Just found this on today’s inspection. The panel is mounted outside the carport. The Square D “Secondary Surge Protector” is mounted to the bottom of the box,with 2 black wires and one white.
The 2 black wires lead up to the service conductors and are tapped into there. The white wire appears to go to the neutral bus.
Is this the correct installation for this? I’ve never seen this device used before.
No, it should be on a load side breaker, not the service conductors. If that thing shorts out you will have a fire.
Every time I see one of those they are double lugged. Is that the recommended method of installation?
Yes.
By connecting the Tytewadd Power Filter across the main breaker of an electrical panel, all circuits in that panel can be protected from damaging moderate surges (those exceeding 130 volts), and also, from very destructive lightning surges that produce amperages ranging into the thousands.
Normally, two different types of arresters are used to achieve this dual level protection, however, the Tytewadd is a multi-purpose unit especially designed to handle both.
Where refrigeration and/or critical equipment is present, it is recommended that the Tytewadd Power Filter be installed on a two-pole breaker in a single phase panel and a three-pole breaker in a three phase panel. Each incoming line must be connected to the surge arrester for full protection.
Tytewadd Power Filters are U.L. Listed and CSA Certified. Tested under ANSI/IEEE C62.1 Standards for Secondary Surge Arresters, they exceed test requirements and are in compliance with CSA Standard C22.2 No. 0-M1982
http://www.tytewadd.com/images/panel.gif
Marcel:) 
These are listed for connection on the load side of a breaker. Whether you “double tap” or pigtail it in depends on trhe listing of the breaker (assuming you don’t have it on it’s own breaker).
The manufacturers say you get the same protection on the load side as you would on the line side. If you have this on the line side of the service disconnect and it shorts out the only thing putting the fire out will be for the leads to blow open or a fireman hosing the place down.
You are not going to blow the primary fuse on the transformer.
Thank guys. Now, the Square D info http://ecatalog.squared.com/pubs/Electrical%20Distribution/Surge%20Protective%20Devices/OEM%20Panel%20Mount%20TVSS/8291-0014D.pdf
says there is a diagnostic light in the middle of this device. The light is out, indicating a fault.
I’m going to recommend the new owners simply have it removed as it’s installed improperly and not working anyway. Since they already have some minor electrical work to be done, this shouldn’t be much of an expense.
