Talk:Fuse (electrical)

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Not a circuit breaker[edit]

A fuse is not a circuit breaker - a circuit breaker is always a resettable electromechanical device. The article talks mostly about household fuses - they are also applied in power distribution up to about 115,000 V. I'll put this one on my list. --Wtshymanski 03:21, 15 Dec 2004 (UTC)


Is it really the case that "most other" jurisdictions consider the branch circuit protection to also protect the flexible cord wires? I could only speak for US/Canadian standards. Does any other part of the world put a fuse in the attachment plug? --Wtshymanski 21:31, 15 Dec 2004 (UTC)

The british BS1363 plug is the only general purpose plug i know of that is normally fused (there is also the british electric clock connector and a few propietry variants of the BS 1363 plug). I have seen some pictures of old spanish installations that had fuses in the sockets though (these were however very old sockets with no earth contacts so they probablly aren't representitive of modern spanish wiring). Plugwash 19:35, 14 October 2005 (UTC)


Although I don't have the knowledge to write it, it would be nice to have a section near the end briefly explaining

  • ATO : (Automotive Technology Organization) fusible part embedded in plastic with two press-in blade connectors in line for ... etc.
  • SFE :
  • MDL :

etc. and add the acronyms to those pages if they exist (SFE does exist but doesn't include this). —Preceding unsigned comment added by (talk) 16:07, 25 November 2008 (UTC)

I believe SFE and MDL are just part numbers of fuses manufactured by Eaton's Cooper Bussmann Business. -- JohnTsams (talk) 17:14, 5 July 2013 (UTC)

Article needs specific national labels[edit]

When reading this article I found numerous references to specific applications that do not give a national or geographic label. For instance, I've lived in the US, Switzerland and GB and can identify some of the applications discussed, but I don't think most people can. It could really be confusing. I realize that Wiki isn't a "technical reference handbook", but I think a lot of people come here for some quick information. I'll do what I can, but ... --TGC55 13:40, 29 March 2006 (UTC)


What is the elctronic circuit symbol for a fuse, the article doesn't say. Philc TECI 13:37, 15 June 2006 (UTC)

I'm sure someone will insert a good picture, but, basically, in ASCII art: ---o~o---
That is, a squiggly piece of metal between two terminal circles.
Atlant 13:45, 15 June 2006 (UTC)
Hmm i've always seen a different one, like the rectangulat resistor symbol but with a line through the middle. Plugwash 00:02, 16 June 2006 (UTC)

There are 3 common fuse symbols. The 3rd one is


Tabby (talk) 12:03, 5 December 2007 (UTC)

Hopefully the ascii art will now encouage someone to produce a nice image :) Tabby (talk) 12:08, 5 December 2007 (UTC)

That's strange, Tabby, but in over 40 years in electronics, nearly 30 of which being a registered professional engineer, I haven't encountered that symbol, either in North American literature or European literature. Can you cite a governing standard that defines this symbol, such as IEC/DIN or IEEE/ANSI/NEMA? It's certainly not part of either of these graphics standards. I have, however, encountered symbols in print publications and on the Web that are obviously improvised by people who have no training in engineering or drafting standards, and now that this symbol has been introduced into Wikipedia, this bit of misinformation appears all over the Web. —QuicksilverT @ 18:03, 27 July 2009 (UTC)

Its not misinformation, all 3 symbols have been used in print for decades. I've seen this one numerous times.

There are often arguments over which of the popular symbols is 'correct' with many different symbols, not just fuses, but I dont think such a concept is of any value. What matters is that they're widely used. Tabby (talk) 13:27, 24 January 2011 (UTC)

The fuse symbol graphic is referenced incorrectly. The symbol with horizontal line through the rectangle is the IEC version, see IEC 60417, symbol # 5016.

doug 17:03, 20 January 2012 (UTC) — Preceding unsigned comment added by Dougp01 (talkcontribs)

Fuse Boxes[edit]

The CU that is so popular in the UK is not the one shown, but an older variant. Its another Wylex, always black, with rounded corners and either a black plastic base, or with older ones a wooden base. These were a common fitting for decades, and masses are still in use, desite their safety issues. Tabby (talk) 10:13, 2 April 2008 (UTC)

Is the mention of Wylex based on sales popularity or did they develop this format of CU? I'm a bit dubious about popularity as I've seen many domestic electrical installations (including similar format CUs) but only about 5 years ago saw my first Wylex, so they may not be common everywhere - MK (and MEM!) were more popular in these parts when I was young. Also, any statement about relative popularity should have a reference; and even with a proper reference it is perhaps too geographically specific for a worldwide article.
Aside from that, the present lower two photographs are of industrial distribution boards using MCBs rather than domestic CUs with fuses, which appears out of keeping with the article. The more complete of the two seems to have three-phase breakers. Definitely NOT a fuse box. (Though it would be interesting to see a picture of an industrial installation with fuses.) Perhaps this section should be renamed Fuses in Building Installations (or something) to include industrial applications...
Anihl (talk) 05:43, 5 October 2008 (UTC)

I've added some imagery and hopefully clarified this section a bit ... I think it could do with some images of cartridge fuse installations - and could do without the MCB installations which I can’t see as relevant. Would anyone object if I removed them? I also have a rather clearer set of images of a 1970s MEM CU similar to the Wylex, if we think they would be an improvement. Not wanting to overload it... Anihl (talk) 23:47, 15 October 2008 (UTC)
There being no objections, have now removed those images, so they're not obtruding into the subsequent section. :-) Could maybe do with a shot of a cartridge-fuse CU, though visually they're not so different from the Wylex... Anihl (talk) 01:36, 15 December 2008 (UTC)

I've seen many homes and commercial buildings built after 1950 that used edison fuses in the midwest USA. At least as late as 1972 fuses were still used, and certainly in the mid 60's they were often still installed in new construction. Rfguy (talk) 04:11, 22 November 2008 (UTC)Rfguy

Here's a pic of the famous Wylex fusebox with original rewirable fuses. Its public domain.

Tabby (talk) 13:38, 24 January 2011 (UTC)


what type of metal is used in small fuses? —Preceding unsigned comment added by (talk) 20:56, 9 November 2008 (UTC)

A: usually tin plated copper (talk) 04:33, 18 April 2016 (UTC)

Section on UK domestic fuses and their markings[edit]

I've added a section on UK domestic fuses and their markings as this was the information I really wanted to see when I initially came to this page. After doing some research I thought I would share my findings for others coming to this page for the same reason as me. Wjoea (talk) 10:23, 5 February 2009 (UTC)

If you could add references, that would be great. If you're not sure how to add the refs, just post the URLs here and I (or someone else) can add them for you. Yngvarr (t) (c) 10:29, 5 February 2009 (UTC)
Hi, I got my information from a number of sources, mostly internet forums - are these allowed as a reputable reference? Not much else on this page has references? Wjoea (talk) 10:54, 5 February 2009 (UTC)
Depends on the source really. If you want to list them here, we can discuss them. I imagine there must be some sort of codified regulations regarding this stuff, so it'll be just a matter of find them. Yngvarr (t) (c) 11:05, 5 February 2009 (UTC)
Not much else here has references in part because forums and hands-on knowledge are not reputable sources. ;-) At the risk of a stunning overgeneralisation, practical and trade topics are less easy to provide good encyclopaedic references for than academic topics, simply because they aren't academic topics (or at least, the few academic electricians have more remunerative things to do than build WP). That and the inaccessibility of engineering standards documents. :-( Anihl (talk) 22:19, 9 February 2009 (UTC)
While it is certainly true (and utterly deplorable) that engineering standard documents tend to be inaccessible, you can get a lot of relevant info from manufacturers catalogs. But IMHO including these as sources could be construed as spamming and would likely be seen as unfair and arbitrary, as in listing a Ferraz Shawmut catalog as source rather than Littelfuse, etc. (Both are fuse manufacturers)
I would strongly argue against including internet forums as sources (or for that matter, using any information you find there) because generally speaking they're 95% BS. Rocknrollsuicide (talk) 02:45, 4 July 2009 (UTC)


I have decided to standardise this article on British English spelling. (The first editor I could find to use words of variable spelling used both.)—Dah31 (talk) 03:00, 16 July 2009 (UTC)

Really? Why? There are bigger problems with the article than spelling. --Wtshymanski (talk) 17:11, 3 August 2009 (UTC)

Wiki myopia[edit]

Three hundred lines on DIN standards and British plugs, and no explanation of how the darn thing works! --Wtshymanski (talk) 17:11, 3 August 2009 (UTC)

Less train spotting detail and more general principles would be in order for an encyclopedia; Wikipedia is not a parts catalog. --Wtshymanski (talk) 19:23, 17 August 2009 (UTC)

Factoring:Wikipedia is not a parts catalog[edit]

There's still a lot to be said about fundamentals of fuses, but instead we have a couple of long parts lists. Automotive fuses and teh stuff about two types of IEC fuses could be spun out to satisfy the parts collectors, leaving space in this article for more on fundamental principles. The big tables are very colorful but tell us nothing that we're not better off getting from a real catalog. I propose renaming the existing section called "standard designs" (which is not a good description anyway) and factor out the fuses listed there to Fuses (IEC Low voltage), and the colorful tables for car fuses can all move to Fuse (automotive). This article can just retain some general observations on the different standards (UL, IEC, ANSI, EN, DIN, BS) and point at the factored-out articles for details. Comments? In particular, anyone to suggest a good reason not to do this? --Wtshymanski (talk) 18:32, 24 August 2009 (UTC)

Sounds good to me. Wizard191 (talk) 18:53, 24 August 2009 (UTC)
fixed the link above, Fuse (automotive) now exists and I shall probably get around to creating IEC 60269 soon, and move the diazed, etc. fuses there. There's a lot more to iec 60269 than is shown here at this point. --Wtshymanski (talk) 03:18, 28 August 2009 (UTC)
Spun out IEC 60269, I've found several references this week (a Knovel subscription is handy to have access to) and this will be my project for the weekend. I've seen the IEC standards, too, and some summary of their prefaces and in scope is needed at IEC 60269. Right now it only has some German and British fuses, but there's also Italian and North AMerican fuses to add (yes, the United States ia an IEC country, too!)--Wtshymanski (talk) 16:11, 29 August 2009 (UTC)

Car-type blade fuses[edit]

I have found that, if I actually draw 15 amps through a 15 amp car-type blade fuse, the plastic melts and becomes welded to the fuse holder. Is this a common problem or did I have a poor-quality fuse? Biscuittin (talk) 10:01, 19 September 2009 (UTC)

The reason I mention it is that, if it is a common problem, it could be included in an "advantages and disadvantages" section. Biscuittin (talk) 19:42, 19 September 2009 (UTC)
Doesn't seem encyclopedia-worthy to me. Are you sufficiently familiar with fuse standards to say that they aren't supposed to melt their cases at "nameplate" current? If it was all that common, surely the standards would have been changed? Can you find any reliable quality sources that discuss the problem? --Wtshymanski (talk) 22:55, 19 September 2009 (UTC)
As an electrician (although not a fuse expert), I think the fuse's marked rating is usually for the protection of a circuit normally using perhaps half to three-quarters of that current, so that a short circuit (causing a large increase in current) would still blow the fuse fairly quickly. As car fuses are frequently used in electric motor circuits, such as fans and wipers, they will be rated as "slow blow", because electric motors take a much higher current than normal when starting up.
Biscuittin, you are operating the fuse at the extreme edge of its operational envelope, so it gets hot without quite blowing ! It is not intended to carry that current continuously. Darkman101 (talk) 19:00, 1 January 2013 (UTC)

MCB's "nuisance" trip[edit]

"MCBs are rather prone to nuisance tripping" No, no they are not. I think most people who saw the time / current curves for MCB's would be quite surprised at how reluctant they are to trip. I'm assuming the original author was referring to RCD's for which a cartridge fuse does not offer a suitable alternative. -- (talk) 03:25, 3 December 2009 (UTC)

In the UK our type B MCBs are far more prone to nuisance trips than fuses, and this is the main reason why fuses are still sometimes installed in domestic CUs. I gather the situation is the reverse in the US, due to the widespread use of thermal element only MCBs. Tabby (talk) 13:41, 24 January 2011 (UTC)

pole fuse[edit]

what is the pole fuse rating in fiji

FSU and SFU[edit]

I was about to buy a fuse and got confused by the term FSU. I found an answer there: . I guess this has to do with which potential the unit ends up at after the fuses breaks? I added it to the disambiguation page for FSU, but thought maybe someone would like to describe it in here. Cyril.holweck (talk) 15:52, 10 June 2010 (UTC)

Pole mounted fuse cutouts[edit]

The fuses appear to be supplying a 3 phase capacitor bank, not a transformer. user:Dgrinkev —Preceding undated comment added 19:18, 22 June 2010 (UTC).

No, that's a transformer. Not all pole-mount transformers are round. I was there when the fuse blew and I took the picture. That was a pumping station for drainage at the dam; we demonstrated that there was no interlock in manual between the two pumps installed at that station. When both pumps were running, the fuse blew after a few seconds. Not normally a problem because one pump should always suffice for the expected volume of leakage water, but we noted this as a possibility in the inspection report anyway. --Wtshymanski (talk) 15:33, 21 October 2010 (UTC)

Characteristic curves graph[edit]

This page should really have some graphs to show the characteristic curves for different fuses, plotting current and time to show that fuses have non linear characteristics. For example see: Thomas d stewart (talk) 15:56, 21 October 2010 (UTC)

Too simplistic[edit]

Breaking capacity section[edit]

Some incorrect information in this section currently.

In the UK, standard practice is as follows for domestic premises mains wiring: CU fuses are rated 1-3kA, PSCC = 6kA. If greater than the fuse's rupturing ability flows, the overload is interrupted not by the CU fuse but by the incomer fuse.

Perhaps rename to Interrupt Rating?

Rated voltage section[edit]

"Voltage rating of the fuse must be greater than or equal to what would become the open circuit voltage. For example, a glass tube fuse rated at 32 volts would not reliably interrupt current from a voltage source of 120 or 230 V. If a 32 V fuse attempts to interrupt the 120 or 230 V source, an arc may result. Plasma inside that glass tube fuse may continue to conduct current until current eventually so diminishes that plasma reverts to an insulating gas. Rated voltage should be larger than the maximum voltage source it would have to disconnect. This requirement applies to every type of fuse."

Again this is too simplistic and not really true. On cars, some loads are inductive, and if a 32v rated fuse blows, the fuse can see far more than 32v. This is acceptable since in time the circuit voltage drops to under 32v, and the circuit can then be interrupted. Tabby (talk) 13:44, 24 January 2011 (UTC)

What does this MEAN? Maybe you should contact the SAE and IEC committees that rate fuses and tell them that 32 V isn't an adequate rating for 12 V automotive applications, though it's really OK becauase the voltage drops? What is your point here? --Wtshymanski (talk) 14:25, 24 January 2011 (UTC)
I agree with Wtshymanski, we're talking about system source voltage and the fuse voltage rating. Maybe rewording of the part regarding arcing would help. Arcs will almost always form in a fuse interrupting a current, especially 120 V and greater. Its how quick the arc is quenched that is important to achieving a high interrupting rating. --JohnTsams (talk) 19:40, 5 July 2013 (UTC)

Asstd corrections[edit]

"Fuse markings[6] will generally convey the following information;

  1. Breaking capacity"

Most fuses in the UK, whether 1.25", 20mm, mains plug, car, or CU, don't have this on them.

"n the UK, older electrical consumer units (also called fuse boxes) are fitted either with semi-enclosed (rewirable) fuses (BS 3036) or cartridge fuses (BS 1361). "

Some new ones are too. MCBs have become more popular now, but rewirable & cartridge fuses are still legal & being installed.

"The "Wylex standard" consumer unit was very popular in the United Kingdom until the wiring regulations started demanding Residual-Current Devices (RCDs) for sockets that"

Ironically the Wylex fusebox pictured is not the type that has been so popular in previous decades. Public domain picture of one at

", it is desirable to blow (clear) only the fuse (or other overcurrent device) electrically closest to the fault. This process is called "coordination" and m"

in the UK its called 'discrimination' Tabby (talk) 13:46, 24 January 2011 (UTC)

If it's an approved fuse, it implicitly must meet the standards for that class of fuse. Let's say that you won't see the kA interrupting rating stamped on the fuse but you will see some approval agency logo, which implies that the fuse meets the standards for that class of fuse. What percentage of the world's fuse applications are for protecting house wires in the UK? --Wtshymanski (talk) 15:17, 24 January 2011 (UTC)


The word "fuse" does indeed derive from the Latin fusus, but the first meaning of fusus is not "to melt" (that would be fundo, fundere). See this Online Latin Dictionary. Fusus is the perfect participle of fundo, fundere and as such its meaning is: extended, spread out, opened wide, which is a more useful way of thinking about the function of a fuse, since when it operates its ultimate function is to open the circuit (by melting). Mousemusic (talk) 08:26, 26 January 2011 (UTC)Mousemusic

WP:BOLD. --Wtshymanski (talk) 14:10, 26 January 2011 (UTC)
 Done Actually the Latin etymology is a back formation. The origin are the French and Italian words for "spindle" (fusée,fuso) [2] walk victor falk talk 12:50, 28 February 2011 (UTC)
Fascinating - this is why I read the talk pages more than the articles themselves. See also Fusee (horology) ! Explains why 'spindle' ! Also related to Rifling - Rifle = Fusil in French ? Fucile in Italian ? Or was it the Match of a Matchlock ... ? Fuse (explosives) wound round a stick. -- (talk) 00:30, 12 July 2012 (UTC)

Packaging types and dimensions[edit]

The section "Packages and Materials" describes how fuses are available in a variety of sizes and shapes but not what those shapes and sizes are. The cartridge fuse is mentioned but the standard types of cartridges (1AG,2AG,...) are not. A picture of blade fuses is shown in a later section but that package is not mentioned in this section. If I were holding a fuse attempting to identify its packaging with this page (and I was) then I would probably be out of luck (I was).

I think this section could really use a table defining some industry-standard fuse cartridges; perhaps multiple tables depending on the diversity of package types (by geolocation or industry?) Some pictures would definitely be useful in this section too.

I found my answer for package sizes at - no promises but at some point I'll try to add the content I was looking for. (talk) 22:05, 21 February 2012 (UTC)

If I was looking for an air cleaner for my car, I wouldn't be looking at an encyclopedia - I'd find a parts catalog. --Wtshymanski (talk) 22:25, 21 February 2012 (UTC)

Speeds, Types and markings[edit]

FF = ultra fast blow
F = fast blow
M = medium blow
TT = very slow blow
L = low blow current
H = HRC = high rupture current
S = sand filled

Notable ?

Can anyone find a better source than ?

-- (talk) 00:39, 12 July 2012 (UTC)

I came to the Fuse page looking for exactly this information. If anyone can confirm it, please add it to the section on "Markings". In addition, logically, T should mean Slow. (Which is what's on the fuse I'm trying to identify.) Darkman101 (talk) 21:56, 1 January 2013 (UTC)

Breaking Capacity -> Interrupt Rating[edit]

Interrupt Rating is more common to fuses where as Breaking Capacity is use on breakers. There are slight differences in the terms. Some fuses have breaking capacities significantly higher than the interrupt rating. The rating just implies the fuse passed the IEC or UL testing for short circuit current interrupting. Interrupt Capacity vs Interrupt Rating | Interrupt Rating --JohnTsams (talk) 21:21, 5 July 2013 (UTC)

Etymology is wrong.[edit]

I don't think this is correct, "In electronics and electrical engineering, a fuse (from the French fusée, Italian fuso, "spindle"[1])".

The word fuse comes from "Fusible Link", "Fusible Cut-out", and "Fusible Safety Shunt". Fusible = easily melted, link = a connection between.

See US patent, US1098870, US502330, US480802.

"...the combination, with the fusible wire of a safety-fuse, of one or more movable disks threading said wire, the openings in said disks being approximately of the size of the wire..."

--JTsams  talk 20:18, 27 May 2015 (UTC)

I came here to say this, so I concur. Here is a source, in French. Ultimately from the Latin verb "fundere" meaning "to melt". Granted, they cite as a reference, which does state that "erroneously attributed to fuse (v.) because it melts", but does not cite further source, contrary to, which bases its articles on the systematic and scientific analysis a a huge corpus.

Herix (talk) 08:49, 29 May 2016 (UTC)

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Horrible content[edit]

Horrible and pathetic content as compared to the German version here ! . needs a total rewrite Shrikanthv (talk) 14:55, 7 February 2018 (UTC)

Looked at a Google translation of the German page and wasn't impressed with it. Too much catalog information, no history, repetitive and scattered discussion of parameters. All the auto fuse stuff is specialized content best suited to its own article. Vast long tables of fuse dimensions for someone's favorite standard. --Wtshymanski (talk) 21:55, 7 February 2018 (UTC)