On Mon, 03 Mar 2008 03:02:34 -0600 bud-- wrote: | snipped-for-privacy@ipal.net wrote: |> On Sun, 02 Mar 2008 17:10:40 -0600 bud-- wrote: |> | snipped-for-privacy@ipal.net wrote: |> |> On Sat, 01 Mar 2008 03:12:55 -0600 bud-- wrote: |> |> | snipped-for-privacy@ipal.net wrote: |> |> |> On Fri, 29 Feb 2008 02:23:56 -0500 Michael A. Terrell wrote: |> |> |> | snipped-for-privacy@ipal.net wrote: |> |> |> |> |> |> |> |> On Thu, 28 Feb 2008 01:45:12 -0600 bud-- wrote: |> |> |> |> |> |> |> |> | Martzloff has also written "In fact, the major cause of TVSS [surge |> |> |> |> | suppressor] failures is a temporary overvoltage, rather than an |> |> |> |> | unusually large surge." |> |> |> |> |> |> |> |> And these would not damage the TV? |> |> |> | |> |> |> | |> |> |> | No. Why do you think it would? if the surge suppresser clips at a |> |> |> | safe voltage to protect from spikes, it won't go any higher with a |> |> |> | overvoltage condition, but the MOV or other protection device quickly |> |> |> | overheats as it tries to maintain the proper voltage. If the line |> |> |> | voltage is high enough, it will trip the Breaker, or blow the fuse for |> |> |> | that AC circuit. The protective device can only dissipate a small |> |> |> | amount of heat before it self destructs. |> |> |> |> |> |> This was a discussion about a suggestion tha the MOV condunction voltage |> |> |> should be higher than now used (330V for 120V systems). He wants to |> |> |> raise that voltage to avoid certain situations causing TVSS failure so |> |> |> the protection against spikes (above 800V) is maintained longer. My |> |> |> position is that the swells as high as 565V RMS could in fact cause |> |> |> damage to the TV. Under his proposal, these would be be suppressed. |> |> |> I think that is a bad idea because these voltage swells really can do |> |> |> damage. |> |> | . |> |> | Surge suppressors are intended to protect against surges. Raising the |> |> | clamp voltage is to lower unnecessary suppressor exposure to surges that |> |> | do not damage connected equipment. |> |> |> |> The last 7 words are the part we do not agree on. |> | . |> | You are disagreeing with Martzloff, who has done a lot of research on |> | surge protection an has numerous published papers. The same immunity has |> | also appeared elsewhere such as a PCMagazine review of plug-in suppressors. |> |> Yes, I am disagreeing with him. I believe he has an agenda of some kind. |> What we have now works. I don't believe he has shown justification to |> make a change. | . | So you assault the character of an electrical engineer that is an | established authority on surges. And your assault occurs in an | electrical engineering forum. Apparently Martzloff even fooled the IEEE | which published his papers. And international conferences that also | published his papers. Too bad they aren?t as smart as you.
I am not being critical of specific statements he makes. From an engineering perspective, he is correct that by using a higher voltage MOV, surge suppressors would last longer. That is not in dispute.
What is in dispute is the worthiness of bothering to do this. He has not supported why this should be done. If MOV voltages go up, then the cost of full protection goes up because additional protection at the lower level is then needed.
|> Yes, I still disagree with him. The "suppressors are not intended to |> protect against" is the point. BUT NOTE THIS VERY CAREFULLY ... I do not |> say he is wrong ... I say he has a twisted agenda in that regard. | . | Again impugning the integrity of an electrical engineer that is a | recognized expert.
Being an expert in engineering has nothing to do with the applicable economics.
|> While |> they may not have been _intended_ to protect against overvoltage, they do |> have that capability and for many people, they have an expectation to do |> such protection. That's why I say leave things as they are. | . | Gee. you forgot the specs from a few manufacturers. What a surprise.
Show me _ANY_ manufacturer that publishes complete specs on what their products _CAN_ do (as opposed to what they merely market them to do).
|> |> | If you keep the clamp voltage low, you are likely not increasing |> |> | protection from swells because a swell may well kill the MOV anyway. To |> |> | protect against overvoltage get a suppressor that disconnects on |> |> | overvoltage. |> |> |> |> The surge suppressor already does this. Sure, it can _die_ while doing |> |> this. The MOV shorts across, causing an increase in current that trips |> |> the supplementary breaker in the strip (usually integrated in the switch). |> |> There, appliance protected by one low cost device. |> | . |> | By the time current reached well over 15A required to trip a 15A breaker |> | in a short time, the MOV would be toast. UL has required since 1998 that |> | thermal disconnects be provided to disconnect overheating MOVs. Or fuses |> | as Greg suggests, but selected by the manufacturer which can have |> | operating characteristics closely matched to the MOVs, may also open. It |> | is unlikely that protection would come from a breaker. |> |> So what if the MOV is toast. It's still the cost effective way to provide |> the protection. It's a rare event. | . | The point of this paragraph, which should be clear to anyone who can | read, is that circuit breakers are not likely to trip. The point was not | toast.
So you think that if an MOV begins a runaway conduction because the peak of an overvoltage causes it to fail, that this won't trip a breaker within a couple cycles?
Maybe the MOV will just clamp for the duration of the cycle peak, and not go into runaway conduction. Then don't worry. See above for the other case.
|> | Repeating: |> | "The IEEE guide goes on a length how the protected load can be connected |> | across the MOVs or connected to the incoming line. If connected across |> | the MOVs, the protected load will be disconnected when overheating MOVs |> | are disconnected on failure." Similar comments are in the NIST guide. |> | |> | Your response was "And you are saying what?" |> |> Maybe if you had included an analysis, I would not have had to ask. | . | Maybe if you had any interest in what other people write you would have | understood.
Well I sure have no interest (anymore) in what you write.
|> Martzloff does not appear to be considering the |> statistical economics. Maybe he has an agenda, like trying to sell more |> of some other kind of protection. | . | Another outrageous slander.
I accuse an engineer of not being an economist ... is a slander? That's very creative.
|> | The "IEEE Recommended Practice for Powering and Grounding Sensitive |> | Electronic Equipment" (Emerald book) does not indicate plug-in |> | suppressors are an effective means of protecting against swells or |> | overvoltage. |> | |> | Perhaps you could use a plug-in suppressor with overvoltage protection |> | built in, as above. |> |> Can you point out a LOW COST ONE? My understanding is they have quite |> a high cost. But if you can point to one or two low cost ones, then I |> would be wrong. | . | You have not pointed to a plug-in suppressor that the manufacturer says | is effective on swells and overvoltage. Maybe you are wrong.
Or maybe the manufacturer is hiding this so they can sell other stuff to unwitting people.
|> | If you want to use failure of MOVs to protect your equipment I would |> | suggest a suppressor from a reputable manufacturer where the |> | manufacturer says the suppressor will protect from swells and |> | overvoltage. Given hype, I suggest using a device where the manufacturer |> | also has a warrantee on protected equipment. |> | |> | Saying plug-in suppressors should protect against swells and overvoltage |> | they are not designed for does not make them effective. |> |> What something is designed for, and what it can do in certain cases, are |> not always the same thing. Then when manufacturers find out that their |> product already cheaply does what customers want that could have been done |> in a more expensive way to drive more revenue, they realise the golden |> goose has escaped the pen and are trying to round it back in. | . | Yea, those manufacturers are really stupid. Just like Martzloff. And the | IEEE. And the NIST.
I have not accused any of them of being stupid. I have accused them of possibly having an alternative agenda.
|> | Or perhaps you could use a device the Emerald book indicates might be |> | effective. For houses that would be a UPS. But make sure the |> | manufacturer says the UPS will protect against swells and overvoltage. |> |> This is exactly what I am describing. They want to sell something that |> is way more expensive, rather than admit that something cheap can do the |> same thing (though self-destructively). | . | You dismiss UPSs, which the IEEE Emerald book says may be effective, for | plug-in suppressors which the Emerlad book does not recommend.
This is the expensive "solution".
| You attack an electrical engineer that is a recognized expert.
... for his economic claims.
| You ignore what I post.
... because it is trash ... because you apparently don't even understand what it is I have said, since your responses don't even address what I was saying.
| There isn?t much point in responding further.
... I guess not.