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Table of Contents:
Five big mistakes you don’t want to make …
When asked questions at my technical seminars, I often ﬁnd they begin with, “Should I do this…” or “Should I do that?” As you might expect, these are always hard questions to answer regardless of the topic, because each individual boater will have different needs and experiences that are unique to his/her situation. However, when it comes to questions regarding the installation of inverters/chargers, my responses apply universally, particularly those that fall into the “should not” category. Some of the content may seem rather obvious, or a bit tongue-in-cheek. I hope I don’t cause shockwaves (yes – all puns intended!), but if you follow the logic presented, hopefully, you’ll quickly get up to speed.
Q: Should I rate my fuse based on the inverter size?
TECH DOCTOR: NEVER rate your fuse according to the rating of the inverter. I can’t tell you how many times I have to re-emphasize and repeat this point. Your fuse is not there there for one primary purpose: to protect the circuit itself. A it’s wired with 4 gauge wire. At a perfectly acceptable load, to protect the inverter, or the electrical load in any circuit. It’s 3,000W inverter with a 350A fuse seems appropriate, unless the wire will burn well before the fuse fails. The fuse is there to protect the wire (or electrical path) from heat, which can cause damage or ﬁre.
Q: Should I put a washer between the cable terminal and the inverter or battery connector?
TECH DOCTOR: NEVER put a washer between the conductor and the connector! All the ground wires in our cars/trucks have those star washers to make a “better electrical connection.” However, that is acceptable in this circumstance because of paint and the low current needs of a 14 gauge wire. On the other hand, when you’re putting (high-resistance) washer between the copper, tin, or brass cable ends and connectors (lower resistance), you create 4/0 welding cable on a 3,000W inverter, and you put a steel an electrical bottleneck that will get extremely hot. I’ve seen tons of inverters in repair with melted insulators around the DC connectors. This is a sure sign that the ﬂat washer, or lock washer, was placed between the connector and the cable. The lock washer, or star washer, is intended to be in direct contact with the bolt head or nut to reduce the chance of loosening.
Q: How do I determine the right cable size?
TECH DOCTOR: NEVER blindly follow the recommended for 3/0 wire for lengths over 5 feet, don’t assume that it cable size, regardless of the installation. If the manual calls includes installations where the battery is 25 feet from the inverter. Voltage-drop calculators are all over the Internet and if you can ensure a voltage drop under 0.25VDC, you’re in and use your math skills to ﬁgure out the proper cable to good shape. Consider the recommendations as a “minimum” eliminate excessive voltage drops. After that, don’t be afraid result of any installation, and voltage-drop management is the key to performance.
Q: Can I install an inverter/charger in the engine room?
TECH DOCTOR: NEVER put your inverter/charger in an engine room or any location containing fuel. Inverter/chargers are ignition sources and are incompatible with combustible fumes. If the only close location is a fuel locker, get bigger cables and move the inverter further away (see cable size paragraph above).
Q: What should I know about neutral and ground connections?