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DC earthing wire for off-grid cabin

Jet

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Jun 22, 2021
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Some background: I have a small solar cabin. The cabins electricity runs off a 600 amp hour 24 volt battery. The main battery cables are 4/0 with a 400 amp fuse. The 24V inverters are equipment grounded to Victron negative bus bar using 2/0. (The inverters also have 2/0 conductors). I bought 2/0 because my original single inverter plan was going to use it as the main battery cable. While the 2/0 wire maybe overkill. I didn't like the idea of putting a 250 or 300 amp fuse on 1/0. The cabin floor sits about 2 feet above the ground.

What size should the grounding wire that runs from the lynx distributor to the grounding rod or copper pipe buried in the ground be? Some people say it should be one gauge smaller than the main battery cable. 3/0 would be huge and inflexible unless I use welding wire. I'm afraid the welding wire would corrode. What do other people do? Do you use normal 4 guage air copper grounding wire? Something larger? Thanks for All your suggestions and Happy New Year!
 
Some background: I have a small solar cabin. The cabins electricity runs off a 600 amp hour 24 volt battery. The main battery cables are 4/0 with a 400 amp fuse. The 24V inverters are equipment grounded to Victron negative bus bar using 2/0. (The inverters also have 2/0 conductors). I bought 2/0 because my original single inverter plan was going to use it as the main battery cable. While the 2/0 wire maybe overkill. I didn't like the idea of putting a 250 or 300 amp fuse on 1/0. The cabin floor sits about 2 feet above the ground.

What size should the grounding wire that runs from the lynx distributor to the grounding rod or copper pipe buried in the ground be? Some people say it should be one gauge smaller than the main battery cable. 3/0 would be huge and inflexible unless I use welding wire. I'm afraid the welding wire would corrode. What do other people do? Do you use normal 4 guage air copper grounding wire? Something larger? Thanks for All your suggestions and Happy New Year!
wire sizing is based on the maximum potential current load over a given distance and temperature. Unfortunately the values you provided do not have enough information to figure out the proper wiring size. Are you only asking about DC or also AC?
 
wire sizing is based on the maximum potential current load over a given distance and temperature. Unfortunately the values you provided do not have enough information to figure out the proper wiring size. Are you only asking about DC or also AC?
I'm asking about grounding DC to Earth. I know some people don't do that but I think you're supposed to. Someone had suggested before connecting the DC Earth to the panels equipment ground. I felt nervous about connecting the two systems there.

If the DC and AC Earth grounding attached to the same grounding stake. Would that be considered a ground loop because the inverter case ground is attached to the Lynx Distributor negative bus bar and the negative bus bar is grounded to the grounding stake and the AC ground is also grounded to the grounding stake. The AC grounding wire runs to the AC panel. Inverters are also connected to the AC panel through the AC supply wire. I realize that usually there wouldn't be current passing through the case and the transformers do separate. The AC and DC somewhat.

Also the battery is 24v 600ah lithium iron phosphate
 
This is the table from the NEC for the grounding wire size. Or you can search for "NEC table 250.66" which seems to apply.

Cool thanks. Do you think 3/0 would be heavy enough for a battery cable for two 24V Victron multi-Plus. Fused with a 350 amp fuse? I haven't actually bought the 4/0 wire and only have a 300 amp class-t fuse now. I was talking in terms of what I was planning on getting. I am building the cabin and working on the electrical right now though.
 
What I've read is that the conventional wisdom is that the battery should NOT be grounded to the earth. DC equipment though, the charge controller for example, should be grounded, but is grounded to the main AC/DC junction bussbar that all other grounding elements are bonded to.

BTW, for my own system, I've followed Midnight Solar's diagrams for DC/AC grounding. It does NOT show grounding to the battery.
 
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