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Hi Ed and all:

How to find ratings for breakers/fuses:
Ohm's law: U=R x I  or  P=U x I
U= Voltage
R= Resistance
I = Amps
P= Watt

If we use your landing light as an example:
12volt and 100 watts: P / U = I   = 100 / 12 = 8.33 amps. Its normal to
"over fuse" by ca. 10%.
8,33A + 10%= 9.17A = closest available fuse = 10A

or, lets say you have a electric heated seat, and all you know is that it
operates on 12V: Measure resistance, lets say 0.9ohms:
U / R = I  =  12 / 0.9 = 13.33A + 10%= 14.67A = closest available fuse= 15A.
You could also tell that the heating element is 160 watts : P=U x I  =  12 x
13.33 = 159.96W.

If you know the length of a wire and the amps running trough it, its easy to
find what cable thickness to use.
My system of finding cable thickness is in mm2. (I don't understand the
"gauge" system)
If it's of interest and somebody could supply me with a conversion table
(?gauge to ?mm2), I can convert my table and post it on LML.

Regards

Roy Valvik
Norway

LML website:   http://www.olsusa.com/Users/Mkaye/maillist.html
Builders' Bookstore:   http://www.buildersbooks.com/lancair

Please send your photos and drawings to marvkaye@olsusa.com.