Samlex America PST-30S-24E - Manual (Page 32)

32 | SAMLEX AMERICA INC.
- Lighting circuits - fluorescent: Voltage drop causes a nearly proportional drop in
light output.
- Ac induction motors: These are commonly found in power tools, appliances, well
pumps etc. They exhibit very high surge demands when starting. Significant voltage
drop in these circuits may cause failure to start and possible motor damage.
- PV battery charging circuits: These are critical because voltage drop can cause a dis-
proportionate loss of charge current to charge a battery. A voltage drop greater than
5% can reduce charge current to the battery by a much greater percentage.
Fuse Protection in Battery circuits
A battery is an unlimited source of current. Under short circuit conditions, a battery can
supply thousands of Amperes of current. If there is a short circuit along the length of
the cables that connects the battery to the inverter, thousands of Amperes of current
can flow from the battery to the point of shorting and that section of the wire will be-
come red-hot, the insulation will melt and the cable will ultimately break. This interrup-
tion of very high current will generate a hazardous, high temperature, high-energy arc
with accompanying high-pressure wave that may cause fire, damage nearby objects and
cause injury. To prevent occurrence of hazardous conditions under short circuit condi-
tions, an appropriate fuse should be used in the battery circuit that will limit the cur-
rent, blow in a very short time and quench the arc in a safe manner. for this purpose, UL
Class T fuse or equivalent with Ampere Interrupting Capacity (AIC) of at least 10,000A
should be used (As per UL Standard 248-15). This special purpose current limiting, very
fast acting fuse will blow in less than 8 ms under short circuit conditions. Appropriate
capacity of the above Class T fuse should be installed within 7” of the battery Plus (+)
Terminal. The fuse will require a corresponding fuse holder.
WARninG!
Use of an appropriately sized external fuse as described above is mandatory to
provide safety against fire hazard due to accidental short circuit in the battery
wires. Please note that the DC side fuse(s) inside the unit are designed to pro-
vide protection to the internal components of the inverter. These fuses will NoT
blow if there is a short circuit along the length of wires connecting the battery
and the inverter.
Recommended Sizes of Wires and external Fuses
The following sizes of wires and external fuses are recommended. The distance of 3 ft. /
6 ft. / 10 ft. is the distance between the battery and the inverter. The running length of
routing of the wire should be considered if the wiring run is not straight but circuitous.
The recommended size of wires will limit the voltage drop to 2% of the nominal battery
voltage (0.24V for 12V battery and 0.48V for the 24V battery)
The length of the wire for calculating voltage drop has been taken as 2 times the
distance between the inverter and the battery assuming that 2 lengths of wires (one
seCtIOn 8 | Installation