another motor question

[electricalperson]

There are three motors, one 5 hp 230 volt single phase motor with a service factor of 1.20 and two 1.5 hp 120 volt single phase motors. using an inverse time breaker the 3 wire feeder conductor protection device after balacing all three motors will be____?

A 60 amp
B 70 amp
C 80 amp
D 90 amp

my calculations came out to be 110 amps. what did i do wrong? :-?

heres the calculation i used 5 hp motor flc = 28 amps 28 x 2.5 = 70
1.5 hp motor = 20 amps each 70+20+20 = 110

 

[augie47]

the 1.5 hp are 120v, so only 1 would be per phase
70+ 20= 90
that correct ?

 

[electricalperson]

the 1.5 hp are 120v, so only 1 would be per phase
70+ 20= 90
that correct ?

i think i understand now. i had no idea thats what i had to do. so each phase will be 90 amps correct?

so if its 230 volts you still would had to add them all together? but if they are single phase L to N you just do the formula for one phase of the 3 wire system?