Questions about surge protectors

Discussion in 'General Electronics Chat' started by tjohnson, Jul 23, 2015.

How old is your surge protector?

  1. Less than one year

    0 vote(s)
    0.0%
  2. Less than five years

    0 vote(s)
    0.0%
  3. Very old

    50.0%
  4. I don't care

    50.0%
  1. tjohnson

    Thread Starter Active Member

    Dec 23, 2014
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    I have several questions about surge protectors:
    1. Is it true that they should be replaced regularly, or is it OK to wait until the "Protected" status light goes out? If they should be replaced, how often?
    2. What are the best brands of surge protectors? I've heard that APC offers a lifetime warranty, but I don't know much more than that.
    3. What is the minimum/ideal joule rating that you would recommend for home office use?
     
    Last edited: Jul 23, 2015
  2. Glenn Holland

    Member

    Dec 26, 2014
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    Surge protectors use a Metal Oxide Varistor (MOV) which should last indefinitely unless there is a severe overvoltage condition.

    MOVs are rated by the total energy during a transient condition (Joule-Seconds). If the energy limited is exceeded, the device will burn up.
     
  3. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    #1 What do you want to protect?
    #2 What types of electrical disturbances do you want to protect #1 from?
    http://thewirecutter.com/reviews/best-surge-protector/

    If this is for a home office/computer system the best device (if you value your information and systems) is an online UPS where the utility voltage keeps the batteries charged and the computer system power is always supplied by the online inverter.
     
  4. tjohnson

    Thread Starter Active Member

    Dec 23, 2014
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    That article says:
    and I've read similar things in other articles. I understand that the MOVs deteriorate over time, but not why it's recommended to replace them every few years. Isn't the purpose of the Protected status light to tell you when the surge protector needs to be replaced?
     
  5. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    The light says you have some protection but that protection could range from a tissue paper to a brick wall. I mainly use the plugin protections as cord organizers. My main utility surge protection device is in the house panel directly connected to the the feed lines and main ground connections with additional surge protectors in sub-panels with all important devices on UPS power.
     
    Last edited: Jul 23, 2015
    tjohnson likes this.
  6. Brevor

    Active Member

    Apr 9, 2011
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    The status light only tells you if the suppressor has taken a surge over its capacity and the MOV's are toast.
     
  7. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    and if it does work it only protects the devices plugged into it before it dies instead of the whole house with a panel protector.
     
    Last edited: Jul 23, 2015
  8. Glenn Holland

    Member

    Dec 26, 2014
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    When a severe transient occurs, the MOV in a surge protector will go into full conduction and create a short between the lines. That will pop the line circuit breaker, but the MOV itself will be cooked. In that case, open up the unit and replace the MOV.

    Large industrial grade surge protectors are available which can survive a severe transient (such as lightning strike), however they're too expensive for household use.
     
  9. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    As per the above and many of the following comments, a sophisticated or glorified fuse.
     
  10. tjohnson

    Thread Starter Active Member

    Dec 23, 2014
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    So if I understand correctly, the Protected light shows that the surge protector has >0 Joules of protection left, but there could be 1000 J left or only 10 J left.
     
  11. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    A fuse is wired in series with the load, and is blown open-circuit by a transient over-current, disconnecting power from the load.

    A MOV is wired in parallel with the load. It clamps a short-duration over-voltage surge by shunting the voltage above the breakover voltage from line to neutral, thereby protecting the load. The MOV can repeatedly absorb surges with a range of energies without damage. If the surge energy exceeds the rating of the MOV, then the surge can damage the MOV. The damage manifests as a permanent change in the ability of the MOV to absorb future surges. The indicator light is trying to tell you if the MOV was damaged by a previous surge...

    I use a protector until the indicator lamp changes state...
     
    tjohnson likes this.
  12. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    They will only deteriorate if, as Mike says, "the surge energy exceeds the rating of the MOV". Naturally, manufacturers will try to scare you into replacing surge-protectors frequently ;).
     
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