Samlex America SAM-1500C-12 - Manual (Page 15)

12 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 13
important Wiring/cabling information
Although wires and cables are good conductors of electric current, they do have some
resistance, which is directly proportional to the length and inversely proportional to the
thickness (diameter) i.e. resistance increases in thinner and longer wires. Current flowing
through resistance produces heat. Cables and wires are covered with insulating material
that can withstand a specified temperature of the conductor under specified conditions.
To ensure that the insulation is not damaged due to excessive overheating, each wire size
has a maximum allowable current carrying capacity called "Ampacity" which is specified
by NEC Table 31.15 (B) (17). Further, NEC also specifies that wire size should be based on
Ampacity - 1.25 times the rated current flow.
resistance of wires and cables produces another undesirable effect of voltage drop. Volt-
age drop is directly proportional to the resistance and the value of current flow. Voltage
drop produces loss of power in the form of heat. In addition, excessive voltage drop from
the battery to the inverter may prematurely shut down the inverter due to activation of
the Low Input Voltage Protection Circuitry of the inverter (10.5 ± 0.5V). DC cables should
be sized to ensure maximum voltage drop is limited to less than 5%.
effects of low voltage on common electrical loads are given below:
Lighting circuits – incandescent and Quartz/Halogen: Loss in light output because the
bulb not only receives less power, but the cooler filament drops from white-hot towards
red-hot, emitting much less visible light.
Lighting circuits – fluorescent: Voltage drop causes an early proportional drop in
light output.
ac induction motors: These are commonly found in power tools, appliances, etc. They
exhibit very high surge demands when starting. Significant voltage drop in these circuits
may cause failure to start and possible motor damage.
requirement of fuse in Battery connection
A battery is a very large source of current. If there is a short circuit along the length of
the cables that connect 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 cable will overheat,
the insulation will melt and is likely to cause fire. To prevent occurrence of hazardous
conditions under short circuit, fuse with Ampere rating ≥ the maximum continuous cur-
rent drawn by the inverter but ≤ the Ampacity of the connecting cable should be used
in the battery connection. The fuse should be fast acting Class-T or Marine rated battery
fuse Type Mrbf. rating of fuse is shown in Table 4.1 below. The fuse should be installed
as close to the battery Positive terminal as possible, preferably within 7”. Please note that
this fuse is required to protect the cable run from the battery to the inverter against short
circuit. The inverter has its own internal DC side fuse(s) for internal DC side protection.
making Dc Side connections
Recommended cable and fuse sizes for connecting battery are given in Table 4.1.
The maximum current for cable sizing / fuse rating has been considered at 1.25 times
rated continuous current draw at the rated output power.
SECTION 4 | Installation