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.
|> | Surge suppressors are not intended to protect against longer duration |> | swells or even longer duration overvoltage. Martzloff's comment above is |> | that the major cause of failure is overvoltage, which suppressors are |> | not intended to protect against. |> |> I've read discussions and online pages to the contrary. If you have put |> forth your theory ahead of time, I could have recorded the locations for |> you. | . | Contrary - overvoltage is the major cause of failure? - you are again | disagreeing with Martzloff. | | Contrary - not intended to protect against swells and overvoltage? - | provide a source that says plug-in suppressors are intended to protect | against swells and overvoltage. Like maybe specs from few manufacturers | that Ed asked for.
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. 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.
| "Put forth your theory ahead of time" - apparently a new newsgroup | requirement?
It's not a requirement to post URLs of things read in the past if there was no expectation to need them. I save many URLs of many interesting things. But I can't save them all.
|> | 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.
| 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.
| What: that is the probable protection route indicated in both guides if | a plug-in suppressor can provide protection from overvoltage. Both | guides make clear not all plug-in suppressors are wired to disconnect | the protected load with the MOVs.
Those that don't have the disconnect need to have that added. That is a lot less expensive than adding a complex overvoltage protection system.
|> Maybe what should have proposed was that we use a more expensive device |> that integrates higher level MOVs with overvoltage sensors. | . | Repeating: | "To protect against overvoltage get a suppressor that disconnects on | overvoltage." They disconnect the load and MOVs.
Or get one that disconnects on MOV overcurrent that is the result of overvoltage. This latter idea will be lower in cost even when considering that each event requires replacing the protection device (because these events are rare). 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.
|> If he can |> show that such a MORE EXPENSIVE device is worth the extra cost in the |> longer term, he wins. But I think he cannot. | . | "He"? Is "he" Martzloff? I have never seen Martzloff indicate a MOV | based surge suppressor should protect against swells or overvoltage.
Maybe he doesn't want them to for some reason.
| 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.
| 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.
| 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).