In a recent attempt to install a macerator, the run-length of wire and amp-draw require #8 wire. This is pretty hefty stuff, and will not easily pull through to the location. Is there anything in the ABYC, etc which allows for a common-ground type of scenario, where I can pull a heavy wire through to the front of the boat, and terminate all the negatives there rather than pulling them back aft? I would then need a wire-size table which takes that into account. Thanks!
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One ground
I've read that it isn't a good idea to have multiple grounds. The theory is that you can set up a voltage ptential between multiple grounds which will cause damaging electrolysis effecting the engine, shaft, prop, etc... Refer to Nigel Calder's book "Boatowner's Mechanical and Electrical Manual" for a complete understanding. Don
I've read that it isn't a good idea to have multiple grounds. The theory is that you can set up a voltage ptential between multiple grounds which will cause damaging electrolysis effecting the engine, shaft, prop, etc... Refer to Nigel Calder's book "Boatowner's Mechanical and Electrical Manual" for a complete understanding. Don
Certainly
Who knows what the ABYC likes, but you can certainly create a remote bus for grounds. To calculate the wire size, add up the current of all loads using the bus, and go to the wire size table with the length of the ground cable back to the primary ground bus multiplied by 2. Include any additional loads that would be added in the future. Sizing is calculated differently for the +12 side. Each load should be considered separately, if it has a separate cable. Use the length times 2 of the +12 cable to find the correct wire size in the table. I'd use the 3% voltage drop table for this, just to be conservative. That's easy for me to say, but it will cost you some $$ for the bigger wire. Hope that helps. Paul sv Escape Artist h336
Who knows what the ABYC likes, but you can certainly create a remote bus for grounds. To calculate the wire size, add up the current of all loads using the bus, and go to the wire size table with the length of the ground cable back to the primary ground bus multiplied by 2. Include any additional loads that would be added in the future. Sizing is calculated differently for the +12 side. Each load should be considered separately, if it has a separate cable. Use the length times 2 of the +12 cable to find the correct wire size in the table. I'd use the 3% voltage drop table for this, just to be conservative. That's easy for me to say, but it will cost you some $$ for the bigger wire. Hope that helps. Paul sv Escape Artist h336
Watch It
You are confusing ground with the negative side of the DC system. All negative wires should either come back to the negative bus at the battery location or at the power panel location. You should never use your ground system to carry battery current. If you do, you will have a ground system that is actually above ground at some locations. This will start corrosion in your ground system. What this means is that you need to run both cables to the macerator. Sorry about that. Your question may be that you want to run a super negative bus through the boat. While this is unorthodox, it can work. Another way to do this is to mount a new small breaker box in a new location and feed items from it.
You are confusing ground with the negative side of the DC system. All negative wires should either come back to the negative bus at the battery location or at the power panel location. You should never use your ground system to carry battery current. If you do, you will have a ground system that is actually above ground at some locations. This will start corrosion in your ground system. What this means is that you need to run both cables to the macerator. Sorry about that. Your question may be that you want to run a super negative bus through the boat. While this is unorthodox, it can work. Another way to do this is to mount a new small breaker box in a new location and feed items from it.
Be aware of "ground" loops
I understand that your meaning of "ground" is the return path of the 12V circuit, not the green AC wire or the common circuit of the underwater metal. My preference is to run dedicated wires to each 12V appliance. However, a properly-sized 12V negative bus will work. The key is that is must be of adequate size for all loads. I absolutely would not use this bus for the return side of any electronics. Is is possible for appliances (like a motor or refridgerator) to put noise onto the negative bus and for this noise to interfere with proper operation of the electronics. For example, I have known refridgerators to cause a hum or staletto noise in a VHF while transmitting, making the transmission unintelligible. This problem is known as having a ground loop where there is voltage induced into a return wire such that different appliances "see" a return voltage that is not zero volts. In my boat, I established a 12V bus for both positive and negative about 6 feet away from the batteries. The busses were made of copper strips that are 1/4" thick, 1" wide, and 6-8" long. All of my appliance connections bolt to these busses. From the busses to the batteries is a 2/0 sized cable. And I also agree that wire should be sized for a 3% drop for everything if at all possible. This will minimize the annoying lamp dimming when appliances cycle too. Rich
I understand that your meaning of "ground" is the return path of the 12V circuit, not the green AC wire or the common circuit of the underwater metal. My preference is to run dedicated wires to each 12V appliance. However, a properly-sized 12V negative bus will work. The key is that is must be of adequate size for all loads. I absolutely would not use this bus for the return side of any electronics. Is is possible for appliances (like a motor or refridgerator) to put noise onto the negative bus and for this noise to interfere with proper operation of the electronics. For example, I have known refridgerators to cause a hum or staletto noise in a VHF while transmitting, making the transmission unintelligible. This problem is known as having a ground loop where there is voltage induced into a return wire such that different appliances "see" a return voltage that is not zero volts. In my boat, I established a 12V bus for both positive and negative about 6 feet away from the batteries. The busses were made of copper strips that are 1/4" thick, 1" wide, and 6-8" long. All of my appliance connections bolt to these busses. From the busses to the batteries is a 2/0 sized cable. And I also agree that wire should be sized for a 3% drop for everything if at all possible. This will minimize the annoying lamp dimming when appliances cycle too. Rich
Vote for Sub Panel
It would be a good idea to install a sub panel near the main battery switch to run motor loads and other heavy electrical loads. To figure line loss the entire round trip from the positive terminal to the electrical panel and then to the device and back again to the panel and the negative terminal has to be used. A sub panel should be able to shorten this considerably. Additionally, the jumper wires from each bus in the electrical panel should be upgraded. The conductors from the battery to the main panel will probably need to be increased in size also. The larger conductor to the main panel will make it more difficult to open and close for service and the large cable on the incoming terminal may be a bit much for the scres. A sub panel for autopilot, refrigeration, macerator, water pump, etc. would be a good idea.
It would be a good idea to install a sub panel near the main battery switch to run motor loads and other heavy electrical loads. To figure line loss the entire round trip from the positive terminal to the electrical panel and then to the device and back again to the panel and the negative terminal has to be used. A sub panel should be able to shorten this considerably. Additionally, the jumper wires from each bus in the electrical panel should be upgraded. The conductors from the battery to the main panel will probably need to be increased in size also. The larger conductor to the main panel will make it more difficult to open and close for service and the large cable on the incoming terminal may be a bit much for the scres. A sub panel for autopilot, refrigeration, macerator, water pump, etc. would be a good idea.
Thanks all
I *think* I understand all the points made :^) And when I said 'ground' I was speaking in the same sense as with automotive (frame). I will stick with 2 wires for now (this is a Cherubini 30', so no fridge, watermaker, etc), although I made an exception in my mast (conduit full) Cheers, -Keith
I *think* I understand all the points made :^) And when I said 'ground' I was speaking in the same sense as with automotive (frame). I will stick with 2 wires for now (this is a Cherubini 30', so no fridge, watermaker, etc), although I made an exception in my mast (conduit full) Cheers, -Keith
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