FORM 150.67-EG1 (219)
JOHNSON CONTROLS
87
Circuit Breaker Calculations
Max Dual Elem Fuse Max CB (MOP)
= 2.25 x Current of largest motor + ∑ (remaining FLAs or RLAs)
For this name plate the formula below was used:
= 2.25 * RLACpr1 + RLACpr2 + RLACpr3 + Qty* RLAFans + 0.49 + FLAPump
This formula will calculate the ACTUAL MOP but a table is referenced to provide the appropriate MOP.
ACTUAL
COLUMN
A
MINIMUM
COLUMN
B*
MAXIMUM
COLUMN
C
0 15 0
15 20 15
20 25 20
25 30 25
30 35 30
35 40 35
40 45 40
45 50 45
50 60 50
60 70 60
70 80 70
80 90 80
90 100 90
100 110 100
110 125 110
125 150 125
150 175 150
175 200 175
200 225 200
225 250 225
250 300 250
300 350 300
350 400 350
Note:
Column B is used to calculate the Minimum
Dual Elem Fuse which is not relevant to this exercise.
Using an approximate match, look up the value of the
calculated ACTUAL MOP in Column A. Find the largest
value i.e. less than or equal to the value in Column A.
Once found, the value in Column C which shares the
same row is the valued USED in the system, e.g. Using
the same example that was used to calculate the MCA,
calculate the MOP:
Ans. ACTUAL = 2.25*20.4 + 20.4 + 0 + 2*2.6 + 5.29 =
45.9 + 30.89 = 76.79Comparing against values in Col-
umn A: 70 < 76.79 < 80, therefore the USED MOP found
in Column C is 70.
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