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#31
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Lem wrote:
Are surge protectors on the main power supply actually needed in the UK? w_tom is currently debating this on sci.electronics.basics and another 4 or so crossposted groups. You may all wish to go to and read that thread too, particularly the exchanges between w_tom and Charles Perry. http://groups.google.com/groups?q=gr...suppressors%22 Tim -- My last .sig was rubbish too. |
#32
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"David Maynard" wrote in message ... half_pint wrote: How about using a plug with the correct sized fuse in it? The proper fuse is always a good idea but fuses do not protect from power line faults. They blow after your 'protected' device is fried and pulling too much current as a result of it. I am sorry but you are wrong. a correct sized fuse will always protect you. Your protected device will never be 'fried' if you use the correct fuse. It is *impossible* unless the fuse is faulty. The blow before the device draws enough current to be damaged, that is how they are designed. Probably a lot cheaper? Probably a waste of money. You probably have a greater chance of deing struck by lightnening. |
#33
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On Sat, 10 Jul 2004 00:42:25 +0100, "half_pint"
wrote: "David Maynard" wrote in message ... half_pint wrote: How about using a plug with the correct sized fuse in it? The proper fuse is always a good idea but fuses do not protect from power line faults. They blow after your 'protected' device is fried and pulling too much current as a result of it. I am sorry but you are wrong. a correct sized fuse will always protect you. Your protected device will never be 'fried' if you use the correct fuse. It is *impossible* unless the fuse is faulty. The blow before the device draws enough current to be damaged, that is how they are designed. Another GUESS, eh? Did you forget to consider that all computer power supplies have a fuse, yet they can (are) still damaged? Suppose you 'd now claim the engineers designing them don't know as well as you how to select a fuse? A fuse is a failsafe for damaged or otherwise compromised equipment, not a preventative measure. |
#34
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Mike Tomlinson wrote:
In article , w_tom drooled: Your reputation would be much enhanced and your posts would be far more legible if you stopped top-posting and replied to each point raised, quoting context, instead of rambling in a long, top-posted, hand-waving rant. Here, here. I second that. Furthermore, many plug-in manufacturers grossly undersized internal components. How would you know? Many good quality European surge protectors illuminate a warning lamp to indicate when the protective devices have degraded such that they are no longer effective and that the protector should be replaced. Some, including Belkin devices, also illuminate a lamp to indicate that the protector has been connected to an outlet with a good earth. Just like the strip outlet surge protector in my 'U.S.' bedroom. Also just like the 'wall brick' one I have in my 'U.S.' dinette. What w-tom fails to mention in his 'whole house' tirade is that the 'whole house' protectors use essentially the same protective devices as the 'plug in' protectors he so derides, albeit of larger capacity. The reason 'plug-ins' use smaller devices is because of the wiring, which all 'surge protectors' depend on to limit the current surge. And because the 'plug-ins' are located at the computer end of the wiring, there is more wiring resistance and, hence, a lower surge current for them to deal with. His claim that the devices in the 'plug-ins' degrades applies equally to his own preferred protection scheme. Given that you in the USA tend to use for your electrical accessories the cheapest and nastiest **** from China, it comes as no surprise that your "surge protectors" do not carry even this basic feature. One of these days you need to take off the 'U.S. bigot' blinders. So again, the plug-in protector still does not provide effective protection. Complete crap. As usual. |
#35
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half_pint wrote: "David Maynard" wrote in message ... half_pint wrote: How about using a plug with the correct sized fuse in it? The proper fuse is always a good idea but fuses do not protect from power line faults. They blow after your 'protected' device is fried and pulling too much current as a result of it. I am sorry but you are wrong. a correct sized fuse will always protect you. I am sorry you're wrong flap_paint. Semi conductor devices are blown by excess Voltage. A fuse only senses the current. Your protected device will never be 'fried' if you use the correct fuse. It is *impossible* unless the fuse is faulty. Rubbish half_faint! The blow before the device draws enough current to be damaged, that is how they are designed. As said before, voltages also kills semiconductor devices. Why do you think there are such things as electrostatic bags? |
#36
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"half_pint" wrote:
"David Maynard" wrote in message ... half_pint wrote: How about using a plug with the correct sized fuse in it? The proper fuse is always a good idea but fuses do not protect from power line faults. They blow after your 'protected' device is fried and pulling too much current as a result of it. I am sorry but you are wrong. a correct sized fuse will always protect you. If the current is enough to melt a wire (the fuse) do you really think it that same current can't have done any damage to your equipment? Your electronics will be dead before the fuse is even warm. A fuse might stop your house burning down after an electrical fault, but it won't protect your PC from a surge. Tim -- My last .sig was rubbish too. |
#37
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w_tom wrote:
It does not matter whether you top post or bottom post. Yes it does. If you're going to go to the effort of writing your massively long posts you might as well format them in a way which makes it easy for the reader to follow the conversation. Tim -- My last .sig was rubbish too. |
#38
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half_pint wrote:
"David Maynard" wrote in message ... half_pint wrote: How about using a plug with the correct sized fuse in it? The proper fuse is always a good idea but fuses do not protect from power line faults. They blow after your 'protected' device is fried and pulling too much current as a result of it. I am sorry but you are wrong. a correct sized fuse will always protect you. Your protected device will never be 'fried' if you use the correct fuse. It is *impossible* unless the fuse is faulty. For a robust motor, or a heating element, or other devices of that type (if it's not actually the device itself that's at fault, as in a stalled motor), yes. Generally because they are simple, robust, electro-mechanical devices whose 'failure mode', that's being protected, is usually a result of over heating and they have thermal response times slower than a fuse. They are also relatively immune from surge remnants left over from the entry point lightning supressors as their electrical response times are too slow to be affected, as long as the surge does not exceed the insulation resistance. For electronic devices, no. And it's inherent to the nature of electronics. By the time an electronic device is pulling excessive current whatever is at fault inside has long since gone to the happy hunting grounds, or else it would not be pulling excessive current. And there's nothing you can do about it by 'sizing' the external fuse as the failed device could be a 100mw component inside a 200 watt computer where the normal operating power fluctuations are hundreds of times larger. And even if you did have a 'constant power consumption' electronic device, for which you could 'tightly' size a fuse, electronic components can, and do, go into catastrophic failure hundreds of times faster than a fuse can blow. Surge -- component failure -- excessive current -- fuse blows The blow before the device draws enough current to be damaged, that is how they are designed. That is certainly the myth. It is not, however, reality. |
#39
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w_tom wrote:
A wall receptacle safety ground is not earth ground. Yes, safety ground and earth ground do connect. But when discussing the earthing of destructive transients, then wall receptacle ground is just too far away from earth ground. Poppycock. Wire has impedance. 18 meters of 2.5 mm copper wire may be less than 0.2 ohms resistance. But same wire would be maybe 130 ohms impedance to a surge. Wire impedance is why a protector must connect less than 3 meters to earth ground. If the plug-in protector attempts to earth a trivial 100 amp transient down that 18 meter safety ground wire, then wall receptacle would be at something less than 13,000 volts. Where is the protection? Does not exist because wall receptacle safety ground is not an effective earth ground. Setting aside your made up numbers, which are irrelevant anyway, it matters not, from the aspect of protecting the device, what potential the 'ground' at the protected device looks like with respect to your treasured 'earth' as long as all conducive paths in/out of the device are clamped to it: the device never sees any potential outside it's limits and that is all that matters to it. Back to your fantasy numbers, you try to invent a 13,000 volts potential with a 100 amp transient while ignoring that the 100 amps would have to arrive at the surge protector down one of those same 'high impedance' wires before it begins the trip down the ground wire you use to fabricate the 13,000 volts which, of course, would mean there could not be the 100 amp surge you pretend because the let though on the input panel lightning suppressors is no where near 26,000 volts (or 13,000 either). What you have inadvertently done is provide the reason why 'small devices', as you derisively call them, are sufficient for down-stream, 'plug in', surge protection: the wiring limits the magnitude of the current surge. snip of w_tom babble |
#40
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So the plug-in protector is at something less than 13,000
volts when attempting to earth a trivial 100 amp transient. "Poppycock", he says so that he need not deal with numbers he does not understand. In the meantime that less than 13,000 volts must go somewhere. How convenient - that modem and phone line is a perfect outgoing path. And so we have modem damage because someone foolishly spent big bucks on a plug-in protector. Someone hoped the protector would provide protection that even its manufacturer does not claim. Suppose the same money was spent on a earthing a 'whole house' protector. Now we have a protected computer (not at thousands of volts relative to earth) AND we have protected all other 50 appliances also. Which should one believe. The person whose entire knowledge of surge protection is limited to the word 'poppycock'. Or numbers based upon basic electrical principles. Wire has impedance which is why real world protectors manufacturers discuss and promote protectors with the short, direct, and independent connection to a common earth ground. Those adjacetives having engineering significance. David can wish that wire limits an incoming current. But that destructive current comes from a current mode source. Voltage will rise, as necessary, to maintain that current flow; a first year engineering concept. Posted are basic electrical principles such as wire impedance and current mode sources that describe how surges can create destructive voltages. David's lucid response includes poppycock and some idea that wire resistance will limit the current out of a current source. Maybe David could cite some EE101 principles. No. Apparently David forgot to take that course. Maybe David should just cite the manufacturer's specification that claims such protection. No, he cannot cite numerical specifications that do not even exist. What can David do? When one cannot dispute the numbers, then one just ignore those numbers? - or instead post: For one who critiques a 'lack of numbers' they are notably missing from you. What more can I do other than hold his hand? You can take a horse to water, but.... It still remains that a surge protector is only as effective as its earth ground which is why the excessively priced and typically undersized plug-in protectors are so ineffective. Which is why the 'whole house' protector remains such a superior option. Since the 'whole house' solution is so effective and so inexpensive, then any significant amount of electronics means a 'whole house' protector is advisable. What other alternative exists? David Maynard wrote: w_tom wrote: A wall receptacle safety ground is not earth ground. Yes, safety ground and earth ground do connect. But when discussing the earthing of destructive transients, then wall receptacle ground is just too far away from earth ground. Poppycock. Wire has impedance. 18 meters of 2.5 mm copper wire may be less than 0.2 ohms resistance. But same wire would be maybe 130 ohms impedance to a surge. Wire impedance is why a protector must connect less than 3 meters to earth ground. If the plug-in protector attempts to earth a trivial 100 amp transient down that 18 meter safety ground wire, then wall receptacle would be at something less than 13,000 volts. Where is the protection? Does not exist because wall receptacle safety ground is not an effective earth ground. Setting aside your made up numbers, which are irrelevant anyway, it matters not, from the aspect of protecting the device, what potential the 'ground' at the protected device looks like with respect to your treasured 'earth' as long as all conducive paths in/out of the device are clamped to it: the device never sees any potential outside it's limits and that is all that matters to it. Back to your fantasy numbers, you try to invent a 13,000 volts potential with a 100 amp transient while ignoring that the 100 amps would have to arrive at the surge protector down one of those same 'high impedance' wires before it begins the trip down the ground wire you use to fabricate the 13,000 volts which, of course, would mean there could not be the 100 amp surge you pretend because the let though on the input panel lightning suppressors is no where near 26,000 volts (or 13,000 either). What you have inadvertently done is provide the reason why 'small devices', as you derisively call them, are sufficient for down-stream, 'plug in', surge protection: the wiring limits the magnitude of the current surge. snip of w_tom babble |
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