Ambient temperature
Cable section
(AWG or kcmil)
30 °C (86 °F)
40 °C (104 °F)
45 °C (113 °F)
50 °C (122 °F)
55 °C (131 °F)
2/0
< 175 A
< 154 A
< 144 A
< 131 A
< 114 A
3/0
< 200 A
< 176 A
< 164 A
< 150 A
< 130 A
4/0
< 230 A
< 202 A
< 189 A
< 173 A
< 150 A
Calculation method for CSA
• Single supply cables (3 PE - configuration (1)):
• Add 10 % to the total compressor current (I
tot
Pack or I
tot
FF from the tables)
• Install the prescribed fuse on each cable
• Parallel supply cable (2 x 3 2 PE - configuration (2)):
• Add 10 % to the total compressor current (I
tot
Pack or I
tot
FF from the tables) and divide by 2
• Multiply the ampacity of the cables with 0.8 (see CEC Part 1 table 5C)
• Install fuses of half the size of the recommended maximum fuse size on each cable.
• When using 2 x 3 phase + 2 PE as in (3):
• Add 10 % to the total compressor current (I
tot
Pack or I
tot
FF from the tables) and divide by √3
• Multiply the ampacity of the cables with 0.8 (see CEC Part 1 table 5C)
• Fuse size: the recommended maximum fuse size divided by √3 on each cable.
• Size PE cable:
• For supply cables up to AWG8: same size as supply cables
• For supply cables larger than AWG8: use maximum allowed ampacity of the selected supply cables
and compare with value in table below (see CEC Part 1 table 17)
< 100 A: use AWG8
< 200 A: use AWG6
< 400 A: use AWG3
Always check the voltage drop over the cable (less than 5 % of the nominal voltage is recommended).
Example of supply cable calculation:
I
tot
= 128 A, maximum ambient temperature is 45 °C, recommended
fuse = 150 A
• Single supply cables (3 PE - configuration (1)):
• I = 128 A + 10 % = 128 x 1.1 = 140.8 A
• AWG2/0 allows a maximum current of 144 A at 45 °C (113 °F), which is sufficient.
• Fuses: 150 A
• Parallel supply cables (2 x 3 2 PE - configuration (2)):
• I = (128 A + 10 %)/2 = (128 x 1.1)/2 = 70.4 A
• For AWG3 at 45 °C (113 °F), the maximum current is 82 A x 0.8 = 65.6 A, which is insufficient. For
an AWG2, the maximum current is 94 x 0.8 = 75.2 A. So 2 parallel cables of 3 x AWG2 + AWG8 are
sufficient.
• Install fuses of 80 A instead of 150 A.
Fuse size is the max. fuse size in order to protect the motor against short circuit. For CSA fuse HRC form II,
for UL fuse class RK5.
Cable sizing according UL/cUL
Calculation method according UL 508A, table 28.1 column 5: allowable ampacities of insulated copper
conductors (75 °C (167 °F)).
Instruction book
86
2920 7101 21
Summary of Contents for QGS 40
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