Disconnect switches - Nonfusible & fusible | 3

ABB differentiates itself in the disconnect switch market by

offering UL98, UL508 and IEC rated switches. ABB’s UL98

listed disconnect range includes 30 to 2,000 A non-fusible and

30 to 1200 A fusible switches. These may be used in a variety

of applications — on service equipment, motor control centers,

or as motor branch circuits. The UL508 listed offering has

clearance distances less than those required by UL98. ABB’s

line of UL508 listed non-fusible disconnects ranges from 16 to

80 A and can be used as motor controllers.

IEC rated switches are available from 16 - 3150 A (non-fusible)

and 30 - 1200 A (fusible).

Selecting disconnect switches

Motor feeder

Motor feeder short circuit and

ground fault protection

Motor disconnecting means

Motor controller

Motor overload protection

OSHA Lockout/tagout disconnect

Motor

Motor branch-circuit

short-circuit

protection

To supply

UL98

Fusible Switches

OS30, OS60, OS100,

OS200, OS400, OS600,

OS800, OS1200

UL98

Non-Fusible Switches

OT30, OT60, OT100

OT200, OT400, OT600,

OT800, OT1200,

OETL-NF1600 thru

OETL-NF2000

UL508

Non-Fusible Switches

OT16, OT25, OT40,

OT63, OT80

(UL98 switches can also

be applied)

Typical control panel

OL

M

Article 430 of the US National Electric Code includes two methods for properly

sizing disconnect switches.

Single motor application

A properly sized disconnect switch for a single motor will:

• Have an ampere rating greater than or equal to 115 percent

of the rated motor full load current; or,

• Have a HP rating greater than or equal to the rated motor

HP (at applied voltage) if the disconnect switch under

consideration is HP rated.

Combination load application

A properly sized disconnect switch for a combination load will

be selected by adding all the simultaneous individual loads in

the circuit under consideration.

Using motor nameplate information, load information, and

tables from section 430 of the NEC, determine one equivalent

full load current and one equivalent locked rotor current. The

equivalent locked rotor current can be used with table 430-

151 to determine an equivalent HP rating. Select a disconnect

switch:

• Greater than or equal to 115 percent of the equivalent full

load current; or,

• Greater than or equal to the equivalent HP rating.

Use of UL98 & UL508 Disconnects according to NEC Article 430