Dave you have been lucky. From Scott's own website.
The PSX that I use are faster than a fuse, which is fast than Scott's circuit breakers. You can't put a price on protecting a 1000 dollar engine. I'll also note the PSX has a transzorb built in for spikes.
IMPORTANT – PLEASE READ!
Reaction time on circuit breakers is always a sticky subject. Fuses are much faster than circuit breakers even though they carry the same rating. Recent research has indicated that circuit breakers are about 40% slower in reaction time than fuses. That’s why many are choosing 10A circuit breakers over 15A – just trying to improve reaction time.
But even that can be tricky: If you’re operating a layout with a couple engines and a host of passenger cars, your amperage draw may be close to 15A just with normal operation. In this case a 10A may have more nuisance interruptions.
Note that fuses and circuit breakers (thermal) actually react to temperature and not the actual amperage draw on the layout. There are other circuit breakers, namely magnetic, but are very expensive ($60 per channel or higher) and are probably out of the budget of the average hobbyist.
The other issue is circuit breakers and fuses will never see a voltage spike and often times voltage spikes are what zap our equipment. (Voltage spikes are caused by running trains…, i.e. going over the gaps in the track, through turnouts, running accessories, blowing the horn on conventional.) That’s why our recommendation when asked “what’s the best circuit protection?” is always a TVS-4 with fuses which provides the best available of both worlds: voltage protection with the TVS and fuses for derailments and other shorts.
Still, a lot of people love our circuit breakers – they like the convenience of pressing the button to reset, but more than likely they are aware of the total current draw of their layout in action and probably selected (guessed?) accordingly.
If you haven't purchased the TVS-4 surge protector and are operating TMCC and/or DCS, you really should consider it.
Scott’s Odds-n-Ends, Inc. November 2007