I personally never let more than 10 amps of power on the rails, when you get to 20 amps and up, a derailment can do a lot more damage. Also, paralleled transformer circuit breakers don't always function like they should. I know this to be true of the PH180. When it's alone, it's a great circuit breaker. However, in parallel, I've seen them do odd things, and a couple times they didn't trip when it was obvious there was a massive overload on the rails. That's also why I steer clear of parallel transformers.