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Surge Protection

(Or, saving your Mac from the big ZAP! )

The following outline, information and link referrals come from a presentation given by SMUG member and President, John Johnson, at the August 14, 2002 SMUG meeting. It has been added here for general knowledge sharing and research purposes by popular request. Please take this as reference material only, and seek professionals guidance when working with electric power. Electricity is not a toy, just ask Ben Franklin.

Why is stable power important?

  • Danger to components, particularly through ports other than power.
  • Modem damage is quite common, for example
  • Loss of data, either because of computer shutdown or reset, or because a component malfunctions due to lack of power (failed HD write operation)

How to protect hardware?

Surge protectors:
Only protect against voltage spikes, not against low voltage.

  • use Metal Oxide Varistors to ``damp'' small line surges.
  • MOV's fail unexpectedly, often in only 100 cycles. Depending upon the construction of the surge protector
  • MOV failure might not actually break the circuit, leaving your computer unprotected.
  • Even worse, MOV failure is a thermal event, creating fire hazard through heat and/or through arcing.

UPS: Uninterruptible Power Supply.

  • Basically a surge protector with a battery
  • These devices protect against brown-and black-outs by tapping reserve power from battery.
  • Typically such devices incorporate MOV's for surge suppression as well.
  • More expensive devices contain software that is capable of shutting down/saving equipment that is connected to the UPS, without the intervention of a human operator.

"Power Conditioners"

  • actively convert whatever power is coming in to some set standard (e.g. given an input between 80-200V, 30-70Hz, they will always output 120V 60Hz).
  • Computers with auto switching power supplies already have this built in.
  • More expensive versions can handle a wider range of power inputs.
  • They tend to be quite expensive, as they are usually aimed at high-end Audio/Video production and commercial applications.

 

What about lightning?

  • Neither a surge protector nor a UPS will protect against a local lightning strike.
  • How close a strike needs to be in order to count as local depends upon your individual connection to the power grid.
  • Lightning will simply arc across MOV's, and batteries do not have enough capacity to absorb the excess power.
  • Lightning can also cause surges on networks, modems, on any wire that is connected either directly to the outside, or is connected to a device that is unprotected.
  • A power surge can traverse networks if only some of the components are protected (lightning to power line burns unprotected printer, then travels back through the network to damage communications ports)

Protecting from lightning

  • Unplugging everything can be effective, but you have to be there to do it.
  • Further, unplugging power isn't enough.
  • All connections that even indirectly connect to an outside utility must be removed (i.e. all cables disconnected).

Protect the entire house

  • All utilities ground to a common point where they enter the house.
  • This can be cheap, especially for new construction, or expensive [to retrofit older homes' utility connections].

Summary:

  • Cheap surge protectors and UPS's (even quite good UPS's) cannot
    protect against direct lightning strikes.
  • They can smooth out smaller line surges.
  • UPS's also will keep your computer operating for a short period when power fails.
  • The sort of surge protection (and brownout protection for UPS's)
    will be more or less useful depending upon the exact power conditions in
    your house/business:
    • are circuits overloaded?
    • Does your computing equipment share a circuit with major appliances, especially AC or refrigeration (this is bad)?
    • Is your Main Fuse Panel overloaded, or close to it?
    • Is the power grid in your area loaded heavily or unevenly (e.g. is there an ice-making plant next door)?

URL's to more information and resources:

A google groups (not plain google) search for threads in the groups:
comp.sys.mac.* containing the words "lightning" and "surge protection" will give you much to consider.

Here is a brief excerpt from a post:

From: w_tom (w_tom1@usa.net)
Subject: Re: lightning killed iMac Ethernet?
Newsgroups: comp.sys.mac.hardware.misc

Some articles that demonstrate the principals:

Serious surge protector manufacturers discuss earthing extensively:

Scary pictures of those more expensive plug-in surge protectors.

Dr A J Surtee wrote an excellent article on protecting from surges in Power Quality Magazine on 4 Feb. 1999 entitled "Principles of Lightning Protection for Telecommunications Facilities". [Which includes] his his six point plan:

The Six Point Plan recommends:

  1. Capture the direct lightning strike at a preferred point on
    purpose-designed air terminals
  2. Conduct the lightning current to ground safely via a purpose-designed insulated down conductor system to minimize the dangers of side-flashing and induction to adjacent RF cables
  3. Dissipate the energy into a low impedance ground system with minimal rise in ground potential
  4. Eliminate earth loops and differentials by creating an equipotential grounding plane under transient conditions
  5. Protect equipment from surges and transients on incoming power lines
  6. Protect equipment from surges and transients on communications and signal lines to prevent equipment damage and costly operational downtime

Notice that it is all a building wide 'system'. Almost none of this is required nor addressed by the National Electrical Code (NEC) which is only concerned with human safety. Your landlord will only be concerned with meeting code.

A minimal residential 'whole house' surge protector costs less than $50 at Home Depot. Maybe you could buy it and have it installed where your power box meets its required earth ground. Visually inspect those AC electric and telephone ground lines which either the landlord or phone company must correct. Verify that the pole transformer is properly grounded - wire not broken by a stray car.

These are things one can do to protect electronics in an apartment.

[end excerpt]

  
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