Settings for the Square D Circuit Breaker

Issue:

Settings for the Square D Circuit Breaker

Settings for the Schneider Circuit Breaker

Resolution:

The three dials: The Long Time Protection (I_r), The Long Time Protection trip time (t_r), The instantaneous trip (I_i), needs to be adjusted during chiller start-up or breaker replacement to prevent nuisance trip.

Example 1:

Chiller (RTAC) was shipped with Square-D-LG-600A breaker with following settings, I_r = 600; t_r = 0.5; I_i = 1.5Ir

-          The Long Time protection (I_r) : 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*I_r =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

Example 2:

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

-          The Long Time protection (I_r) 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*I_r =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.

Example 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 1.5I_r (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:

1.       Dial description see below.

2.       Additional information, click here

.

Notes:

Dials Description

The trip unit I_n value (A) is visible on the front face of the circuit breaker. This is the maximum current that the trip unit can carry continuously with the contacts closed without temperature rise exceeding UL requirements (104 ^oF)

The trip unit face contains three dials for setting protection functions.

Long-time protection (Ir):

Protects equipment against overloads

Is standard on all distribution trip units

Uses true rms measurement

Long-time delay (tr):

Adjust time delay for long-time protection

Is standard on 3.2 and 3.3 trip units

Instantaneous protection (Ii):

Protects equipment against solid short circuits

Is standard on all distribution trip units

Uses true rms measurement

Protection Type

A.     For motor trip units, the dials are:

         for setting full load amp and

         Short-time protection.

Short-time protection (Isd):

Protects equipment against impedance short circuits

Is standard on 3.2S and 3.3S trip units

Uses true rms measurement

Full load amp protection (FLA):

Protects equipment against overloads

Is standard on all motor trip units

Provides setting for trip class

Uses true rms measurement

B.      For distribution trip units, the dials are:

         setting long-time Protection

         Setting long-time Delay, and

         instantaneous protection, depending on the trip unit

Long-time Protection (Ir):

Protect equipment against overload and it is I²t  IDMT ( Inverse Definite Minimum Time).

It is set with the I_r pickup and the t_r trip time delay dials.

The Default I_r pickup setting value is the maximum dial position I_n

The long-time protection tripping range is 1.05-1.20 I_r

Long-time Delay (tr):

Time delay (t_r) setting: Default value is 0.5, that is, 0.5 seconds at 6 I_r

                For 60 Hz frequency  1 cycle = 1/60 = 0.01666 sec, then 0.5 sec correspond to  30 cycles

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Instantaneous Protection (I_i)

-          To set the I_i pickup use the I_i dial

-          The I_i pickup setting is in multiples of I_n

-          Default Ii pickup setting value is 1.5 I_n. Use 4  6 I_r

-          Accuracy range is +/- 10%

-          The Hold time is 10 ms

-          he maximum breaking time is 50 ms

Short Time Protection:

Short-Time Protection (Isd)

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 I_sd pickup

-          Has fixed short time delay t_sd on this trip unit

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

-          The I_sd pickup setting value is in multiples of I_r

-          The default I_sd pickup settings value is 1.5 I_r (minimum dial value)

Short-Time Protection (tsd)

• 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.

Ground Fault Protection

Equipment ground-fault protection protects the conductors against overheating and faults from ground-fault currents ( ≤ 1200 A ).

• Ground Fault  ( Ig )
  • Ground-fault pickup ( Ig ) (A) sets ground current level where circuit breaker will trip after the preset time delay.
  • A, B, C, D, E, F, G, H, J
• Ground Fault ( tg )
  • Ground-fault delay ( tg ) (B) sets the length of time that the circuit breaker will carry a ground-fault current above the ground-fault pickup current level before tripping.
  • Setting the ground-fault delay ( tg ) to the 0 setting turns off zone- selective interlocking.
  • ON - 0.1, 0.2, 0.3, 0.4
  • OFF - 0.4 0.3, 0.2, 0.1, 0

Changes:

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)

Document Identifier: DOC-107856