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Author Topic:   Fuse, Wire Size for Bait Tank Installation
andrey320 posted 08-02-2015 11:35 AM ET (US)   Profile for andrey320   Send Email to andrey320  
Hello all.
Seeking some advice on this install. Going with a timer switch to allow me to use a smallish separate battery (18AH AGM deep cycle), rule 360 pump, and a 14 gallon Kodiak tank.
Two questions so far (still in the acquiring parts stage) -
1. What size fuse should I use? The switch says 10, I believe a 2.5 is recommended for the pump.
2. What is the size of the wire my Rule 360 came with? I'm going to buy some cable glands to pass the wires through a Pelican case (holding the battery, fuse and switch) and need to know the size. I guess I can also stick the wire into the cutouts of my wire stripper and see where it fits snugly.

Thank you!

andrey320 posted 08-02-2015 11:58 AM ET (US)     Profile for andrey320  Send Email to andrey320     
Scratch that second question... I'll measure the wire (realizing wire gauge size and insulated wire size are different things)....
jimh posted 08-02-2015 02:30 PM ET (US)     Profile for jimh  Send Email to jimh     
In electrical power distribution, a branch circuit is typically protected by a fuse. The fuse is chosen to protect the conductor of the branch circuit. Typically in power distribution a branch circuit may provide power to several loads, and each load can be protected by its own fuse.

In the circuit under discussion here, there appears to be only one load on the branch circuit, the RULE 360 pump's electric motor. The branch circuit can therefore be protected by a single fuse, located near the source of the power feeding the branch circuit, and sized according to the current needed by the pump motor.

andrey320 posted 08-02-2015 04:59 PM ET (US)     Profile for andrey320  Send Email to andrey320     
Thank you Jim.
padrefigure posted 08-04-2015 09:36 AM ET (US)     Profile for padrefigure  Send Email to padrefigure     
You should be able to find the wire size marked on the leads of the pump. Unless it is a very high capacity, it is probably 18AWG. Also, be careful sealing a battery inside an airtight container. Part of the chemical process that produces electricity releases Hydrogen gas which is explosive if concentrated. There are some sealed batteries approved for this type of installation but they are typically used in emergency lighting installations. A normal lead acid or AGM battery will probably be a problem.
n1ywb posted 08-04-2015 11:40 AM ET (US)     Profile for n1ywb  Send Email to n1ywb     
Here's a handy table which gives maximum current for various size wires for both chassis and distribution applications. I would go by the power distribution table in this case. Chassis wiring implies a very short length, like inches.
jimh posted 08-04-2015 01:30 PM ET (US)     Profile for jimh  Send Email to jimh     
A much handier table is given in the discussion about wire conductor size for power distribution. See

Wire Conductor Size for Power Distribution

In designing power distribution for 12-Volt circuits, one must always consider the length of the conductor due to the requirement to limit voltage drop to a small percentage of the supply voltage. In a 12-Volt system, a drop of 3-percent means only a drop of 0.03 x 12 = 0.36-Volt is allowed. The conductor size must be chosen to keep the voltage drop within this tolerance. There is a very simple rule of thumb that I have developed for sizing conductors for distribution of power:

HEBERT'S RULE--The maximum length (in feet) of a conductor that can be used for two-way power distribution is equal to the system voltage (in Volts) if the current is to be at the maxim rated current of that conductor for power distribution as figured according to the 1-Ampere/700-circular mils rating system.

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