Hello everyone, So I'm attempting to install a new inverter in my boat and it requires that I hook it up to the positive and negative batteries terminals and also has a screw that's supposed to be attached to the "negative DC bus" behind the fuse panel. Well rather than attaching it directly to the batteries, as the batteries are stored outside of the cabin in one of the hatches near the cockpit I'm trying to wire the inverter directly to the backside of the fuse panel where the DC power comes in. I know where the positive cable is on the backside of my fuse panel but I don't know where to hook the negative cable coming off my inverter. I know where the "negative DC bus" is behind my panel but this is where the other grounding wire is suppose to go... and I figured I shouldn't attempt to attach both this wire and the wire that is suppose to go to the negative battery terminal to the same place... or can I do this. I know this other grounding cable that is suppose to go to the negative bus has a more technical name but I can't recall it right now (and I'm not at the boat at the moment to look at it). If anyone can be of any help about how I do the negative power cable to the inverter it would be greatly appreciated... I'm trying to find a way to wire this into the back of the fuse panel. Thanks in advance, -Levin
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Living on 12 Volts
Levin, I'm not going to give a specific answer, it depends on many actors. Worst Marine, and all chandlerys carry "Living on 12 Volts" and it is worth the twenty bucks, or the library. Ask around at your marina, you should find a guy that will show you how his is wired, and knowing THAT works will help. Call Bill on 'Blue Horizon'(on VHF) he has a permanent mooring there in the marina, he's handy and has installed an inverter on his boat.
Levin, I'm not going to give a specific answer, it depends on many actors. Worst Marine, and all chandlerys carry "Living on 12 Volts" and it is worth the twenty bucks, or the library. Ask around at your marina, you should find a guy that will show you how his is wired, and knowing THAT works will help. Call Bill on 'Blue Horizon'(on VHF) he has a permanent mooring there in the marina, he's handy and has installed an inverter on his boat.
Inverter, not charger?
Do we understand that you are wiring just an inverter? And what is the wattage rating? Normally inverters and inverter/chargers are wired next to the battery bank. This is because of the large cables, probably #2 size. You could run long ones but it is expensive and, sometimes, difficult. My own inverter/charger sits right over the batteries. One heavy red cable to a house positive and one heavy black to a house negative. No other wire to the panel. I am looking at my Xantrex(Heart) installation wiring diagram and see no other examples. The concern would be that the wiring from the panel would be undersized for the load. You will probably find #10 wiring on the back of the panel. This might be OK if it is strictly an inverter, depends upon what kind of 110AC appliances you plan to use. Remember that the 12 volts from the battery to the inverter has to come through those small #10 wires. But if also charging then the current could be quite high if the batteries are down when it is turned on. I assume the wire to the "negative bus" is a safety issue. To make sure the inverter case is at the same ground as your panel and appliances. Since that is where you are installing it then yes, both wires would go to the same terminal.
Do we understand that you are wiring just an inverter? And what is the wattage rating? Normally inverters and inverter/chargers are wired next to the battery bank. This is because of the large cables, probably #2 size. You could run long ones but it is expensive and, sometimes, difficult. My own inverter/charger sits right over the batteries. One heavy red cable to a house positive and one heavy black to a house negative. No other wire to the panel. I am looking at my Xantrex(Heart) installation wiring diagram and see no other examples. The concern would be that the wiring from the panel would be undersized for the load. You will probably find #10 wiring on the back of the panel. This might be OK if it is strictly an inverter, depends upon what kind of 110AC appliances you plan to use. Remember that the 12 volts from the battery to the inverter has to come through those small #10 wires. But if also charging then the current could be quite high if the batteries are down when it is turned on. I assume the wire to the "negative bus" is a safety issue. To make sure the inverter case is at the same ground as your panel and appliances. Since that is where you are installing it then yes, both wires would go to the same terminal.
Yep Levin, Ed's right.
We don't know how big your inverter is. Its' capacity dictates cable size. It's very unusual to run the ground to the panel bus. The reason it's not done is that wires become longer and that degrades inverter performance. Find the recommended wire size in your installation manual and keep them as short as possible. And like most things electrical on a boat, success depends on capacity. Batteries too, especially with an inverter, more is better.
We don't know how big your inverter is. Its' capacity dictates cable size. It's very unusual to run the ground to the panel bus. The reason it's not done is that wires become longer and that degrades inverter performance. Find the recommended wire size in your installation manual and keep them as short as possible. And like most things electrical on a boat, success depends on capacity. Batteries too, especially with an inverter, more is better.
Another thing to consider:
All of your DC wiring in and at the panel is probably sized as it should be. If you add an inverter (which can take some serious load) at the DC panel, you are going to upset something. Consider that a 1kw inverter is going to draw more than 85 amps (and probably over 100). Your DC panel isn't rated for anything like that, I suspect. Looking at a user guide for a Xantrex 1kw inverter, I see this Note: Never use a cable longer than 5 feet. (for the DC input wiring) And they call for a minimum of 2AWG wire size and a 150 Amp fuse. Do yourself a favor: Mount the inverter as close to the batteries as you can. The AC wiring is MUCH less a problem, as the voltage is 10 times higher and the current is 1/10 as much. Cheers, Bob s/v X SAIL R 8
All of your DC wiring in and at the panel is probably sized as it should be. If you add an inverter (which can take some serious load) at the DC panel, you are going to upset something. Consider that a 1kw inverter is going to draw more than 85 amps (and probably over 100). Your DC panel isn't rated for anything like that, I suspect. Looking at a user guide for a Xantrex 1kw inverter, I see this Note: Never use a cable longer than 5 feet. (for the DC input wiring) And they call for a minimum of 2AWG wire size and a 150 Amp fuse. Do yourself a favor: Mount the inverter as close to the batteries as you can. The AC wiring is MUCH less a problem, as the voltage is 10 times higher and the current is 1/10 as much. Cheers, Bob s/v X SAIL R 8
Keep cool
I was told once of an inverter placed under the nav station. Close to the switch panel but it charred the wood. They put out a lot of heat and should probably be place outside with the batteries
I was told once of an inverter placed under the nav station. Close to the switch panel but it charred the wood. They put out a lot of heat and should probably be place outside with the batteries
Really Bad Idea
Stop, bad idea. Don't connect inverter to your DC panel. The DC supply cables running from the battery switch to the DC panel has a fuse on one or both (e.g. positive & negative) cables located near the battery switch, probably in the 100 Amp (Beneteau 393) or smaller range. These fuses protect the supply cables, should it be shorted at any point up to the DC panel. The cable and the fuses are not large enough to also support anything but the smallest inverter. E.g. if your DC Panel is drawing 30AMP to support refrigeration, lights, VHF, fans, stereo, etc. then a 90% efficient inverter load over 750 watts (6.3 amps AC) will fry the fuses near the battery switch, even less if the fuses are in a hot engine compartment.
Stop, bad idea. Don't connect inverter to your DC panel. The DC supply cables running from the battery switch to the DC panel has a fuse on one or both (e.g. positive & negative) cables located near the battery switch, probably in the 100 Amp (Beneteau 393) or smaller range. These fuses protect the supply cables, should it be shorted at any point up to the DC panel. The cable and the fuses are not large enough to also support anything but the smallest inverter. E.g. if your DC Panel is drawing 30AMP to support refrigeration, lights, VHF, fans, stereo, etc. then a 90% efficient inverter load over 750 watts (6.3 amps AC) will fry the fuses near the battery switch, even less if the fuses are in a hot engine compartment.
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