Using two anti-surge plugs

On Apr 26, 2007, at 8:21 AM, spugh wrote:

> Is this just 'one of those things' or is there a general (known)
> problem with using two anti-surge plugs together? Any electrical
> geniuses out there know the answer.

The instructions which come with the surge protectors I've bought
generally say not to put them in series, without explaining why.
That often doesn't stop me from doing it, as it is getting harder to
find "plain" plug strips these days.

But the effect you saw is rather unexpected.

You say "fuses"--that could imply older wiring. Perhaps the grounds
are not correct?

   --John

At 08:21 04/26/07 -0700, spugh wrote:
>Is this just 'one of those things' or is there a general (known) problem
>with using two anti-surge plugs together?

I don't know of any reason it would cause this kind of problem. I could
believe that they might interfere with each other in their intended
function, which might be why the packages generally say don't do that. But
I don't have any good reason to believe even this -- the package wording
may be just CYA stuff.

Taking out the entire house is seriously bizarre. Are you absolutely
certain it wasn't an external loss of power that just coincided with your
actions? And do you really have fuses and not circuit breakers? If so, your
wiring is so old that I'd blame almost anything on it, including my
thinning hair.

This is not to say strange things never happen. Not long ago I tried to
install a switch illuminator -- one of those light switches that glows when
the light is off -- controlling a compact fluorescent light. Turn off the
switch and the light flashes every few seconds. But at least in that case,
I figured out why.

>Any electrical geniuses out there know the answer.

How about someone who knows enough to be dangerous?

Edward

(whose 1953-built house still has a lot of the original wiring yet has
circuit breakers, and who *really* wants to get all that old wiring replaced)

--
Art works by Melynda Reid: http://paleo.org

>Is this just 'one of those things' or is there a general (known)
>problem with using two anti-surge plugs together? Any electrical
>geniuses out there know the answer.

I've done this without any problem, but I've heard it's a bad idea,
so I changed my setup.

I have images in my mind about why it might cause problems, but when
I find myself anthropomorphizing electricity I generally have to
concede that I don't know what I'm talking about.

--
Andy Carroll
Toronto, Canada
http://flickr.com/photos/andys_camera/

--On April 26, 2007 8:21:30 AM -0700 spugh <spughmac.com> wrote:

> I recently acquired an anti-surge plug that provided both plug and
> telephone line protection (DSL). I plugged this into an existing
> anti-surge block and it worked just fine. Some hours later, I turned on a
> light switch on the same fused electrical circuit as the (now double)
> anti-surge plugs and all the electrics in the house went out. Isolating
> the fused electrical circuit (the fuse had not blown) did not bring the
> power back on - I had to de-activate all the electrical fuses
> individually reconnecting them one by one, except the offending circuit.
> I then removed the new anti-surge plug and returned to the original
> single anti-surge plug, reconnected that circuit, and everything is now
> working fine.

Your terminology confuses me a bit. Do you have fuses (these burn up when
there is too much current and have to be replaced) or circuit breakers
(these are like switches, they turn off when too much current is present,
but can just be flipped back on.) If you have fuses you should've lost at
least one fuse (a whole house fuse it sounds like). If you have circuit
breakers, it sounds like the main breaker for the house flipped off. I
can't think of a way that all circuit breakers in a house would flip off
though.

I don't think this was caused by stacking surge strips in series, you don't
really add any extra protection by doing this either. Surge protection does
wear out over time. I believe most of the cheaper ones are done after a
couple of years.

Most surge protection works by using metal oxide varistors (MOV), or
variable resistors, wired from hot to ground. The resistance across the
device goes down as voltage goes up. So at low voltage (technically
anything under 400 volts is low voltage) the MOV resistance is very high
and no current goes from hot to ground, instead it goes to the device that
is plugged in. When a high-voltage spike comes in, the resistance drops
and current will flow to the ground wire instead of the plugged in devices.
Depending on what the resistance drops to, this can damage the MOV (hence
the wear out factor after a few years) or will actually short and cause the
upstream circuit breaker to shut down.

It sounds like one of the MOVs failed in a mode where the resistance wasn't
zero, but allowed enough current through that when combined with the rest
of the electrical loads in the house -- overloaded your house master
circuit.

My house has a 100 amp service. This means I can draw 100 amps of power
from the power company before my master circuit breaker turns off. However
I also have 13 circuit breakers sized between 15 and 20 amps each, plus
some big circuits for AC and washer/dryer.

If I put 11 amps of power on each circuit breaker, none of the individual
circuit breakers will go off because each circuit is under it's rated
capacity. But I've exceeded the capacity of my house load, so the main
circuit breaker will switch off.

It sounds like your surge suppressor failed in such a way that the closest
fuse did not blow, but something upstream did and shut off the whole house.
Whenever you turned on power to that one branch, with the surge still in
line, the current draw shot up again and shutdown the house.

Thanks to everybody for their comments. I should, perhaps, have pointed out that I live in an old stone house in S France and here fuses are still common and only just being replaced by circuit breakers. The wiring is old (maybe 20 years) but it works (with care), much better than my old London house where we were still stretching various thicknesses of wire over chunks of ceramic only 4 years ago! Sometimes I think my whole life has been a replay of 'the way we used to live' but I quite like it.

As for my problem, 'tant pis' as we say here. It is all working fine now and maybe this is just one problem that I will have to blame on a higher power, in this case EDF (the French utility company).

Simon

Thanks very much, kevinv. A wonderfully clear explanation that even made sense to a dumbo like me. It seems to me that your description of what went wrong is spot on. What I didn't mention is that when the system went down, if I pressed the reset or on button on the mains connector/disconnector, power would flash on for a millisecond before shorting out again. What puzzled me is that the local circuit fuse didn't trip/blow. Well you read that problem brilliantly. I am very grateful. And enlightened.

Sorry for the loose description and terminology

All the best,

Simon

A small side-note to the topic of fuses (the kind that burn out): they often fatigue over time and blow even though their rating has not been exceeded... The fuses depend on getting hot due to the current flow through them; they "blow" once they get hot enough to melt. Under normal use they heat up or cool down every time the current draw changes - and this causes them to expand and shrink which "works" the material back and forth (similarly to bending a wire back and forth). Eventually they can fail due only to the mechanical fatigue which results. In short (ahem), a blown fuse is not always an indication of excess current ;<)

The earlier surge protection discussions are well worth reading since everyone's situation will vary and some protection schemes are unique for a given situation. However, I would replace any fuses with circuit breakers immediately.

I'm an old-time "belt and suspenders advocate (I use a primary and backup approaches for most things--2 active Macs and 2 backup Macs). I'm also a certified manufactrung engineer in factory automation who started working at AT&T manufacturing when quality was God back in the 1960s.

Unfortunately, there are many disagreements among electrical engineers as to what is the best approach for surge/power protection. Also, if you have the time, look at how the electrical/elctronics industry and building codes disagree on lightening rods--some swear by them, others swear at them but there are many systems sold and used every year. Yes, lightning rods are in the building codes!

The point of all circuit protection products is to minimize or avoid building/circuit damage and protect human life.

If any type of surge protector does its job correctly, it likely will be destroyed in the process, a bargin considering your hardware and data.

I use a multiple stage approach that works for me: 1. I use whole house surge protection at the electric meter supplied by the electrical utility or one can use a whole house protector that is mounted to the circuit breaker panel but outside at the meter is best. 2. Use a "voltage regulator" transformer to cope with brown-outs (power companies reduce their supplied voltage) to everyone at times in many parts of the country. Brown-outs can also damage computers. 3. Use an UPS (Uninterruptible power supply/supplies) to give yourself enough time to save data and shut down if you have a power failure. If you have an automated UPS, fine. You WILL have surges when power is restored period. I started with the APS brand but other brands seem equally adequate but none are perfect which is one reason I use the series approach. I also work from a home office now so protection/replacement costs are my own. Over the years, I've replaced a few UPS units but no Macs. 4. According to the Institute of Electrical and Electronic Engineers (the largest professional engineering group in the world):

" Telephone and cable lines can also conduct high voltage -- for full protection, you should also guard against surges from your telephone or cable lines. Any lines carrying signals into your home can also carry a power surge, due to lightning or a number of other factors. If your computer is connected to the phone lines via a modem, you should get a surge protector that has a phone-line input jack. If you have a coaxial cable [broadband] line hooked up to expensive equipment, consider a cable surge protector. Surges on these lines can do just as much damage as surges over power lines."

Surge protectors are used on paired-conductor telecom circuits to provide protection against unwanted electrical energy surges. These protectors may have capacitance, inductance, or series resistance that can affect transmission.

UPS and other circuit designers rarely agree on anything so look at for the "rated" protection that will clamp voltages and power surges to the lowest level possible.If the manufacturer offers a substantial warranty for replacing equipment if anything goes wrong, they probably have the better protection schemes.

5. Consider using a laptop with an extra battery or two and a wireless connection for data protection. You can be assured that with anything less than a direct lightening strike to the laptop, which will likely send you to the hospital, you will be relatively safe. New AirPort or routers are relatively inexpensive compared to Macs or PCs. 6. Backup to both an external hard drive and DVDs as frequently as you need to to protect data. ALL computers and drives will fail at some point--the only question is when.

For further information (and some sources will have conflicting advice), use google to check out options. Try "using two surge protectors in series" first and "UPS (Uninterruptible power supplies) next."

I find it easier to use the same brand for all circuit/data protection since their tech support will not want your electronics fried!

Try: http://en.wikipedia.org/wiki/Surge_protector

http://computer.howstuffworks.com/surge-protector.htm for "How Surge Protectors Work"

www.apc.com for American Power Conversion Corp., an old line UPS and surge protection company.

I hope this helps. Whatever you do, get at least one UPS unit with power and data protection. Comprehensive power and data protection can be very expensive.

What is the value of your equipment and do you really need it ready for use 24/7 all year? I would always opt for more protection instead of less. If one type of protection was incorrectly manufactured or has defective components [unfortunately, a common occurance worldwide as consumers expect lower costs and higher performance].

I backup regularly which gives me peace of mind. I hope this helps. Sorry about the length of my comments but they will give you a broader perspective

Terry

On 2007-05-17, at 02:14, garth wrote:

> A small side-note to the topic of fuses (the kind that burn out):
> they often fatigue over time and blow even though their rating has
> not been exceeded...

According to the electricians working in a client's office building,
the same is true of circuit breakers: the more they're tripped, the
easier they are to trip in the future.

Moral: at least in New Zealand, it often only takes a single 2400 W
heater to take out the whole side of an office floor, making people
who bring in their own heaters very unpopular!

At 06:01 05/18/07 -0700, TEThompson wrote:
>Any lines carrying signals into your home can also carry a power surge

And even lines which are purely internal, in my experience.

Before my tale, note that networking cable should not be run unprotected
from one building to another, for exactly the reasons which Terry
discusses. If it's not possibly to protect them adequately (like
underground), use optical.

I lost two network cards to lightning within a couple of years. Both were
on computers not directly connected in any way to the outside. Both were on
UPS. I don't recall whether I had phone line protection, but the phone
lines were not connected to either of the computers in question. Phone line
came to computer A, which had an Ethernet connection to computers B and C
-- the exact topology is lost in the recesses of my memory, but reaching
the Ethernet required going through at least a modem, a serial port, a
motherboard, and a NIC. But the damaged NICs were in computers B and C.
Nothing else in those computers were damaged, nor was anything in computer
A damaged. (All were Macs, though computer A was running BSD Unix, back
before routing boxes became as cheap as modems.)

The key: the distance between B and C was about 40 feet, and the damaged
NIC were attached to this cable. I don't know any details of electrical
fields near lightning. But the lightning strikes were only about 100 yards
from the building with the computers, so it's easy for me to believe that
there could be an electrical potential of tens or hundreds of volts over a
distance of 40 feet. This would not normally be noticeable, since the
potential over distances the size of a human body would be too small to
create a shock.

After the second occurrence, I discovered that there are surge protectors
for 10BaseT cabling. I used them for a couple of years, until I moved to a
location where all the computers are in one room.

So the idea of using wireless communication for electrical safety is a good
one, at least when the distances are substantial.

The damage occurred in a structure with a metal roof, which I would have
expected to provide some protection. Apparently my expectation was incorrect.

Edward
--
Art works by Melynda Reid: http://paleo.org