Cross sectional area current capacity

Gardner · Jun 15, 2015

How would you go about figuring the current carry capacity of 2.08mm2 copper conductor? In so far no reg tables have none standard size.

Darkwood · Jun 15, 2015

7029 dave said:
DW on the team then, well done, nice to see. Regards Dave.

Congrats... your the first to spot it to my knowledge ..was wondering when someone would see it

Gardner · Jun 15, 2015

darkwood said:
Congrats... your the first to spot it to my knowledge ..was wondering when someone would see it

What am I missing lol?

davesparks · Jun 15, 2015

Gardner said:
What am I missing lol?

He's become a moderator

There'll soon be more staff members than members soon!

Richard Burns · Jun 15, 2015

Gardner said:
You wouldn't happen to know what equation is used in other regs like the IEC? My understanding is, and I could be wrong, that table 4D5 and others were derived via thermodynamic equations made by the IEC.

I would agree with the above posts about cable sizing too many variable in standards compliance and cable design.

However this webpage seems to discuss the methods used in IEC60287. I feel it is not worth working it out when the standard cables have been calculated (probably well on the side of caution!) for you.

Edit just found this
IEC METHOD
IEC 60287 provides method for calculation of current carrying capacity of cable for different design parameters of cable (cross section, thermal resistivity, thickness of layer … etc.) as well as for different environment (ambient temperature, soil condition, depth of cable, spacing of phases … etc.).The current rating (ampere) using in the IEC standard is:

where Δθ [[SUP]o[/SUP] C] is temperature rise between ambient temperature and cable conductor temperature, W[SUB]d[/SUB] [W/m] is dielectric loss of cable insulation, T1, T2, T3 [K.m/W] are equivalent thermal resistances calculated from the cable material’s thermal properties, T4 [K.m/W] is the cable external thermal resistance, R[SUB]ac[/SUB] [Ω/m] is the AC electrical resistance of the cable conductor at maximum temperature and λ1 and λ2 are the ratio of losses in the metal sheath to total losses in all conductors and the ratio of losses in the armouring to total losses in all conductors, respectively.

derbylad · Jun 15, 2015

Gardner said:
How would you go about figuring the current carry capacity of 2.08mm2 copper conductor? In so far no reg tables have none standard size.

I would start by ripping this 2.08 mm or 14 AWG whatever it is straight out. Then replace with 1.5 mm or 2.5 mm depends what the load is.

GB.Kayak · Jun 15, 2015

Gardner said:
How would you go about figuring the current carry capacity of 2.08mm2 copper conductor? In so far no reg tables have none standard size.

Is it solid or stranded wire and what is the insulation material?

... and what is the installation method?

GB.Kayak · Jun 15, 2015

darkwood said:
Congrats... your the first to spot it to my knowledge ..was wondering when someone would see it

Well done dw!

amlu · Jun 16, 2015

when i heard of a american cable been mentioned i would open a awg table and look up for an answer...
15/20/25 depending on insulation used.
https://en.wikipedia.org/wiki/American_wire_gauge

Marvo · Jun 16, 2015

Richard Burns said:
.........The current rating (ampere) using in the IEC standard is:

View attachment 29359
where Δθ [[SUP]o[/SUP] C] is temperature rise between ambient temperature and cable conductor temperature, W[SUB]d[/SUB] [W/m] is dielectric loss of cable insulation, T1, T2, T3 [K.m/W] are equivalent thermal resistances calculated from the cable material’s thermal properties, T4 [K.m/W] is the cable external thermal resistance, R[SUB]ac[/SUB] [Ω/m] is the AC electrical resistance of the cable conductor at maximum temperature and λ1 and λ2 are the ratio of losses in the metal sheath to total losses in all conductors and the ratio of losses in the armouring to total losses in all conductors, respectively.

Not sure I can see that formula catching on TBH

DPG · Jun 16, 2015

Is this for the cabins you were making which were intended for UK use? If so, wouldn't it be better to use standard UK wiring types? Daz

HappyHippyDad · Jun 16, 2015

Richard Burns said:
I would agree with the above posts about cable sizing too many variable in standards compliance and cable design.

However this webpage seems to discuss the methods used in IEC60287. I feel it is not worth working it out when the standard cables have been calculated (probably well on the side of caution!) for you.

Edit just found this
IEC METHOD
IEC 60287 provides method for calculation of current carrying capacity of cable for different design parameters of cable (cross section, thermal resistivity, thickness of layer … etc.) as well as for different environment (ambient temperature, soil condition, depth of cable, spacing of phases … etc.).The current rating (ampere) using in the IEC standard is:

View attachment 29359
where Δθ [[SUP]o[/SUP] C] is temperature rise between ambient temperature and cable conductor temperature, W[SUB]d[/SUB] [W/m] is dielectric loss of cable insulation, T1, T2, T3 [K.m/W] are equivalent thermal resistances calculated from the cable material’s thermal properties, T4 [K.m/W] is the cable external thermal resistance, R[SUB]ac[/SUB] [Ω/m] is the AC electrical resistance of the cable conductor at maximum temperature and λ1 and λ2 are the ratio of losses in the metal sheath to total losses in all conductors and the ratio of losses in the armouring to total losses in all conductors, respectively.

Or you could just just my super scientific graph

(please dont!)

DPG · Jun 16, 2015

No units on your x-axis Tut tut

Daz

Gardner · Jun 16, 2015

darkwood said:
This is because its under different regulations and the cable standards are also manufactured to differing regulation too, we have our own BS standards we follow and the cable we buy is manufactured to either EU or BS requirements.

I think the insulation might have something to do with it... My understanding is that typical PVC insulated wires used in the UK are made for 70*C operation, while the 2.08mm2 PVC seems to be made for 90*C operation hence the higher current allowance in other regs.

Gardner · Jun 16, 2015

amlu said:
when i heard of a american cable been mentioned i would open a awg table and look up for an answer...
15/20/25 depending on insulation used.
https://en.wikipedia.org/wiki/American_wire_gauge

But what installation method are those values based on? I will do some more research on this.

Darkwood · Jun 16, 2015

Also to note here is that the cables may be required a derating factor if connected to equipment rated at 70c, through experience that is most switchgear etc out there.

Gardner

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