suep
New User
- Location
- Norcross, GA, Fulton
- Occupation
- Engineer
240.86(C) Motor Contribution. Series ratings shall not be used where
(1) Motors are connected on the load side of the higher rated overcurrent device and on the line side of the lower-rated overcurrent device, and
(2) The sum of the motor full-load currents exceeds 1 percent of the interrupting rating of the lower-rated circuit breaker.
1. The PANEL is a 25kAIC panel but has a main bkr 35kAIC. The series rating document shows, the downstream HD and JD can be series rated upto 35kAIC. The following motor loads are being fed from the feeder breakers.
a. Three HD(18kAIC) breakers - one HD - 60A bkr feeds motor M1 => FLA = 47A
b. Two - JD breakers (18kAIC) - feeds other panels
c. One - LG breaker (35kAIC) - feeds multiple motor M2 LS =>FLA=316A (Total FLA of all the motors)
Please help me understand the following:
A) The panel is 25kA, so does it mean that the main and feeder breakers are series rated upto 25kA, (even though the SR table shows 35kAIC)?
B) LG breaker is fully rated with 35kA, so does this series rating code 240.86 (C ). 2 apply?
C) 1% of the interrupting rating of the lower-rated CB (18kA) is 180A. FLA of M2 is 316A but LG is not series rated. However, M1 has FLA of 47 and HD is series rated. Code says "Sum of these motor full-load current".........................
If LG is not series rated, do we take M2 FLA in consideration too? is it M2 + M1 or Just M1?
D) If all the motors have VFD and motors have no fault contribution, does this 240.86 (C) apply at all?
all the calculations are the same but there will be no fault current contributions from the motors, do we still have to check it against this code 240.86?
(1) Motors are connected on the load side of the higher rated overcurrent device and on the line side of the lower-rated overcurrent device, and
(2) The sum of the motor full-load currents exceeds 1 percent of the interrupting rating of the lower-rated circuit breaker.
1. The PANEL is a 25kAIC panel but has a main bkr 35kAIC. The series rating document shows, the downstream HD and JD can be series rated upto 35kAIC. The following motor loads are being fed from the feeder breakers.
a. Three HD(18kAIC) breakers - one HD - 60A bkr feeds motor M1 => FLA = 47A
b. Two - JD breakers (18kAIC) - feeds other panels
c. One - LG breaker (35kAIC) - feeds multiple motor M2 LS =>FLA=316A (Total FLA of all the motors)
Please help me understand the following:
A) The panel is 25kA, so does it mean that the main and feeder breakers are series rated upto 25kA, (even though the SR table shows 35kAIC)?
B) LG breaker is fully rated with 35kA, so does this series rating code 240.86 (C ). 2 apply?
C) 1% of the interrupting rating of the lower-rated CB (18kA) is 180A. FLA of M2 is 316A but LG is not series rated. However, M1 has FLA of 47 and HD is series rated. Code says "Sum of these motor full-load current".........................
If LG is not series rated, do we take M2 FLA in consideration too? is it M2 + M1 or Just M1?
D) If all the motors have VFD and motors have no fault contribution, does this 240.86 (C) apply at all?
all the calculations are the same but there will be no fault current contributions from the motors, do we still have to check it against this code 240.86?
