Didn't you understand my answer?
What's the inrush current?
Manufacturers don't like warranty claims, and TVs are high-production volume items, so the acceptable probability has to be very small.
Ten Amp Fuse in a Telly Plug (aka plugtop)
- Thread starter charliegolf
- Start date
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We've talked recently ('the other way around') of the arbitrary 5A/6A OPDs conventionally used for 'lighting' circuits. In cases such as we discussed recently, there can be an argument for having a 16A MCB. In other situations, such s you just mentioned, 2A or even 1A would probably be more than adequate.
It seems that no thought goes into any of this - it's all seemingly down to tradition and habit (with maybe a very-long-ago historical 'good reason', which is no longer relevant).
Kind Regards, John
Of a 50W SMPSU? I don't know (if an SMPSU has a significant 'inrush current' at all), but I'm quite sure that it is a hell of a lot less than 10A, almost certainly less than 3A, and very probably less than 1A. It is, after all, not a motor or a welder!
The probabilities of blue moons occurring is pretty small! Also, would one make a 'warranty claim' for a blown fuse? I would have thought that they would be more worried 'the other way around' (were it not for the TV's presumed internal fuses).
Also, don't forget that fuses are tolerant of brief 'inrush currents' (when they exist) well in excess of their rating. A 3A BS1362 needs about 5A (probably at least 25 times the running current of the TV) to blow in one second - and, indeed, at least almost 5A to blow ever.
Kind Regards, John
You might be surprised. I don't have any figures for modern TVs, but I've seen (very brief) transient currents of 180A into an old CRT model. (I used to work for a manufacturer of, among other things, TV power switches.)
Consumers make warranty claims for the most trivial of reasons. Many people would only know that their TV isn't working, and would expect the retailer to replace it. The retailer might well expect the manufacturer to credit them for the value of the TV plus a handling charge - many retailers (e.g. supermarkets) don't have the expertise to check a fuse, and even if they did, what would they do with a 'repaired' second-hand TV set?
Claims can cost a lot of money to sort out.
I'm not forgetting that, but remember there will be some distribution of the fuse characteristics. Also, smaller rated fuses are mechanically less robust and are therefore more likely to fail open-circuit due to a combination of mechanical and thermal effects.
Incidentally, my 32" Samsung LED TV has a 5A fuse in the plug!
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That's moving the goalposts a long long way! As I implied, on the face of it, I can't see why an SMPSU should have an appreciable 'inrush current' at all, let alone as much (proportionately) as a motor or welder!
Indeed, and I was quoting the 'lower limit' of that distribution (I'm not sure what the range given in the curves is - maybe 5% - 95%). At the 'upper limit', it would take about 10.3A to blow a 3A BS1362 in 1 second.
I'm sure that's true, but it must be very rare. In well over half a century of living with fuses of all types, I cannot recall a single occasion on which one has gone o/c 'spontaneously (i.e. without good cause) - and, in my earlier days, many were very small in rating (hence 'fragile') - usually 100mA or 50mA ones in electronic equipment.
All of my TVs (all LED), of all sizes, have 3A fuses in their plugs.
Kind Regards, John
I can't see why it shouldn't!
No you weren't, you were quoting the lower limit of the characteristic, not of actual production.
I've known a few. Samsung have quite possibly had more experience than you and I.
Fitted by the manufacturer, or by you? Mine came fitted with the 5A from Samsung.
Couldn’t tell you what size fuse is in my TV. Am I all that fussed? Nope. I presume a company like LG has done their type testing well enough to know what fuse to put in the plug.
Is the difference between a 3a and a 13a going to realistically make the blindest bit of difference to me? Nope.
Is the difference between a 3a and a 13a going to realistically make the blindest bit of difference to me? Nope.
That's surely the wrong way of looking at it. If there is no credible mechanism whereby a piece of equipment could have a massive inrush current, then it's hard to see how it could have one.
Fair enough - as I said, I wasn't sure what I was quoting. However, is there not a requirement for the production variability to be within the limits of the characteristic (with a specified probability). If not, then what does the latter actually mean?
Maybe, but I think you are probably clutching at straws!
Fitted by me if the manufacturer had fitted a fuse with a rating greater than 3A. Most, like yours, came with a 5A, but I don't think I've seen 10A (or 13A!).
Kind Regards, John
It's quite hard to see how they could do that, given that we are presumably talking about very rare events and a wide range of possible faults.
In any event, as I keep saying, in the case of items like TVs it is almost certain that there will be internal fuses, hence making the question of what is in the plug rather moot.
Kind Regards, John
Whilst PATesting I was surprised to see a latge batch of identical hairdryers had 7amp fuses fitted in their non-moulded plugs.
Can't recall what what the exact wattage was, but was expecting something like a 5 or 13amp fuse I suppose.
It is true that many fitted plugs nowadays do have 13amp fuses when something smaller would be adequate.
Table lamps and other plug-in lighting always seem to have 3amp fuses, as one may (or may not?) expect.
I said in an earlier topic about the packs of BS1362 fuses one would buy from the DIY shop which would specify which fuses to go in which appliances with suggest wattages.
Typically a pack of fuses would, as I'm sure you all know anyway, contain 3, 5 and 13 amp fuses.
I've also said before that I was taught, rightly or wrongly, to always select a fuse just slightly over the required current, and that was at school, home, college, apprenticeship and even today people talk about it.
That said though, no one ever went to great lengths to find something like a 7amp fuse in an attempt to match the required current.
Can't recall what what the exact wattage was, but was expecting something like a 5 or 13amp fuse I suppose.
It is true that many fitted plugs nowadays do have 13amp fuses when something smaller would be adequate.
Table lamps and other plug-in lighting always seem to have 3amp fuses, as one may (or may not?) expect.
I said in an earlier topic about the packs of BS1362 fuses one would buy from the DIY shop which would specify which fuses to go in which appliances with suggest wattages.
Typically a pack of fuses would, as I'm sure you all know anyway, contain 3, 5 and 13 amp fuses.
I've also said before that I was taught, rightly or wrongly, to always select a fuse just slightly over the required current, and that was at school, home, college, apprenticeship and even today people talk about it.
That said though, no one ever went to great lengths to find something like a 7amp fuse in an attempt to match the required current.
I remember someone had a faulty battery charger which instantly blew 3amp fuses. In a moment of desperation (he needed his battery) he stuck a 13amp fuse in the plug, which blew something up in the charger and scorched the carpet - so certainly a real-life example of fuses in action.
This is the main fuse in my TV. It is a few years old.
It is 6.3A
It is 6.3A
You didn't just take the back off your TV for us, did you?!
Interesting - it must be intended for a lighting circuit
What is the alleged running current or power of the TV?
Kind Regards, John
No, I remembered I had the picture from when I had to change the board.
Interesting - it must be intended for a lighting circuit
180W - even though it's LED.
I brought it with me and it's quite happy with the 16A RCBO.
I hate to keep on
but as most places don't have any fuses to argue about, the discussion must be purely academic.DIYnot Local
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