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is a coordination study requried at 120V

is a coordination study requried at 120V

(OP)
is a coordination study required at 120V?
I never seen a coordination study done on a 120V lighting panel or 120V control panel.
My Reviewing Engineer is asking for one on my control panel which is all 120V, and all the same 1489 circuit breaker type just with different amperage.
I believe the breaker that is closes to the fault would trip first and not trip an upstream breaker because they all have the same curve.
Any suggestions?

RROC

RE: is a coordination study requried at 120V

If its for a legally required emergency circuit, then yes.

As for coordinating Id say its a gamble. Molded cases breakers are far from exact creatures, and when a fault does occur its often a competition on who will trip first, especially when the fault current is large since it can exceed the magnetic trip rating across several breakers. Ie, I know of short circuits near a homes electrical panel that not only triped the 20amp branch breaker, but also the 100amp main breaker. Looking at the trip curves that can be explained since most residential breakers have a magnetic pickup of around 10-15x the handle rating. So a 20amp breaker would have a magnetic pickup of around 240 amps, while the main would start picking up around 1,200 amps. Assuming a strong utility source (say 9,000amps of available short circuit current) and the fault was close enough to the panel (little circuit length (impedance) to limit the fault current sufficiently) both breakers could see over 1,200 amps, ie 2,000amps. In that case it would be competition on who would trip first. Either the branch, or main, or both would trip.

RE: is a coordination study requried at 120V

Quote (OP)

Is a coordination study required at 120V?
.......
My Reviewing Engineer is asking for one on my control panel which is all 120V.
In this case, Yes.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: is a coordination study requried at 120V

What Bill said; are you looking for grounds with which to challenge your Reviewing Engineer?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: is a coordination study requried at 120V

Considering the coordination study could probably have been done in 20 or 30 minutes.... well assuming you have the software that makes it easy anyway.

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