Are mains surge protectors needed in the UK?

[Michael Salem]

Surge protectors (be they capacitors, varistors, or anything else) must
absorb the energy they're dealing with. Anything physically small will
vaporise and give little protection against a direct lightning strike on
the building, though they may protect against surges from further away.

I would expect a suitable Uninterruptible Power Supply to provide
reasonable lightning protection -- some APC units guarantee this, though
you'd have to ensure that all computers, monitors, etc. on a network are
powered through the UPC for safest results (or use fibre optic cabling
or wireless networking).

Surge protectors are probably of some use. A lightning rod for the
building is important. Personally I unplug computer equipment from mains
and phone during electrical storms if possible, But, in a city
environment, I haven't come across lightning damage, though I've heard
of it.

Obviously there are differences between a building in the middle of a
city and a house on a lone mountaintop!

Best wishes,

 

[David Maynard]

writes

[drivelectomy]

typically undersized. No sense wasting good money on
ineffective protectors that don't even claim to protect from
the typically destructive transient. A protector is only as
effective as its earth ground - which plug-in power strip and
UPS manufacturers fear you might learn.

And in Europe, the "earth ground" on mains wiring is good, hence plug-in
surge protectors do the job they were designed to do, shunting the surge
to earth.

In the States, not all power outlets can be assumed to have an earth
connection,

You mean a separate earth. Neutral is, of course, earthed. The problem is,
even though it is supposed to be on the large terminal in two prong sockets
you can't always count on the wiring to be proper in older homes. Modern
construction is 3 prong.

so plug-in surge protectors have to shunt surges to the
other phase line, which makes them vastly less effective.

No, they expect an earth ground too. The problem is people who don't
understand it and use 3 to 2 wire plug converters (actually, it has the
earth terminal brought out for a separate connection but no one uses it)
and then wonder why the surge protector didn't work.

 

[Conor]

The proper fuse is always a good idea but fuses do not protect from power
line faults. They blow after your 'protected' device is fried and pulling
too much current as a result of it.

Or don't blow at all. Sister in Law is running a washing machine and
tumble drier off an extension. THe tumble drier developed a fault this
week. THe extension cable got red hot - too hot to touch. To get that
hot it had to have exceeded the plug fuse rating. Neither the fuse in
the extension chord or the fuse in the tumble drier mains plug blew.

 

[Graham W]

writes

[more crap from w_tom]

An effective protection must shunt (divert,
connect, short circuit) the direct strike to earth so that the
direct strike does not find a better path via TVs. In your
case, that solution was a lightning rod

Really? Care to tell me how a lightning strike is going to discriminate
between a roof-mounted lightning rod and a TV aerial? (hint: in the
UK, most houses have a roof-mounted TV aerial.)

I'm never one to jump to the defence of w_tom's American based
opinions but I think his 'lightning rod' = our 'earth-spike' and thus he
is talking about the effective ground rather than the place where
the strike enters the system. AICBW 8¬)

 

[Parish]

Or don't blow at all. Sister in Law is running a washing machine and
tumble drier off an extension. THe tumble drier developed a fault this
week. THe extension cable got red hot - too hot to touch. To get that
hot it had to have exceeded the plug fuse rating. Neither the fuse in
the extension chord or the fuse in the tumble drier mains plug blew.

The "fuse" isn't an M5x25 bolt is it? ;-)

Parish

 

[Johannes H Andersen]

Lightning isn't the only cause of surges. I've seen excessive voltage
several times over the last few years. Switching transients, etc.

Ignore w_tom, his pontification has run before at lentht. He doesn't
understand the UK wiring system.

 

[Bagpuss]

The "fuse" isn't an M5x25 bolt is it? ;-)

Thats the Commodore 64 internal fuse replacement isn't it?

 

[David Maynard]

Or don't blow at all. Sister in Law is running a washing machine and
tumble drier off an extension. THe tumble drier developed a fault this
week. THe extension cable got red hot - too hot to touch. To get that
hot it had to have exceeded the plug fuse rating. Neither the fuse in
the extension chord or the fuse in the tumble drier mains plug blew.

Yeah. That can happen. Obviously, since it did If it's not sized right
the wire resistance of the extension can act as a current limiter
'protecting' the fuse.

 

[David Maynard]

writes

[more crap from w_tom]

An effective protection must shunt (divert,
connect, short circuit) the direct strike to earth so that the
direct strike does not find a better path via TVs. In your
case, that solution was a lightning rod

Really? Care to tell me how a lightning strike is going to discriminate
between a roof-mounted lightning rod and a TV aerial? (hint: in the
UK, most houses have a roof-mounted TV aerial.)

I'm never one to jump to the defence of w_tom's American based
opinions

As an American myself I can testify that w-toms's opinions are unrelated to
nationality.

but I think his 'lightning rod' = our 'earth-spike' and thus he
is talking about the effective ground rather than the place where
the strike enters the system. AICBW 8¬)

A lightning rod is simply an earthed conductive pole mounted atop the
building to provide a more attractive target for lightning and shunt the
energy to ground.

So the question was valid and the answer would be that the lightning rod
should be configured so it provides a lower impedance path to earth than
the 'aerial-thru-tv-set' path and located higher than the aerial. While
debatable, one rule of thumb for the 'zone of protection' is a 45 degree
cone extending downward from the rod. The antenna should also be earthed
and equipped with a lightning arrester.

 

[Strange Lad]

I thought BT master sockets, NTE5s, have a built in lightning arrestor?
Maybe they don't, or he has an old type?

Parish

Dunno. It is an old Victorian house but I don't know how old the sockets
were. All I saw was his knackered computer.

Strange lad

--
I do not consider it an insult, but rather a
compliment to be called an agnostic.
I do not pretend to know where
many ignorant men are sure --
that is all that agnosticism means.
Clarence Darrow

 

[w_tom]

Yes, utility switching does cause transients. But nothing
that should overwhelm internal protection in household
appliances. If switching transients were so destructive, then
we all would be replacing RCDs, dimmer switches, and clock
radios weekly. Once numbers are applied to those switching
transients, then those transients become irrelevant.

 

[w_tom]

Please find the manufacturer datasheet that claims surge
protectors "absorb the energy they're dealing with". Surge
protector components absorb energy just like a wire absorbs
energy. Does a wire also stop, block, or absorb surges? They
are called shunt mode devices for very good reason. The
protector does not stop, block, filter, or absorb surges - as
so often promoted by myth purveyors.

Furthermore, if a component vaporizes, then the surge
protector was defective by design - grossly undersized. MOV
manufacturers even provide charts on life expectancy. The
number and size of transients determined when the MOV has
degraded. Not vaporized. There is no part on the chart for
vaporization because that is a failure beyond what MOVs are
designed for. Surge protectors shunt every surge without
human knowledge. Eventually, MOVs degrade - and do not
vaporize.

This assumes the protector is properly sized. Since they
are not selling effective protectors, then many plug-in
protectors are so grossly undersized as to be vaporized. Then
the naive consumer recommends these ineffective and grossly
overpriced products to friends. It is how a product gets
promoted by myth purveyors. Effective (properly sized)
protectors shunt transients to earth ground without damage.
That is the difference between real world protectors and the
junk sold as plug-in protectors.

In the big city, electronics for TV and FM stations atop the
Empire State Building is struck about 25 times per year
without damage. In the WTC, that was 40 times per year. Why
no damage? Incoming lightning is earthed - and is not stopped
or absorbed by protectors or UPSes. So what is the difference
between the big city and atop a mountain? The big city
suffers more strikes in the same location. (BTW, a valley
between two mountains is just as likely to be struck. Geology
and not height more determines frequency of strike.)

That plug-in UPS offers the same protection circuit found in
power strip protectors. A plug-in UPS for surge protection
is also mythical. Notice a fundamental difference between
plug-in UPSes and building wide UPS systems. The building
wide system has the short connection to earth ground;
therefore can provide effective protection. The plug-in UPS
does not even claim (see its numerical specifications) to
provide protection from the destructive type of transient.

 

[w_tom]

A wall receptacle safety ground is not earth ground. Yes,
safety ground and earth ground do connect. But when
discussing the earthing of destructive transients, then wall
receptacle ground is just too far away from earth ground.

Wire has impedance. 18 meters of 2.5 mm copper wire may be
less than 0.2 ohms resistance. But same wire would be maybe
130 ohms impedance to a surge. Wire impedance is why a
protector must connect less than 3 meters to earth ground. If
the plug-in protector attempts to earth a trivial 100 amp
transient down that 18 meter safety ground wire, then wall
receptacle would be at something less than 13,000 volts.
Where is the protection? Does not exist because wall
receptacle safety ground is not an effective earth ground.

Ineffective plug-in protectors such as Belkin fear you
might learn these facts. Belkin and others avoid all
discussion about earthing to make their sales. No earth
ground connection (using two wire or three wire plugs) means
they don't provide effective protection.

We install surge protector to earth direct lightning
strikes. Done routinely since before WWII. Your telco does
not shut down for every thunderstorm to protect their
multi-million dollar computer. 'Whole house' type protectors
with the less than 10 foot connection to earth ground have
been proven that effective for too many generations. And yet
today, still some recommend those ineffective plug-in
protectors such as the Belkin.

Every single wire (that is all AC wires and both phone
wires) must make a connection to earth ground. Some wires are
connected directly (ie AC neutral wire). Other wires must
make that earthing connection via a surge protector. But that
connection must be less than 3 meters and must be all wires to
same earth ground.

Defined is protection from direct lightning strikes because
lightning seeks earth ground. No earth ground (or earthing
wire too long) means no effective protection. What plug-in
protectors fear you might learn: a surge protector is only as
effective as its earth ground.

Properly noted is that protection is layered. That is not
layers of protectors. That is layers of earthing. Earthing
(not the protectors) is protection. Primary protection is
provided by the utility (see pictures cited below).
Secondary protection is the building's (service entrance)
'whole house' protector. So what is a plug-in protector?
Where is that plug-in protector's nearest earth ground?
Adjacent to 'whole house' protector. So where is the
layering by a plug-in protector? No layering exists because,
at best, it can only connect to same earth ground as the
'whole house' protector. Layering for protection - the earth
ground at pole and then the earth ground at building.

Again, protection is the earth ground - not inside a
protector. Layering is defined by the earth ground; and not
by protectors. Important pictures demonstrate why the
'Primary' protector can be compromised:
http://www.tvtower.com/fpl.html

Again, every incoming utility wires must be earthed to a
single point earth ground before entering the building.
Earthed directly or earthed via a 'whole house' protector.
Protection from direct lightning strikes is about earthing.

 

[w_tom]

Wall receptacle is safety ground; not earth ground - as
explained in another post in this thread. However let's
assume the plug-in protector does earth a destructive
transient via wall receptacle. Now that transient is on a
wire bundled with other wires. Induced transient is now
created by that plug-in protector. By earthing on safety
ground wire, we have now induced transients on all other
adjacent wires. What kind of protection is that?
Ineffective.

Same problem applies to the service entrance and single
point earth ground. All earthing wires must be installed from
each utility wire to earth ground separated from all other
wires. Too many installers want to be neat. They make clean
sharp bends and nylon ty-wrap all wires together. IOW they
compromise the protection 'system'. Even sharp wire bends
increase wire impedance. Earthing wires must be shorter (less
than 3 meters), no splices (which wall receptacle safety
ground wires violate), not inside metallic conduit, and
separated from all other wires.

Just more reasons why plug-in protectors are so
ineffective. Therefore plug-in protectors avoid all
discussion about earthing. They fear you might learn about
the less than 3 meter necessity. So they avoid all discussion
about earthing. They would even encourage the consumer to be
confused about safety ground verse earth ground.

And in Europe, the "earth ground" on mains wiring is good,
hence plug-in surge protectors do the job they were designed
to do, shunting the surge to earth.

In the States, not all power outlets can be assumed to have
an earth connection, so plug-in surge protectors have to
shunt surges to the other phase line, which makes them vastl
less effective.

--

A. Bottom posters
Q. What's the most annoying thing on Usenet because they
complain too much and make their posts harder to read?

 

[David Maynard]

Yes, utility switching does cause transients. But nothing
that should overwhelm internal protection in household
appliances.

Except that it can and sometimes does.

If switching transients were so destructive, then
we all would be replacing RCDs, dimmer switches, and clock
radios weekly. Once numbers are applied to those switching
transients, then those transients become irrelevant.

That's as illogical as saying if lightning strikes were so destructive we'd
be replacing RCDs, dimmer switches, and clock radios every time it rained.

Neither are 'destructive' till the relatively infrequent occurrence when
they are.

 

[Johannes H Andersen]

Some deja vu. You're not in the States m8. In a densely populated
country like the UK, most of the risk are spikes from manmade
installations, induction from heavy machinery, fuse testing, outages.
A simple protector is well worth having and a once only investment.

 

[Mike Tomlinson]

You mean a separate earth.

I do, yes.

Neutral is, of course, earthed.

This is the distinction made in the wiring code between the "grounded"
and the "grounding" terminal... which causes confusion all of its own

No, they expect an earth ground too.

I've been over this with w_tom at considerable length in the past (feel
free to have a google.) Because American electrical outlets can't be
guaranteed to have an earth terminal (for example, in older construction
as you point out), the makers of surge protectors for the American
market have to wire them to the lowest common denominator, so that a
surge on phase is shunted to neutral using one MOV.

In the UK and Europe, two MOVs are used - one to shunt phase to earth,
and another to shunt neutral to earth. This makes surge protectors made
for this market much more effective.

 

[Mike Tomlinson]

I'm never one to jump to the defence of w_tom's American based
opinions

Quite wise, IMHO.

but I think his 'lightning rod' = our 'earth-spike' and thus he
is talking about the effective ground rather than the place where
the strike enters the system. AICBW 8¬)

You miss the point. If you have a lightning rod and a TV aerial on the
roof of a house, the lightning rod, even if it is higher than the
aerial, is not going to save your TV set from a direct strike. Your TV
will blow up regardless.

 

[Mike Tomlinson]

Wall receptacle is safety ground; not earth ground

Please explain the difference. I could do with the laugh.

- as
explained in another post in this thread.

I see no explanation elsewhere.

However let's
assume the plug-in protector does earth a destructive
transient via wall receptacle.

Which it does in the UK and Europe.

Now that transient is on a
wire bundled with other wires.

So? The transient is shunted to earth via a low impedance path.

Induced transient is now
created by that plug-in protector.

Induced on what? The earth wire? That's what it is there for!

By earthing on safety
ground wire, we have now induced transients on all other
adjacent wires.

Absolute crap. There are three wires - phase, neutral and earth. A
transient on the phase wire is shunted to earth by the surge protector.
What do you mean by "all other adjacent wires"? If you mean low voltage
cabling, for example twisted-pair Ethernet cabling, any electrical
installer worth his salt (i.e. not you) knows that you /do not/ run low
voltage cabling in the same conduit as mains power. It's called
segregation.

What kind of protection is that?
Ineffective.

Very effective.

One well-known maker of surge protectors in UK and Europe, Belkin, gives
a free £10,000 warranty on equipment connected via any of its products.
If the surge protector fails and the equipment is damaged, you can claim
the cost of a replacement. If their products were that ineffective, do
you think they'd offer the warranty?

Same problem applies to the service entrance and single
point earth ground. All earthing wires must be installed from
each utility wire to earth ground separated from all other
wires.

In your American Mickey Mouse electrical installations, yes. In the UK
and Europe, it's unnecessary.

Too many installers want to be neat. They make clean
sharp bends and nylon ty-wrap all wires together. IOW they
compromise the protection 'system'. Even sharp wire bends
increase wire impedance. Earthing wires must be shorter (less
than 3 meters)

Why less than 3 metres? This is another of the claims you frequently
make without a shred of evidence to back it up. And remember, we are
discussing this in relation to UK and European wiring practice. I
sincerely doubt you have ever worked on an electrical installation
outside the US (thank god for that too.)

Just more reasons why plug-in protectors are so
ineffective.

What reasons? Where? I see only more hand-waving from you.

I've come to the conclusion that you must work for a maker of these
"whole house" surge protectors that you constantly advocate. Your
opinion is therefore biased, not objective, and worth **** all.

HTH. HAND. FOAD.

 

[Bob Eager]

In the UK and Europe, two MOVs are used - one to shunt phase to earth,
and another to shunt neutral to earth. This makes surge protectors made
for this market much more effective.

Indeed. I think (can anyone confirm?) that sometimes three MOVs are
used, with one between phase and neutral...