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DC Disconnect and Over-current Protection
975-0367-01-01
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For safety purposes and to comply with regulations, battery over-current
protection is required. Fuses and disconnects must be sized to protect the wiring in
the system and are required to open before the wire reaches its maximum current
carrying capability.
The National Electrical Code (NEC) in the US requires both over-current
protection and a disconnect switch for residential and commercial electrical
systems. Local electrical codes for other countries may also require this and
should therefore be referred to during such installations. The over-current
protection and a disconnect switch are not supplied as part of the inverter,
however, Xantrex offers a DC rated, ETL Listed, circuit breaker disconnect
module specifically designed to meet NEC compliance. Two amperage ratings are
available: a DC250 (250 amps) and a DC175 (175 amps) in either single or dual
breaker configurations for single- or dual-inverter installations.
Important:
Xantrex™ DC disconnects are not designed to accept doubled (paralleled)
cables which may be required for long cable runs. Also, the plastic red and black covers
on the DC inverter inputs are not designed to accommodate dual cables. If dual cables are
used, the optional
-
TR
CONDUIT BOX
Some installations may not require conduit or a disconnect device, although
over-current protection is still required. Refer to your local electrical codes for the
proper size disconnect device for specific cable diameters. Table 2-5 provides a
guideline for selection of appropriate DC over-current protection based on cable
size used.
Table 2-5 Battery Cable to Maximum Breaker/Fuse Size
Cable Size Required
2
#2 AWG (33.6 mm
)
2
#1/0 AWG (53.5 mm
)
2
#2/0 AWG (67.4 mm
)
2
#4/0 AWG (107 mm
)
2
350 MCM (177 mm
)
a.Table 2-5 is based on installation using no more than three 75°C copper conductors in
a maximum 30°C ambient, and then applying the worst case conditions between the CEC
Part I 2006 Edition, Table 2 and the NEC ANSI/NFPA 2005 Edition, Table 310.16.
b.Based on available Bussman™ JJN series of Class T fuses.
Important:
The NEC allows rounding to the next standard fuse size from the cable
rating ONLY when a matching fuse size is not available, otherwise the correct fuse size
must be used (i.e. 230 amp cable size rounds up to a standard 250 amp size). Cables
enclosed in conduit or raceways have substantially lower continuous current carrying
ability, due to heating factors, than those in free air.
This manual for use by qualified installers only
http://www.wholesalesolar.com/inverters.html
DC conduit box must be used.
Rating
Max. Breaker/Fuse Size
115 amps
125 amps
150 amps
150 amps
175 amps
175 amps (or DC175 breaker)
230 amps
250 amps (or DC250 breaker)
310 amps
350 amps
DC Wiring
a
b
2–9
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