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Home > Archive > Electrical Engineering > June 2006 > Whole-house surge supressors: any good?
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Whole-house surge supressors: any good?
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| Adam Corolla 2006-06-07, 5:21 pm |
| A recent nearby lightning strike toasted some expensive appliances including
my central air/furnace blower, thermostat and garage door opener.
I am thinking about buying one of those whole-house surge suppressors you
install right below the electric meter. I would have to have a pro put it
in as I am not experienced with this.
Does anyone know if the things actually work? Looks like they cost between
$200 and $300 dollars or so, which I don't mind paying if it will offer some
added protection. (I know nothing will protect from the surge if the strike
is close enough, but I have no protection now and I'm paying for it.)
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| Protector is as effective as its earth ground. Earth ground is THE
most critical component of a protector 'system'. Distance to earth
ground is essential. Shorter distance via protector means better
protection. 'Whole house' or power strip: they are both shunt mode
protectors. They both work by earthing a transient. But that
connection to earth should be as short as possible: 'less than 10
feet', no sharp bends, no splices, not through metallic conduit, and
not bundled with other non-earthing wires.
None of this is defined by code. Code only addresses human safety.
Transistor safety requires earthing to both meet and exceed post 1990
earthing requirements.
Another factor is quality of earth. If soil is not conductive or if
a current earth ground is not THE most conductive earthing, then
earthing 'system' should be enhanced - more rods, a halo ground, etc.
What is sufficient for code is not always sufficient for lightning
protection.
Every incoming utility must be earthed 'less than 10 feet' to a same
earthing electrode. Damage can result if building uses multiple
earthing electrodes - not interconnected. All earthing wires should
route to earthing independently to meet at the common earthing
electrode.
Telephone NID already has a 'whole house' protector. But that NID
earthing connection must also meet above requirements - including 'less
than 10 feet'.
Any utility wire not earthed at service entrance will only carry a
destructive surge through household appliances. For example, assume
cable is not earthed. So a surge enters on cable, passes through cable
modem, TV, or simply jumps to a computer network wire. Now it has a
destructive path through appliances, through AC electric 'whole house'
protector, into earth. IOW every incoming wire must make that earthing
connection - either by direct connection or via a 'whole house'
protector.
Simple rules to make a 'whole house' protector effective. Quality of
earthing defines quality of that protection.
Meanwhile, above is a discussion about earthing one transient.
Distance to earth and quality of earth ground defines protection from
one transient. Life expectancy of a protector is defined by number of
joules. Minimally acceptable AC electric protector is 1000 joules,
50,000 amps. Minimal so that protector remains functional. If in a
neighborhood with frequent lightning damage, then more joules should be
considered.
Adam Corolla wrote:
> A recent nearby lightning strike toasted some expensive appliances including
> my central air/furnace blower, thermostat and garage door opener.
>
> I am thinking about buying one of those whole-house surge suppressors you
> install right below the electric meter. I would have to have a pro put it
> in as I am not experienced with this.
>
> Does anyone know if the things actually work? Looks like they cost between
> $200 and $300 dollars or so, which I don't mind paying if it will offer some
> added protection. (I know nothing will protect from the surge if the strike
> is close enough, but I have no protection now and I'm paying for it.)
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"Adam Corolla" <nospam@nospam03550265902.com> wrote in message
news:B_-dnR0Dq6asshrZnZ2dnUVZ_oGdnZ2d@giganews.com...
> A recent nearby lightning strike toasted some expensive appliances
including
> my central air/furnace blower, thermostat and garage door opener.
>
> I am thinking about buying one of those whole-house surge suppressors you
> install right below the electric meter. I would have to have a pro put it
> in as I am not experienced with this.
>
> Does anyone know if the things actually work? Looks like they cost
between
> $200 and $300 dollars or so, which I don't mind paying if it will offer
some
> added protection. (I know nothing will protect from the surge if the
strike
> is close enough, but I have no protection now and I'm paying for it.)
I agree with the other poster comments. A tested ground <5 ohms is much
better than what the code uses for safety, <25 ohms.
Most panel manufactures make "plug in breaker type surge" arrestors that can
perform better than the wired ones. IEEE 519 says you need to protect 2 of
the 3 zones. Simple answer is ya need on in the panel and one at the
appliance.
I replace my ses one every odd numbered year. And the plug strip ones every
even numbered year. All of these units are U.L. tested ONCE. I live in a
seasonal lightning area. I have not lost any electrical device since
starting this program. Not saying that this year I will not. Do not for get
your garage door opener.
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| TimPerry 2006-06-08, 12:21 am |
| Adam Corolla wrote:
> A recent nearby lightning strike toasted some expensive appliances
> including my central air/furnace blower, thermostat and garage door
> opener.
>
> I am thinking about buying one of those whole-house surge suppressors
> you install right below the electric meter. I would have to have a
> pro put it in as I am not experienced with this.
>
> Does anyone know if the things actually work? Looks like they cost
> between $200 and $300 dollars or so, which I don't mind paying if it
> will offer some added protection. (I know nothing will protect from
> the surge if the strike is close enough, but I have no protection now
> and I'm paying for it.)
i use this company's products at several commercial locations.
http://www.transtector.com/
for 200 amp service a parallel type MOV protection cost me about $500. (3
phase)
for parallel type silicon protection $1,000 (3 phase)
the difference? MOV breaks down over time and number of hits.
single phase units most likely will be less costly.
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| Tom Horne, Electrician 2006-06-08, 1:21 am |
| Adam Corolla wrote:
> A recent nearby lightning strike toasted some expensive appliances including
> my central air/furnace blower, thermostat and garage door opener.
>
> I am thinking about buying one of those whole-house surge suppressors you
> install right below the electric meter. I would have to have a pro put it
> in as I am not experienced with this.
>
> Does anyone know if the things actually work? Looks like they cost between
> $200 and $300 dollars or so, which I don't mind paying if it will offer some
> added protection. (I know nothing will protect from the surge if the strike
> is close enough, but I have no protection now and I'm paying for it.)
>
>
Square D makes one that protects the power, telephone, and cable lines
in single unit. It is UL classified as a Transient Voltage Surge
Suppressor. It is hard wired to the panel and the other two services
are brought there to it before they go to the equipment they serve. In
especially lightning prone areas it should have a secondary surge
suppressor ahead of it. The earthing electrode should be built to
communications protective standards. That may require a full or partial
ground ring together with driven rods to provide a low enough impedance
so that the surges and spikes can dissipate without causing damage. If
any wired utility enters the home at a location remote from the others
then the grounding electrode system must be extended to that location by
running a bare number two copper conductor from the power electrode to
the one for the physically separate wire entrance point. The best route
for running that bonding conductor is to run it as a ground ring buried
at least thirty inches deep. In that way it serves as an additional
electrode.
--
Tom Horne
"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison
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| Adam Corolla wrote:
> A recent nearby lightning strike toasted some expensive appliances including
> my central air/furnace blower, thermostat and garage door opener.
>
> I am thinking about buying one of those whole-house surge suppressors you
> install right below the electric meter. I would have to have a pro put it
> in as I am not experienced with this.
>
> Does anyone know if the things actually work? Looks like they cost between
> $200 and $300 dollars or so, which I don't mind paying if it will offer some
> added protection. (I know nothing will protect from the surge if the strike
> is close enough, but I have no protection now and I'm paying for it.)
>
>
The best information I have seen on surge protection is at
http://www.mikeholt.com/files/PDF/L...sion_May051.pdf
This is a guide published by the IEEE in 2005 whose title is "How to
protect your house and its contents from lightning: IEEE guide for surge
protection of equipment connected to AC power and communication
circuits" This is a guide for wide circulation, not a technical paper.
Surge suppressors at the service panel clamps the voltages between wires
to a ‘safe’ value and also bypasses most of the surge to earth. Some
panel manufacturers make surge suppressors that plug in to a panel ,
like a block of 4 circuit breakers - very convenient. Also available
are surge suppressors that attach to the side of the panel through a
knockout and wire to 2 circuit breakers. Both of these connect
downstream from the main breaker. It is very important to keep lead
length as short as possible and avoid bends. Power utilities may also
supply a suppressor that plugs in between the meter base and the meter.
This sounds more like the device you describe, connected ahead of the
service disconnect. This is about all you can do for your furnace and
thermostat. If the garage door opener is in a detached building it will
not necessarily be protected. A plug-in surge suppressor could be used.
The IEEE guide also points to potential problems with outside A/C
compressor/condenser units.
The IEEE guide has information on values for clamping voltage and
current rating. Energy rating (Joules) is not useful in comparing
different surge suppressors.
The neutral is connected to the building ground/bond wires at the
service panel. It is also important to connect the protective devices
for other incoming wires - phone, CATV - close to this same common
point. This also applies to satellite dishes. This is single point
grounding. The phone NID/protector should be close to the panel, with a
short ground/earthing wire from the NID to the ground/earthing conductor
coming out of the panel. Same with the CATV ground block. Results of
long ground/earthing connections are illustrated in the IEEE guide.
In my opinion, single point grounding is more important that a really
low ground- earth resistance for a house. Even if the ground-earth
resistance is a very low 5 ohms, a moderate lightning induced surge
could result in an earth current of 20,000 amps. That would result in a
piece of land around the grounding electrode rising to 100,000 volts
above ‘absolute’ earth. A ground ring around the house, described by
Tom, would result in the whole building rising, an advantage. For new
construction, the rebar in the footing all the way around the house
could be bonded and the footing could be connected as a Ufer
ground/concrete encased electrode to do the same thing, described
previously by <gfretwell>.
Particularly for high value equipment, plug-in surge suppressors are
effective as insurance or even primary protection. They work primarily
by clamping, not earthing. They can protect if a suppressor is not
connected at the service, and are particularly effective if a single
point ground is not provided and equipment is connected to power in
addition to phone/CATV/dish/LAN. In that case a multi-port protector
(SRE) has to be used, as described it the IEEE guide. The surge guru at
the NIST (Martzloff)wrote in a reference for rural electrical coops:
“Whole house protection consists of a protective device at the service
entrance complemented by TVSSs [surge suppressors] for sensitive
appliances [electronic equipment] within the house.” A computer may be
high value not because of its cost but the value of the information on it.
bud--
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