Noob Question regarding hookup wire voltage ratings 300V 600V - Page 1
Forum section: electronics / beginners

author: chirality
author_rank: Contributor
timestamp: November 21, 2017, 09:15:33 pm
content: I'm trying to better understand hookup wire voltage ratings so I can safely use the right one in projects that connect to mains voltage.Here in United States, it seems like very common hookup wire, solid or stranded, in 14-24awg for electronics is UL1007 (300V rated) and thicker insulated UL1015 (600V rated, 105C). I know there are other standards, like MIL or something (?), but I don't know under what circumstances they are typically used...Anyway, is UL1007 300V rated wire safe enough to handle 120V (or even 240V) household mains power? Say, to hookup a mains input receptacle to a step-down transformer (inside an enclosure).I'm confused because I have the impression that since 120V household voltage is RMS, the absolute peak to peak voltage is closer to 340V and therefore UL1015 600V wiring would be necessary. Is this correct? Are the ratings on wire 'DC max' or 'AC max'?

author: tomy983
author_rank: Contributor
timestamp: November 21, 2017, 09:56:22 pm
content: I can't really answer your question, but I can tell what we normally use in Italy (240V).BTW, all conductors are always with double insulation, either a molded cable, or within a plastic tube or plastic box...This is what is commonly found in our homes:http://www.baldassaricavi.it/repository/public/products/1/N07V-K.pdfHope it helps.

author: Zero999
author_rank: Super Contributor
timestamp: November 21, 2017, 11:14:02 pm
content: Presumably you're just talking about the voltage, rather than the current rating.The chances are the cable insulation will be able to take many thousands of volts, before the insulation breaks down and it arcs over. The mechanical characteristics of the insulation such as: abrasion resistance and temperature rating, are far more important.What class of insulation do you require: functional, basic, or reinforced (look them up using a search engine if you don't know what they mean)? That kind of hook-up wire typically only has basic insulation at best and is only strong enough to be used inside an appliance.

author: saturation
author_rank: Super Contributor
timestamp: November 22, 2017, 12:21:23 am
content: UL wire specifications are in working voltage, not peak. Its Vac rms, so UL1007 is 300Vac rms.UL 1015 is the equivalent ofhttps://www.nationalwire.com/pdf/MIL-DTL-16878-1.pdfbut note how much more MIL spec requires.

author: chirality
author_rank: Contributor
timestamp: November 22, 2017, 02:44:39 am
content: Quote from: saturation on November 22, 2017, 12:21:23 amThanks for clearing this up for me.Whenever I'm shopping for hookup wire, I often will come across tables that list the specs like this:http://www.standard-wire.com/comparison_chart_ul_wires_cables.htmlSo I was never too sure how to interpret the voltage rating given there's a choice between 300V and 600V. Is Mil spec meant for aviation, aerospace, military, automotive applications?Quote from: Hero999 on November 21, 2017, 11:14:02 pmYes, just talking about voltage. I'm just looking for general purpose hook-up wire that would go inside metal and/or ABS 'project box' enclosures, but can handle mains rated voltages/current when necessary which for me would be 120V 15-20A max.

author: IanB
author_rank: Super Contributor
timestamp: November 22, 2017, 02:58:11 am
content: If I were doing this I would just buy mains rated appliance flex and use a short length of that, removing the internal insulated conductors from the outer sheath if needed. I don't recall how common it is to find double insulated appliance flex in the USA. It is universally available in the UK in current ratings from 3 A to 13 A. You would just buy it by the meter at any hardware store.

author: chirality
author_rank: Contributor
timestamp: November 22, 2017, 04:00:41 am
content: Quote from: IanB on November 22, 2017, 02:58:11 amI've actually done that before-- removed the inner insulated conductors from 18awg 6ft power cords. Although I can get cords rather cheaply from second-hand stores, a lot of the cables have rating markings only on the outside jacket and not on any of the inner ones.Sadly, most hardware stores, at least the 'big-box' ones here no longer seem to carry a large assortment of wire other than those one would typically use for building construction.

author: Zero999
author_rank: Super Contributor
timestamp: November 22, 2017, 08:47:44 am
content: Quote from: chirality on November 22, 2017, 02:44:39 amAre you sure you need the full 20A, which would require 12AWG wire? If not, add a suitable fuse, at the end of the mains cord and use wire suitable for the fuse rating, after it.

author: saturation
author_rank: Super Contributor
timestamp: November 22, 2017, 02:56:36 pm
content: Enjoy, welcome.You only need the additional wire specs if designed into your product. In general, most consumer grade wire of "X" thickness of similar material, say PVC, will be similar to the MIL spec but its never really been tested for same. The actual formulation of PVC matters [ e.g. stabilizers, plasticizers] as well as the quality control of the maker.Specs besides working voltage are a concern when you are say, hooking up direct to mains were surges and transients above "steady state" aka working voltage can happen, and want to really control for it to define the risk or arcing from dielectric breakdown. This is why the wires on most reputable surge protectors are extremely beefy to exceed most CAT ratings, so it rated to take worse case transients enough for the surge suppressive elements to do its job, usually > =CAT III for plug in surge protectors.A rule of thumb is the dielectric breakdown occurs at least 5-10x the rated working voltage but at Vp not Vac rms. So 300V wire should withstand 1500Vp-3000Vp.UL does not specify transient rating, AFAIK nor is it specified in the USA by the NEC, so that transient parameter is 'undefined', they are most concerned only with working voltage, temperature and the conditions the conductor will be exposed too, e.g., underground, underwater etc.,https://www.ul.com/wp-content/uploads/2014/04/WC_MG.pdfQuote from: chirality on November 22, 2017, 02:44:39 am