Arc Fault Circuit Interruptors

[Mike Tomlinson]

In article , Andrew Gabriel writes

Unsleeved plugs and unshuttered sockets - ditto.

[dorothy.bradbury]

There are several types of AFCI:

detecting series arcing: o Break in say vacuum cleaner or laundry iron flex Live conductor o Both are *very* common in the UK

Neither fault will cause an MCB or RCD/RCBO to trip, unless there is an (eventual) carbon path to earth which may take some time.

For detecting parallel arcing: o Traditional L-N arcing which may not trip the MCB o Generally this is higher current so MAY soon involve L-E

The more advanced AFCI cover both.

AFCI is something the UK could benefit from on ring-mains, with irons & vacuum cleaner flexes coming under very severe duty. I've seen 2 of my own vacuum cleaner flexes fail near the plug, and the Philips irons (butyl, cotton-covered, not silicone) can overkink or even have cable kinked in the box - a series arc fault in waiting.

Remember arc temps can be *extremely* high indeed, and easily enough to ignite magnesium let alone typical insulation/dust etc.

-- Dorothy Bradbury

for fans, books & other items (Direct)

[Steve Walker]

I actually think that "burn" is a good way of explaining to children that they shouln't mess with it - every child gets burnt at some point (even if its just a hot radiator) and they can relate to the terms "burn", "hot", etc. Saying that electricity can kill you doesn't mean a lot to a child that is too young to understand death.

Steve W

[Steve Walker]

Not entirely - the extension at the back of my house (built before I moved in is wired in aluminium). I haven't had chance to change it yet, so in the meantime I've checked all the connections and also that the circuit breaker is suited to the lower current rating.

Steve W

[Peter Parry]

A strong case for never using a vacuum cleaner by the sound of it.

[dorothy.bradbury]

The 2 failures were over 18yrs admittedly. Both cables failed within 1" of the plug, one moulded-on & one not.

The iron failure was most disturbing as it was in 10 months, with nothing but usual wrap-the-cable-around-the-iron base storage. It wasn't wrapped kinked, the cable was supplied kinked in the box and the normal use buckled the inner cores into a "knot". Then it smoked one day, series arc smouldering away.

Silicone iron cables (eg, higher end Tefal) don't suffer from this.

Yes, I don't care much for vacuum cleaners. For arthritis I use 2 Miele's, a 300 & 400 for down & up (HEPA). Both are quite heavy, and the castors just sink into carpet - I'm sure they were sized for hard floors where they are super-smooth.

Ended up using a Miele-hose-coupler & extra hose to double the hose length so it reaches down the stairs instead of chasing me down.

However, a central vacuum cleaner has always interested me: o Quieter, re non co-located o Long light hose without rigid couplers to roll on :-) o No heavy motor unit & cable to drag about, fail or fall over

The USA ones have dust-bins more suited to CNC-Machining-R-Us and an overall size which threatens to suck up late postman (ok, which I might use to threaten to suck up late postman, I admit it).

There is a market for something smaller. Considering the under-stairs location, with above-upper-floor socket and below-lower-floor socket, it's not difficult to implement one really. The hoses can be a pain, since ~20-30ft of hose has a mind of its own.

Less chance of the cat making it to the bag anyway :-)

-- Dorothy Bradbury

[Andrew Gabriel]

In the case of a portable appliance which fails in use, you are extremely unlikely to be hurt, and you are present to take the measures necessary to remove further risk of danger. I've had an iron flex go bang and I've had other appliance flexs simply lose continuity when the conductors break, but spectaclar as the iron was, I wasn't ever in any series danger. I suspect there are far more effective ways to spend the money and improve safety in the UK than by installing AFCI's.

The problem in the US is this type of thing happens inside the building fabric where you might not be aware until there's a sizable fire burning in an area you have no access to, like inside a partition wall.

[Owain]

"dorothy.bradbury" wrote | [central vacuum cleaners] The USA ones have dust-bins more suited | to CNC-Machining-R-Us and an overall size which threatens to suck | up late postman (ok, which I might use to threaten to suck up late | postman, I admit it).

Upon first reading, I wondered why you were accumulating deceased carriers of Her Majesty's Mails about your premises :-)

Owain

[dorothy.bradbury]

Post office wish to do the same, even their mail has been rough lately :-)

-- Dorothy Bradbury

[Martin Angove]

Surely though, the fact that both appliances were well-used portable devices means that, even without an Arc-Fault device there is little real danger - unless that is you're in the habit of leaving the iron switched on between sessions? I think anyone smelling smoke from the vicinity of an appliance they are currently using will whip the plug out sharpish. Also, a series fault is most likely to begin to manifest itself in random cutting-out of the appliance, at which point most people will rapidly get very annoyed and either arrange a repair or (more likely these days) bin the thing and buy new.

I can see the use of an AF device where fixed wiring or permanently wired equipment is prone to such a failure, but as has been argued in this thread, this seems to be more a feature of the bad wiring practice in the US than here. The occasional user who regularly runs over an extension lead on his office chair excepted, of course :-)

The temptation due to cost, surely, will be to fit AF devices to cover several circuits at once. This is already the case with RCDs, and look at the arguments we've had here recently about the merits of this! The alternative is to fit devices individually to circuits requiring such protection. I know it's a bit of a false comparison, but £60 from Screwfix for a 12-way split board with main switch, RCD and 10 MCBs just doesn't compare with £20 for a 9-way board with main switch and 9*£30 for RCBOs.

Hwyl!

M.

[C-H Gustafsson]

Aluminium wiring was used in the 1960's and 1970's. It has been out of use in North America for many years, except in larger sizes. The AFCIs are only required for new homes, which use copper wiring. I therefore see no connection between aluminium wiring and AFCIs. (No pun intended)

Some European countries have used aluminium wiring too and you can still buy solid aluminium wires 2.5mm2 to 16mm2 made to Russian standards. It is quite a bit cheaper than the copper wire, even if you take into account that you need to use one size larger wire.

Unlike the Europeans who use "whole house" RCD's, North Americans prefer RCD equipped sockets. As RCD's prevent many electrical fires, this practice increases the risk of fires in the house wiring. Unsurprisingly, the AFCI contains an RCD. This alone will reduce the risk of fire.

/Clas-Henrik

[Huge]

[12 lines snipped]

I have been visiting the USA regularly for nearly 30 years, and my parents live there. In that time, the only RCDs I've seen have been plug-in ones used on appliances plugged in in bathrooms (!).

[Steve]

How ? 20mA to ground is hardly a major power dissipation.

Steve

[Andy Hall]

I've seen wall plate types quite regularly in hotel bathrooms in the last few years. Most of the big chains seem to have them. e.g.

don't seem common in houses though.

.andy

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[Huge]

OTOH, The Fairfield Inn in Exton, PA, where I stayed last, which has just been refurbished, had an RCD on the coffee maker in the bathroom, but none on the socket...

[Andy Hall]

Maybe it varies by state, city or county or something. AIUI, the equivalent to building control handles electrical code enforcement.

.andy

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[Huge]

[27 lines snipped]

Since everything else does, you are indubitably correct.

[Andy Hall]

I believe so, but from talking to friends and colleagues who live in neighbouring jurisdictions, there are some variations in terms of what an inspector will require. Perhaps it's a similar situation to here, where building inspectors rigorously apply some aspects of the building regulations but turn a blind eye to others....

.andy

To email, substitute .nospam with .gl

[Steve]

So what is the N.E.C. NOT the National Electric Code ?

Steve

[Owain]

"Huge" wrote | OTOH, The Fairfield Inn in Exton, PA, where I stayed last, which has | just been refurbished, had an RCD on the coffee maker in the bathroom, | but none on the socket...

One can see why Americans think British hotels backward. I've never stayed in one that had a coffee maker even in the bedroom.

But I think putting a coffee maker next to someone having a crap is a strange idea from a nation obsessed with hygiene.

Owain