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McGarry and Madsen's home inspection blog for buyers of
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How do I find the right whole house surge protector?
Wednesday, December 26, 2018
They are called either a “Transient Voltage Surge Suppressor (TVSS)” or "Surge Protective Device (SPD)” in technical bulletins, and here’s the important features to look for when shopping for a whole house surge protector:
- UL 1449 Listed and UL logo - If the label says “UL 1449,” it means that Underwriters Lab has repeatedly subjected samples of the product to surges of different amperages to verify its integrity. The third edition of this spec requires passing a total of 21 surge tests for their approval.
- Surge rating of 20,000 to 40,000 amps.
- Internal fuses and a failure-light that indicates the system is still functional when lit.
The surge protector can be mounted in two open slots in the panel, like the Square D one shown at the top of the page, or on the side or bottom of a surface-mounted panel, or in the wall adjacent to the panel. Some models are also rated for exterior installation.
But it should not be mounted so that the device obstructs full closure of the panel dead front, as in the photo below. And, although mounting it inside the panel is allowed by the electrical code, the status light that tells you if it’s still functioning will become hidden and useless.
Cost runs between $200 and $500 installed by an electrician, depending on the specs you request. We recently had an Eaton “Ultra" Surge Protector added here in The Villages, Florida, for $315. This model is a “Type 2,” meaning that it is rated for installation after the main breaker and must be installed using a dedicated circuit breaker. A 50-amp breaker is recommended by the manufacturer, but only requires a #14 copper connecting wires because they do not carry load current. Instead, the wires only send short-duration currents that are associated with the transient surge event.
An alternate solution is “Type 1” SPD, which is rated for installation ahead of the main disconnect and a breaker is not required for installation. Some surge protectors are rated for either Type 1 or Type 2 installation.
Also, because a surge protector will not function properly without a good ground connection, be sure your electrician verifies that there is low resistance to current flow to the ground.
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