Re: Power Conditioners?

Bob Lombard wrote:
bud-- wrote:
Bob Lombard wrote:

You see, I am having difficulty extracting a specific recommendation from your posts. My interest is not trivial, because I lost some stereo system components last summer, when lightning struck a maple tree that is about 10' from my house. Static electricity in some form (I suspect ball lightning, but I wasn't in the room) entered my bedroom and 'stunned' the electronic control for my adjustable bed (I say 'stunned' because it didn't work for a week or so, then functioned again). The - oh hell, I'm going to call it ball lightning - entered my workroom and permanently did in an integrated amp, tuner and computer connected to a UPS/surge protector - without damaging the UPS or popping the MOVs.

Ball lightning is extremely unusual and is not likely to be the cause.

Lightning rods protect only from a direct lightning strike to the house. And they protect only the house, not electronics in the house. Standard installation of rods includes a power service panel suppressor. That does not necessarily protect everything either.

A lightning strike will produce large earth currents. The earth currents from a very close strike can lift the "ground" potential at your house above "absolute ground" potential, which can in effect produce a surge between "building ground" and power/ phone/cable(center conductor) entry wires, which is equivalent to a surge coming in.

Protecting phone and cable wires requires a *short* ground wire from the cable and phone entry protectors to the "ground" at the power service. The power service is preferred because the goal is to minimize the voltage between power and signal wires. High voltage between power and signal wires is likely to cause most equipment damage. The author of the NIST guide has written "the impedance of the grounding system to 'true earth' is far less important than the integrity of the bonding of the various parts of the grounding system." (In some houses, the phone/cable entry points are too far distant from power to adequately limit the voltage - example in the IEEE guide starting pdf page 40.)

Note that a cable entry ground block does not limit the voltage between the center conductor and the shield. The voltage is limited only by the breakdown voltage of an F connector, which is high enough to damage equipment (2000-4000V according to the IEEE guide).

The IEEE guide has as best protection:
1 earthing the building "ground"
2 short interconnection between phone/cable entry protectors and power ground
3 surge suppressor at the power service
4 plug-in suppressors at sensitive equipment

Some possibilities for damage to equipment connected to the UPS:
- Is the UPS listed under UL 1449 (if US).
- If all interconnected equipment was not plugged into the UPS high voltage can develop between equipment on the UPS and equipment not on the UPS. The high voltage shows up on the interconnect between equipment (audio line, cable, ...)
- If equipment has an external connection (phone, cable, satellite) that does not go through the UPS there can be high voltage between the power wires and signal wires. (This may be the most common cause of damage to equipment.) Even with a service panel suppressor and proper grounding of phone and cable entry protectors, the signal and power wires can form a loop antenna that can directly pickup radiated energy from the near strike.
- Surge came in on power wires, and MOVs were damaged and disconnected. The UPS may have indicator lights to indicate protection loss. Else you would have to measure to see if MOVs have the appropriate voltage across them. You wouldn't necessarily see anything.
- With a very close strike (10 feet from the house more than qualifies) you can have direct pickup, with wiring acting as an antenna. There was a limited examination of equipment failures by an insurance company, a utility, and others. One of the cases was a multichannel amp which was damaged by a lightning strike in the back yard. The cause was direct pickup, with speaker wires acting as an antenna. There is not a good way to protect from this other than protection manufactured into the equipment. The closer the equipment was to the 'tree' the more likely damage from direct radiation.

Examining the equipment to find out how it failed would give you an idea of the cause (but isn't necessarily easy).

Some of the above could apply to your 'stunned' bed.


Thanks Bud. What happened to my equipment, then, was probably direct pickup, though the phone ground is about 40' from the service ground and the grounds aren't connected anyway.

The phone "ground" is at least connected to an electrode like a ground rod?

Assuming the US-NEC is enforced, the "grounds" are required to be interconnected. Phone companies are, in general, very good about connecting to the power ground system.

Read the example in the IEEE guide starting pdf page 40. That example has a 30 ft "ground" wire from a cable entry protector to the power service. A surge on the entering cable produces a 10,000V difference between power and cable wires. In your case, with no connection, the difference could be worse.

If you had a strong surge that produces a 1000A current to earth, and the resistance to earth is a quite good 10 ohms, the building "ground" will be 10,000V above "absolute" earth potential. If the earthing electrode is a single ground rod, the voltage from the building "ground" to earth over 3 feet from the rod will be at least 7,000V. Your power and phone earth connections are more than 3 feet apart.

And when lightning struck your tree, the currents in the earth could produce far different voltages at the phone earth connection and the power earth connection. If phone wires were connected to the damaged equipment it could have easily caused at least some of the damage. Even if the phone wires went through the UPS, the voltage and energy could exceed what the UPS was built to withstand. (And it is unlikely any suppressor monitors whether phone line protection remains functional.)

The phone entry protector should be connected to the power earthing system. If it was my house, I would then run the phone wire to the vicinity of the power service, install a second protector there, and distribute the phone wires from that point. If you don't do that, the IEEE guide (in the example above) says for equipment connected to both phone and power "the only effective way of protecting the equipment is to use a multiport [plug-in] protector."

--
bud--

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Relevant Pages

  • Re: Whole house phoneline surge protection
    ... I'd have to install quite a few surge ... "How to protect your house and its contents from lightning: IEEE guide for surge protection of equipment connected to AC power and communication circuits" published by the IEEE in 2005. ... Your symptoms sound like high voltage between phone wires and the power system ground. ... Wall warts generally are more immune to voltage from phone wires to power/ground wires - might point to a phone entrance protector. ...
    (alt.home.repair)
  • Re: "chain" surge suppressers?
    ... The NIST guide cites US insurance information that indicates equipment most likely to be damaged by lightning is computers with modem connection and TV/related equipment - presumably with cable connection. ... If a surge comes in on power wires and produces 1000A to earth through a very good 10 ohm impedance to earth, the 'ground' at the service panel rises 10,000V above 'absolute' ground potential. ...
    (alt.home.repair)
  • Re: power conditioner or battery back-up?
    ... through to your equipment JUST before the power goes out. ... prevents damaging voltages between power and signal wires. ... NO - but that does not mean that a surge protector installed at the ...
    (alt.home.repair)
  • Re: Does as GFCI give you some surge protection?
    ... computer's power plug all go to a common-mode voltage plus or minus line ... All interconnected devices, like a computer and printer, need to connect to the same surge protector. ... If a device, like a computer, has external connections like phone, all those wires have to run through the surge suppressor for protection. ... The voltage on all wires connected through the suppressor (power, phone, cable TV, ...) is clamped to the common ground at the suppressor and the voltages are held to a value that is safe to the connected devices. ...
    (alt.home.repair)
  • Re: Lightning Protection - "The Extra Step" - Un-Plugging the AC Power - Question :
    ... Un-Plugging the AC Power - Do You? ... Many Do Not 'un-plug' the AC Power Cord from their Equipment. ... Some simply 'Turn-Off' the AC Power Strip (Surge Protector). ...
    (rec.radio.shortwave)