Settings for the Square D Circuit Breaker

Chiller (RTAC) was shipped with Square-D-LG-600A breaker with following settings, Iᵣ = 600; tᵣ = 0.5; Iᵢ = 1.5Iᵣᵣ

• The Long Time protection (Iᵣ) : Factory set 600
  • It should be matching the MOP Electrical data of the chiller, in this case 500A.
  • Move dial to 500 notch value, with this value the long-time protection tripping range (1.05-1.20Ir) is 525A to 600A
• The long-time protection trip time (tᵣ): Factory  is set 0.5 sec.
  • The breaker will trip on current of 6*Iᵣ =3000A in 0.5 sec ( 30 cycles). Leave the settings as it is.
    • The instantaneous trip (Iᵢ) , short circuit protection.
    • Set value to overcome XLRA of the compressor/circuit.

Set value = XLRA/MOP

A circuit with two compressors each with XLRA = 1065 A, the set value = 2x1065 / 500 = 4.26, then adjust it value to 5

Chiller (CGAM) was shipped with Square-D-LG-400A breaker with following  settings, Iᵣ = 200; tᵣ = 0.5; Iᵢ = 1.5Iᵣ

• The Long Time protection (Ir) should be matching the MOP Electrical data of the chiller, in this case 300A.
  • Move dial to 300 value, with this value the long-time protection tripping range (1.05-1.20Iᵣ) is 315A to 360A
• The long-time protection trip time (tᵣ) Factory  is set 0.5 sec.
  • The breaker will trip on current of 6*Iᵣ =1800A in 0.5 sec ( 30 cycles). Leave the settings as it is
    • The instantaneous trip (Iᵢ) , short circuit protection.
    • Set value to overcome XLRA of the circuit/chiller.
      • Set value = XLRA/MOP

A chiller with four (4) compressors each with XLRA = 320 A, the Set value = 4x320 / 300 = 4.26, then adjust it value to 5

For two compressor chiller, the instantaneous dial set = 2x320/300 = 2.13, set value to 3.

1. Chiller (CGAM) was shipped with Square-D JDL26225 breaker with Thermal Magnetic Trip with following range Hold = 1125, Trip = 2250
   • The HOLD value , short circuit protection.
   • Set value to overcome XLRA of the Chiller
     • Set value = XLRA * Number of Compressors
     • A circuit with four compressors each with XLRA = 320 A, the set value = 320*4 = 1280, then adjust it  higher than 1125

For Motor protection

• Short-Time Protection (Isd): protects all types of electrical distribution applications against short-circuit current.
  • Minimum dial set value is 1.5Iᵣ (1.5 x500=750A).
• Evaluate Short circuit current available at the compressor terminal to proper dial setting.
  • To start up you could us.e XLRA as reference point. 2x1065/500 = 4.26; set it 5

Note:

• Dial description see below.
• Additional information, click here

• Protects equipment against overloads
• Is standard on all distribution trip units
• Uses true rms measurement

• Adjust time delay for long-time protection
• Is standard on 3.2 and 3.3 trip units

• Protects equipment against solid short circuits
• Is standard on all distribution trip units
• Uses true rms measurement
• Protection Type
  • For motor trip units, the dials are:
    • for setting full load amp and
    • Short-time protection.

• Protects equipment against impedance short circuits
• Is standard on 3.2S and 3.3S trip units
• Uses true rms measurement

• Protects equipment against overloads
• Is standard on all motor trip units
• Provides setting for trip class
• Uses true rms measurement
  • For distribution trip units, the dials are:
    • setting long-time Protection
    • Setting long-time Delay, and instantaneous protection, depending on the trip unit

• Protect equipment against overload and it is I2t  IDMT ( Inverse Definite Minimum Time).
• It is set with the Iᵣ pickup and the tᵣ trip time delay dials.
• The Default Iᵣ pickup setting value is the maximum dial position In
• The long-time protection tripping range is 1.05-1.20 Iᵣ

• Time delay (tᵣ) setting: Default value is 0.5, that is, 0.5 seconds at 6 Iᵣ
• For 60 Hz frequency  1 cycle = 1/60 = 0.01666 sec, then 0.5 sec correspond to 30 cycles

• To set the Iᵢ pickup use the Ii dial
• The Iᵢ pickup setting is in multiples of Iₙ
• Default Iᵢ pickup setting value is 1.5 Iₙ. Use 4  6 Iᵣ
• Accuracy range is +/- 10%
• The Hold time is 10 ms
• The maximum breaking time is 50 ms

Values of Iᵢ

Short-time protection on Micrologic 3.2 s and 3.3 trip units protects all types of electrical distribution applications against short-circuit current.

• Is definite time
• Has adjustable Isd pickup
• Has fixed short time delay tsd on this trip unit

Set the Isd pickup using the dial face of the 3.2S or 3.3S trip unit. The tsd time delay is fixed and cannot be adjusted.

• The Isd pickup setting value is in multiples of Iᵣ
• The default Isd pickup settings value is 1.5 Iᵣ (minimum dial value)

• Short-time delay ( tsd ) sets the length of time that the circuit breaker will carry an overcurrent above the short-time pickup current level before tripping.  It is adjustable on the 5.0A and 6.0A trip unit and factory set to zero on the 2.0A trip unit.
• The I²t-on / I²t-off option provides improved selectivity with downstream protective devices:
  • With I²t-off selected, fixed time delay is provided.
  • With I²t-on selected inverse time I²t protection is provided up to 10 x Ir.  Above 10 x Ir, fixed time delay is provided.
  • Setting tsd to the 0 setting turns off zone-selective interlocking.
• Short-time protection uses true RMS measurement.

Micrologic Trip Unit Short-Time Delay Values

Other Question/Problem/Cause Statements

• Chiller Main Breaker Trip
• Why is the Chiller Main Breaker trip?
• Why chiller does have bigger breaker size?
• Main Circuit Break Trip?
• High Ambient Temperature
• Chiller has 500A when Electrical Data said 400A
• Chiller Trip during start-up
• Where should the settings be for the Square D circuit breaker?
• How do I set up the circuit breaker?
• Circuit breaker is tripping?
• Schneider Breaker Settings?
• Square D Breaker Settings?
• Schneider Circuit Breaker?
• Suction Temperature too High - CGAM?
• Settings for the Square D Circuit Breaker
• Settings for the Schneider Circuit Breaker
• Schneider Circuit Breaker Settings
• Square D Circuit Breaker Settings

Facts

• Chiller Trip During Start up
• Air-Cooled Chiller (Pueblo) (CGAM 20-130 Ton)
• Air-Cooled Chiller (Pueblo) (RTAC)
• Compressor Chiller (Pueblo) (RTUD 70-200 Ton)
• Water-Cooled Chiller (Pueblo) (RTHD)
• Water-Cooled Chiller (Pueblo) (RTWD)