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 sizing
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 sizing
Hello 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 Hennis
CTR Services
P.O. Box 254
14237 FR 1155
Cassville, MO 65625-0254
417-396-0228
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Posted by: DAN HENNIS <dhennis@centurytel.net>
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