by: Jack Colton
Customer: I'm planning to install the inverter in my car. Why do Wagan power inverter documents specify a battery protection fuse placed within one foot of the positive battery terminal? Is this really necessary?
Answer: Yes. Batteries used to start cars and power inverters store large amounts of energy. A direct short circuit across inverter cables can literally cause wiring to melt and a battery to explode. A fast-acting, non-sparking fuse placed close to the battery ensures personnel protection from harm and can prevent fires and battery explosion.
Customer: But, my car battery starter cable does not have a fuse.
Answer: Vehicle starting batteries are under the hood and ahead of the firewall which provides protection for driver and passengers. All other circuits in the car are protected by non-sparking, sealed, fuses in a fuse block. Similarly, at home, all circuits that feed outlets, switches and appliances have fuses or circuit breakers in a central panel. These are important to prevent electrical fires if wiring or appliances have a short circuits. At home, electric breaker panels are not located where explosive gases are present so circuit breakers are used.
Customer: Why is a non-sparking fuse specified? Can I use a circuit breaker?
Answer: Car batteries are usually flooded batteries that produce explosive and corrosive gases. Further, there are some gasoline fumes in small quantities present under the hood. Anything that sparks can ignite those fumes. Circuit breakers are not usually spark proof. A sealed, non-sparking fuse will not ignite gases if the fuse blows.
Customer: I know that fuses are rated in amps. How many amps does my fuse need to be?
Answer: Fuse amp ratings need to be at least 20% more than the maximum current the fuse is to normally handle. So, if the inverter can draw up to 100 Amps from the battery, the fuse should be rated at least 120 Amps. Of course, the wiring must be heavy enough to handle the current without more than 5% voltage loss.
Customer: I'm also thinking about installing a power inverter on my boat. Are there any special precautions I need to take for my power inverter installation?
Answer: Yes. Power inverters aboard vessels have some special installation requirements. Power inverters are considered to be sparking devices so they may not be located where gasoline, diesel, alcohol, propane or battery gasses are present. These special locations are designated as “No-Spark Areas”. Also, wiring that connects to inverter AC output and DC input must have insulation that is resistant to attack from marine fuels. Battery protection fusing must be no more than eight inches from the positive battery terminal. Of course, a fast-acting, non-sparking fuse must be installed.
Additional inverter installation requirements for vessels are related to the operating environment. All inverters must be operated in cool, dry, dust free and fume free locations. Power inverters certified as having passed UL458 Marine Standards are resistant to direct water sprays and can operate in high humidity areas.