MOVs are like circuit breakers?


I was doing some research on surge protectors and the articles suggested getting one with internal circuit breakers. So then I emailed a few companies to ask about their surge protectors and they said that the new ones don't use circuit breakers, they use MOVs. So, what's the story here? Do only older surge protectors have circuit breakers? Do MOVs work the same way?
I noticed that the older surge protectors do have a little reset button on them that the newer ones don't have. I assume the ones with the button have circuit breakers and the ones without the button have MOVs, would that be correct? Maybe, it's me but it seems like the ones with the reset button would be better.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

http://en.wikipedia.org/wiki/Metal_oxide_varistor
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Mike S. wrote:

MOVs are more like fuses than circuit breakers. Often they only work once.
After that, you're unprotected.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

MOVs are not like fuses or circuit breakers. MOVs are a device that shorts out when the voltage goes too high. Fuses and breakers do the opposite - they go open circuit. They are not mutually exclusive - they can work well together. A MOV can be used to trip a breaker on a voltage spike. Normally, they are used to short the voltage spike to ground, thereby limiting the voltage that gets to the protected equipment.
Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I've seen quite a number of MOVs blow apart from absorbing surges. And many times,the protected circuit still worked once the blown fuse and MOV were replaced.
--
Jim Yanik
jyanik
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
HeyBub wrote:

Hi, Please refrain yourself from making a statement like this. Sounds like you have no idea what MOV is. You won't even recognize it if you happen to see one.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

All power strips (protector type or the better $3 ones) require a 15 amp circuit breaker for human safety. A power strip without that circuit breaker should be removed as a threat to humans.
Circuit breaker is a series mode device - are open circuit when current is excessive.
MOVs are shunt mode devices that are closed circuit when voltage is excessive.
MOVs are not located between AC electric and appliance. Fuse (circuit breaker) is. MOVs must become conductive to earth destructive transients - for transistor safety. Fuse cuts off (obstruct) current so that a damaged appliance does not create fire - for human safety.
MOVs are not a one shot device. MOVs that become one shot devices are in violation of the MOV manufacturer's specifications. Many power strip protectors are grossly undersize (too few joules) so that MOV's smoke promotes more sales. .A vaporized MOV means it provides no effective protection. A minimally sufficient MOV earths a transient and remains functional. To be effective that means a short and dedicated earthing connection not found on power strips.
This has no relationship to a circuit breaker that is required for human safety - so that electrical damage does not cause fire and other human safety problems.
MOVs and circuit breakers perform completely different functions, are located in completely different locations (series verses shunt), and have completely different purposes (human safety verses transistor safety).
Best power strip is the $3 type that has that all so necessary 15 amp circuit breaker.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Mike S. wrote:

The best information I have seen on surges and surge protection is at: http://www.mikeholt.com/files/PDF/LightningGuide_FINALpublishedversion_May051.pdf - the title is "How to protect your house and its contents from lightning: IEEE guide for surge protection of equipment connected to AC power and communication circuits" published by the IEEE in 2005 (the IEEE is the dominant organization of electrical and electronic engineers in the US).
And http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf - this is the "NIST recommended practice guide: Surges Happen!: how to protect the appliances in your home" published by the National Institute of Standards and Technology (the US government agency formerly called the National Bureau of Standards) in 2001
UL listed plug-in surge suppressors will always have a circuit breaker (or fuse). A service panel protector will connect to a breaker in the panel and may have internal fuses.
The actual surge protection in almost all residential protectors are MOVs. MOVs clamp the voltage between wires to a safe level. In a service panel protector that dumps most of the surge energy to earth. Circuit breakers and fuses can not provide surge protection because they act far too slowly. "New ones don't use circuit breakers, they use MOVs" - sounds like someone who is incompetent.
MOVs have an energy/Joule rating. If they absorb enough energy (clamp-voltage times current times time) they will fail, which is usually as a low resistance with high heat. UL requires MOVs to be disconnected when they overheat - could be by an contacting fuse. With a high energy rating, MOVs can take a large number of hits. The current rating of protectors is very important - the IEEE guide gives recommendations.
Franois Martzloff, who was the surge guru at the NIST and wrote the NIST guide, has said "in fact, the major cause of TVSS failures is a temporary overvoltage, rather than an unusually large surge."
Plug-in suppressors can be wired with the protected load across the MOVs, so the load is disconnected if the MOVs are disconnected. Or they can be wired so the protected load is not disconnected. The literature should tell you which way the device is wired. Across the MOVs is a good idea.
Contrary to the assertions of some, both the IEEE and NIST guides say plug-in suppressors are effective.
Interconnected equipment (computer, monitor, printer, ...) needs to be connected to the same plug-in suppressor, or interconnecting wires, like LAN need to go through the suppressor. Other external wires like phone, cable TV, ... also need to go thorough the suppressor. The voltage on ALL wires (power and signal) to protected devices needs to be clamped to the common ground. This is described in both guides.
-- bud--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Francois Martzloff also wrote in conclusions of his 1994 IEEE paper:

When promoting for a plug-in protector industry, then forgetting to provide all facts is necessary. Martzloff even notes what we had seen almost a generation ago. The plug-in protector can even contribute to damage of adjacent appliance. Effective protectors are close to earth ground (a 'less than 10 foot' connection) and distant from the protected transistors. That separation is additional appliance protection.
Plug-in protectors too close to the appliance can create 'objectionable differences in reference voltages' - can contribute to damage of an adjacent appliance. Any protection that works adjacent to an appliance is inside the appliance. Protection that may be overwhelmed if a protector is not properly earthed where a surge enters the building. What kind of protector is properly earthed? 'Whole house' type.
Meanwhile plug-in protectors with necessary approval ratings also create other worries that its promoter hope you don't learn. View these scary pictures: http://www.westwhitelandfire.com/Articles/Surge%20Protectors.pdf http://www.hanford.gov/rl/?page=556&parent=554 http://www.zerosurge.com/HTML/movs.html http://www.nmsu.edu/~safety/programs/gen_saf/surgeprotectorfire.htm
A fuse or circuit breaker (a series mode device that opens on excessive current) is completely different from an MOV (a shunt mode device that shunts, closes, conducts, clamps during excessive voltage). A circuit breaker is for human safety. A properly sized and earthed MOV is for transistor safety.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
w_tom wrote:

With minimal reading and thinking ability w_ could have read in the same document: Mitigation of the threat can take many forms. One solution, illustrated in this paper, is the insertion of a properly designed surge reference equalizer.
A surge reference equalizer is a plug-in surge suppressor that has connections for signal wires in addition to power wires. It is described in both the IEEE and NIST guides and was described in the last paragraph of my post.

I agree with w_ when he said: "It is an old political trick. When facts cannot be challenged technically, then attack the messenger." My only interests in surge protectors are that I have two.
For necessary facts read the IEEE and NIST guides.

Martzloff notes in the NIST guide just 6 yeaars ago that plugin suppressors are effective.

As described in the IEEE guide plug-in suppressors work by CLAMPING the voltage on all wires (power and signal) to the common ground at the surge suppressor. They do not work primarily by earthing.

If you dont have technical arguments try pathetic scare tactics.

For anyone with minimal reading skills the hanford link talks about "some older model" power strips and specifically references the revised UL standard, effective 1998, that requires a thermal disconnect as a fix for overheating MOVs. Overheating was fixed in the US in 1998. w_ can't understand his own links
None of these links indicate the problem suppressors shown had UL labels. And none of these links say there is any problem with suppressors under the current UL standard. Or that plug-in suppressors shouldn't be used. The links do give info on how to use plug-in suppressors.
I recommend reading the IEEE and/or NIST guides. Both say plug-in suppressors are effective. Never seen - a link from w_ that say plug-in suppressors are not effective.
-- bud--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Political tricks are providing half facts that Bud forgets to mention. Even Martzloff defines earthing as essential to protection. Even one of Bud's citations (that he misrepresents as a recommendation) shows a plug-in protector putting a TV at 8000 volts. What kind of protection is that? Bud claims that TV charged to 8000 volts via power cord during a surge is not harmed? That is not what his own citation says. Bud hopes you don't understand the warning. Why is a TV charged to 8000 volts? Because a surge was not earthed before it entered a building - because the surge was shunted (diverted, clamped, connected) to the TV by a plug-in protector - or why responsible manufacturers instead market 'whole house' protectors.
This time Bud says a protector needs no earthing. He has posted the "surge reference equalizer" claim - a protector needs no earthing. Funny. Even IEEE recommendations (recommendations are in standards; not in IEEE papers) demand earthing as essential to protection. But if Bud spins enough half truths, then you might also believe Saddam really did have WMDs.
No earth ground means no effective protection. Even IEEE demands earthing for protection in standards such as the Red Book (Standard 141), Green Book (Standard 142), and Emerald Book (Standard 1100). That earthing must both meet and exceed post 1990 National Electrical Code requirements. Instead, Bud will sell a magic box that somehow stops and absorbs what three miles of sky could not. Effective protection was never about stopping or absorbing - which is why your telco does not shutdown and disconnect with each thunderstorm. Effective protectors shunt (connect, clamp, divert, conduct) surges to earth. They do what Ben Franklin's lightning rod also did in 1752. No earth ground means no effective protection.
For example, IEEE Red Book (Standard 141) says:

Could they be any more blunt? Bud hopes you ignore what the IEEE recommends.
Take a $3 power strip. Add some 10 cent components. Sell it for $25 or $125 as a plug-in surge protector. See that profit margin? No wonder promoters will post half truths incessantly. Plug-in protectors without that earthing hope you need learn this: No earth ground means no effective protection.
Notice what happens when protectors are so profitable as to be grossly undersized. Again, the scary pictures: http://www.westwhitelandfire.com/Articles/Surge%20Protectors.pdf http://www.hanford.gov/rl/?pageU6&parentU4 http://www.zerosurge.com/HTML/movs.html http://www.nmsu.edu/~safety/programs/gen_saf/surgeprotectorfire.htm

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
w_tom wrote:

Martzloff wrote the NIST guide that says plug-in suppressors are effective.

<etc>
The 8kV is part of an explanation in the IEEE guide of how a plug-in surge protector with power and signal ports works. Since earthing is not primarily used, w__ cant understand the example.

Pathetic. I never said a protector needs no earthing. I repeated what the IEEE guide describes - repeating again since w_ couldnt understand the first time: As described in the IEEE guide plug-in suppressors work by CLAMPING the voltage on all wires (power and signal) to the common ground at the surge suppressor. They do not work primarily by earthing.

First IEEE guide is misrepresented as a technical paper. You have to be stupid to think the IEEE would release a guide to the general public that is not consistent with the IEEE color books
And from the guide: "The information contained in IEEE Press/Standards Information Network publications is reviewed and evaluated by peer reviewers of relevant IEEE Technical Societies, Standards Committees and/or Working Groups, and/or relevant technical organizations. The authors addressed all of the reviewers' comments to the satisfaction of both the IEEE Standards Information Network and those who served as peer reviewers for this document. "The quality of the presentation of information contained in this publication reflects not only the obvious efforts of the authors, but also the work of these peer reviewers."
The guide obviously represents the thinking of the IEEE.
And further - `surge reference equalizers , the same as the IEEE guide, are in the IEEE Emerald Book "IEEE Recommended Practice for Powering and Grounding Sensitive Electronic Equipment". The Emerald Book is an IEEE standard, and the most appropriate color book for what we are talking about.
w_, who cant understand simple language in the IEEE and NIST guides, probably thinks Sadam had WMDs.

Statement of religious belief in earthing. Since plug-in protectors do not depend primarily on earthing w_ attacks, defending his religious belief by trying to discredit or misrepresent conflicting information.

Statement of religious belief in earthing #2. Clear in the IEEE guide - plugin suppressors work primarily by clamping the voltage on all wires to the common ground at the suppressor, not earthing, stopping, absorbing, diverting.

<etc>
Bud hopes you read the IEEE and NIST guides. Both recognize plug-in suppressors as effective.

Statement of religious belief in earthing #3. Not shared by the IEEE or NIST.

Ho-hum - repeating: For anyone with minimal reading skills the hanford link talks about "some older model" power strips and specifically references the revised UL standard, effective 1998, that requires a thermal disconnect as a fix for overheating MOVs. Overheating was fixed in the US in 1998.
w_ still can't understand his own links.
And still no links that say plug-in suppressors are not effective. There are 97,463,861 web sites, including 12,587,333 by lunatics, and w_ can't find another lunatic that says plug-in suppressors are not effective.
But the IEEE and NIST guides both say plug-in suppressors are effective.
-- bud--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.