How to Choose an SPD
My recent Post “What’s wrong with this SPD installation?” generated some discussions. (See Post here)
I think some clarification is necessary to return the discussion to performance and applications, and away from generalizations and marketing.
This discussion started with an obvious retrofit application and common mistakes in installation. Lead length is important, but it is only one of several factors that should be carefully considered before selecting any SPD for external or internal installation. And yes, a fully UL listed Type 1 or Type 2 SPD can be retrofitted internally within switchgear or panels. Choose your manufacturer and installer wisely. Consider all the factors that go into a quality SPD:
kA rating,
Modes of discrete component protection,
Types of surge addressed (impulse and ring wave),
Physical size and weight of SPD (will it fit in space available),
Warranty (number of years and does it include replacement of SPD for lightning damage),
PE Certified Independent 3rd party testing to ANSI/IEEE Standard C62.41.2-2002 and C62.45-2002 with multiple voltage and current levels of impulse and ring wave surges, both voltage driven pulses from 2 kV to 6 kV, and current driven pulses from 10 kA to 20 kA.
Test results should be for the specific model being proposed, not a category, or product line generalization,
Published Voltage Protection Ratings (VPRs) from the National Recognized Testing Lab (NRTL) that conducted the testing for the ANSI/UL 1449 Standard Listing of the SPD,
Can it be serviced/replaced without de-energizing the entire panel if there are critical loads that cannot be stopped,
Does the manufacturer provide assistance, supervision, training, inspection, and/or certification of the installation, and
Any site-specific requirements like alarms, remote monitoring capabilities, enclosure types, etc.
The top five or six manufacturers of quality Surge Protective Devices, both internal and external, will provide answers to all of these issues. And in most cases, they are competitively priced.