Stranded Wire Gauge

I think you're mixing up units. Wire can be measured in circular mils or in mil^2, but not both together. The thing to watch for in stranded wire is the filling factor which makes measurement difficult. In essence, you have to measure each strand, then multiply times the number of strands (although, for standard stranding schemes, the filling factor is known and can be used directly).

I'll give you the cmils^2 versus cmils versus mils^2. It stemmed from a typo I made a while back and carried along.

Anyway, I am measuring the cross-sectional area of individual strands. This image is an example (not my present 28 AWG cable).

Sorry about my lack of clarity. Standard English is not my first language. So, anyway, I gather you have 7 strands. Is that correct? What is the diameter of each?

No apology needed. Standard English isn't mine either: I speak American English.

Average diameter: 4.64 mils.

Standard deviation: 0.18 mils.

Quantity measured: 28 wires: 196 strands

Seven strands per wire.

Average area: 150.4 cmils

Thanks. Now I understand. The standard deviation is a little large but generally fits in with what I've seen, but the average is too low. My best guess is that either the strander set his tension too high or the #36 was too small to start with. We recently bought a lot of wire from a well-established company and got quotes based on how accurately we wanted the stranding dimensions held. I used to wind coils and the better companies (REA, Phelps-Dodge among others) guaranteed tolerances. I don't have experience with off-shore copper guys.

Tom

Thanks TVP45,

Do you have any thoughts on whether these wires should be considered 28 AWG or 29 AWG?

I don't think there is a commonly available 7 strand #29 (but I'm not sure with new suppliers). Did you check metric to see if this is just a mislabel?

TVP45,

I greatly appreciate your input and expertise. I didn't mean to confuse what I am looking for.

I am not looking for 29 AWG wire. I have specs for 26-28 AWG. My supplier provided wire with 150 cmils cross-sectional area. This is close to the 28 AWG value, but if i read the specification as 'hard limits, the cable fails to meet the criteria.

My underlying question is: with a cross-sectional area of 150 cmils, is my cable 28 AWG (in-spec) or 29 AWG (out-of-spec)?

Thanks,

MoF

I think I now understand your question. I believe we use "in spec"/"out of spec" differently. I am almost certain that what you have is "bad" 28AWG. I base this on two things: (1) Philip Crosby's dictum that getting a VW when you ordered a Cadillac is poor quality but so is getting a Cadillac when you order a VW, and (2) I can understand making wire slightly smaller either through overtensioning or through substitution (at the current price of copper, 3% reduction is significant; there should be a weight portion of the price, but really, who checks?). In any event, I suspect low 28AWG rather than generous 29AWG (even if there is a 7 strand 29).

Tom

An alert inspector is well aware of wire gauge defeciencies and inconsistencies by "foreign" suppliers. Quick glance of markings is reason to decline acceptance. Don't subject your business or reputation to another "lead paint" or "dog food" scandal.

Check the markings on the wire cover. Count the strands. Gauge each strand at different locations along a sample. Compare as measured to be within specs for compliant wire. The inspector will not be so lient.

Contact the inspector and get prior approval for the intended use.

Check out this Wikipedia link about AWG: http://en.wikipedia.org/wiki/American_wire_gauge as well as the links at the bottom of the article.

An informative Wikipedia link about Circular Mils is found here: http://en.wikipedia.org/wiki/Circular_mil

Thanks Bill, But neither get me closer to finding an answer to my question.