Multiple Power Strips Connected In Series

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!

 

Hi,

One reason is due to the fast rise of current in transients the inductance
of the added length of wire defeats the transprotection.
One inch of wire ( type used in the power strips ) is about 19nh. if you add
the 1000 amps possible and the length of wire at a high di/dt then many
volts can be generated and addition the phone leadin may have lower
impedance ( more current ) than the power leads due to the transmission line
effect of the telephone line.

Ray

 

There's really no reason not to. If they all have circuit breakers,
which most do, the upstream guys will trip if they're overloaded by
the total load. If you put the lighter loads towards the end of the
string, voltage drop along the total length of power cord will be
minimized. As far as length goes, it's not much different from a long
extension cord.

John

 

Here's what I found in groups:

----------

http://groups.google.com/groups?q="...afe=off&selm=&rnum=1

Putting power strips in series only degrades their performance.

http://groups.google.com/groups?q="...7l1ag$-cruz.ca.us&rnum=2

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

http://groups.google.com/groups?q="...elm=&rnum=4

- Multiple AC power strips in series.

http://groups.google.com/groups?q="...selm=&rnum=6

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

http://groups.google.com/groups?hl=...5%40bgtnsc06-news.ops.worldnet.att.net&rnum=4

{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.

 

The breaker in the first strip has to handle the whole load, so
when you add the 14th computer, the whole string goes down. ;-)

Cheers!
Rich

 

Right. So be sure to pile up all of your electrical appliances next to
the wall outlets. ;-)

Cheers!
Rich

 

Here's another source:
http://www.eeel.nist.gov/817/817g/spd-anthology/files/Text Part 4.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]

 

What does a surge seek? Destructive transients are
typically longitudinal mode. IOW they seek earth ground. If
not earthed at the building entrance, then they will seek
earth ground destructively through household appliances. Too
many fail to learn of multiple types of transients. The
destructive transient is not stopped, blocked, or absorbed.
And yet that is what a plug-in protector must do. Is that
plug-in protector going to stop what miles of sky could not?

Introduction to protection principles in "Pull the wall plug
or not?" in nz.comp on 7 Sept 2004 at
http://tinyurl.com/5ttwl

For more technical sources, then three consecutive posts: "
Belkin Surgemaster worth the money?" in the newsgroup
uk.comp.homebuilt on 29 Sept 2004 at
http://tinyurl.com/6zfps

Surge protection demonstrated by a simple example:
"Whole house surge suppressors" in alt.home.repair on 12 Jul
2004 at
http://tinyurl.com/6gl67

Transients first form a complete electrical path from cloud
to earth. Only after current is passing through everything,
then something in that path fails. Destructive transients seek
earth ground. Earthing - and not some protector - defines a
protection 'system'. A surge protector is only as effective
as its earth ground. Too many forget about essential earthing
and instead hope what they see on retail shelves is actually
protection. No earth ground means no effective protection.