Whole-house surge supressors: any good?

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.)

Reply to
Adam Corolla
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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. M> A recent nearby lightning strike toasted some expensive appliances including
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I agree with the other poster comments. A tested ground

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i use this company's products at several commercial locations.

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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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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.

Reply to
Tom Horne, Electrician

The best information I have seen on surge protection is at

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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 .

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.


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