Quincy Compressor QCV 045, Instruction Book

Page: 51 / 56

Section VIII - Technical data
51
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)).
Maximum allowed current in function of the wire size:
AWG or kcmil Maximum current
10 < 30 A
8 < 50 A
6 < 65 A
4 < 85 A
3 < 100 A
2 < 115 A
1 < 130 A
1/0 < 150 A
2/0 < 175 A
3/0 < 200 A
Calculation method for UL:
 Single supply cables (3 1 PE - configuration (1)):
 Add 25 % to the total current from the tables (see UL 508A 28.3.2: "Capacity shall
have 125 % of the full load current")
 Install the prescribed maximum fuse on each cable

Parallel supply cable (2 x 3 2 PE - configuration (2)):
 Add 25 % to the total current from the tables and divide by 2
 Multiply the capacity of the cables with 0.8 (see UL 508A table 28.1 continued)
 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 25 % to the total current from the tables and divide by √3
 Multiply the capacity of the cables with 0.8 (see UL 508A table 28.1 continued)
 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 the supply cables
 For supply cables larger than AWG8: use maximum allowed capacity
< 100 A: Use AWG8
< 200 A: Use AWG6
< 300 A: Use AWG4
Always check the voltage drop over the cable (less than 5 % of the nominal voltage is
recommended).
Example of supply cable calculation: Itot = 128 A, maximum ambient temperature is 45
°C, recommended fuse = 150 A
 Single supply cables (3 1 PE - configuration (1)):
 I = 128 A + 25 % = 128 x 1.25 = 160 A
 For AWG2/0, the maximum current is 175 A, which is sufficient => use AWG2/0
 Install the prescribed maximum fuse (150 A) on each cable

Parallel supply cable (2 x 3 2 PE - configuration (2)):