Sunny Boy 2500U
Installation and Operator’s Manual
SB2500U-11:NE
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16
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SMA Regelsysteme GmbH
2.3.2 Connection to Electrical Utility Grid
The Sunny Boy must be connected to the grid with 3 cables
•
with two phases (L1) and (L2) and one equipment-grounding conduc-
tor(Protective earth (PE)).
WARNING:
Make sure the main 240 V breaker in the main utility breaker
box is switched OFF before you connect the AC terminal block.
The grid impedance value at the connection point should be as low as possible to
avoid an increase of the AC-voltage to non-permissible values while the Sunny Boy
feeds to the grid. This also results in a higher system efficiency.
EXAMPLE:
The impedance is the sum of the electricity grid impedance at
house distribution and all impedance values of cables and clamping
points.
NB: Impedance values are
•
ca. 0.44
Ω
for a 70 feet (16.4 m) cable with a cross section of
AWG 14
•
ca. 0.40
Ω
for a 100 feet (33 m) cable with a cross section of
AWG 12
•
ca. 0.43
Ω
for a 175 feet (57 m) cable with a cross section of
AWG 10
The total impedance of the grid plus the interconnecting ac cables should be less
than 1.25 Ohm.
