Lightning & Surge Protection 101 - Part 3

Posted by Mike Agri on 12/7/2011

Part 1 | Part 2 | Part 3 | Part 4 | Part 5

Find & Seal All Open Doors

Commercial grade solid state components have long been known to be subject to something I call “infant mortality” – They either “die young” [fail within 30 seconds to 30 days from initial power up], or live long, productive lives. When a system that has been functioning normally suddenly fails catastrophically, probability is high that an external event precipitated the failure.

Sometimes, if you get lucky, the entry point for damaging events will be all too obvious [burnt PC boards, exploded components, individual circuit devices destroyed, etc.] The hard part comes when you have to decide what did the damage, why it was able to affect the system as it did, and most importantly, how do you stop it from happening again. In many ways, coming up with the right answers is analogous to decoding a “who done it” novel, and may require some investigatory and\or forensic skills. In my personal experience, I have found that until I can satisfactorily explain the sequence of events and the mechanism that caused the observed damages or behaviors, I probably have not found the condition that created the behavior or allowed those damages to occur.

Hard-wired systems can suffer damages from lightning, electrical, EMI, or RFI related issues. Some common points of entry include:

- The AC feed to the system [strikes, spikes, surges, harmonics, dirty neutrals, etc.].
- Municipal\Central Station connections.
- Ground.
- Harmonics and phase imbalances caused by non-linear loads [ VFDs, motors, copiers, etc.].
- Sprinkler system supply pipes.
- Overhead or underground input or output connections and associated wiring.
- Cabling run in contact with, or in close proximity to EMI or RFI sources of energy emissions.
- Additions to existing systems that are inconsistent with original installation methods, i.e., new wire or cabling not enclosed in ferrous metal raceway and fittings.
- Radiated energy entering uncovered junction boxes, splice cans, etc.
- Improper connections to other systems or circuits not intended or approved.
- Improper mixture of power limited and non-power limited conductors in same raceways, splice boxes, etc.
- Unintended overloading of circuitry or power supplies.
- Switched, undersized, or shared neutral conductors.

Remember, any unintentionally grounded conductors or circuit components can provide a path for rogue voltages or frequencies into your system, or can prevent circuits from functioning when needed, so if you are working with systems that sense field wiring and\or internal ground faults, removing the ground reference conductor is not a wise “fix”.

In certain occupancies, like hospitals, high level care nursing care facilities, high tech research facilities, military installations, etc., it is entirely possible that you may have to deal with some or all the above, to some degree. It is also entirely possible that deficiencies involving other trades may be contributing to the conditions that become part of “your” problem.

Next time: Being the Detective that Solves the "Case"

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