The Q&A clears up any confusion around what the rule is:
Quote:
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Thank you for catching the potential ambiguity in Rule <R55>. The intent is that each power regulating device (speed controller, relay module, etc.) must be protected by one circuit breaker, and each circuit breaker must protect only one power regulating device. Please refer to Rule <R55>, as amended in Team Update #8.
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(bold emphasis is mine)
What I don't get, exactly is WHY?
I mean, it makes sense that you don't want to have three motors, each capable of drawing 15A running through three spikes, back to a single 20A breaker.... but what about three spikes that each only drive a solenoid valve? It would be more than safe to hook every spike controlling a solenoid valve up to the same 20A breaker with absolutely no danger of popping the breaker, or overheating the wire.
What is also odd is that the rules specifically state that you may hook up more than one solenoid valve (or other low-current application) to a single spike. So it is okay to have three solenoid valves powered by one 20A breaker, so long as they all run through the same Spike Relay, but NOT okay to have three solenoid valves powered by one 20A breaker when they run through three different Spike Relays.
I will concede that this rule might make tech inspection easier... one breaker, one spike... that's pretty easy to check, but I'm just a bit perturbed that a rule interpretation 2/3 of the way through build season requires us to re-wire part of our control board for no particularly apparent (to me) safety or engineering reason.
Jason
PS - In the big picture.... Overall, I'm actually pretty happy with the rules, can live with this interpretation, and really don't expect a "why" answer all the time from GDC, which has done an exemplary job of keeping up with the many (often repetitive) Q&A questions. I'm also pleased to be having this little rant here and now, and not on a Thursday after a tech inspector has interpreted rule 55 differently than we have. But I would have been much happier to see the allowance for multiple low-load devices extend all the way back to the breaker. It just makes sense to me.