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ISW Inverter 700-4000: DC Wiring
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DC Wiring Instructions 




The following points must be observed for the DC Wiring:


• The DC positive and negative cables connected to the GP-ISW from the battery bank should be linked together with zip ties or electrical tape every 6”. This helps to reduce radio frequency interference and reduces the effects of inductance both of which improve the Inverter waveform and reduces the wear of the Inverters filter capacitors.


• To ensure optimum Inverter performance the number of connections between the battery bank and the GP-ISW unit should be minimized except from the over-current and battery disconnect devices. All additional connection points will cause extra voltage drops.


• The Battery bank voltage must match the DC voltage required by the GP-ISW, which is 12V or 24V (note that the Inverter is either 12V or 24V, and is not switchable.


• All DC cable wire terminations should use a crimped and sealed copper ring terminal lugs.


• Make sure all cables have a smooth bend radius and no kinks are present.


• Colour code all DC Cables coming to / from the battery bank. Use coloured electrical tape or heat shrink tubing. Red for positive (+), Black for negative (-) and Green for DC ground.


DC Wiring Sizing


The distance between the battery bank and the GP-ISW should be as short as possible to achieve maximum efficiency and to reduce fire hazards. The size of the cable should be thick enough to limit the voltage drop to less than 2% when carrying the maximum input current to prevent frequent low-input voltage warnings and shutdown. Only use high quality copper wire.


For greater efficiency, the cables should be as short as possible. The combined cable length should be no more than 10ft (3m). Keeping your wire runs as short as possible helps to prevent: low voltage shutdowns and nuisance tripping of the DC breaker because of increased current draw. The table below shows the recommended DC cable size, fuses/circuit breakers and DC grounding cable sizes for the GP-ISW (Note: these values are correct for cables in free air, not conduit)


Model Wire AWG Inline Fuse / Circuit Breaker
GP-ISW700-12 #6 F-110A
GP-ISW700-24 #10 F-110A
GP-ISW1000-12 #4 F-110A
GP-ISW1000-24 #8 F-110A
GP-ISW1500-12 #2 F-200A
GP-ISW1500-24 #6 F-200A
GP-ISW2000-12 #2/0 F-300A
GP-ISW2000-24 #4 F-200A
GP-ISW3000-12 #4/0 F-400A
GP-ISW3000-24 #2 F-300A
GP-ISW4000-24 #2/0 F-400A


DC Overcurrent Protection & DC Disconnect


Batteries are capable of providing very large currents in case of a short circuit, if this occurs with no DC overcurrent protection, it will result in overheating and melting of the cables and possibly serious injury and/or fire.


DC overcurrent protection is not included with the GP-ISW Inverters. It must be installed between the Inverter and battery bank for safety reasons and to comply with code regulations.


The fuse should be as close to the positive battery terminal as possible. Use Bussmann ANN Class T series fuses (will also require Fuse Block 4164) or equivalent. Ideally the fuse/circuit breaker should be installed within 18” (45cm of the battery). The fuse required for DC Cable lengths up to 10ft is detailed in the above table.


In all installations a battery disconnect switch is required, if you install a circuit breaker for overcurrent protection this will suffice as a disconnect switch. If you install a fuse for overcurrent protection then a separate disconnect switch will need to be installed.


Preparing the DC Cables


Go Power! supplies 2 ring lugs with the GP-ISW which can be used for the Inverter end of the DC Cables. Source the correct ring terminals for the batteries you are using.


• Cut the negative and positive cables to the required length.


• Strip off enough insulation so you can install the ring lugs provided.


• Use the correct crimp connector to install the ring lugs.


• Attach the connectors to both ends of both cables. Make sure no stray wire strands protrude from the connectors.


DC Cable Connections


When installing the battery cable ring lug onto the GP-ISW DC terminal and the battery post - do not put anything between the ring lug and the metal surface. Incorrectly installed hardware causes a high resistance connection which could lead to poor Inverter/Charger performance and may melt the cable and terminal connections. Tighten the terminal connections securely (torque to 9 – 10 ft-lbs, 11.7 – 13 Nm) and periodically check the connections to make sure they remain tight and secure.


To help prevent seizing and corrosion around the terminals the use of an anti-seize lubricant is highly recommended. Apply the antioxidant grease or spray after all the connections are made and tightened.


Wiring the Inverter to the Batteries


WARNING: Lethal currents will be present if the positive and negative cables attached to the battery bank touch each other. During the installation and wiring process, ensure the cable ends are insulated or covered to prevent shorting the cables.


WARNING: DO NOT connect the DC Wires from the battery bank to the GP-ISW until all the DC and AC wiring is complete and the AC overcurrent protection has been installed.


The GP-ISW comes in 12V or 24V versions. Make sure the battery bank is wired in series, parallel, or series-parallel to match the voltage of your inverter. The interconnecting wires between the individual batteries must be sized and rated exactly the same as those used between the battery bank and Inverter.


To ensure the best performance from your Inverter system, batteries should be the same size, type, rating and age. Do not use old or untested batteries.


DC Positive and Negative Wires:


• Connect the negative cable from the battery bank negative terminal to the Inverters negative terminal. Mount the DC circuit breaker or fuse assembly and leave open (no power to the GP-ISW). Connect the positive cables from the circuit breaker / fuse to the battery bank and to the Inverters positive terminal (Note: DC circuit breaker and fuse not included).


• Ensure the DC wire connections are flush on the surface of the DC terminals and the hardware used to hold these connections are stacked correctly. Verify all DC connections are secured tightly.


• Attach the red and black terminal covers over the Inverters DC connectors and secure them in place with the supplied screws.


DC Grounding


To protect against electrical shock hazards the GP-ISW metal chassis must be connected to the DC grounding system. The DC grounding system is sometimes referred to as the Earth ground or another designated ground. For example on an RV, the metal frame of the RV is designated as the negative DC ground / RV ground.


The DC ground wire connection on the GP-ISW is used to connect the exposed chassis of the Inverter to the DC grounding system. Use copper wire that is either bare or provided with green insulation. The size of this conductor should be coordinated with the size of the overcurrent devices used.


DC grounding involves proper grounding of the negative of the battery, the DC panel and the DC side of the GP-ISW. The DC panel is normally used to connect the batteries and distribute DC power to the Inverter and to the other DC loads.


A common earth ground should be used to bond the Inverter, negative bus bar and the negative battery terminal. All connections must be tight against bare metal. Use star washers to penetrate paint and corrosion.


Products covered in this article: GP-ISW-700, GP-ISW-1000, GP-ISW-1500, GP-ISW-2000, GP-ISW-3000, GP-ISW-4000

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