Raychem44 wire lies about it's size

[Simon]

I always found Raychem 44 type wire to seem smaller than commercial cable and just put it down to thinner insulation. On a job at my last job I discovered that it is 30% more resistive than pure copper wire would be and I put it down to it not being pure copper as it also has good mechanical properties.

But the other day I had time to look into it properly, and it turns out that they lie about the gauge. As it is you won't find resistivity tables from TE who bought Raychem although I once found an old Raychem datasheet with wire resistivity on it hence I found out it was higher.

The cable is 150C rated (there is type 55 that is 200C rated and I assume the same deception). But this is because it is meant for applications like hot engine bays. It looks like TE have been burning the candle at both ends. On the one hand the cable is defacto in say military vehicle applications in engine bays as well as around the vehicle, on the other hand it will get hotter carrying the so called rated current than cable of the real size but in a non hot ambient will tolerate it as the insulation is 150C rated, but you can't do both with it.

A 16AWG or 1.3 sqmm wire is for example actually 18AWG or 0.8 sqmm

[tom66]

Have you accounted for the stranding?  Raychem 44 is stranded, and so the diameter from TE might be specified as the effective AWG diameter for terminating into connectors and such.  Stranding will make the wire more resistive.  In fact probably 25-30% more resistive is about right.

I doubt TE are lying to save a few cents on the cables, that would get them into huge trouble if these wires ended up in mission critical systems.

[Simon]

stranded wire is 20% more in cross section compared to the same AWG solid. When you crimp you crush the wire into a cold weld, stranded or not the copper content will be what it is, the air does not count. I have always had to strip 16AWG cable with 18AWG strippers, and that includes the air. The tool is 1mm in diameter which is 0.75sqmm not 1.3sqmm gaps in the stranding included, other 16AWG strips with 16AWG strippers.

[tooki]

stranded wire is 20% more in cross section compared to the same AWG solid. When you crimp you crush the wire into a cold weld, stranded or not the copper content will be what it is, the air does not count. I have always had to strip 16AWG cable with 18AWG strippers, and that includes the air. The tool is 1mm in diameter which is 0.75sqmm not 1.3sqmm gaps in the stranding included, other 16AWG strips with 16AWG strippers.

There is zero chance that they are fudging any numbers. The military would skin them alive if they tried to pull any shenanigans. This isn’t a Chinese fly-by-night, it’s a huge company with a reputation to maintain.

TE gives the stranding specs and they’re exactly what they’re supposed to be, but because this wire can be ordered with a large array of conductor materials (even aluminum!), you can’t make any sweeping statements about the resistivity of the entire series. You’d need to look at exactly which part you are using.

Also, one reason for not finding specs in the datasheet/catalog is because like many mil-spec parts, they simply leave it up to the relevant military specification to actually spell out the specs. In the case of SPEC44, this is AS81044.

If you look at AS81044 itself (https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=32010 ) you’ll find a table on page 7 of the stranding and resistance specs. They vary significantly by material.

As for stranded vs. solid:

“Cross-section” of wire means the copper area, you do not include the air. So saying “stranded is 20% more in cross section” is dead wrong by definition. I know what you mean, but I think it’s important to mention this. 18AWG stranded has the same cross-section as 18AWG solid. Most, but not all, wire strippers state their sizes for solid wire. (I’d love to see this changed, since we use mostly stranded wire nowadays, other than in-wall mains wires.) With a stripper labeled for solid, you should never be able to strip stranded wire in the nest of the stated AWG, never mind in one with a thinner gauge (higher gauge number).

So when you say that you’ve always had to strip 16AWG with 18AWG strippers, that’s categorically impossible, except in the unlikely scenario that you were stripping 16AWG solid wire with a stripper labeled for 16AWG stranded wire, because 16AWG stranded has a larger overall conductor diameter than 16AWG solid, and that in turn is larger than 18AWG stranded, and that larger than 18AWG solid. (16AWG solid has a practically identical diameter to the overall conductor diameter of 18AWG 19x30 stranded.)

Have you accounted for the stranding?  Raychem 44 is stranded, and so the diameter from TE might be specified as the effective AWG diameter for terminating into connectors and such.  Stranding will make the wire more resistive.  In fact probably 25-30% more resistive is about right.

TE isn’t listing a conductor diameter at all. AWG is always a cross-section, so the resistivity is the same regardless of the stranding. (The ampacity, however, may vary, since the air gaps can affect heat dissipation.)

Wikipedia sums it up nicely: “AWG can also used to describe stranded wire. The AWG of a stranded wire represents the sum of the cross-sectional diameter of the individual strands; the gaps between strands are not counted. When made with circular strands, these gaps occupy about 25% of the wire area, thus requiring the overall bundle diameter to be about 13% larger than a solid wire of equal gauge.”

TE lists the conductor stranding specs, and they’re exactly what they should be, identical to two other brands I compared (Alpha and Belden).

*One can, of course, also provide an overall conductor diameter as well, which will vary depending on the stranding and any platings applied, since they do not count towards the cross-section.

[Simon]

Wikipedia sums it up nicely: “AWG can also used to describe stranded wire. The AWG of a stranded wire represents the sum of the cross-sectional diameter of the individual strands; the gaps between strands are not counted. When made with circular strands, these gaps occupy about 25% of the wire area, thus requiring the overall bundle diameter to be about 13% larger than a solid wire of equal gauge.”

Ah yes that was more like it than my 20% recollection. If 25% of stranded wire is gaps then that means that stranded is 33% larger than solid (25/75) I found raychem wire to be 30% more resistive, I measured it and compared, at the time I put it down to the materials, but still I have always had to strip Raychem 44 with strippers one gauge smaller when in fact as the strippers state for solid the correct gauge size should be too small.

I had to deal with all of this in detail when at my last job we used equipment on a 24V system that would stop working at 22V and it was a long way away from the supply, just 13A ended up sent over wire that added up to about 6 sqmm.

I could say that the strippers may have been inaccurate, but when the wire should be bigger than the stripper of the correct size and that instead just grazes the insulation and the wire strips with the next size down like it's the right size considering it is 13% more in diameter, something is not adding up.