Table 3, Battery Cable To Maximum Breaker/Fuse Size - Xantrex 120 VAC/60 Owner's Manual

Sw series inverter/chargers

Table of Contents

DC DISCONNECT AND OVERCURRENT PROTECTION

For safety and to comply with regulations, battery over-current protection is required. Fuses and

disconnects must be sized to protect the wiring in the system. The fuse or disconnect is required to open

before the wire reaches its maximum current carrying capability.

For residential and commercial electrical systems, the National Electrical Code requires both overcurrent

protection and a disconnect switch. These installation parts are not supplied as part of the inverter.

However, Xantrex offers a DC rated, UL listed, circuit breaker disconnect specifically designed for use

with Trace™ inverters for applications requiring NEC compliance. Two amperage ratings are available - a

DC250 (250 amps) and a DC175 (175 amps). These disconnects are available in a single or double pole

configuration to handle either one or two inverters. The DC disconnect enclosure will accommodate up to

four smaller breakers for use as DC load disconnects, PV array disconnects, etc. and the top is designed

to allow direct connection of up to two Xantrex charge controllers. The Trace™ DC disconnect is not

designed to accept doubled (paralleled) cables which may be required for long cable runs. Also, the plastic

red and black covers on the end of the inverter is not designed to accommodate dual cables. If dual

cables are used, the optional conduit box (SWCB) should be used.

When sizing the DC disconnect, the expected continuous load on the inverter is used to determine the DC

current involved. You must account for the efficiency loss through the inverter (see the POWER VS.

EFFICIENCY section on page 59 in this manual) which increases the DC current draw. Divide the

maximum continuous current draw by the lowest efficiency to determine the DC current, a 25% safety

margin should be included to comply with the code requirements. When a breaker has been selected as

the overcurrent device, tighter sizing may be acceptable since the breaker is more easily reset when

compared to a high current, bolt-in type fuse.

Marine and RV installations typically do not require conduit or a means of disconnection, although

overcurrent protection (fuse) is required. Xantrex offers a fuseblock (TFB) that provides the code required

inverter overcurrent protection for residential, commercial, RV and Marine applications.

TFB's include a fast acting, current limiting class-T fuse to protect your battery, inverter and high

amperage cables from damage by short circuits and overloads. This fuse provides extremely fast

protection when a short circuit occurs. When properly selected, it also has a time delay that allows the

inverter to surge to full power without blowing the fuse. A slide off cover prevents accidental contact with

the fuse's live terminals. For maximum protection, install the fuseblock within 18 inches (45 cm) of the

battery. The fuses are available in 110, 200, 300, and 400 amp sizes.

Use Table 3 below, to determine the proper size disconnect (breaker) or fuse for the battery cables you

are using. These recommendations may not meet all local code or the NEC requirements, consult your

applicable electrical code for more information regarding acceptable fuse and cable sizes.

CABLE SIZE

REQUIRED

# 2 AWG

00 AWG

0000 AWG

*The NEC allows rounding up to the next standard fuse size from the cable rating, i.e. 150-amp cable size

rounds up to a standard 175-amp fuse or breaker size. The term "free air" is defined by the NEC as cabling that

is not enclosed in conduit or a raceway. Cables enclosed in raceways or conduits have substantially lower

continuous current carrying ability due to heating factors.

Contact your Xantrex dealer to order the inverter disconnects/fuses or see the OTHER PRODUCTS

section in this manual on page 129 for more information.

2001 Xantrex Technology, Inc.

5916 - 195th Street N. E.

Arlington, WA 98223