User:JohnIGoodwin/sandbox

Electrical Plug-top Fuses and ‘Ring’ Circuitry As Used in Domestic & Small Office Electrical Systems, Throughout Great Britain & its Colonies. The ‘fusing’ arrangements that began life as an important safety feature to prevent fire in whatever premises were connected using ‘Ring’ circuitry or multi-way adaptors, have now been grossly abused by the uninformed, making British Electrical Systems unsafe to use in many instances. The information in this entry has been derived principally from the British Standards publications numbered BS545, BS646, BS1361, BS1362, BS88, BS4373, IEC60320, and IEC60309, etc.. This article is not intended to discuss the detailed electrical technicalities of ‘Ring’ circuitry [1], but to primarily address the grossly neglected parts of the British Electrical systems that concern the connection of various, mostly Domestic, electrical appliances to their source of power – mostly via a wall-socket, or similar receptacles. It concentrates upon the safety aspects of making an electrical connection. Various regulations, that are frequently reviewed, have never attempted to consider the abuse of the construction of the appliance power-line, and correctly applying the safety precautions supposedly inherent in the plug-top fusing system.

Historical Background. The concept of introducing a fuse into a plug-top, began before 1935 as BS646 (major definitions in 1935 & 1958), using the British ‘Round-pin’ system that had developed originally for publically-supplied Direct Current power from the late 1880’s onwards, later covered by a multitude of British Standards specifications, although it is now referred to overall as the BS545 system somewhat incorrectly, that was not actually fully defined until 1951, after the BS1363 ‘Rectangular-pin’ system was defined for the first time in 1946 and implemented in 1947; the latter never truly replaced either of the former major systems, and all three systems persist and even inter-mix to a limited extent. New appliances using ‘Round-pin’ fittings are still being sold, in the form of ‘transformer’ power-units used with some razors manufactured by ‘Phillip’s’; as sold within the ‘Rest-of-World’ outside of Britain, the Americas, and Australasia, the dreadful ‘EuroPlug’ is fitted, together with a moulded-in extension piece to fit the Swiss recessed sockets. The version for the British market is otherwise identical, but has 5-amp ‘Round-pins’ fitted instead, that will fit little else of modern usage other than the special BS4373 ‘Shaver’ isolating transformer unit (now bastardised to include other fittings and often a dangerous means of switching voltage), and also ‘fused’ ‘EuroPlug’ adaptors; both are BS646 fittings that have persisted, and are fused with the tiny one amp cartridge fuse; the power-unit hangs-out precariously, due to the unnecessary inclusion of the Swiss extension piece, and the pins do not fit the Swiss wall-sockets! Those two-pin fittings actually pre-date BS546, since that specification relates solely to three-pin fittings, but two-pin fittings managed to get bound-up with those.

The concept of introducing a fuse into a plug-top, was first defined in the BS646 system. That involved primarily the ‘MK’ (Multi-Konnector) style of plug-top (identifiable from its ‘square’ profile (to accommodate the fuse)), as opposed to the ‘triangular’ profile of the corresponding BS545 fittings, with similar plug-tops of marginally different designs from a multitude of other manufacturers), but was also adopted in the ‘Wylex’ pattern of plug-tops, that had previously existed unfused, and developed subsequently as a BS1363 fitting – all ‘Wylex’ versions looking superficially ‘the same’, having a ‘round’ body-shape, an enormous ‘round’ centrally-located Earthing pin, and flanked by ‘rectangular’ Load-Bearing pins (being the logical precursor of the present BS1363 ‘Rectangular-pin’ plug-top). A variety of other manufacturers produced BS545 and earlier largely unclassified fittings, but others were covered by a plethora of older minor individual standards.  Although the BS1363 system is typified by the ‘MK’ version of the plug-top and a variety of minor variations upon that from other sources, (at least) six distinctly different major variant forms exist. The original circuitry was based on 15- and 30-amps, whereas current installations have been ‘upgraded’ to use 16- and 32-amps; for simplicity, only the later values are generally mentioned with respect to the circuitry, but the plug-tops have been addressed by their original ‘titles’.

The declared purpose of the introduction of the fuse appears to now be impossible to find documented since ‘standards’ define ‘what’ as opposed to ‘why’, but was almost certainly developed solely to make the electrical connections of its time period safer; it originally had nothing to do with ‘Ring’ Circuitry, but ‘Ring’ circuitry was subsequently applied to some BS646 circuits. ‘Round-pin’ systems of that time, used essentially connections of six different primary sizes of wall-sockets and plug-tops viz:- 2-amp, 5-amp, 15-amp, 25-amp, 30-amp, and 50-amp, in a variety of typically ‘Round-body’ or ‘Rectangular-body’ patterns that bore little resemblance to the patterns made by ‘MK’ and the broadly similar ones used by other manufacturers in more recent times. The final three power-ratings for very heavy currents were for ‘Industrial’ purposes, and have long disappeared from usage, so will not be discussed further here, having generally been superceded by individual ‘hard-wiring’ or heavy-current connectors represented in modern times by the British ‘Commando’ system, now somewhat incorporated within the IEC60309 specification. The first three size-rated versions existed in both three-pin and two-pin forms, but the two-pins forms of those declined in usage, except for special purposes – but some still in use today. Two-pin versions of the heavy-current versions may also have existed, but if so then seemingly no evidence of such has been left. The three-pin versions became classified as BS545, but the two-pin versions were excluded from that category. The three-pin BS545 versions are currently available to purchase from Builder’s Merchants and ‘D I Y’ retailers, but BS646 ones are harder to find and are significantly over-priced.

New installation of BS646 plug-tops and their fuses, continues in a limited way in specialist situations such as theatrical and shop lighting, where the ‘round-pin’ fittings are used both to deter ‘unauthorised’ connections, and the individual fuses are used to attempt to prevent the failure of one unit taking-out all the lamps hung on the same circuit; new BS546 fittings are also still fitted Domestically for specialised lighting, and to ‘restrict’ usage. Different physical sizes of BS646 one-amp fuses are in current use in clock-plugs and shaver sockets, rated at one amp. The use of BS545 fittings and older non-classified versions that were logically the same, has lingered on where originally installed; most that did exist have had a facelift applied by substitution with BS1363 wall-sockets & plug-tops within the previously established radial circuitry; some systems did need old wiring replaced due to deterioration of exposed cabling, and often ‘Ring’ circuitry replaced the originally ‘Radial’ arrangements.

Power-Cording, and the Related Sizes of Plug-tops. Wall-sockets were originally connected using ‘radial’ circuitry, whereby normally each 15-amp socket was fed from its own individual cable, but multiple sockets of lesser power were sometimes connected in series on one circuit that delivered sufficient power to supply all concurrently. The size of each plug-top was directly related to the size of the power-cord that was needed to supply the amount of current that was intended to be served; the early power-cording was extremely bulky, as compared with the power-cording used today to carry the same amounts of current; there were no cord-grips fitted to plug-tops in the present-day manner, but ribbed sections of the ‘Bakelite’ plug-top around the cable inlet had to grip the power-cord in place, when the screws within the base of the plug-top were tightened in the process of reassembling the plug after wiring it. That meant that one of just three sizes of power-cording had to connect all appliances, and that appliances fitted with lower-ratings of power-cord could not be used with larger plug-tops, because the power-cording could not be secured; obviously the larger power-cords would not fit inside of smaller plug-tops. Appliances requiring less power had to be wired-up using either two-amp or five-amp plug-tops, according to the size of their power-cording. As a result of that, smaller appliances could not be connected to larger wall-sockets, because their smaller plug-tops would not fit into the larger pin sockets, that also had broader pin-separations. In a strictly ‘Domestic’ situation, main ‘living’ rooms generally had only one 15-amp wall-socket (generally for an electric fire), a kitchen may have had one five-amp wall-socket (for a clothes iron, or other ‘kitchen’ appliances), but bedrooms often had no source of power other than for room lighting – that was sometimes used to power a small appliance such as a clothes iron via a five-amp two-pin connector from a bayonet-fitting lamp-socket hanging from the ceiling. During the 1930’s, it became standard practice to fit two-amp three-pin wall-sockets to all/most bedrooms, and as supplementary sockets in ‘living’ rooms. Plug-tops having power-cord clamps were subsequently manufactured in in somewhat small sizes that are the versions currently sold. The use of three-pin 2-amp wall-sockets persists in University Halls of Residence, and cheap guest houses, to restrict power usage, and the tiny two-pin non-switched variety find continued usage as table lighting within restaurants, due to their small footprint.

Adaptors - & House Fires Caused by Over-Powered Appliances. The problem of flexibility to connect small appliances to larger wall-sockets than originally intended, was overcome by the use of adaptors, but clearly there would have been no means provided to connect in the other direction. A series of three power-related ‘thorn-shaped’ (Old English ‘Th’ ‘combined’ symbol, often mis-represented as ‘Y’) fittings permitted a plug-top of the same size as the wall-socket to be connected to the top ‘branch’ of the adaptor, whilst one plug-top of (the same or) a smaller size could be connected to the side branch of the adaptor. Other styles of ‘block’ connectors developed. Further adaptors were often ‘chained’ serially (on both ‘legs’ of the branch) to permit additional or even smaller plug-tops to connect via the one wall-socket Whilst such adaptors thus offered the convenience of connecting more appliances concurrently, and with greater flexibility as to the location where connected, that introduced the possibility of overloading the circuitry by drawing too much power at once, particularly as the practice of ‘stacking’ multiple adaptors together to build a ‘Christmas Tree’ also occurred; such might over-heat & ignite when grossly over-loaded. Pins and sockets did not always ‘mate’ very well, and significant amounts of heat were often generated, making power fittings too hot to be touched; such occurred quite regularly; fortunately, all wall-sockets at that time had power switches located at the base of the array. There would appear to be no multi-way or down-sizing adaptors currently sold to fit BS545 wall-sockets; users would have to adapt BS1363 ‘trailing-cable’ socket sets to run from a BS545 wall-socket, or import ‘adaptor’ fittings from South Africa or Hindustan, or purchase 50+ years-old second-hand products.

Adaptors Causing Appliances to be Served Too Much Power. Using step-down and multi-way adaptors introduced a further problem, in that small appliances requiring say less than two amps worth of power, could now be inappropriately exposed to as much as 15/16-amps worth of power (and other combinations of course), by connecting those to a socket of greater power, thereby causing a fire hazard when the appliance malfunctioned and drew excessive amounts of power through both itself its low-rated power-cording.

That fire-risk was addressed in 1935 by the introduction of BS646 plug-top fuses, thus extending a greater degree of control than imposed by the fuses within the Consumer Power-Distribution Unit – by controlling the power at individual plug-tops. Unfortunately, no means existed to prevent a mixture of both BS546 & BS646 & earlier non-classified fittings being used concurrently.

The development of lighter power-cording, and cord-grips, lead initially to the introduction of the non-fused 10-amp plug-top - that fitted into the 15-amp sockets (or via its own adaptor as a supplementary fitting) – thus introducing the concept that just one size of plug-top might be used for ‘all’ purposes – provided that the amount of power that could be drawn could be strictly limited to the needs of the connected appliance. That in turn meant that it would then be possible to both increase the amount of power to be served by one circuit, and safely increase the number of appliances that could be connected concurrently - but it took a while for that idea to crystallise, and required a means of preventing old connectors being carried-over to a new system – as occurred with the BS545 & BS646 systems.

The Development of the British ‘Rectangular-pin’ Electrical System. Please note that the system has not been referred to as either the ‘13-amp system’, that would be totally incorrect & very misleading, or the ‘BS1363 system’ that very few users would understand. The idea for the improvement of the British electrical systems began as far back as the 1920’s, but it took the devastation of World War II to provide the impetus for such to be finalised; the vast expense of replacing buildings, and the limited-supplies and great cost of obtaining sufficient copper for replacement power-cables, caused the search for a replacement system to accelerate.

Lord Reith – the first Chairman of the British Broadcasting Corporation (BBC), and Minister of Works for the duration of WWII, chaired a committee from 1942 to 1946 to develop what has now become known by some as the ‘BS1363 Electrical System’. That developed the concept of the ‘Ring’ circuit to save copper, and that necessitated the use of the ‘fused’ plug-tops to govern the power applied to individual appliances – as the danger of supplying too much power to minor appliances was considered to be a major fire-risk. Other ‘foreign’ systems fail to identify that risk, and frequently make up to 32-amps worth of power available viz. Schweiz & Australia.

The saving in copper resulted from the fact that using the ‘Ring’ technique, it was often possible to service all rooms on one floor of a building using just one circuit, that utilised similar amounts of copper as constructing just two conventional ‘radial’ circuits would have done to span similar distances. Standard ‘Ring’ circuits generally served 32-amps worth of power, that in theory could be provided using merely one complete ‘ring’ of 16-amp cabling, because every wall-socket was fed with power from both ends, and thus spread the load; nowadays, 20-amp cabling is used in order to safeguard against imperfections in the installation. One physical size of plug-top was to be used, fitted with an appropriate value of fuse to limit the amount of power that could be drawn from the circuit. It was of course still possible to install radial circuitry serving 16-amps worth of power, but the appliances to be connected anywhere all had to be ‘fused’ appropriately, and likewise ‘spurs’ cabled for 16-amps. It is in fact possible to install circuits within Domestic & Small Office premises that serve up to 128-amps worth of power, though values that high are rare; 80-amps is relatively common, as indicated by open-shelf stocks within major chains of Builder’s Merchants. However, it is in fact very common for a conventional BS1363 wall-socket to be installed on a circuit that serves at least 48-amps worth of power; the obvious example of this involves the ubiquitous ‘cooker’ panel that is installed in the majority of British homes. Though now no longer an ‘approved’ design, millions exist and will continue to do so for the foreseeable future, as of course NO changes to electrical systems have ever been made retroactive; those panels are individually rated for 45-amps, but have connectors fitted for their inclusion in a ‘Ring’ circuit, though most are connected ‘Radially’. The most common version of those panels, always incorporated a single BS1363 power-socket, so any device powered from that would be powered via the same cabling as the cooker, and thus served at least 48-amps worth of power!, because higher values of cabling & fusing work mostly on multiples of 16.

Over-Engineered BS1363 Plug-top Fittings? Despite the amount of power flowing through a connected appliance being ‘controlled’ by a plug-top fuse, most users & electricians fail to appreciate that all the three pins within every plug-top also individually bear whatever is the full amount of power flowing through a circuit (irrespective of what passes through the connected appliance), since the pins & sockets become part of the ‘Ring’ circuit power-transmission pathways. Particularly foreign electricians and EEC Committees, appear to be unable to comprehend why British BS1363 plug-tops have been ‘so grossly over-engineered’; they haven’t! Plug-top Fuses. BS1362 fuses for BS1363 plug-tops are available in a total of seven value ratings – 1, 2, 3, 5, 7, 10, & 13-amps – but notably NEVER 16-amps as might have been expected for use in extension cabling. BS646 fuses are available solely in 1, 2, 3.15, and 5-amp values; there are no higher values available (and never have been) – even to go into the BS546 15-amp plug-top; however some of the fuses relating to the BS1361 fusing arrangements for Consumer Power-Distribution Boards will fit, and are safe to use; the values 4, 6.3, 8, and 10-amp (and other values already available in BS646 ratings) can be used, but are more expensive to purchase than those in the BS646 versions. The seemingly anomalous values of 3.15 & 6.3 possibly relate to the wattage values involved, but seems somewhat pointless as fuses have never been built to that degree of accuracy. Strangely, fuse values are always quoted using the nominal amperage that they carry, rather than the more appropriate Wattage (nominal amperage varies with nominal voltage, whereas theoretically Wattage remains constant, and it’s the Wattage that the device has to control). Note that some 10 and 15-amp versions of BS1361/BS88 fuses are unsuitable for use as BS646 ‘substitutes’, because their bodies are physically larger, so won’t fit. The explanation as to why BS1362 fuses for the BS1363 system had to be a physically-different size from the BS646 ones, appears not to be readily accessible, or why higher-rated versions of the BS646 type were never made, or why a fused version of the 15-amp plug-top was produced without having ‘matching’ fuses available; the reason may have been simply that the fuse box would have already contained a 15 amp fuse, so fitting that size of fuse into a plug-top on a 15-amp rated circuit would have introduced redundancy. The existence of a BS546-fused 15-amp plug-top that was intended to take a 5-amp maximum-value fuse appears to defy explanation. The BS1362 range of fuses originally included 250, 500, and 750-milliamp versions, but such appear to be no longer available, and have rarely seen the light of day. Note that plug-tops fitted with a BS646 fuse, are always referenced – somewhat inappropriately – as ‘BS546-fused’ plug-tops, never as BS646 plug-tops.

In the ‘Wylex’ range of plug-tops, the 3 Kw version accepts the full range of BS1362 fuses, the 2-amp & 5-amp versions were (apparently) always fused (and take the BS646 fuse in an appropriate rating for the appliance). The 15-amp plug-top version was (apparently) never fused, presumably for the reasons already postulated for the ‘BS546-fused’ 15-amp plug-top, but logically should have contained the ability to be fitted with a fuse of lower rating when used on a ‘Ring’ circuit. The ‘Dorman & Smith’ design of plug-top was an early contender to use the BS1363 system, but refusal was given by the manufacturer to the suggestion to share the use of their pattern, so that system used its own unique design whereby a threaded extension was included with their similar but otherwise unique pattern of fuse (the Dorman & Smith ‘prototype’ fuse was in fact the precursor of the BS1362 fuse, and the committee had already been considering using a similar fuse-fitting for their own development). The threaded extension part enabled the fuse to be screwed ‘upwards’ into the base of the plug-top and thus have the major part of its body projecting outwards, to become used as the actual ‘Live’ pin of the plug-top; the Dorman & Smith pattern of fuse is now difficult to obtain, and the plug-tops were said to be unsafe to use, because it was alleged that the fuse worked loose during usage, and it was further claimed that the pin could become detached and be left hanging out of the wall-socket. On reflection, it seems quite unbelievable that such a fusing system could be adopted, but it found favour because it was deemed to be virtually impossible to substitute some inappropriate object in lieu of a fuse of an appropriate fitting. The Dorman & Smith systems was mostly to be found in East ‘London’ (actually originally part of South West Essex).

The Wylex system has largely fallen out of use, except perhaps for specialised purposes (it was/is used to serve low-voltage power in laboratories, in addition to standard ‘Domestic’ usage). Five other variant patterns of the ‘Rectangular-pin’ plug-top are based essentially upon the ‘MK’ pattern (‘T’ Earth, ‘Round’ Earth, ‘Walsall Gauge’, & ‘Britmac’ x2) plus one other totally unconventional design (‘Electrac’ EPOS, UPS, & ‘Clean Earth’ – all closely related, but engineered to be non-interchangable by the use of a ‘keyway’ device known as a ‘nib’); all comply with the BS1363 specification and use the standard BS1362 fuses; all of those are current usage, albeit in very limited quantities in specialised situations.

Determination of the Correct Rating of Plug-top Fuses to be Fitted. EVERY plug-top designed for use on either the BS646 system OR the BS1363 system OR the Dorman & Smith variant system MUST be fitted with an appropriately-made fuse of the power-rating relevant to the appliance to which its plug-top connects. Believe-it-or-not, inappropriately educated manufacturers in China peddle incorrectly-constructed plug-top versions that are fitted with their own attempt at a BS1363-fitting plug-top that sometimes has no provision to contain ANY fuse whatsoever. Most appliances made there DO contain a plug-top fuse – but almost always incorrectly rated - almost always 13-amp – quite regardless of the power-rating of the appliance; such manufacturers from within South East Asia & China, plus Eastern Block countries including former East Germany, build appliances that include power-cords that are rated below the amperage supported by whatever fuse is included within plug-top; they frequently include IEC60320-C13/C14 connectors that are rated for merely 5-amps (the supposed system standard is 10-amps) on a power-cord rated 10-amps, and using a 13-amp fuse within the moulded-on plug-top; nowadays, they even go to the lengths of fitting a label onto the visible exterior of the plug-tops to advertise their dirty deed; such a power-line is detachable from the appliance with which sold, thereby making it inappropriately transferrable to another appliance whose power-requirements could be very different! Similar problems occur with every minor appliance that includes a power-cord that connects to its ‘transformer’ unit using an IEC60320-C13/C5/C7 ‘Kettle’, ‘Cloverleaf’ or ‘Figure-of-Eight’ connector. Most appliances currently sold in Britain are unsafe to use as purchased, until the educated users (are there any left?) have rectified the power-line by fitting the correct value of fuse and glued-together (or replaced) the detachable fittings; plug-tops without fuse provisions have to be removed and destroyed. Most appliances that get supplied without any plug-top fuse whatsoever, are often grossly inferior ‘transformer’ units supplied as chargers with e.g. telephones, made (of course) in China or Korea. Apart from suing the retailers that peddle that junk, or scrapping the product and purchasing a correctly-made charger, the cheapest recourse would be to acquire a ‘WA-7F’ ‘Travel Adaptor’ piece made solely by ‘WonPro’ in China; the only practical way of acquiring such item is via E-Bay, from Rebecca Kong whose company Anson Technology in Hong Kong has a ‘special relationship’ with ‘WonPro’ that enables that company to purchase individual pieces of any product directly from the factory; the E Bay listings will shew solely a selection of the most frequently ordered products, but all others are often obtainable by sending a message via E Bay; several of such adaptors should be obtained, and used ‘permanently’ with each affected product, after scrapping the 13-amp fuse inappropriately supplied within and replacing that with a 1-amp version. It is not practical to obtain that item any other way, as normally ‘WonPro’ sell solely to small distributors that order a minimum of 1,000 pieces of each part required, and those distributors do not normally advertise the availability of the products. Note that ‘WonPro’ products (and almost all ‘travel’ products produced by other manufacturers) are not sound, and thus not generally endorsed here, but if used solely as suggested here, that particular piece will be restricted to low-current usage, and the Polarisation in China is of the British ‘Standard’ form, and the product is ‘Standard’ mounting, and thus safe to use within Britain purely for low-current purposes; that particular piece is not safe to use genuinely as a ‘Travel Adaptor’ since it does not attempt correct any ‘electrical’ incompatibilities, and in particular in use within Britain, cannot safely handle power in excess of 3 amps; it must be used solely with a BS1363 plug-top connector, otherwise the Polarisation will be incorrect.

Determination of the Correct Rating of Fuse to Use. To determine the correct rating of fuse to fit an appliance, locate its power requirements - normally recorded on the base-plate - and expressed in Watts. (Unfortunately, that value is not always sufficiently detailed). Divide that by 250; 250 is the correct voltage to apply in the calculation in all circumstances, as it’s the generalised nominal voltage for all 200-250-volt systems; it does not vary according to the nominal voltage of the individual systems, that can vary by country. Britain is still using 240-volts – not 230-volts with which some EEC Committee members have fraudulently postulated as a ‘common’ voltage applicable for all EEC territories; such people have evidently failed to observe that significant parts of Europe are still using 120-volts and similar!, so there’s no such thing as a ‘common voltage’ in Occidental Europe, and may perhaps never will be!

The result of the calculation has to be ‘rounded’ to fit the range of fuses available; that is not a simple mathematical rounding, but one designed to be a ‘best-fit’ between the (supposedly) available fuse values – taking into consideration that for all fuses there is at least a 1- to 2-amp over-run possible before a fuse ‘blows’. So e.g. an appliance using a current between 5 and 6 amps can use a five-amp fuse, but if the calculation results are between 6 and 7, then the 7-amp value should be used - and so on; appliances using IEC60320-C5/C7 fittings are somewhat anomalous, since the moulded-on power-fittings plus power-cord are rated at 2.5 amps maximum, so connected appliances should use either a 1-amp or 2-amp fuse according the appliance requirements – never a three-amp fuse because no appliance connected in that way should have been designed to draw more power; anything fitted with the atrocious ‘EuroPlug’ is bound by the same rules, but you will find products made by the usual bunch of miscreants drawing 5-amps, and sometimes offering ‘optional’ ‘Earthing’ kits to go with their ‘double-insulated’ products (genuinely double-insulated products allegedly do not require ‘Earthing’).

Fitting a plug-top fuse of a higher rating than strictly necessary, exposes the appliance to a significant risk of fire occurring WHEN (NOT IF) it malfunctions. Always fit a fuse of the lowest possible rating, in order to afford the greatest degree of fire-protection. NEVER be tempted to use a higher rating of fuse to try to circumvent the issue because a fuse of the correct value is not to hand; NEVER be tempted to fit a paper-clip instead, or replace the old fuse wrapped-up in metal foil.

Surge Currents, and Value of Fuse to be Selected. All appliances experience a surge current upon start-up; normally that is negligible, but motorised appliances experience a significant surge, that almost certainly necessitates fitting the next higher rating of fuse to what might have otherwise been expected. Starting-up an appliance using whatever fuse value was inappropriately-fitted by the manufacturer, and measuring the current-drawn on a power-meter or electrician’s meter, will then indicate approximately the correct value of fuse that should be fitted in place of the incorrectly supplied one. Unfortunately, appliances are rarely marked with the power drawn by the surge at start-up. If an under-rated fuse has been fitted and blows because of that, it’s no problem; just replace the blown fuse with the next higher value from the series.

The ‘13-amp’ Fuse. The ‘13-amp’ value of that beast has unfortunately lent its name to the British ‘Rectangular-pin’ system, and with that has arisen the popular mis-conception as to the nature of the British ‘Ring’ Circuit system and the value of the fuses required to be fitted to the plug-tops.

Note that it is never mandatory to use British ‘Ring’ circuitry when British ‘Rectangular-pin’ FUSED plug-tops are utilised (or the BS646 versions); that the system never actually delivers 13-amps worth of power (it’s ALWAYS HIGHER); only Danmark has a truly 13-amp system for power, and then not always installed as such. The 13-amp value of fuse is rarely the correct value to EVER be used! Back in the late 1940’s someone somewhat inappropriately chose ‘13’ as the rating for the maximum amount of power to be drawn from the newly-designed electrical system; clearly the sort of inane decision likely to be made by a committee, since the entire system is based upon 16 amps, and multiples of that, and the highest amount of power that it was designed to serve to individual ‘pluggable’ appliances was three Kilowatts (3,000 Watts); that’s merely 12 amps nominal – when calculated as above - and a fuse of that rating would likely have stood as much as 16-amps; even a 10-amp fuse would likely bear more than 12-amps.

Unfortunately, the electrically naïve – be they users, electricians, manufacturers or EEC/ITC Committees – have been brainwashed by that number, and as a consequence of that have fitted 13-amp fuses to almost everything made, or mislead others to do something similarly inappropriate; often the power-cording provided is rated lower than the fuse supplied! An EEC committee of inappropriately educated administrators examined the British system, and decided that fuse values of solely 3, 5, and 13 were adequate for all purposes TO PROTECT THE POWER CORD, and that if the appliance required further ‘protection’ then a fuse should be fitted within the D.C. part of the appliance. NOTA BENE - the BS1363 fuse (and BS646 ones) is there NOT to protect the power-cord, NOR to protect the appliance; it’s there to protect the building from being destroyed/damaged by FIRE! The requirements dictate that the fuse be fitted to restrict to the greatest degree reasonably possible, the amount of power that the appliance may draw. By a corollary of that, one presumes that naïve manufacturers decided that if there were no power-cord, then no fuse at all would be necessary! Any appliance that draws too much power, has probably already been destroyed beyond economic repair. It should also be noted, that in order to maximise profits, many manufacturers do not bother to obtain and fit a full range of power-cords that supply just the minimum amount of power, but for their own convenience fit just the ‘next one up’ in their standard range of sizes (generally 6-amps, 10-amps, and 16-amps - other than for very minor items) – so an appliance generally gets equipped with a higher-rating of power-cord than actually necessary, but that is no justification whatsoever for fitting a higher rating of fuse; quite the reverse – of course.

The vast majority of Domestic appliances are designed to draw merely less than 2 amps!, and have insignificant power-cording. A relative few might require 3 to 5 amps; a very small number might need 7 to 10 amps. Only 3 Kw electric kettles (most are 10-amps or less), 3 Kw electric fires (generally obsolete), 3-way multi-adaptors, ‘trailing-cable’ sets etc., and extension reels of cable, actually require to handle 3 Kilo-Watts of power (12 amps – but ‘cabling’ should be 16-amps). Any fuses of 13-amp values found fitted to anything else, MUST be removed and destroyed! (Destroyed to prevent others misusing them subsequently). Additionally, take and destroy all two-way multi-fit adaptors, that ALL have NO fuse at all, and any plug-tops that have no facility to include a fuse – including all battery chargers and the like that incorporate a transformer. Sue and prosecute the retailer that sold all such devices, or any appliance that came fitted with an inappropriate value of fuse (retailers are obliged by law to check what they sell and supply the correct value of fitting).

It should be noted that – in British Law – there is a required obligation for manufacturers and installers to manufacture and install everything correctly, regardless of the complications involved in the technical nature of what is concerned. They are required to exercise sound judgement in everything done. That involves questioning everything, and not blindly adhering to any supposed standards. Having performed an action according to the alleged standards, will not exonerate the perpetrator of the deed from criminal conviction, or mitigate the sentence and or damages awarded.

When stocking-up with replacement fuses, there will NEVER need to buy the 13-amp value, since there will be many of those found inappropriately fitted – and thus require scrapping. Most retailers fraudulently peddle just the 3, 5, and 13-amp values of fuse instead of stocking the complete range as required by law; it is to make bulk purchases of the full range of values (excluding the milli-amp ones) from numerous suppliers on E Bay & the like.

It is very rare for normal Domestic users to have to replace a plug-top fuse, once the correct value has been installed. When one of the existing fitments blows, that generally means that the attached appliance has developed a fault; in today’s economic environment, that generally results in the scrappage of the appliance (including its generally moulded-on plug-top), as few appliances nowadays are repairable at reasonable cost. What must on no account be done, is to fit a fuse of a higher value as an ‘automatic’ reaction to sidestep the problem; recheck the value fitted – it maybe that the calculations to determine the correct value to fit, were a little too close to the mark, in which case review the situation - do not just increase the value for no scientifically-valid reason. On no account ever try to evade the issue, by substituting a paper-clip, or by refitting the blown fuse wrapped in ‘silver-foil’. The fuse is there to prevent causing a fire! – not to offer the user the opportunity of starting one!

Older Fusing Arrangements. The same rules about plug-top fuses apply to functionally-similar ‘wire’ or cartridge fuses (but nowadays ‘circuit-breakers’ that simply require resetting) fitted to Consumer Power-Distribution Units, except that there, each circuit is only ever fitted with the one value of ‘fuse’; there is no ‘choice’ to be made, because the ‘exact’ value that the circuit was built to handle must always be the one fitted. On a ‘Ring’ circuit, such fuses generally blow only if too many appliances have been hung on one circuit – rare in the case of a ‘Ring’ circuit, but it does happen. On the pre-BS1363 circuitry, appliance failures will blow the board fuse, since there is no plug-top fuse to operate first. When dealing with older-style fuse-boxes using fuse-wire rather than cartridges or circuit-breakers; be sure to replace the burnt-out piece of fuse wire with JUST ONE STRAND of the correct rating; winding several strands of the same wire around the terminals, multiplies-up the actual value fitted by the nominal value for every ‘half-turn’ (i.e. strand) of wire applied!

‘Travel Adaptors’ – and Fusing. ‘Travel Adaptors’ are another category of electrical device that are rarely ever fitted with any fuse whatsoever when connected to a British ‘Ring’ circuit system – or the prior ‘Round-pin’ system. The concept of connecting an appliance fitted with a foreign plug-top to the British ‘Ring’ circuitry, or any other heavy-current circuit, demands that action be taken by the traveller to ensure that he complies with the BS1363 standard - to connect via a fusing piece.

Essentially, almost all ‘Travel Adaptors’ are lethal devices that the naïve are conned into purchasing by fraudsters that are marketing dangerous products in order to make a quick and exorbitant profit, that although such adaptors may attempt to provide a solution of sorts to get say ‘round-pinned’ plug-tops to fit ‘square-pinned’ wall sockets, NEVER make any attempt whatsoever to address the electrical differences, such as voltages, Polarisation, mains Frequency, Standard or Reverse mounting, power-cord exit mode, and amount of POWER supplied.

Commercially-made adaptors are not available to fit the complete range of Domestic connections, and some adaptors provided do not actually fit the wall-sockets for which they were supposedly intended!; others exert inadequate adhesion to the socket, so fall out, and the size & weight of the adaptor itself may exacerbate that. Incorrectly Polarised fittings can KILL, and using ‘Travel Adaptors’ frequently REVERSES THE POLARITY of the original connection. So-called ‘indeterminately Polarised’ systems such as German ‘Schuko’ are LETHAL, as is the French system that is a stolen version of ‘Schuko’ and not dependably installed with its supposedly ‘Reverse’ Polarisation. So-called ‘Russian Schuko’ can be lethal if it actually has ‘Earthing’ side-clips installed; it’s the ‘Earthing’ side clips on a ‘Schuko’ system (or pins on other systems), and ‘Live’ appliance casings, that cause electrocution when incorrect Polarisation is encountered for ANY reason – and many/most ‘Travel Adaptor’ connections ARE wrongly Polarised! Although none of those defects listed can actually be moderated or prevented by ‘fusing’, in this case we are addressing the total absence of fusing arrangements in such adaptors, to protect against building fire. Whilst the same solution already given for making chargers safer can be applied to ‘Travel Adaptors’, there is a better solution to cure all the ills, and that is to reject the trash and build a set of ‘D I Y’ ‘Travel Adaptors’, and include appropriate fusing with that. Currently there is nothing whatsoever published to assist with that, but shortly a 500-page book from the author of this article, will be appearing to address all the issues concerned.