The items I am enquiring about are marketed by APC and are called "SurgeArrest Panelmount" SPD's.
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Line transient supressors are not wired in series with your load; rather they are wired parallel across your incoming line & therefor will not constrain dynamics. Larger primary wholehouse surge arrestors (such as the Joslyn gas discharge arrestor that I use) are wired directly across the incoming line coming into the fuse panel, & are enclosed within their own box. The smaller panel mount primary arrestors are mainly intended to prevent a house fire & are not that good for supressing incoming voltage spikes; in addition if M.O.V. based, they degrade slightly with each hit as do any metal oxide varistor devices.
Downline from the primary arrestor you should also have secondary protection; this is where MOV based devices are prevelant & again will not constrain dynamics as they are wired parellel to your line. You can install your own MOV's across the outlets needing protection, or you can install line conditioners containing MOV's (such as Chang) or you can add MOV's to your existing Hydra if it does not already have that feature. You can even wire MOV's right inside of your components as I've done occassionally.
No you cannot stop a lightning transient cold. You can however, diminish the deleterious effects to the point that equipment may not be damaged at all or at least damaged less than with no protection at all. I've had personal experience with both scenarios. Anyone who tries to argue that transient supression is a waste - can you can pay Mike's next repair bill? If not, then any negatory advice in that regard is worth exactly what it cost.
Bob is 100% correct! My day job is in industrial electronics and control. I have designed equipment that monitors a water tower. They are one of the best lightning rods know to man. I have personally hade to repair a site that had a lightning hit so strong that the transformer that was on the electric pole was on the ground. The electric meter was in little pieces. My power supply was destroyed, but the down stream equipment fas fully functional after replacing the power supply board. This power supply has an extensive surge protection system of coils, MOV's and TVS diodes.
In my installations I use surge suppression devices on the incomming line all the time. The MOV bassed devices do indead degrade with exposure and should be replaced every so often. The gas discharge tubes are very rugged but do not clamp the incomming transient at a low enough level to protect audio electronics. The recomendation of multiple locations of MOV based suppression is a very good idea. The MOV work in conjunction with the wiring impedance to limit the surge to an acceptable level. I would think that a Gas Discharge device at the service entrance, a big MOV device at the breaker to the stereo, and a surge protector at the outlet would provide a level of saftey from transients.