Multiple power strips daisy-chained, code?

[krw]

So again: What is wrong with daisy-chaining 15A-rated power strips
connected to an outlet that is on a 15A circuit with a 15A breaker in there?

So again: they're not rated for such use.

 

[Joerg]

So again: they're not rated for such use.

So again: If it clearly says 15A on there, why not?

 

[Michael]

Well, we must surge protect plus switch a partial panel of switches
while not switching some others.


Then why do most have screw mounting features on the back _and_ a UL
blessing?

Joerg, I'm no electrician but I _think_ I've got it right when I state that U.L.'s mission is to
certify the inherent safety of devices, as opposed to certifying said devices for any specific
uses. My rifle doesn't explode when I fire it (properly constructed and therefore safe to use) but
this does _not_ mean that it won't kill when improperly used.

Hmmm .... I wonder if U.L. has any regulations at all regarding screw mounting slots on strips.
Probably, but I would guess that their extent would probably go no further than making sure a
mounting fastener could not contact any "hot" part of the strip.

Your fire guy would suffer apoplexy were he to see how this electrical engineer uses power strips in
his home. Not only do I have hook-ups similar to the one you describe but I use 12-14" "pigtails"
to attach my wall-warts to strips and wall sockets alike. Said pigtails are commercial ones and
have molded connectors. I prefer the pigtails that have a socket integrated in the plug so that
plugging a pigtail into a wall socket doesn't result in the "loss" of that socket.

Does TUV have anything to say about the ways in which power strips are used in Germany?

 

[krw]

Let's face it, the majority of power strips will find a permanent home
underneath computer tables, on lab benches and behind entertainment
centers. I don't think folks at UL will be so naive as to believe that
all Americans would install 10 or more wall-mounted outlets behind their
monstrous TV/stereo cabinets.

Homeowners can get away with a lot of sins that commercial
establishment's can't. Your church is a "commercial"
establishment, for this purpose.

It would be time that they agree on stuff. Mankind does not need this
much redundant (and costly) bureaucracy ;-)

"UL approved" doesn't mean it isn't dangerous. UL is not the
controlling authority *anywhere*. NFPA is, though your
town/city/county may have some differences, mostly the controlling
NEC publication date.

That is true with most any cert. But if you buy from reputable brands
such as Leviton you should be ok.

....unless they're counterfeits. ;-) Using a counterfeit of "most
any cert" isn't as likely to get someone killed.

 

[krw]

So again: If it clearly says 15A on there, why not?

Ever hear of a "fire marshal"? "Ambulance chaser"? Insurance
company?

 

[Joerg]

Ever hear of a "fire marshal"? "Ambulance chaser"? Insurance
company?

Sure but this does not answer the technical question why it dangerous.
The fact that some local authority says so does not mean it's true.
Since they have the final say anyhow I am looking for some official
document that says it's ok, in order to convince them. The only
alternative is punching holes in the wall (again ...), running oodles of
feet of wire, set a couple of new breakers, with some luck the panel
ain't big enough, and so on.

 

[krw]

Sure but this does not answer the technical question why it dangerous.

It likely isn't, if you know what you're doing. It isn't listed to
be used that way since no one wants to stand behind every
combination of uses. Again, these things are for temporary use
only.

The fact that some local authority says so does not mean it's true.

No, it means that they're the authority. Seriously.

Since they have the final say anyhow I am looking for some official
document that says it's ok, in order to convince them. The only
alternative is punching holes in the wall (again ...), running oodles of
feet of wire, set a couple of new breakers, with some luck the panel
ain't big enough, and so on.

If you can get a PE to say THAT APPLICATION is OK, and stand behind
it with his license and LEO insurance, go for it. That's the only
way to trump an inspector, even if the inspector is wrong about the
code (or law). I ran into this when building a garage. The
inspector was clearly wrong (and had failed his exam, three times)
but was still the town inspector. His ignorance (and stubbornness)
cost me over $1000. A PE would have cost even more (and likely
died laughing).

 

[krw]

However, agencies must work together. For example, if a code would say
that power strips are not to be mounted anywhere but UL blesses lots of
them with mounting hardware/moulding (which they do) then this would not
be right.

Since when did the law have to be "right".

All I remember is that the safety guys I experienced never complained
about the connections of power strips. As long as they were rated
230V/16A. They did ask me to unplug them once though, so they could be
tested for proper functionality of the PE. I still have one of them
somewhere, with a very official looking yellow TUEV sticker.

We were only allowed to use specific power strips. Generally they
were made with the "Wire Mold" channels and industrial/hospital
grade outlets and SO cable. The box store variety were forbidden.
They'd cut the plug off, then scream and yell at your manager if
you were caught with one. Interestingly, the power distribution
widgets that fit under the monitor with switched outlets in the
back were allowed.

 

[Joerg]

[email protected] says...>
[...]

Sure but this does not answer the technical question why it dangerous.

It likely isn't, if you know what you're doing. It isn't listed to
be used that way since no one wants to stand behind every
combination of uses. Again, these things are for temporary use
only.

If that is so then UL should definitely stop certifying power strips
that have clearly visible mounting hardware and clear instructions on
the packaging on how to screw them down onto wood and drywall. Heck, one
even came with two screws and wall anchors.

No, it means that they're the authority. Seriously.

I know. They can sometimes stop you just because they can.

If you can get a PE to say THAT APPLICATION is OK, and stand behind
it with his license and LEO insurance, go for it. That's the only
way to trump an inspector, even if the inspector is wrong about the
code (or law). I ran into this when building a garage. The
inspector was clearly wrong (and had failed his exam, three times)
but was still the town inspector. His ignorance (and stubbornness)
cost me over $1000. A PE would have cost even more (and likely
died laughing).

A friend of ours said he always leaves an obvious but not blatantly
obvious bug in his electricity hook-ups. He said the local inspector
hates do-it-yourselfers and then gets a high when he finds the error.
"Aha, I knew it!" Then you have to pay for a 2nd inspection where, of
course, the "error" is corrected. Cheaper than if he doesn't find an
easy bug and starts chasing (expensive) hairs in the soup.

This inspector is said to be very friendly. So if I could show him an
official document that either endorses multiple properly rated power
strips or clearly does not prohibit them I might be able to convince
him. However, it seems this whole area is as muddy and obscure as I had
assumed :-(

 

[bud--]

For reliable information on surges and surge protection read a guide from
the US NIST at:
<http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf>

Or a more technical guide from the IEEE:

Meanwhile, that surge protector did not provide and does not claim
to provide surge protection.

Complete nonsense.

Effective protection has
always been at the breaker box where surges are earthed before
entering the building.

Service panel suppressors are a good idea.
What does the NIST guide say?
"Q - Will a surge protector installed at the service entrance be
sufficient for the whole house?
A - There are two answers to than question: Yes for one-link appliances
[electronic equipment], No for two-link appliances [equipment connected to
power AND phone or cable or....]. Since most homes today have some kind of
two-link appliances, the prudent answer to the question would be NO - but
that does not mean that a surge protector installed at the service
entrance is useless."

Service panel suppressors do not prevent high voltage between power and
phone/cable wires. The NIST guide suggests most equipment damage is caused
by high voltage between power and signal wires.

Because of that all interconnected equipment needs to be connected to the
same plug-in suppressor, or interconnecting wires need to go through the
suppressor. External connections, like phone, also need to go through the
suppressor.

Will that silly little power strip stop what three miles of sky
could not? Of course not. And yet that is what the power strip must
do.

w has a religious belief (immune from challenge) that surge protection
must directly use earthing. Thus in his view plug-in suppressors (which
are not well earthed) can not possibly work. The IEEE guide explains
plug-in suppressors work by CLAMPING (limiting) the voltage on all wires
(signal and power) to the common ground at the suppressor. Plug-in
suppressors do not work primarily by earthing (or stopping or absorbing or
magic). The guide explains earthing occurs elsewhere. (Read the guide
starting pdf page 40).

And finally, scary pictures of another problem seen by most
fire departments:
http://www.hanford.gov/rl/?page=556&parent=554

The village idiot ignores what his own hanford link says. It is about
"some older model" power strips and says overheating was fixed with a
revision to UL 1449 that required thermal disconnects. That was 1998.
There is no reason to believe, from any of these links, that there is a
problem with suppressors produced under the UL standard that has been in
effect since 1998. None of these links even say a damaged suppressor had a
UL label.

Responsible companies such as
Siemens, Leviton, Intermatic, Cutler-Hammer (Eaton), Square D, and GE
provide these effective solutions.

And all make plug-in suppressors except SquareD.

For it's "best" service panel suppressor SquareD says "electronic
equipment may need additional protection by installing plug-in [surge
suppressor] devices at the point of use."


For real science read the IEEE and NIST guides. Both say plug-in
suppressors are effective.

There are 98,615,938 other web sites, including 13,843,032 by lunatics,
and w can't find another lunatic that agrees with him that plug-in
suppressors are NOT effective.

And w can not answer simple questions:
- Why do the only 2 examples of protection in the IEEE guide use plug-in
suppressors?
- Why does the NIST guide says plug-in suppressors are "the easiest
solution"?
- Why does the NIST guide say "One effective solution is to have the
consumer install" a multiport plug-in suppressor?
- Why do w's "responsible companies" make plug-in suppressors?
- Why does "responsible company" SquareD say "electronic equipment may
need additional protection by installing plug-in [suppressors] at the
point of use"?

What about systems where Neutral is not connected to ground? (europe)
Shall the cable and phone line shields be connected to ground?

I believe there is more than one earthing scheme used. My understanding
is that neutrals are earthed somewhere, maybe only at the utility
transformer end.
And "ground" might refer to a power system grounding conductor or the earth.

In general, I assume that plug-in suppressors in Europe would have a
power "ground" wire (connected to earth), and that at a plug-in
suppressor the cable ground would connect to that wire (or could be
clamped to it) and all other wires - power, telephone, cable center
conductor - are clamped to the same ground/earth wire at the suppressor.
That means the voltage between wires going to the protected equipment is
safe for the protected equipment.

In the US, I believe connecting the neutral and "ground" wires together
at the service and earthing both at the building is an advantage for
surge protection. If a strong surge comes in on 'hot' power wire there
is arc-over when the voltage from busses to
enclosure(/"ground"/neutral/earth) reaches about 6kV (US). When
established, the arc voltage is hundreds of volts. This both limits the
voltage that the building 'sees' and dumps most of the surge energy to
earth.

And the universal US practice of having a phone wire entrance protector
that limits the voltage from phone wires to the power ground system is
also a major advantage. I believe BT does not usually do that. Don't
know about the mainland. US practice also has the cable shield, at
building entry, connected to the power ground system. Short connections
from phone and cable entry protectors to the system ground at the power
system is one of the major protection schemes in the IEEE guide.
Currents to earth from a strong surge can lift the building "ground"
well above "absolute ground". A significant part of the protection is
keeping the power and phone and cable wires near the same potential.

Don't know if that completely answers your question.

 

[[email protected]]

Let's face it, the majority of power strips will find a permanent home
underneath computer tables, on lab benches and behind entertainment
centers. ...
It would be time that they agree on stuff. Mankind does not need this
much redundant (and costly) bureaucracy ;-)

UL is about safety of the device. Other codes address other issues
such as how electric is installed (ie NFPA) or how all devices (UL
listed or others) are used (ie state fire codes).

Some states (ie NY) that any power adaptor (UL or other) can only
connect to a wall receptacle - not to any other adaptor. Others (ie
college campuses) ban all but one type of power strip - and demand it
be UL listed and only connect directly to a wall receptacle, etc.

Each organization has specific domains to regulate or list. You are
required to meet some codes (ie state fire coded) but are encouraged
to use only better (ie UL listed) devices. Some locations permit
using non-UL listed devices. Others do not.

Any power strip should only connect directly to a wall receptacle.
Daisy chaining power adaptors is simply a bad idea in any
jurisdiction. Especially in a building that will house a crowd or
that remains unsupervised for long periods. No way around that safety
no matter how others may rationalize it or use profanities.

Some power devices without UL listing are acceptable in some
environments. But since it is being used in that environment, it
should also be UL listed. Would you apply same commercial
restrictions also on all homes? The code only appears complex because
it is also flexible. Your church should meet stricter requirements.
Even if not required by code, daisy chaining power adaptors in the
building is a bad idea.

Adding additional wall receptacles is usually quite easy. And safer
according to that fire marshal.

 

[Rich Grise]

The fire marshall wasn't happy with daisy-chained power strips at
church. There is only low power stuff hanging off of them and we need
the 2nd one for those big wall warts (wider spaces, more stable). The
first strip doesn't have enough slots anyhow and you can't get partially
switched power strips with remote switch any other way. Only the first
one has surge protection.

Anyhow, are there "official" regs, codes and whatnot that talk about
this situation?

The only way to determine this is to ask the fire marshal if he's
forbidding it, and if so, ask him to show you chapter and verse of the
applicable reg.

If he's just "unhappy", but can't show you the reg, then apologize for
his unhappiness and thank him for his time.

Cheers!
Rich

 

[Rich Grise]

Most safety folks do but not one was ever able to explain to me exactly
what could go wrong, provided all strips are capable to handle full
circuit current.

The thought is that at some point someone will put 10 amps load on the
first strip, then put 10 amps load on the second, and because the
first strip is rated at 13 amps (typically) all heck will break loose.[/QUOTE]

If you call popping the breaker "all heck", then I guess you're right. ;-)

Cheers!
Rich

 

[[email protected]]

Why is it that power strips -- some of which only have four outlets -- require
circuits breakers but extensions cords -- some of which have three outlets --  
do not?

Not all adaptors are UL listed. Some jurisdictions don't care if
non-UL electrical devices are used. Others go so far as to ban all
but one type power adaptor. Some jurisdictions - ie colleges -
completely ban extension cords. Depends upon which jurisdictions
apply to your question.

 

[Rich Grise]

At least the ones I know look just like the contacts on a regular wall
outlet. And they should. If I was a UL inspector I would flag and refuse
a product that has sub-par amperage on individual outlets. What would
prevent a consumer to plug a space heater or a vacuum cleaner into a
power strip?

In my office I have a string of THREE power strips; when I plug my space
heater into the third one, all the computers shut down when the breaker on
the first strip pops. ;-)

Then again, the closest thing to a fire inspector I've seen at this
factory is the guy that comes and recharges the fire extinguishers. ;-)

Cheers!
Rich

 

[Rich Grise]

So again: If it clearly says 15A on there, why not?

Because those guys (the other responders) are idiots? ;-p

Cheers!
Rich

 

[Rich Grise]

Well, we didn't want this to turn into a science project but we may have
to. Thing is that we want to turn all but two outlets off with a switch
and those two must remain on. Plus all of them surge protected. The
power strip we have now has a lighted switch on a long cable that we
mounted in a convenient position. But the man didn't like it.

Again, ask him what he doesn't like about it, and if he gets poopy, demand
to see chapter and verse of the reg he's enforcing.

Cheers!
Rich

 

[Rich Grise]

Only if the power strip you're using has the outlets "side by side" rather
than in-line. This does seem to becoming the more popular style, though, for
whatever reason.

There are some power strips with rotating sockets (e.g.,
http://www.amazon.com/Belkin-BP112230-08-Pivot-Plug-Surge-Protectors/dp/B000JE9LD4 -
- I have a couple, and they're great!). Also some "medussa" type power strips
with just 6 individual outlets hanging, e.g., 6" from a big "tap."

And of course plenty of power strips that try to make some accomodation for
wall warts.

I've been known to plug in two wall warts by using one of those "ground
cheater" things (the two-to-three prong adapter that we all use to float
the scope ;-) ) just to extend the outlet so the second wart kind of
overlaps the first, as if it's humping it. ;-D

Cheers!
Rich

 

[Rich Grise]

" Every power strip must have a circuit breaker for an always
necessary additional protection layer."

Why is it that power strips -- some of which only have four outlets -- require
circuits breakers but extensions cords -- some of which have three outlets --
do not?

So you don't have to go all the way downstairs to reset the breaker. ;-)

Cheers!
Rich

 

[Joerg]

The only way to determine this is to ask the fire marshal if he's
forbidding it, and if so, ask him to show you chapter and verse of the
applicable reg.

If the admin can't get this clarified I will. But one has to be careful
not to rock the boat too much because if he says the water runs up the
drain then the water does run up the drain. But it was said he's a very
friendly guy.

If he's just "unhappy", but can't show you the reg, then apologize for
his unhappiness and thank him for his time.

Oh, I will