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#11
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Yes, utility switching does cause transients. But nothing
that should overwhelm internal protection in household appliances. If switching transients were so destructive, then we all would be replacing RCDs, dimmer switches, and clock radios weekly. Once numbers are applied to those switching transients, then those transients become irrelevant. Bob Eager wrote: On Thu, 8 Jul 2004 23:41:08 UTC, w_tom wrote: The frequency of destructive surges is about once every eight years. What is that frequency in your neighborhood? Lightning isn't the only cause of surges. I've seen excessive voltage several times over the last few years. Switching transients, etc. |
#12
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Wall receptacle is safety ground; not earth ground - as
explained in another post in this thread. However let's assume the plug-in protector does earth a destructive transient via wall receptacle. Now that transient is on a wire bundled with other wires. Induced transient is now created by that plug-in protector. By earthing on safety ground wire, we have now induced transients on all other adjacent wires. What kind of protection is that? Ineffective. Same problem applies to the service entrance and single point earth ground. All earthing wires must be installed from each utility wire to earth ground separated from all other wires. Too many installers want to be neat. They make clean sharp bends and nylon ty-wrap all wires together. IOW they compromise the protection 'system'. Even sharp wire bends increase wire impedance. Earthing wires must be shorter (less than 3 meters), no splices (which wall receptacle safety ground wires violate), not inside metallic conduit, and separated from all other wires. Just more reasons why plug-in protectors are so ineffective. Therefore plug-in protectors avoid all discussion about earthing. They fear you might learn about the less than 3 meter necessity. So they avoid all discussion about earthing. They would even encourage the consumer to be confused about safety ground verse earth ground. Mike Tomlinson wrote: In article , w_tom writes In the meantime, plug-in protectors are not effective, cost tens of times more money per protected appliance, and are typically undersized.No sense wasting good money on ineffective protectors that don't even claim to protect from the typically destructive transient. A protector is only as effective as its earth ground - which plug-in power strip and UPS manufacturers fear you might learn. And in Europe, the "earth ground" on mains wiring is good, hence plug-in surge protectors do the job they were designed to do, shunting the surge to earth. In the States, not all power outlets can be assumed to have an earth connection, so plug-in surge protectors have to shunt surges to the other phase line, which makes them vastl less effective. -- A. Bottom posters Q. What's the most annoying thing on Usenet because they complain too much and make their posts harder to read? |
#13
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w_tom wrote:
Yes, utility switching does cause transients. But nothing that should overwhelm internal protection in household appliances. Except that it can and sometimes does. If switching transients were so destructive, then we all would be replacing RCDs, dimmer switches, and clock radios weekly. Once numbers are applied to those switching transients, then those transients become irrelevant. That's as illogical as saying if lightning strikes were so destructive we'd be replacing RCDs, dimmer switches, and clock radios every time it rained. Neither are 'destructive' till the relatively infrequent occurrence when they are. Bob Eager wrote: On Thu, 8 Jul 2004 23:41:08 UTC, w_tom wrote: The frequency of destructive surges is about once every eight years. What is that frequency in your neighborhood? Lightning isn't the only cause of surges. I've seen excessive voltage several times over the last few years. Switching transients, etc. |
#14
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In article , David Maynard
writes You mean a separate earth. I do, yes. Neutral is, of course, earthed. This is the distinction made in the wiring code between the "grounded" and the "grounding" terminal... which causes confusion all of its own No, they expect an earth ground too. I've been over this with w_tom at considerable length in the past (feel free to have a google.) Because American electrical outlets can't be guaranteed to have an earth terminal (for example, in older construction as you point out), the makers of surge protectors for the American market have to wire them to the lowest common denominator, so that a surge on phase is shunted to neutral using one MOV. In the UK and Europe, two MOVs are used - one to shunt phase to earth, and another to shunt neutral to earth. This makes surge protectors made for this market much more effective. -- A. Top posters. Q. What's the most annoying thing on Usenet? |
#15
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In article , w_tom
writes Wall receptacle is safety ground; not earth ground Please explain the difference. I could do with the laugh. - as explained in another post in this thread. I see no explanation elsewhere. However let's assume the plug-in protector does earth a destructive transient via wall receptacle. Which it does in the UK and Europe. Now that transient is on a wire bundled with other wires. So? The transient is shunted to earth via a low impedance path. Induced transient is now created by that plug-in protector. Induced on what? The earth wire? That's what it is there for! By earthing on safety ground wire, we have now induced transients on all other adjacent wires. Absolute crap. There are three wires - phase, neutral and earth. A transient on the phase wire is shunted to earth by the surge protector. What do you mean by "all other adjacent wires"? If you mean low voltage cabling, for example twisted-pair Ethernet cabling, any electrical installer worth his salt (i.e. not you) knows that you /do not/ run low voltage cabling in the same conduit as mains power. It's called segregation. What kind of protection is that? Ineffective. Very effective. One well-known maker of surge protectors in UK and Europe, Belkin, gives a free £10,000 warranty on equipment connected via any of its products. If the surge protector fails and the equipment is damaged, you can claim the cost of a replacement. If their products were that ineffective, do you think they'd offer the warranty? Same problem applies to the service entrance and single point earth ground. All earthing wires must be installed from each utility wire to earth ground separated from all other wires. In your American Mickey Mouse electrical installations, yes. In the UK and Europe, it's unnecessary. Too many installers want to be neat. They make clean sharp bends and nylon ty-wrap all wires together. IOW they compromise the protection 'system'. Even sharp wire bends increase wire impedance. Earthing wires must be shorter (less than 3 meters) Why less than 3 metres? This is another of the claims you frequently make without a shred of evidence to back it up. And remember, we are discussing this in relation to UK and European wiring practice. I sincerely doubt you have ever worked on an electrical installation outside the US (thank god for that too.) Just more reasons why plug-in protectors are so ineffective. What reasons? Where? I see only more hand-waving from you. I've come to the conclusion that you must work for a maker of these "whole house" surge protectors that you constantly advocate. Your opinion is therefore biased, not objective, and worth **** all. HTH. HAND. FOAD. -- A. Top posters. Q. What's the most annoying thing on Usenet? |
#16
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On Fri, 9 Jul 2004 16:39:26 UTC, Mike Tomlinson
wrote: In the UK and Europe, two MOVs are used - one to shunt phase to earth, and another to shunt neutral to earth. This makes surge protectors made for this market much more effective. Indeed. I think (can anyone confirm?) that sometimes three MOVs are used, with one between phase and neutral... -- Bob Eager begin a new life...dump Windows! |
#17
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Mike Tomlinson wrote: [...] I've come to the conclusion that you must work for a maker of these "whole house" surge protectors that you constantly advocate. Your opinion is therefore biased, not objective, and worth **** all. This explains w_tom's surge of mains FUD surge protector posts... |
#18
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Long before computers existed in homes, why were LED clocks
and radios replaced daily? Because switch generated transients were and remain destructive? Why are RCDs and dimmer switches - things more easily damaged and without any external protection - also failing daily? Because again those transients from switching are so destructive. Put some numbers to those switch generated transients. Some who promote utility switching as a source of destructive transient never provide numbers and ignore those above real world examples. They are promoting junk science made obvious by their fear of numbers and a shortage of weekly examples. We can see from dialy damaged electronics equipment that those transients are so destructive. You are replacing RCDs daily because of daily utility switching and the resulting transients? We also don't put umbrellas over that RCD because rain also does not damage the RCD. Why install protection when sufficient protection already exists? Utilities are reconfiguring their grids every month for maintenance, reconfiguring loads, and adjusting voltages. Transients from such events can be seen sometimes as often as daily. So where are all those damaged refrigerators? Transients are well below what all appliance must be designed to withstand without damage. We install surge protection for a so destructive surge more typically known as lightning. Other far less frequent events do occur. Unfortunately some people confuse blackouts and brownouts with surges. Surge protectors do nothing for a blowing fuse or a utility line snapped by a construction machine. Furthermore, destructive transients of all types are made irrelevant by the less expensive and more effective 'whole house' protector. David Maynard wrote: w_tom wrote: Yes, utility switching does cause transients. But nothing that should overwhelm internal protection in household appliances. Except that it can and sometimes does. If switching transients were so destructive, then we all would be replacing RCDs, dimmer switches, and clock radios weekly. Once numbers are applied to those switching transients, then those transients become irrelevant. That's as illogical as saying if lightning strikes were so destructive we'd be replacing RCDs, dimmer switches, and clock radios every time it rained. Neither are 'destructive' till the relatively infrequent occurrence when they are. |
#19
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w_tom wrote:
Long before computers existed in homes, why were LED clocks and radios replaced daily? Because there are and were millions of them. Next! Come back when you've learnt some statistics. Or run for office. Tim -- My last .sig was rubbish too. |
#20
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Mike Tomlinson wrote:
In article , David Maynard writes You mean a separate earth. I do, yes. Neutral is, of course, earthed. This is the distinction made in the wiring code between the "grounded" and the "grounding" terminal... which causes confusion all of its own Hehe. true. But 'neutral' and 'ground' are separate wires in 3 prong plugs even though 'neutral' is earthed at the entry, as is the 'ground' wire. The 'ground' is really 'protective (as in human safety) ground'. Aside from the voltage and U.S. wall outlets being one phase of 230/240 (for 115/120), the U.S. and U.K grounding scheme is essentially the same. FUSING and ring vs star wiring is another matter. No, they expect an earth ground too. I've been over this with w_tom at considerable length in the past (feel free to have a google.) Because American electrical outlets can't be guaranteed to have an earth terminal (for example, in older construction as you point out), the makers of surge protectors for the American market have to wire them to the lowest common denominator, so that a surge on phase is shunted to neutral using one MOV. In the UK and Europe, two MOVs are used - one to shunt phase to earth, and another to shunt neutral to earth. This makes surge protectors made for this market much more effective. I don't know where you're getting you're information on 'U.S.' surge protectors but I have the advantage of possessing more than one of them and that description is inaccurate. The typical surge protector is 100% 3 prong, sockets and plug, with 3 MOVs: one from each 'power' wire to protective ground (what you call earth) and one between the two with, usually, a cap in parallel plus, on the premium models, additional noise suppression (LC). I may have missed one but I am not aware of any 'U.S.' surge protectors that are 'designed' for a 2 prong outlet, or come with a 2 prong plug, nor, for that matter, any PCs that come with 2 prong plugs. |
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