When Lightning Strikes- Whole house Surge protection

Submitted by DonHester on Mon, 11/11/2013 - 11:57.

When Lightning Strikes- Whole House Surge Protection

Surge protection devices (SPD), surge suppressors, transient-voltage surge suppressors (TVSS), lightning arrestors and such are devices that are designed to limit excess energy from the electrical system to provide protection of electrical equipment. They do this by shorting excess voltage to ground.

(melted ground clamp from voltage surge)

These devices are mainly designed to handle transient surges. Surges can come from various sources, they can enter externally such as from lightning or utility surges or they can be generated internally by equipment and appliances.

This is where a whole house surge protection comes in. A whole-house surge protector works because electricity is sort of like water and seeks a common level. This allows the surge protector that is not “in series” with a piece of equipment, like a computer, to still “drain” a surge providing protection of the equipment.

So during a recent home inspection I found a “Whole House Surge Arrestor” not installed properly. They wired to the SPD directly to the main service conductors which is improper. These devices are designed to be wired to circuit breakers. We also have a double lug of the main lugs which is a “no no”.

(Improper wiring of Whole House Surge Protection)

(Double lug of main lugs)

It is very important to follow the manufacturer’s installation instructions, paying particular attention to fuse or breaker requirements and lead lengths. The surge protectors need to be connected to an appropriately rated circuit breaker not into the main lugs. Where possible should they should go to the first breaker at the top of a panel. This ensures optimum protection of all loads connected to the panel.

Here is a manufacturer’s drawing for installation of the Whole House Surge Arrestor.

(Manufacturer's wiring diagram)

As always these devices should be installed by a qualified and competent electrician. And since we still have Ohm’s law and Kirchoff’s Laws that applies in relation to transient voltage, having the lowest impedance (and shortest wire distances) in the grounding system the better (less impedance equals better protection). This brings us back to proper grounding and bonding of the electrical system which should be evaluated when installing these devices. National Electrical Manufacturers Association (NEMA) information http://www.nemasurge.org/faqs/

Another aspect is that whole house protection should be coupled with point of use surge protectors. And like many things you get what you pay for so try to get best you can afford. These devices will need to be replaced over time because they eventually fail from repeated surges. Higher quality devices will have warning lights to let you know they are still functioning.

All of these devices need a grounding conductor to work properly so in older homes you may need to upgrade your wiring to provide protection. The warranty offered by most surge protector manufacturers is only valid if the surge protector is used in a properly grounded outlet.

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Plato

NCW Home Inspections, LLC is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…

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When Lightning Strikes- Whole house Surge protection