK cable ratings are a bit optimistic, I would have no problem with 2.5mm on a 20 amp outlet circuit, knowing that the load is liable to be variable and usually much less than 20 amps. I might however think twice about 2.5mm for a long hour load of a full 20 amps, and would prefer to use 4.0mm in such a case.

 

[Besoeker]

I would have no problem with 2.5mm on a 20 amp outlet circuit, knowing that the load is liable to be variable and usually much less than 20 amps. I might however think twice about 2.5mm for a long hour load of a full 20 amps, and would prefer to use 4.0mm in such a case.

Might be a wise move.
From table 4D2A, 2.5mm² single-phase in a wall (and much wiring is) is rated at 18.5A

 

[Smart $]

Is there a document that is accepted across the EU that I can refer to when directing the customer to size supply wires and ground? Is BS7671 only a british regulation, or has it been adopted by the EU? It sounds like it would almost be impossible for me to do, and would have to be done by the individual installing the machine.

Can anyone think of any situations where sizing the fuses and conductors according to the NEC would be less than what I would need following the European standard?

It seems like the NEC calculations will always be the worse case scenario...

Assuming your machine has a properly sized main disconnect and ocpd, why be concerned about their fusing and sizing the supply conductors?

Just give them current ratings (minimum circuit and maximum overcurrent) at whatever voltage(s) for which the machine is designed. And, as is pretty much standard in the US, verbiage to the effect of installing the supply to local electrical regulations.

 

[mbrooke]

I still suspect it has more to do with operating temp than anything else, and it's probably a leftover from the days of rubber insulation. We have blanket ratings for 14 and 12 AWG that have nothing to do with the amperage the conductors can safely carry. 14 AWG in free air is rated for 35A in the NEC, and at 90C it's rated for 25A but we're only allowed to fuse it at 15A max.

I found some tables with standards from Europe, but I need some time to translate them. Not gonna happen tonight

If you can eventually that would be of big help. I often find myself adapting EU machines to NEC installations and it always has me wondering.

 

[PetrosA]

Ok, here's a rough translation of the tables based on what's available at this page:

http://www.hal.trzepak.net/faq/winxp/obciazalnosc.htm

Don't treat this as an official translation of an official document of any kind

http://petroselectric.com/technokabel tables.pdf

Sorry I couldn't embed it here, but it's a few bytes over the size limit.