Technical information

The sizing of the disconnecting means for a motor starter depends on how many

motors are sectioned and the type of sectioning used:

a) single motor, disconnecting device defined in curr ent: the rated current of the

disconnecting means must not be less than 115% the current of the motor;

b) single motor, disconnecting device defined in hp (pow er): for NEC and CEC it

is enough that the size of the disconnecting means in hp is greater than the

power of the motor,while UL508A requires to establish the current on the

basis of tables 50.1 and 50.2 and then apply the 115% rule described in the

previous point;

It is recommended that you follow this criterion for simplicity' sake.

c) mor e than one motor: refer to the case of a single motor with current equal to

the sum of all the motor currents (as usual the FLA for the USA and value of the

motor plate for Canada).The sizing is done in current by applying the lower

limit of 115%: in the case of the disconnecting means defined in hp (power)

the value obtained from tables 50.1 and 50.2 must be taken as rated current.

Note that a self protected combination motor starter type E cannot section

multiple motors.

EXAMPLE

The disconnecting means chosen must have power sizes not lower than 5 hp.

The suitable IEC/UL/CSA component is a 194E-25 disconnect switch with a

rating of 5 hp.

In a NEMA starter a 1494F-N30

able to section 7.5 hp will be

used: if the installation is directly

on the machine a 1494F-NP30

“enclosed” disconnect can be

used.

1.3.1.3 Overload protection

193-E UL 592 NEMA

BRANCH CIRCUIT