[C38] Wiring Question

[Les]

Hi, Steve, 
	The master switch on the power panel routes the starting current to the
engine.  Peak this is about 300A.  
	I think I used #2 for that run from the batteries to the switch and
from the switch back to the engine.  If you have the 12V Bible, they
have some nice calculations in there for that.

	The rest of your calculations seem OK.  I am running 12ga for the
lighting when I redo mine, and should be quite sufficient for the runs
which average about 18' one way.  I would also caution you to use only
marine grade wire, because standard copper will fail in short order with
corrosion eating it away at each connection.  Avoid those riveted 3x
terminal thingies like the plague.  They invariably corrode and cause
poor connections.

	The reefer might like a 1% drop, because each bit of drop to a
motorized device will cause current to go up approximately 2% to sustain
the load.  This is rule of thumb, but you can look it up in some of the
books on electrical wiring if you want precise numbers.

	Also use the terminals that heatshrink with heat glue to seal the
connections.  It will save you beaucoup problems later.

Regards,
Les H
On Wed, 2008-05-14 at 00:07 -0700, Steve Smolinske wrote:
> I am getting ready to replace some of my wiring and my electrical
> panels.  I have been drawing up my schematics and would love some
> input on my calculations and assumptions.  I have based my assumptions
> on an all night sailing scenario with continous use of systems that
> would quickly draw down my batteries but conservation is another topic
> at this time Im more interested in determining proper wire size for
> peak usage.   Ive assumed that I would be using:  3 cabin lights (4.5
> amps), Running Lights (2.5 amps) VHF (2 amps), Depth and Knot (2
> amps), Wind (2 amps), Auto Pilot (1 Amp) Radar (8 amps) GPS (3 amps)
> Heater (8 amps) and Refrigeration (5 amps) for a total of 38 Amps
> multiplied by postive and negative wire run length of 15 feet (Battery
> Cable to the batt switch then from there AWG 6-8 to the pos. bus and
> from the neg. bus back to the battery) which equals 570 Famps.  Based
> on the wire charts for a 3% drop this puts me in the 6-8 AWG wire size
> to and from the batteries.   Any comments on any of these numbers is
> greatly appreciated.   Refrigeration, Heater and lights are  variables
> calculated on the high side just to be safe.   
>  
> Thanks all, 
>  
> Steve
> Peregrine #312
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