Wire thickness for soldering iron cable - Max Amps - Page 1
Forum section: electronics / beginners

author: BinaryBits
author_rank: Contributor
timestamp: August 03, 2022, 07:23:39 am
content: So I ordered some 5 Core Silicone cable, which is advertised and used by people as Soldering iron cable. But I am a bit skeptical about the individual wire thickness, they are like 1mm each, including the insulation. I think each wire has 35x0.08 strands? So maybe AWG24 or something similar?When I check the "Wire thickness vs Amperage" charts online they show that AWG24 can carry 2.1 Amps, and another chart showed 0.57 Amps when the wires are in a bundle (which they are).So my question are....is this enough to use for soldering irons, which are often up to 80 Watts?I want to use this cable for hot tweezers which has 2 x 40W heaters, and for soldering irons which are 40W and 60W, and maybe even 80W.Also, the Hot Tweezers and the 40W iron is powered by only 12 volts.So can it safely be used for 40W (12V) and up to 80W irons, even though the charts seems to say otherwise....since people are using this exact same cable as soldering iron cable? This cable was actually sold by the company KSGER who makes soldering stations.Thanks in advance.By the way: If somebody knows where one can find real super flexible soldering iron cable, like the one Weller uses, I would be glad to hear it. Since this cable is not as flexible as for example the Weller ones. Probably because this cable only has Silicone on the cable sheathing, but the individual wires is not coated with Silicone, but with FEP (Fluorinated Ethylene Propylene).

author: Gyro
author_rank: Super Contributor
timestamp: August 03, 2022, 08:30:41 am
content: Silicone Rubber(as opposed to Silicone) cables are usually rated for a higher maximum current than ordinary PVC insulation because of their higher temperature capability. The main factor becomes whether the voltage drop is acceptable along the length of the conductors, ie. whether you get a significant drop in the element power. It's important that the internal conductor insulation i also Silicone Rubber or similarly heat resistant. Yes the conductors are bundled, but how many of them are actually carying element current? The cable is also moving in free air as opposed to being constrained in a fixed cable loom in a piece of equipment.Acceptability also depends on the iron. If it is temperature controlled, it will only pull maimum load for a few seconds before dropping to a much lower idle power dissipation. I don't know if your hot tweezers fall into that category.There is certanly a bit of a trade-off between voltage drop on the cable and flexibility in this application. Cables that have all Silicone Rubber insulation will be more flexible.

author: tooki
author_rank: Super Contributor
timestamp: August 03, 2022, 06:10:17 pm
content: Quote from: Gyro on August 03, 2022, 08:30:41 am”Silicone” means “siloxane polymer”, and those are oils, rubbers, or stuff in between (gels). Silicone rubbers (what’s used as insulation) are asubsetof silicone, and thus, it’s absolutely correct to say just “silicone”, since wire insulated in silicone gels or oils don’t exist (since they wouldn’t even be possible) and thusallsilicone-insulated wires are silicone rubber insulated, meaning it’s not necessary to specify.What would be wrong is any terminology using just “silicon” without the “e”.

author: Gyro
author_rank: Super Contributor
timestamp: August 03, 2022, 06:13:57 pm
content: It was more an issue of what they are sold (described) as, ie. the search term.

author: tooki
author_rank: Super Contributor
timestamp: August 03, 2022, 06:19:54 pm
content: Quote from: Gyro on August 03, 2022, 06:13:57 pmAs someone who’s shopped for lots of silicone wires, I totally disagree about it being necessary to add “rubber” to the search.

author: tooki
author_rank: Super Contributor
timestamp: August 03, 2022, 06:33:51 pm
content: Quote from: BinaryBits on August 03, 2022, 07:23:39 am(Silicone wire dimensions from my favorite aliexpress vendor for that product.) PVC-insulated 24AWG is usually 1.3mm outer diameter (OD), and silicone around 1.6mm. A 1mm OD would be between 30AWG (0.8mm OD) and 28AWG (1.2mm OD).30x0.08mm is AWG26, which has an OD of 1.5mm. See the attached table for specs.Maximum current for a wire (from the wire’s point of view, not the circuit’s) is dictated by how much heat it can tolerate. This is frequently referred to as the “ampacity” of a wire, and there exist standards for that. Bundles of wires have less airflow and thus will heat up more for a given current.

author: Gyro
author_rank: Super Contributor
timestamp: August 03, 2022, 06:47:29 pm
content: Quote from: tooki on August 03, 2022, 06:19:54 pmFeel free, I have no strong feelings on the subject.Edit: You have forgotten the table attachment.

author: BinaryBits
author_rank: Contributor
timestamp: August 07, 2022, 09:06:41 am
content: The product information says that the individual wires has 35x0.08 Strands, but I don't find any AWG´s that has 35 strands, only 30 and 40, so I'm not quite sure about the AWG number on these wires.But it seems Silicone....rubber insulation is thicker than some other insulations, meaning they give the wire a thicker outer diameter? These wires has FEP as insulation (which also can handle up to 200℃), so that might give them a bit thinner outer diameter, compared to Silicone rubber insulated wires? The total combined diameter of the wire strands seems to be around 0.4-0.5 mm.I will use cable lengths of around 1.5 m. And the soldering gear that this cable is going to be used with are temperature controlled.I guess I can do some tests for voltage drop on the cable?Also, I assume it makes a difference if the strands are copper or Aluminium/Aluminum, when it comes to max amps?Any ideas what the wire thickness normally used on the heater wires on for example JBC, Weller, Hakko irons is?Earlier i took the cable from an old Weller LR-20 iron and it had pretty thick heater wires (thicker than the 3 other wires), but my Weller WP-80 iron has a cable with a total outer diameter of 4.8mm, and I think it has 6 wires inside, so the wires cant be too thick (I don't want to open to find out)?

author: Gyro
author_rank: Super Contributor
timestamp: August 07, 2022, 09:34:41 am
content: Yes, a voltage drop test is a good idea. If this becomes an issue, reducing the cable length is an option (1.5m sounds quite long). Temperature controlled gear is good because the controller will simply put out more volts to maintain temperature, as long as it's still within its capability, mitigating any additional voltage drop on the cable.Avoid Aluminium strands like the plague - I assume you mean Copper clad Aluminium (CCA). They have far higher resistance than Copper for a given cross section. I don't know, but I suspect that Aluminium may have a shorter flex life too. CCA is increasingly found in dodgy Chinese mains leads and cables - they can be identified by scraping the strands with a blade and finding silver colouring inside. Also be aware of Copper clad Steel (identified with a magnet).

author: sleemanj
author_rank: Super Contributor
timestamp: August 07, 2022, 10:12:24 am
content: Rule of Thumb for Silicone Wire....Take the cross sectional area in mm2multiply it by 25 and that’s a reasonable current capacity in Ampsunfortunately the reference where I got this many years ago has disappeared from the net now (and not in the wayback and I never PDF'd it) but was based on 80 circular mils per amp.Anyway by that rule of thumb with 35 strands of 0.08mm35 * (0.04 * 0.04 * 3.14) = 0.176mm2multiply by 25 gives about 4.4 AmpOf course this says nothing about voltage drop over the length, and is probably best considered a free-air situation rather than a cable bundle.For 40W at 12v you only need 3.3 Amp, it's common for soldering irons to run at higher voltage than that though. Ultimately, more volts means less copper.

author: tooki
author_rank: Super Contributor
timestamp: August 08, 2022, 06:05:10 am
content: Quote from: Gyro on August 03, 2022, 06:47:29 pmOh, shoot! Thanks for letting me know. I’ve been having frequent issues with the forum giving me an error when posting (“connection was lost”), and going back to the form, it won’t submit without completely reloading the page, so attachments are lost (the text I copy to the clipboard first) and I have to remember to reattach them. That’s probably what happened.

author: tooki
author_rank: Super Contributor
timestamp: August 08, 2022, 06:16:00 am
content: Quote from: BinaryBits on August 07, 2022, 09:06:41 amYeah, 35x0.08mm is a strange value. Can you verify it says 35x0.08mm, and not 35x0.08mm2?Quote from: BinaryBits on August 07, 2022, 09:06:41 amSilicone is not as tough as most other insulation materials (for example, in abrasion resistance), so it has to be thicker. So silicone wire that’s used for protected applications (like inside an RC car or drone) is a bit thicker, and silicone test lead wire has thicker insulation still.

author: tooki
author_rank: Super Contributor
timestamp: August 08, 2022, 06:17:54 am
content: Quote from: BinaryBits on August 07, 2022, 09:06:41 amAvoid aluminum wire like the plague. It’s harder to work with, less durable, and just a bad idea overall.