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Choosing a new soldering iron...
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Re: Choosing a new soldering iron...

by sirket on Sun May 23, 2010 9:07 pm

mojo wrote:Umm... Yes, it will.

Um, no it will not. A live lead might only deliver 100 milliamps across your heart- but that will kill you, and still not trip the fuse.

Don't take this the wrong way but do you understand what a fuse is? It is a designed to fail if too much current is drawn through it. In the event of you getting electrocuted it will fail as more than the rated current flows through it (and you).

Surely you must have the wrong end of the stick.

More than the rated current does not have to pass through a fuse for you to get electrocuted. If you had any idea what you were talking about you would know that. The resistance of the human body is high enough such that enough current can flow to stop the heart, but not enough to trip a breaker. This is why GFCI was created. You literally have no idea what you're talking about.

I specifically said how it good British plugs with fuses are. You suggested otherwise, I responded with supporting evidence.

I never said one was better or worse- all I said is that they were unnecessary in the US system.

Anyway, your argument still does not stand up. If you have an outlet with a single 13A breaker on it and plug a 60W table lamp into it then that is clearly more dangerous than having a 1A fuse and totally unnecessary. That is precisely why British plugs are fitted with the lowest possible rated fuse. They teach children about it in school. It's really, really basic safety.

If the wire on the lamp is 14 gauge, the wire to the outlet is 14 gauge, and the socket is rated for 15 amps, then a fuse in the plug isn't going to provide you with any additional protection.

What you seem to be saying, in a nutshell, is that you are smarter than all of the electrical engineers that created the US NEC. Frankly, I'm honored that you are willing to humble yourself by talking to me.

Fuses react faster to over-current than circuit breakers too.

Man- you literally have no idea what you're talking about. Both fuses _and_ breakers have rated blow times. You can get slow blow fuses and fast trip breakers.

15 amps is higher than the maximum commonly available fuse for a British plug which is 13A. Most appliances use a 3A fuse.

I'm not sure I understand your point- 3A will kill you as surely as 15 amps. 1ma passing through the heart can cause fibrillation. Above 200ma the heart muscle can not move. It doesn't matter how far above.

You can die from high currents (above an amp- as a result of burns and cellular damage) but the voltage needs to be much higher. The resistance of the human body is high enough that currents above an amp are nearly impossible at mains voltages.

I'm not really sure how to convince you that lower current is safer if it is not already apparent to your understanding of electricity. You might as well say that you can die in a car crash at 1MPH (technically true) and that the difference between crashing at 70MPH and 140MPH is largely irrelevant to survivability which is clearly not the case.

You are completely mistaken here. 500 ma is more than enough to kill someone. It doesn't matter whether it's one amp, or 30 amps. Your argument is also _completely_ wrong because this is not why British plugs have fuses. Wikipedia and several other resources I've checked all state the actual reason. You've changed your argument several times in this thread- and you've been wrong every time.

http://www.interpower.com/ic/UK_fuse_plug.htm
(among a hundred other similar statements)

The simple fact of the matter is that you are far less likely to die with a 1A fuse than with a 15A breaker. Fuses are also faster than breakers so you are exposed for a shorter time, increasing your chances.

I would _love_ to see you back this up with real world research. You are wrong. Period. Heart stoppage can result from less than 100ma of current. Death as a result of burns and cellular death require larger currents than can be induced by household voltages. Because the US system is 110v there is even less chance of electrocution- either from heart stoppage or burns.

True but it's still a substantial saving in copper. Come on, do you seriously think that the government of the UK would not have bothered to find out if their great copper saving measure actually worked before telling everyone to do it?

I am merely suggesting that the savings probably isn't that significant. It would depend on the rooms and the layout and so on. It would not have had to be significant in the post war years to justify it having been implemented. Any savings would have been enough.

True, it's a major hassle having to turn off every electrical item in a room before working on an outlet (which I do every day just for fun). It's not like there is any benefit either, other than other appliances being off so that you know the whole ring is even if the socket itself is damaged, but I can't imagine how that could ever be of use to anyone.

I prefer my system in which I can leave the lights on in the room, but turn the outlet off. That way I have light and can see what I'm doing without having to use a flashlight.

It is more safe.

You are wrong- and I've proven it several times. You simply have no understanding of the human body or the effects of electricity thereupon.

It had nothing to do with cost, it was due to a shortage of copper, as I already said.

My apologies- I was referring to today.

We used lead up until the 70s. It was probably a bad idea in hindsight.

That would explain this entire thread then :)

So what level of protection does the very thin and cheap power cable that only provides maximum 60W have? A 15A breaker? Even on the 120V system that is 1800W. Sounds like a brilliant idea having 1800W available to a $5 lamp.

The wire that feeds my lamp is 16 gauge and can easily carry 15 amps over it's 6 foot length. I'm not certain what "thin and cheap" wire you are referring to.

I've said two things in this thread- that there is a reason we don't use fused plugs in the US, and that a sponge is an excellent choice for cleaning a soldering tip. You've attacked both, and for the life of my I can not figure out why. Your attitude seems to be that your way is the only one that can be correct and damn everyone else. You like to tell people on this board how to do things while I'm trying to provide them with information so that they can make their own decisions. When someone disagrees with you- you are willing to make claims (wet sponges ruin soldering irons!) with no more basis than your own limited experience. It's not helpful.
Last edited by sirket on Sun May 23, 2010 10:31 pm, edited 1 time in total.
sirket
 
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Re: Choosing a new soldering iron...

by sirket on Sun May 23, 2010 9:24 pm

Let me rephrase this in a nutshell:

I = V/R

Voltage = 220v
Resistance of human body = 1000 ohms (a low estimate)

I = 220v/1000ohm

I = 220ma

It does NOT matter to the human body whether the fuse is rated for 1amp or 15amps. 220 ma is all that can flow and it's more than enough to kill you. (Even if you assume an absurdly low 300 ohm resistance you're still only going to pass 750 ma- not enough to trip even your 1amp fuse).

In the US system the numbers are even more damning for your argument- at most 110ma will flow. Still plenty to kill you, but still not enough to trip any fuse or breaker.

Translation- Fuses exist in the British system because of the small cord fire hazard presented by the high current main ring- not to prevent electrocutions. I'm terrified someone is going to read your posts and assume that since their plug has a 1amp fuse that they are somehow safer. They aren't.

The end.
sirket
 
Posts: 128
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Location: NYC

Re: Choosing a new soldering iron...

by sirket on Sun May 23, 2010 10:21 pm

Furthermore:

Wires are rated to carry a maximum _continuous_ current- but they can carry a MUCH higher transient current (short circuit til the breaker trips).

It all comes down to heating.

A 22 gauge wire (ludicrously small- individual Ethernet conductors are 24 gauge: http://en.wikipedia.org/wiki/Category_5 ... Category_5) 6 feet long (typical lamp length) will produce 45 watts of heat at 15 amps. Eventually the heating may become a problem- but not until long after the breaker has tripped. If you use something sane like 18 gauge wire- then you only produce 15 watts of heat. Such a wire could carry this current without a problem.

In the British system (220v at 32 amp), the same wire would produce 204 watts of heat! That's a huge difference and the reason British plugs are fused.

Moreover- all of these calculations assume a failure scenario in which the wire is asked to carry more than its "rated" current, but less than the breaker current. If the device could fail in such a way as to draw more current than intended, then it is required to have its own fuse, appropriately rated. Other than that- I have no idea how this would happen (in the US system anyway). If the wire shorts (because you ran over it with your vacuum)- then the breaker trips.

The electrical engineers that created the US NEC are not stupid. Fused plugs make sense in British wiring. They make no sense at all in the American system.

If my calculations are wrong, please let me know. If they aren't- then can we please move on to something productive?
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Re: Choosing a new soldering iron...

by adafruit_support_bill on Mon May 24, 2010 7:21 am

This thread has gone pretty far off topic and things are getting personal again. I am locking this thread.

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Please be positive and constructive with your questions and comments.