From each separate system to the bus bar, is normally the largest size just for that individual system. You did not mention what you will be grounding to: dyna-plate, boat shaft, or other path to earth ground. That wire size should be the largest for all systems.
In a boat with a mechanical engine, that is normally the 12/24 volt systems ground. Which is earthed via the engine block via the shaft. Which is normally the largest gauge anyways do to being the lowest voltage, highest amperage circuits on a normal boat.
On an electric boats that may not be the case. So first you need to understand what is the lowest resistance path to earth ground, that is also correctly sized to handle the combined grounding needs of all systems that are connect to the grounding system. This assumes none of those systems are floating systems, and have no earth ground by design and then should be heavily insulated, with all devices attached to that system electrically isolated. So if you chose to float your 48 volt traction pack, then for example make sure your battery charger connected to mains power has isolated outputs. (normally this only apply to fairly high-end and specialty chargers.)
So the first thing you need to do is identify your path to earth ground. If you removed the old engine, you may no longer have one. And will need to create a new properly sized earth ground.
On Jan 26, 2019, at 6:00 AM, Chris Hudson clh5_98@yahoo.com [electricboats] <electricboats@yahoogroups.com> wrote:
Brian,
Even though not considered high voltage, some people keep their 48V system ungrounded. I think this is addressed in the high voltage standard TE-30, although I've never seen it.ChrisSent from myPhone
On Jan 25, 2019, at 21:27, DAN HENNIS dhennis@centurytel.net [electricboats] <electricboats@yahoogroups.com> wrote:I don"t do ABYC very well yet, but I believe the NEC wants your first choice. Think of it logically, if your supply is say 15 amps, then use the size for that supply. Each supply gets a wire to the buss. It does no additional good to put #2 for a ground when a 12 is the supply size. (IMHO)Dan----- Original Message -----
From: kd5crs@gmail.com [electricboats] <electricboats@yahoogroups.com>
To: electricboats@yahoogroups.com
Sent: Mon, 21 Jan 2019 11:45:35 -0500 (EST)
Subject: [Electric Boats] Ground wire sizingHello all, I have a sanity-check question to make sure I'm interpreting ABYC correctly for my electric boat conversion.I have 3 electrical systems onboard:1. Shore power, 120VAC 30A, dock only, no inverters. 10AWG from inlet to main panel. Branch circuits (all 15A breakers) are 12AWG.2. 48V electric motor, max amperage 120A. 2AWG from pack to motor.3. 12V accessory power... Actual max amperage is very low (just LED running lights and a radio), but I'm sizing the wires from the battery to the DC panel for the max panel amps, so I'm using 4AWG from battery to panel. Branch circuits are 16AWG.My plan is to use a bus bar (probably the Blue Sea MaxiBus 250A 4 post) as the common grounding point.I'm looking at ABYC E-9 (13) figure 15, DC NEGATIVE SYSTEM - DC GROUNDING SYSTEM. My takeaway here is that each system should using a grounding wire the same size as its biggest wire size. So the Shore power panel to ground should be 10AWG, the 48V battery to ground should be 2AWG, and the 12V battery to ground should be 4AWG. However, the alternate interpretation is that all wires should be the largest size, so all three need to be 2AWG.So which way is right: each system uses the size of its largest conductor (10, 2, and 4, Dr Pepper time), or every system uses the size of the largest conductor (2AWG).Thanks,Brian
--Dan HennisCTR ServicesP.O.. Box 25414237 FR 1155Cassville, MO 65625-0254417-396-0228
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