Multiple Power Strips Connected In Series

[Sean]

Hi,

I've known this was 'taboo' for as long as I can remember. What I'd
like to know is why is it a bad idea to connect multiple power strips
(with surge suppression and/or line filters) in series; especially
when using computers.

I found several references which say not to do it, but no simple
practical explanation as to why.

The only way I can think to demonstrate it is to get a half a dozen of
them and connect them up in series, and stick meters at the wall,
between each, and at the end. I suspect that doing so will show some
form of degradation, but what I'm not sure what it will be or why it
will occur.

Any detailed explanation and or pointer to a web site where this is
explained would be appreciated.

Thanks a 10E6!

 

[Sean]

Here's what I found in groups:

----------

http://groups.google.com/groups?q=%22power+strips+in+series%22&hl=en&lr=&newwindow=1&c2coff=1&safe=off&selm=3C53C05E.3EDB9999%40usa.net&rnum=1

Putting power strips in series only degrades their performance.

http://groups.google.com/groups?q=%22power+strips+in+series%22&hl=en&lr=&newwindow=1&c2coff=1&safe=off&selm=57l1ag%248ia%40comix.comix.santa-cruz.ca.us&rnum=2

Someone wires 5 power strips in series and you're at the end.

http://groups.google.com/groups?q=%22power+strips+in+series%22&hl=en&lr=&newwindow=1&c2coff=1&safe=off&selm=356bc688.7250064%40news.ricochet.net&rnum=4

- Multiple AC power strips in series.

http://groups.google.com/groups?q=%22power+strips+in+series%22&hl=en&lr=&newwindow=1&c2coff=1&safe=off&selm=3677540f.539729%40news.ricochet.net&rnum=6

"Does 5 power strips in series violate some kind of NEC code or
ordinance"?

http://groups.google.com/groups?hl=en&lr=&newwindow=1&c2coff=1&safe=off&threadm=rtf78.8801%24zT.730405%40bgtnsc06-news.ops.worldnet.att.net&rnum=4&prev=/groups%3Fq%3D%2522power%2Bstrips%2Bconnected%2522%26hl%3Den%26lr%3D%26newwindow%3D1%26c2coff%3D1%26safe%3Doff%26selm%3Drtf78.8801%2524zT.730405%2540bgtnsc06-news.ops.worldnet.att.net%26rnum%3D4

{Dialog where a power strip is diagnosed as a problem}

http://support.jp.dell.com/docs/systems/ph2o/solving.htm#1111403

Check for interference— Electrical appliances on the same circuit or
operating near the computer can cause interference. Other causes of
interference: power extension cables, too many devices on a power
strip, or multiple power strips connected to the same electrical
outlet.

OPNAV INSTRUCTION 5100.19D VOLUME II CHANGE TRANSMITTAL 1 30 AUGUST
2001 - C0804

s. Use onlt Navy-approved power strips for computer equipment,
printers, and peripherals. Never use power strips in series
(connected to one another).

---------------

I see no hard evidence one way or the other at this point.

Most computers have switching power supplies, is there any evidence
that the combination of line filters and or surge suppressors
adversely affects them?

I have seen UPS devices have problems if they are fed anything but
current streight from the wall socket. They detect a small flux in
the supply as intercepted by the power strip and switch into battery
mode.

I'm beginning to think that this has all the makings of an urban
legend. Maybe it is time to contact MythBusters.

 

[Sean]

Here's another source:
http://www.eeel.nist.gov/817/817g/spd-anthology/files/Text%20Part%204.doc

From "Coordination: 1980" - F.D. Martzloff

Fact 3.
Without substantial connected loads in the system, the open-circuit
surges appearing at the service entrance propagate along the branch
circuits with very little attenuation.

Conclusion 4.
Coordination of surge suppressors requires a finite impedance to
separate the two devices, enabling the lower voltage device to perform
its voltage-clamping function while the higher voltage device performs
the energy-diverting function.

Conclusion 5.
The concept that surge voltages decrease from the service entrance to
the outlets is misleading for a lightly loaded System. Rather, the
protection scheme must be based on the propagation of unattenuated
voltages

Conclusion 6.
Indiscriminate application of surge protectors may, at best, fail to
provide the intended protection and, at worst, cause disruptive
operation of the suppressors. What is needed is a coordinated
approach based on the recognition of the essential factors governing
devices and surge propagation.

There is a wealth of papers concerning surge suppression available tn
the directory of the example above, that I am trying to sort through.

More Later [YMMV]