Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 2 replies
  • Subscribers 34 subscribers
  • Views 453 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

SPD Protection.

Zoomup

I recently bought a 1 metre long two way 13 Amp trailing socket extension lead. It contains a varistor with a thermal fuse attached to its side, and two neon indicators. It is well made and clearly has been designed well. The varistor is connected to L. and N. The thermal fuse is held tightly on one side of the varistor disc. Neon light 1 indicates mains present. Neon light 2 indicates that the varistor is still in circuit and that the thermal fuse is still intact.

Total cost delivered= less than £9.00. Compare that cost with the units designed for permanent installations.

Varistor - Wikipedia

Z.

  • 0

    M.O.V. S.P.D. failure: a quote:

    “Cumulative degradation occurs as more surges happen. For historical reasons, many MOVs have been incorrectly specified allowing frequent swells to also degrade capacity.[13] In this condition the varistor is not visibly damaged and outwardly appears functional (no catastrophic failure), but it no longer offers protection.[14] Eventually, it proceeds into a shorted circuit condition as the energy discharges create a conductive channel through the oxides.”

     

    A 130 volt, 150 J MOV that has undergone catastrophic failure, apparently as a result of a lightning strike, showing evidence of heat and smoke. The 3 amp fast-blow fuse immediately in front of the varistor blew during the same event.

    A series connected thermal fuse is one solution to catastrophic MOV

  • 0

    The varistor is connected to L. and N. 

    Compare that … with the units designed for permanent installations.

    Is missing ⅔rds of the protection - nothing L-PE or N-PE  (perhaps OK if you only use Class II equipment, but a waste of £9 as far as any Class I equipment is concerned)

    The other big difference is likely to be the size of surge it's capable of withstanding, and the level of protection it provides downstream …. not known of course, but experience suggests that the highest quality is rarely found in the bargin basement.

       - Andy.

Community Rules & Guidelines