What exactly is a kcmil?.
I realise that it is used on the larger sizes of wire in the US, but what does this term mean?
Sorry but I don't understand this term.

Mike take a look here.

http://www.bluesea.com/techtalk/circularmils.htm

This is a little dated as they say MCM we used to use that term now we use Kcmil.

It is the same measurement with a different abbreviation.

Bob

1 Circular Mil = 1 cmil

1000 Circular Mil = 1 Kcmil

A 250 Kcmil conductor is a conductor with an area of 250,000 Circular Mils

[This message has been edited by iwire (edited 03-12-2004).]

Iwire,
Thanks, mate!.
We have a term over here in New Zealand, (and this is used in a few Non-US countries)
it is called Square Millimetres and gives the Cross-sectional Area of a particular wire or cable, based on the size of the individual wires and the number of such wires.
Here, the wires number 1,3,7,19, in numbers of strands, as the cables get bigger.
That doesn't include CEMPEX flexible Mains conductors that we use inside switch panel enclosures, that may have up to 2000 fine wires, but has the same size as a 1/0 conductor.
Different strokes for different folks, you know!.

Rule of thumb: 1 sq mm = 2 kcmil

A little history about MCM.... The first M is Italian for "mille" which means thousand. For some strange reason, it got changed to KCM, I believe to mean "Kilo".

C-H, Sandro,
Thanks for your advice.
I just have a wee bit of trouble getting my head around that term.
I think that it is because it is not a familiar one, ie not Metric!.

I believe that the change from the use of M to mean 1000x to the use of K is part of a general trend to use metric prefixes. If CM is circular mil, then is MCM 1000000 circular mils or 1000 circular mils.

The problem is that depending upon where you are coming from, the answer is _clearly_ 1000, unless you come from some place where the answer is _clearly_ 1000000.

-Jon

In our state DOT we still use "M" gallons for measurement/payment of water to construction contractors. Apparently it continues to confuse some people from what I've heard. I would much rather use K gallons (or circular mils) instead, it seems that a lot more folks understand K = 1,000 from my experience.

FWIW.....

MCM is still the common term here. I see kcmil on engineering drawings but that is about it's only usage.
I guess we are just slow to change the old ways.

GJ

Which in turn came from the old Latin, hence the similar use of M for 1000 in Roman numerals (e.g. MMIV = 2004).

It crops up in other fields as well, e.g. in property tax assessments where the "millage" rate is applied as an amount per thousand.

Mike,
The U.K. has used sq. millimeters for wire sizes since 1970, but prior to that we had SWG (Standard Wire Gauge) which works in a similar way to AWG, i.e. bigger number = smaller wire.

House wiring cables however, were generally listed by number of strands and size, e.g. a common size was 7/.029 meaning seven strands, each 0.029" diameter.

I'm not aware of circular mils ever being used to designate conductor sizes here.