Wire size vs current capacity tables.

[Oldcodger]

Does anyone have access to this sort of table. I've googled with no results and any searches on here bring me back to this part of the forum. Or if not, can anyone suggest the capacity of a 16 x .02 mm ( measured as .028 mm dia) wire, with twisted dia of 1mm).
I bought it as .5 mm CSA, rated as low voltage ,11A capacity, but on receipt I'd not be happy asking it to carry the stated 11A .Aside, I've got some Halfords 5A auto cable which is 22/.25mm diameter.( twisted dia is 1.33mm)
I've also got a similar cable of two wires composed of 22 cores of .25mmdia ,with a twisted dia of 1.15mm). It's ex a table lamp fused at 3A.
Normally we are not overly bothered by current carrying capacity, but on this project , I'm looking at circa 6A ,possibly more. Voltage is not a consideration as th upper limit is 24v.

[joebog1]

https://en.wikibooks.org/wiki/Engine...ic_Engineering

There is a very good one there, if you want more I have several different ones I have used over the years.

Joe

[Herald1360]

There's a lot of useful wire info at the back of this (large) Alpha Wire catalogue:


http://www.alphawire.com/MasterCatal...talog_2011.pdf


There are other similar ratings tables about, mostly in wire and cable manufacturer's data.


16/0.2 (not 16/.02, though it's colloquially just called "1602") is nominally 0.5 sq mm (not mm) CSA and is about 22AWG which has a single wire in free air rating for 35C rise of about 8A with two loaded wires (as in a mains flex) rated at 5A for the same rise. See graph on p539 of Alpha catalogue.

16/0.2 is actually slightly larger CSA than 22AWG minimum dimensions and a single wire 35C rise rating of 11A is feasible. If the insulation is higher temp rated than PVC, even higher loadings may be possible without insulation overheating problems.


For 10C rise the corresponding ratings for 22AWG are about 4.3A and 2.7A.


Twin flex PVC insulated using 16/0.2 wire is generally rated for 3A using the 10C rise rating.


Automotive cable is normally thicker for similar current ratings since voltage drop in a 12V system is often more of a problem than temperature rise and the wires may also be in looms with large numbers of loaded wires.

[Diabolical Artificer]

See here - https://www.vintage-radio.net/forum/...d.php?t=160243 and here - https://www.powerstream.com/Wire_Size.htm and here - https://duckduckgo.com/?q=wire+gauge...ty&t=lm&ia=web and here - https://duckduckgo.com/?q=wire+gauge...ages&ia=images

Hope that helps, Andy.

[David Simpson]

The IET(formally IEE) have for many years published Handbooks/Guides/Pamphlets etc. in support of their "Wiring Regulations". The WR's give definitive details & tabulations of permitted Cross Sectional Area/Current Carrying Capacity/Volts Drop per Meter & so on.
Cheapo wee reels of auto wiring from Halfords might do for heater wiring in vintage radios. BUT - don't get it mixed up with wiring you might use for HT Power Supplies etc. It has a totally different spec. insulation & heat dissipation - wise. And certainly not for mains wiring.

Regards, David

[Herald1360]

True enough, though copper and PVC are the same whatever end use the wire is aimed at. If they're each thick enough for the current and voltage rating required, then using for hookup wire will be fine. Just don't use something of dubious origin for any mains carrying wiring!


Automotive stuff of our sort of vintage will likely have much thicker PVC than required just for 12/24V just for abrasion resistance etc but modern stuff looks very flimsy and "cost engineered" by comparison.

[emeritus]

Current rating differs for free air and enclosed (such as conduit) installations. I have a reeled extension lead that is rated at 13A when unwound but only 6A when wound on its drum. A recent poster on the forum mentioned having come across such an extension lead which could not be unwound as the insulation of the cable had fused together into a solid mass.

[tritone]

I very often use CSA Tri-rated 20 AWG, 0.75mm, stranded copper machine panel wire, rated for 14A, 600V/1000V UK, 105'C, BS 6321, from Cyinder Cables, UK. Top quality stuff and it's a very flexible wire too.

I'd say the 22 AWG, 0.5mm of the same wire would suit you.

https://storage.googleapis.com/wp2-b...cable-spec.pdf

I have plenty of the 20AWG in the above description ^ if you want a few meters FOC ? I only have white, pink, blue, brown, purple and grey the moment.

Tritone.

[Oldcodger]

Thanks to all. It is 16/.2 , and with Herald's info it will do what I need it for. I was slightly worried over the difference in size between it and a reel of stated as 5A from Halfords. ( I use this as a source of low voltage hook up wire).
Herald - I agree on ye olde car wiring. I've just had to replace a headlamp connector and thought the size of the wire very small to carry a 55w ( circa 4.5A) .
I never use anything dubious for mains and will make a meter lead from mains cable to be certain that I can use it on mains ( using the old principle of only one lead in hand at any one time ).

[G4_Pete]

Hi appreciate you have your solution but for interest some years ago I carried out some tests on 1602 ptfe covered wire to test the fuse type to protect it in a given service. I ran it as a single strand and then a section folded over to simulate 5 pieces of wire running together. It ran 8 Amps in air with no perceptable rise on the single wire and slight warming on the 5 core part. I then wound it up to 10 Amps with a thermocouple in the twisted section and in one minute it had risen to 54 deg C when I stopped the test.
The resistor shunt and second meter was a cross check on the current which was derived from a low voltage transformer.

Pete

[Oldcodger]

pete- I remember years ago that there was a problem with PTFE- known as fume disease, where the user got problems similar to flue, aftr soldering PTFE and over heating ( as I rmmbr) the insulation.

[broadgage]

So many factors influence the current carrying capacity of wires that it is hard to give any very reliable or definitive advice.
In view of the modest currents involved in most electronic goods, I would advise a cautious approach when selecting internal wires. If in the slightest doubt, go up a size.
For home built projects, or for the "one off" repair of commercially produced apparatus, the cost of going up one wire size is utterly trivial. It is a "waste of thinking" to calculate in detail as to the possible suitability of say 0.5mm wire, under ideal conditions. Just use 1.0mm and sleep happily.

By contrast, when specifying many miles of heavy power cables, the costs can run into millions of pounds, and detailed calculations and analysis can be justified to avoid the use of say 4 parallel cables each 240mm, when 3 cables could have sufficed. And even then experts have been known to be "over optimistic" Remember Auckland !

[Herald1360]

sq mm ? Or mm diameter/radius?

[broadgage]

I was referring to square millimetres of cross sectional area, the generally accepted way in which cable sizes are expressed in the UK and Europe.

[Herald1360]

Fair enough- as in 2.5mm T&E, 6mm T&E etc.


Not being an electrician, smaller gauge wires in electronics were generally referred to at work by the stranding as in 16/0.2, 14/0076 etc or the "equivalent" AWG number.