Fire proof PTFE 120Vac exension cable? - Page 1
Forum section: electronics / beginners

author: incf
author_rank: Frequent Contributor
timestamp: April 24, 2025, 05:18:44 pm
content: Suppose you have a product/device that you wish to stress test unattended for long periods of time, and various reasons (it might be made of flammable material, contain batteries, etc.) if the device fails it could catch fire.Do fire proof extension cords exist made of PTFE or some other material? Disposable of course. 2-prong is fine.I know that material ratings of normal extension cords are such that they are "supposed to eventually go out" - but I don't trust them.*I really don't want to use a cover blanket of inert gas. I'd rather put the DUT into a metal test box (with fire proof extension cord coming out) and walk away while it runs a stress test for a few weeks.Alternatively, are there other solutions to this problem? Maybe armored cable with plugs on both ends might self-extinguish better than plain extension cord would?

author: Berni
author_rank: Super Contributor
timestamp: April 24, 2025, 05:43:50 pm
content: I don't see why someone would make such an extension cord given that exposing an extension cord to fire is not exactly a normal use case. Also even if you did have an extension cord that is completely fire resistant (like mineral insulated wire, ceramic socket..etc) whatever off the shelf appliance mains plug you plug into the extension cord is still going to be made out of the typical plastic materials that will definitely fill the room with toxic smoke when heated to temperatures seen in a fire.However nobody is stopping you from just buying PTFE wire and putting connectors on the end to make your own cord.If you are paranoid of a fire then string your text box with fire detection cable and then connect live and earth to it, so as soon as something gets toasty in there you will get a earth fault and the GFCI will quickly shut things off.

author: David Hess
author_rank: Super Contributor
timestamp: April 24, 2025, 06:20:06 pm
content: I looked for plenum rated power cables, however because running power cords through plenum areas is forbidden, they do not exist.I think you will have to make your own. If it is really that important, get some plenum (CMP) rated speaker cable and use that to make an extension cord.

author: incf
author_rank: Frequent Contributor
timestamp: April 24, 2025, 06:29:09 pm
content: Quote from: Berni on April 24, 2025, 05:43:50 pmI'd imagine industrial users (eg. steel foundry, or any other process that uses high temperatures) would happily find a number of uses for a 200C rated PTFE temporary power/extension cable if regulations permitted them to.There are many places in which power (even temporary cords) must travel through areas with elevated temperatures for routine operation, maintenance, cleaning, etc..

author: Berni
author_rank: Super Contributor
timestamp: April 24, 2025, 07:13:02 pm
content: PFTE will not survive molten metal dripping on it.While it is a very heat resistant material, it will still decompose above 500°C and rather worryingly it decomposes into HF, once that stuff finds something wet (including lungs), it becomes hydrofluric acid. On top of that PFTE in thickness appropriate for use as an extension cord make the wires rather stiff, so it would be a nightmare to coil up or stay along a route once layed down. People would hate using it. Tho i do keep some PFTE wire on hand as it comes in very useful in certain use cases.Conditions this extreme are simply too much for an extension cord to make sense.In general pretty much any reasonable extension cord will survive 100°C and that is plenty for what a cord might reasonably encounter. Also bearing a UL label and similar certification is means the materials it is made of will not sustain a fire.That being said when testing something that might catch fire indoors, the fire itself is not the bad part. As long as you put the thing into a clear empty corner of concrete/brick walls and is reasonably enclosed there is very little risk of the fire spreading out. However the problem is that the combustion has the possibility of creating a lot of dirty smoke that will coat everything in crud, smell horrible, or even create a deadly atmosphere in the room. Having a fancy extension cord does nothing to mitigate that.

author: TimFox
author_rank: Super Contributor
timestamp: April 24, 2025, 07:28:09 pm
content: Plenum-rated cables (usually some type of Teflon insulation) are not rated to be fireproof: they are designed not to give off harmful vapors."Plenums" are typically volumes of air above a dropped ceiling, used as low-pressure air returns in ventilation systems.If cables gave off fumes, the plenum would distribute them around the building.A quick check of McMaster-Carr indicates 120 V extension cords for "abrasion resistant", "harsh environments" (up to 220oF = 104oC), and "welding" (resists welding slag) usage, but none are "fire-proof".

author: Stray Electron
author_rank: Super Contributor
timestamp: April 24, 2025, 08:11:53 pm
content: Quote from: incf on April 24, 2025, 05:18:44 pmThat's what I would do. And I'd a couple of temperature sensors connected to fire alarms. I would also connect the sensors to relays that would cut off the AC power if things went awry.If you're not going to be moving your test stand around then wire it up with THHN wire inside of a conduit. The other thing that you could do is to do like some of the automobile manufacturers and put a short section (6 inches or so) of smaller wire in the power circuit so that it acts like a fusible link and any short will damage it first. Then place the small wire section inside of a fire proof container. Auto makers use wire that is the next smaller available gauge (18 gauge in a 16 gauge circuit). And instead of making the small wire section undersized for the required amperage I would make the main wire larger than needed.Because: using a simple fuse would be too easy!

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: April 24, 2025, 08:25:20 pm
content: Not exactly what the OP is looking for, but L-com has an LSZH power cord that we specified for an airborne application where the aircraft crew were concerned that our equipment had power cords that could generate smoke in the cabin under overload conditions.https://www.l-com.com/power-products-n5-15-to-c13-lszh-power-cords-18awg-2-metersAs others have pointed out, you can make your own. Specify an M1252 cable such as this one:https://www.digikey.com/en/products/detail/alpha-wire/M1252-WH005/3838637Or use M27500 cable (aerospace grade), but these are expensive. Yes, they are pretty stiff and hard to work with. The connectors will likely have to be something other than NEMA 5-15 and the like since they're all plastic - maybe a 38999?The tougher industrial-rated cables I've used are Type-W, these are rated for abrasion and crush resistance though and not for fire resistance.

author: David Hess
author_rank: Super Contributor
timestamp: April 25, 2025, 12:24:12 am
content: If you really want something which will withstand high temperature operation, an extension could be made with high temperature appliance wire. Silicone and Teflon insulation is used for some, but even higher temperature wire with mica and fiberglass insulation exists as well.

author: amyk
author_rank: Super Contributor
timestamp: April 25, 2025, 05:20:16 am
content: Quote from: David Hess on April 25, 2025, 12:24:12 amFiberglass insulated wire will definitely not burn. If the question was asked a century ago, the standard response would be asbestos insulated wire, which is what that replaced.

author: Berni
author_rank: Super Contributor
timestamp: April 25, 2025, 05:22:59 am
content: This is the wire that is truly fire proof:https://en.wikipedia.org/wiki/Mineral-insulated_copper-clad_cableIt can survive up to 1000°C since above that the copper it is made out of melts. But it is annoying to work with and terminate, so for that reason this wire is only used for the most critical infrastructure. It is designed to not short out even if the room it is running trough is actively on fire. But yeah it is even less flexible than the already not very flexible PFTE cable, so it is for permanent installation.