General
All tables are based on the operation of the motor
and controller in the same ambient temperature,
40°C (104°F) or less. Always be certain the
correct thermal units are installed in the starter
before operating the motor. Each thermal unit
shall be installed such that its catalog number is
visible. On melting alloy thermal units the ratchet
wheel must engage the pawl assembly.
Selection Procedure
1. Determine motor data:
a. Full load current rating
b. Service factor
NOTE: If motor full load current is not known, a
tentative thermal unit selection could be made,
based on horsepower and voltage. Refer to
Page 22.
2. Motor and controller in same ambient
temperature:
a. All starter classes, except Class 8198:
1. For 1.15 to 1.25 service factor motors use
100% of motor full load current for thermal
unit selection.
2. For 1.0 service factor motors use 90% of
motor full load current for thermal unit
selection.
b. Class 8198 only:
1. For 1.0 service factor motors use 100% of
motor full load current for thermal unit
selection.
2. For 1.15 to 1.25 service factor motors use
110% of motor full load current for thermal
unit selection.
3. Motor and controller in different ambient
temperatures:
a. Multiply motor full load current by the
multiplier in Table A. Use the resultant full
load current for thermal unit selection.
4. Locate proper selection table from index,
Pages 19 and 20.
a. The proper thermal unit number will be found
adjacent, to the right of the range of full load
currents in which the motor full load current
or resultant full load current falls.
5. See Page 21 for calculation of trip current rating.
