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Discussion Starter #1 (Edited)
I'm trying to determine what size wire and fuse/breaker to use between my house battery and the Blue Sea 12v fuse block. My 12v load circuits are as follows:

1. TV - 2.3 amps
2. Two Rigid scene lights - 1.5 amps total
3. Fantastic Fan - 1.8 amps
4. MaxxAir Fan - 4.2 amps
5. LED 3w Lights, 9 total on three circuits (main, over bed, over counter) - 2.25 amps total
6. Fridge - 5.0 amps
7. Water Pump - 7.0 amps max
8. Two USB iPhone chargers - 2.0 amps?
9. One cigarette type charger (possible occasional use) - ??? amps
10. Composting toilet fan - ??? amps

Everything listed comes to about 19 amps. It could be slightly more if adding the last two items. The distance the wire will run from my battery to the fuse block will be about 6'. I typed it into the BlueSea calculator and it says I need to use #12 wire (12v, 20amps, 2% drop, 90degree, 6' run). Does that sound right? That seems kind of small. I wired my whole van using #12 , maybe I went way overboard.
 

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2014-159 HR in CT
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1) On wiring, "overboard" is good! Just more space for all those electrons to move around in!

2) For your main feeds to a panel, I would put in (3) #12 's in parallel. It's easier wire to work with and terminate, offers extra capacity for not yet discovered accessories you may want to add, and you probably have some extra #12 around.

Just MHO,
ed
 

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2014, 138WB, High Roof, Gas, SW MT
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Hi,
It seems like sum of the loads you list is more 26 amps?

But, I'd use more than that -- you may want to plug a 15 amp device into that lighter socket, or you may want to add a heavier duty 12 volt appliance later. I'd go for at least 50 amps, which could be a #8 wire. Does the info on the BlueSea panel say anything about the max size of the wire/fuse coming into it?

Gary
 

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Discussion Starter #4
-- you may want to plug a 15 amp device into that lighter socket, or you may want to add a heavier duty 12 volt appliance later. I'd go for at least 50 amps, which could be a #8 wire. Does the info on the BlueSea panel say anything about the max size of the wire/fuse coming into it?

Gary
All I could find on the fuse block was no more than 100 amps total and no more than 30 amps for any particular circuit.
 

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Discussion Starter #5
1)
2) For your main feeds to a panel, I would put in (3) [URL=http://www.promasterforum.com/forum/usertag.php?do=list&action=hash&hash=12]#12 [/URL] 's in parallel. It's easier wire to work with and terminate, offers extra capacity for not yet discovered accessories you may want to add, and you probably have some extra [URL=http://www.promasterforum.com/forum/usertag.php?do=list&action=hash&hash=12]#12 [/URL] around.
ed
3 #12 wires in parallel? Would that be to make up three separate wires, all full length and all three going from the battery to the fuse block? I wasn't even aware you could do that. I'm learning as I go.
 

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Another word for amps is current or flow.

If a #12 wire provides a path for 20amps to flow without any overheating, etc., then (2) #12 wires will let 40 amps flow.

If wire is like a pipe, then 2 pipes let twice as much water flow, right?

On some occasions, I have found it easier to get 2 or 3 smaller wires from point to a to point b than 1 big thick wire.

Some of the high power ham radios I have are provided with a power cord that has 2 smaller wires for + and 2 smaller wires for -
 

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If the Blue Sea will take it, stranded #4AGW is available at H-D in custom cut lengths and very cheap. Consider overbuild big time! If red is not available tape each end with red electrical tape to indicate that it is a positive wire.
 

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2015 Promaster 3500 159 Ext gas silver
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I also used a Blue Sea Fuse Block and ended up with #6 stranded cable connections. My Victron 50/100 solar converter and 45 amp PD charger also needed connections so I purchased #6 welding cable from Amazon for all the runs. My high amperage connections to the 460 amp battery pack, 2kw inverter and engine battery link are all 1/0 welding cable. Where crimped lugs are involved it's simpler not to have too many wire sizes even if there is some overkill involved. It's also a lot cheaper to buy bulk length cable.
 
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Discussion Starter #10
Where crimped lugs are involved it's simpler not to have too many wire sizes even if there is some overkill involved. It's also a lot cheaper to buy bulk length cable.
That's how I ended up using all 12 gauge for the individual load wiring. It was cheaper to buy a roll of it than buy smaller quantities of two or three different size wiring.
 

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That's how I ended up using all 12 gauge for the individual load wiring. It was cheaper to buy a roll of it than buy smaller quantities of two or three different size wiring.
El Guapo
I made the same decision for all the regular loads except that I used 14 ga. On my heaviest load which is the water pump at about 4 amps I ran double 14ga although it probably wouldn't have been necessary.
 
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