mm2 ampacity restrictions

[Gardner]

Under BS7671, what is the amperage of 1.5mm2, 2.5mm2 and 4mm2 copper conductor restricted to when inside a race way or cable of no more than 3 current carry conductors? Thank you! :smiley2:

 

[davesparks]

It's ok, as long as you don't mind the mistakes, particularly those in the cable current rating tables.

 

[shanky887614]

It's ok, as long as you don't mind the mistakes, particularly those in the cable current rating tables.

not all of the editions are dodgy mate, if you get it direct from amazon usually its safe.

or better yet from iet through amazon or direct from the horses mouth

 

[davesparks]

I'm not talking about the dodgy copies!
Mine is a genuine one from the IET and apparently 6mm has a current rating of 2Amps when clipped direct.

 

[shanky887614]

I'm not talking about the dodgy copies!
Mine is a genuine one from the IET and apparently 6mm has a current rating of 2Amps when clipped direct.

what table?

cant find that value in my digital version i got direct from them through there server

table f6 for 6mm ive got 47amps

 

[davesparks]

It would have been the first print run of the green run so they've probably fixed it by now

 

[shanky887614]

It would have been the first print run of the green run so they've probably fixed it by now

bollox honestly mate you got a fake, i got this as soon as it came out

was using red at college when i bought this

 

[davesparks]

Right, it's 4mm rather than 6mm in table f4(i)

I've checked it against other people's copies in the past and they all were the same.

And I'm NOT your mate, please don't refer to me as such.

 

[shanky887614]

Right, it's 4mm rather than 6mm in table f4(i)

I've checked it against other people's copies in the past and they all were the same.

And I'm NOT your mate, please don't refer to me as such.

then you have all gotten fake copies,

i got mine

 

[Simonslimline]

Right, it's 4mm rather than 6mm in table f4(i)

I've checked it against other people's copies in the past and they all were the same.

And I'm NOT your mate, please don't refer to me as such.

Yes mine is the same. Bought it from waterstones & it is a genuine copy. Just a typo.

 

[davesparks]

Read the above post, the almighty skanky has spoken and pronounced that every copy with that error in is a fake!
Just because so many people have that version and have bought it from so many places it doesn't mean anything, there is obviously one huge counterfeit operation selling ten times as many copies as the genuine ones.

 

[HandySparks]

...the almighty skanky...

:biggrin: Deliberate 'typo'?

BTW, my copy was direct from the IET and has that error.

 

[Gardner]

Guidance Note 3 explains our testing procedures.

Thanks! I will read up on it. If anything the theory first.

Errr, i don't think they will have GN.3 readily available in the States!! lol!!

Pointless doing any ELI or live tests on a trailer at the factory anyway... They will only make sense when the trailer is hooked up to the power supply at the location it is to be used....

We don't sadly, however we do have other tools in the shop that could probably make do.

Well he has a PDF of BS7671 from the internet apparently. I don't expect that is readily available either, hence the PDF. I only mentioned it as it might be something he would be interested to read.

I am interested in reading it. I have been now for some time because of this project. This is the first PDF that comes up on Google on BS7671. Can anyone confirm this is a fake or real?

http://www.thailandlift.org/documents/BS7671-2008.pdf

Don't think it makes interesting reading......for anyone.
It's just a must have for us sad punters in that field when you need a reference....

Only when studying theory. Mike Holt's Forum has made the NEC exciting... to a degree anyway. So Id imagine the same will happen here. (Hopefully)

Maybe!!....

Unlike the UK and Europe, Testing isn't high on the priority list as far as small and domestic installations are concerned, in the States. There isn't even a section within NFPA 70 (NEC) on the requirements of testing installations, in fact the only measurement i can remember ever seeing in the NEC is the max of 20 or 25 ohms for a single earth rod..... They rely in the States on State employed NEC Electrical inspectors, what sort of tests these guys carry out (if any) i couldn't say.

Unfortunately you are correct. This is one thing I hate about our system. Testing is non existent in small applications like residential or commercial. Absolutely no testing of any kind takes place. None. The NEC electrical inspectors perform little if any testing. At most they will plug in an outlet tester just to make sure the outlet has correct polarity and a functioning ground (if the light lights up on the tester ground is ok), perhaps even trip GFCIs. But other than nothing. There real job for an inspector is just to visually inspect everything. If no NEC violations can be visually seen, it passes inspection. The sad part is others in the trade think I am crazy for wanting actual testing.

In fact, when AFCIs (Arc Fault Circuit Interrupters) were required for general use residential circuits a few years back, the ones that had 30ma differential protection caught a lot of wiring errors. Complaints were and are still common of them tripping on new home construction. Turns out electricians were making tons accidental neutral to ground and crossing neutrals between circuits... all code violations that testing would have caught. Without a doubt older installations before the AFCI requirements have boat loads neutral to earth faults. I have seen it first hand.

Its safe to say anyone who spends time in Canada or America is bathing in Magnetic fields :frown2::frown2:

Very few Master Electricians will own an earth loop impedance tester, GFCI tester, earth leakage clamp tester, etc. Even fewer will own a MFT tester, which i would say in the UK at least, the vast majority of electricians will own.

99.999% of them have never even heard of a loop fault impedance tester. Earth fault loop impedance is not required in the NEC hence unheard of.





Typical US journeyman electricians test kit will include ...A good digital multimeter with attachments for various temp probes etc, a basic IR tester, one or more Amp Clamps, volt stick, maybe a two lead volt tester etc... A companies test kit will expand the typical test equipment by providing 3 or 4 point Earth tester, milli ohm high res ohm meter, IR temp or thermal imaging camera, phase rotation tester, etc....

Pretty much. You are Correct. Generally American electricians will have a ohm/voltage meter, volt stick, Ir tester, and an amp clamp, ect. Some have other tools like a phase rotation monitor/circuit tracer but little in the way of testing. Tools like that are just for trouble shooting. A few do have a megger which I consider essential. But again, scarce.

It's a different matter for heavy industry, maintenance departments will often carry an extensive inventory electrical test equipment, often covering both MV and LV installations....

Correct, but sadly its more when the problem happens, not before hand.

Earth fault loop impedance is first predicted by calculation at the design stage and then tested by carrying out a live test known as an earth fault loop impedance test.

The purpose of this is to ensure that there is an earth path of sufficiently low impedance to cause the operation of the OCPD within the required time of an earth fault occurs at the furthest point of the circuit.

I think what you are talking about is the continuity of cpc test carried out as a dead test before live testing starts.

Out of curiosity, is the test just to ensure the earth conductor is intact all the way back to the source? If the Equipment grounding conductor is sufficently sized as per NEC tables and in connected all the way back to the source neutral terminal, it will trip the breaker under a fault with minimal voltage gradients during the fault.


Thanks everyone thus far!

 

[Gardner]

Gardner,

Does your company need to produce/attach any form of installation compliance certificates for these trailers they are exporting into the UK/(EU) that confirms compliance with say BS 7671?? Or do you have an agent or the like, to provide/carry out certificate conformance inspection and testing??

Just wondering, as the power supply and earthing arrangements to these trailers could well be different at every location they are used. (eg Temp mains building supply, Generator supply)

Good question. There will be some testing but Im not sure what kind yet. Most likely an agent will give a certificate of verification.

As for power, it will be a pin and sleeve. Earthing will be TN-S No TT that I know of and TN-C-S is a dangerous for a trailer (at least according to NEC type thinking)

 

[shanky887614]

Thanks! I will read up on it. If anything the theory first.




We don't sadly, however we do have other tools in the shop that could probably make do.








I am interested in reading it. I have been now for some time because of this project. This is the first PDF that comes up on Google on BS7671. Can anyone confirm this is a fake or real?

http://www.thailandlift.org/documents/BS7671-2008.pdf









Only when studying theory. Mike Holt's Forum has made the NEC exciting... to a degree anyway. So Id imagine the same will happen here. (Hopefully)







Unfortunately you are correct. This is one thing I hate about our system. Testing is non existent in small applications like residential or commercial. Absolutely no testing of any kind takes place. None. The NEC electrical inspectors perform little if any testing. At most they will plug in an outlet tester just to make sure the outlet has correct polarity and a functioning ground (if the light lights up on the tester ground is ok), perhaps even trip GFCIs. But other than nothing. There real job for an inspector is just to visually inspect everything. If no NEC violations can be visually seen, it passes inspection. The sad part is others in the trade think I am crazy for wanting actual testing.

In fact, when AFCIs (Arc Fault Circuit Interrupters) were required for general use residential circuits a few years back, the ones that had 30ma differential protection caught a lot of wiring errors. Complaints were and are still common of them tripping on new home construction. Turns out electricians were making tons accidental neutral to ground and crossing neutrals between circuits... all code violations that testing would have caught. Without a doubt older installations before the AFCI requirements have boat loads neutral to earth faults. I have seen it first hand.

Its safe to say anyone who spends time in Canada or America is bathing in Magnetic fields :frown2::frown2:






99.999% of them have never even heard of a loop fault impedance tester. Earth fault loop impedance is not required in the NEC hence unheard of.





Typical US journeyman electricians test kit will include ...A good digital multimeter with attachments for various temp probes etc, a basic IR tester, one or more Amp Clamps, volt stick, maybe a two lead volt tester etc... A companies test kit will expand the typical test equipment by providing 3 or 4 point Earth tester, milli ohm high res ohm meter, IR temp or thermal imaging camera, phase rotation tester, etc....

Pretty much. You are Correct. Generally American electricians will have a ohm/voltage meter, volt stick, Ir tester, and an amp clamp, ect. Some have other tools like a phase rotation monitor/circuit tracer but little in the way of testing. Tools like that are just for trouble shooting. A few do have a megger which I consider essential. But again, scarce.








Correct, but sadly its more when the problem happens, not before hand.








Out of curiosity, is the test just to ensure the earth conductor is intact all the way back to the source? If the Equipment grounding conductor is sufficently sized as per NEC tables and in connected all the way back to the source neutral terminal, it will trip the breaker under a fault with minimal voltage gradients during the fault.


Thanks everyone thus far!

efli is bassically checking the resistance L-E at the supply through the supply transformer to its star point then through the return earth path to make sure it complies to the max values in the iee wiring regs.

each mcb/fuse etc has a max zs, if it doesnt comply then a different type or a bigger cable is required

 

[Engineer54]

Originally Posted by davesparks
Earth fault loop impedance is first predicted by calculation at the design stage and then tested by carrying out a live test known as an earth fault loop impedance test.

The purpose of this is to ensure that there is an earth path of sufficiently low impedance to cause the operation of the OCPD within the required time of an earth fault occurs at the furthest point of the circuit.

I think what you are talking about is the continuity of cpc test carried out as a dead test before live testing starts.

Out of curiosity, is the test just to ensure the earth conductor is intact all the way back to the source? If the Equipment grounding conductor is sufficently sized as per NEC tables and in connected all the way back to the source neutral terminal, it will trip the breaker under a fault with minimal voltage gradients during the fault.

Earth fault loop impedance testing is basically to confirm or otherwise that a sufficient low impedance exists to cause the operation of the protective device, within the required time anywhere on the circuit under test. eg Zs

Earth Loop testing at the origin of the supply ''Ze'' will confirm if any earthing exists and will give a value for that earth. An earth loop tester will also give the PEFC and PSCC at the origin of the installation....

I'm sure others here will give you a more in-depth explanation... lol!!