The run cap changes make sense. Thank you.
I already have bleed resistors sized for shared use like drawn. I'll have to order more smaller ones to do this, but it makes sense.
Changing the start cap bank makes sense if i will start idler 1 or idler 2 by themselves. My plan was to start idler 1 every time and use it to start idler 2. Do you not think that would work? This design wasn't intended to start idler 2 by itself (and it definitely won't!).
I like idea of the metering on its own small breaker. Thank you.
I will look into the motor starters vs magnetic contactors.
Thanks
SAF has done a useful "all one place" post. VERY useful!
It isn't all that different from the FOUR idler rig I've been re-doing my own one into. I do more tests and experiments than making of chips, so flexibility is key.
Here's a coupla kinda "borderline" possibilities to add to the mix that you might find of use:
NFPA 70 is a FIRE protection (and reduced risk of electrocution) Code. Insofar as possible, it stays TF
out of what goes-on INSIDE the enclosures of serv-ED "systems". That's UL /CSA / TuV turf .. if any certifications are sought at all.
So.. "I could be (in the) wrong",, but the way I choose to interpret that for my use, is to carry multiple, individual runs of "lesser" breakers from the primary Square-D QO Load center to my idler's. Largest a 10 HP, then 2 X 7.5 HP, one X 3 HP.. which is basically a "trimmer".
Now.. RPC as they are, the two feeds from singe phase are common in copper to two of the 3-Phase legs.
Which means.. that I MUST have BOTH the contactors present to interrupt input side AND output side, and-then-also the reliable
control logic to insure it actually OPERATES that way.
Then, too - given "shit happens" - alarm / monitoring to detect a fault in the anointed scheme.. and do "something safer" should any part of it fail to operate according to plan.
EVEN IF... that emergency response is the classical "crowbar" circuit .. that trips the breakers with such a vengeance it would be prudent to replace them after the fault is cleared.
Not a choice I expect to have to implement, but neither would it be "new ground" on a Telco pension!
Shorter take for your two 20 HP units is that I would be feeding them from TWO upstream breakers rather than one, making the investment in extra contactors ... plus not terribly complex logic. You don't need as much of that for two idlers as I do for FOUR ..
Why wuddja BOTHER?
Redundancy. Independence. Flexibility. Done and tested Day One to a plan.
Fewer potential surprises, later?
Done the way I am going, I don't end-up with a single, complex, 4-idler animal.
I have instead a collection of independently but "pre-wired as cooperative"
modules I can not only put online in any combination as suits. I can re-purpose, re-locate, re-assign, dispose of, or swap independently.
Annnd my "worse case" starting load is only 10 HP for a rig that as
presently enabled, tops out at 28 HP "worth" of idler-power. I'd have done your 2 X 20 as a 20 and two 10's, for example.
At which point, you have 20 or 40. but I would have 10, 20, or 40. Most often utilized? Sod's Law sez it's the 10 HP!
4 Idlers worth. Because I can.
CEO, C&W Mercury:
Ich: "Ian? You are running the whole show. How the Hell did YOU end up stuck with PABX extension: "666"?
Ian: "I got first choice!"