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Author Topic:   Fuse Size
cwolf posted 08-11-2009 01:55 PM ET (US)   Profile for cwolf   Send Email to cwolf  
I have a bait tank that utilizes two bilge pumps and I have them both wired to one circuit switch. One pump draws 2.5 amps and the other draws 1.5 amps. I'm not really sure what size fuse to use at the switch. I've been using a 5 amp assuming that the combined load is just shy of that. Does this sound correct?
davej14 posted 08-11-2009 02:44 PM ET (US)     Profile for davej14  Send Email to davej14     
The fuse should be sized to protect the smallest gauge wire in the circuit in the event of a short circuit.
Bella con23 posted 08-11-2009 03:18 PM ET (US)     Profile for Bella con23  Send Email to Bella con23     
Well put!
jimh posted 08-12-2009 08:21 AM ET (US)     Profile for jimh  Send Email to jimh     
In a branch circuit with two loads whose total current demand will be 4-amperes, a fuse rated at 5-amperes is a good choice.

The purpose of fusing the branch circuit is to prevent damage in the event of an overload current on that branch circuit. In the case of this particular circuit, we can assume it is on a small boat. Regulations require that all wiring on a boat be done with a wire of a minimum of 16-AWG. The current carrying capacity of a 16-AWG conductor is far in excess of 5-amperes. Thus using a fuse of 5-amperes protects the conductor against any current overload, as well as protecting the devices.

cwolf posted 08-12-2009 02:16 PM ET (US)     Profile for cwolf  Send Email to cwolf     
Thank you Jim for the detailed info.

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