| The heart of many Plug-In Type surge suppressors available today is a small electronic component called an MOV (Metal Oxide Varistor). The role of the MOV is to divert surge current, however, MOVs wear out with use. As more surges are diverted, the MOVs life span shortens, and failure becomes imminent. How soon? How many surges can they handle? No one knows until failure occurs! There is no forewarning or visual indications given - just failure. And while failing, they can reach very high temperatures, and actually start fires. See examples of catastrophic MOV failures in the photos below. |
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This MOV (the yellow disks) fractured cleanly. Surge protection is lost, and the "protected" computer was severely damaged, but there is no fire danger. This unit continues to deliver power, and all lights and switches operate without any indication of failure. |
| This model is an example of dangerous construction, where failed MOV is packed too tightly between adjacent components and cannot split open. This unit is still a live short circuit and sparks violently when plugged into a live receptacle. |
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Plastic cased MOV surge protectors above show identical burn failures. Left unit was found smoking under an office desk, nearly on fire. Both units continued to deliver power without indication of any problem. |
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| You're betting your precious computer on this!!! |
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Circuit board removed from plastic case, showing all 6 MOVs (yellow disks). One leg of each MOV has been cut and there is therefore no protection, but "Protection Working" LED continues to glow green. |
| All 6 MOVs removed from circuit board, but "Protection Working" LED (immediately above large yellow capacitor) remains lit. |
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Industry experts estimate surge probabilities in terms of thousands of surge occurrences. What do MOV manufacturers publish regarding their product's surge capability?
This table shows three manufacturer's surge ratings for two popular sizes of MOVs used in Plug-In Type surge suppressors.
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| Metal-Oxide Varistor Endurance Ratings |
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Panasonic |
Siemens Components, Inc. |
Harris Semiconductor |
| 14mm MOV |
10 surges of 1,000 amps |
10 surges of 1,000 amps |
10 surges of 1,000 amps |
| 20mm MOV |
100 surges of 1,000 amps |
100 surges of 1,000 amps |
100 surges of 1,000 amps |
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| A "best case" rating is 100 surges - far under the new commercial standard of 1000! |
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Be proactive before it's too late!
The article below is only one of many documented cases of Plug-In surge suppressors overheating, catching on fire & destroying valuable computers, data servers, large screen televisions, etc.
Surge Suppressors (MOV Based):
Article found using Google to search for surge suppressor fires
From February 1994 to February 1995, two families on Brainbridge Island lost their homes due to fires caused by Multiple Outlet Power Surge Suppressors! Failing devices are in the photos below, luckily these were caught prior to a fire starting. Do not confuse surge suppressor strips with the general purpose multiple outlet type. The surge suppressor strip contains a Metal Oxide Varistor (MOV) designed to limit power current surges or "spikes" that can damage electronic equipment. The varistor traps the over-the limit part of the current surge and dissipates it as heat. All MOVs gradually deteriorate with use. A basic problem with these kind of surge suppressors is that they divert the surge and you are never quite sure if your electronic equipment is protected or not...
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WARNING:Change to ZeroSurge
before it's too late...
MOVs Burns Down Buildings
Title:
Faulty Surge Protection Device Likely Cause of Mobile Office Fire
Date:
May 24, 2006
Identifier:
2006-RL-HNF-0016
Lessons Learned Summary:
A failed surge protection device (SPD) was the likely cause of a fire that destroyed a mobile office structure at Hanford. Surge protection devices can fail after extended use. Most SPDs have a metal oxide varistor (MOV) that provides the surge protection. Suppressing voltage spikes and transients shortens the life of an MOV. Upon failure, the MOV can reach very high temperatures and cause a fire.
Discussion of Activities:
On January 27, 2006 a fire occurred in MO-304, a mobile office building in the 200 East area. A formal investigation, conducted by the Hanford Fire Department, determined that the  most probable cause of the fire was a failed SPD that was located on top of a computer printer. Due to the severe damage to the suspect SPD, there is no detailed information regarding the make or model number available.
Also identified during the investigation was that at least 2 and perhaps as many as 4 power strips/SPD’s were "daisy chained" together. This was not a contributor to the fire, but is not in compliance with HNF-RD-11827, Hanford Electrical Safety Program Requirements, Section 3.3, #20 and Electrical Safety Compliance Guide, ESCG-2002-001, issued December 10, 2002.
Analysis:
Surge protection devices, or SPD, are also known as transient voltage surge suppressors (TVSS). Most SPDs have a metal oxide varistor (MOV) that provides the surge protection. MOVs wear out with use, and suppressing voltage spikes and transients shortens their life. MOVs can reach very high temperatures as they fail and can ignite the epoxy coating and start a fire. Prior to 1998, most SPDs sold had no protection to guard against a fire caused by a failing MOV in a SPD. In February, 1998, Underwriters Laboratories (UL) issued the second edition of UL Standard 1449, Transient Voltage Surge Suppressors. The second edition of UL 1449 requires that a SPD either fail in a safe manner or survive connection to twice the nominal voltage for seven hours. The easiest way for a SPD to pass this test is to employ a thermal cutout device at the MOV.
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