SMA SC 250U - Manual (Page 32)

6 Electrical connection SMA America, LLC
32 DISU_SCUS-IA-IUS111711 Installation Guide
6.2 Cable requirements
6.2.1 Cable requirements for DC, AC and PE connection
☐ Connect all cable to the Disconnect Unit using copper or aluminium conductors that are suitable
for temperatures of +194 °F (+90 °C) and in accordiance with National Electrical Code
®
ANSI/NFPA 70.
☐ Use the screw terminal or the screws included in scope of delivery for mounting cable lugs only.
Cable lugs have to be UL listed compression lugs with two securement holes (
1
/
2
in. (13 mm)
in diameter) and a distance between the holes of 1
3
⁄
4
in. (44 mm). Both holes have to be
utilized in installation. The width of the lugs has to exceed the washer diameter of 1
1
⁄
4
in.
(32 mm) to ensure defined torque values listed below.
The screw terminals can be connected with 1 or 2 conductors each.
☐ For individual cable sizing refer to article National Electrical Code
®
310.
Screw terminals are pre-mounted upon delivery. If they have to be fixed again on the copper busbar,
use a torque of 27.5 ft.-lb. (37 Nm).
6.2.2 Additional cable requirements for DC connection
• Use the screw terminals or cable lugs to connect DC cables to the DC load break switch as
described in section 6.3.2 and 6.3.3.
• Connect 2 conductors per input terminal maximum.
• The DC inputs are isolated from the enclosure and the system grounding. If required by section
250 of the National Electrical Code
®
, ANSI/NFPA 70, the installer is responsible for this
grounding.
8"3/*/(
Risk of fire
Caused by mix-up of DC and AC cables during installation.
• To reduce the risk of fire, flag all DC cables with home run numbers and AC cables with phase
designations by appropriate labels prior to installation to avoid the risk of mix-up.
Connection method Cable size Torque
Cable fixing in screw terminal 4 AWG … 600 kcmil
(25 mm² … 304 mm²) 41.5 ft.-lb. (56.5 Nm)
Cable lug, aluminum on copper
busbar 4 AWG … 800 kcmil
(25 mm² … 405 mm²) 27.5 ft.-lb. (37 Nm)
Cable lug, copper on copper
busbar 4 AWG … 800 kcmil
(25 mm² … 405 mm²) 44 ft.-lb. (60 Nm)