Fuse Vs Breaker

[oakleyb]

I'm looking into replacing my distribution panels with circuit breakers but i'm confused, some of my current items only have 1amp fuses but many of the supplied panels come with 5\10\15 etc. The cost of the lower rated breakers is extreme. How do people use breakers with speed \ depth etc ?

 

[pmagowan]

They are to protect the wire so rate them accordingly. I put all the low power instruments on one breaker anyway. Each instrument should have its own protection for its internal wiring.

 

[oakleyb]

They are to protect the wire so rate them accordingly. I put all the low power instruments on one breaker anyway. Each instrument should have its own protection for its internal wiring.

Thanks for the reply, are you saying each item should have an inline fuse as well ?

 

[pmagowan]

Thanks for the reply, are you saying each item should have an inline fuse as well ?

Read the instructions, most will have their own internal protection unless they specifically say they need protected with a fuse. I am not sure modern ones are allowed to be sold without adequate protection. Your breaker is for your wiring and should be rated to protect it. That is my understanding.

 

[William_H]

As said the fuse/cb is there primarily to protect the wire from getting hot /melting/burning in the case of excess current from a short circuit. Hence fuses are usually rated to the size of the wire but also to the max current draw of the service. Now low current instruments provide a bit of a conundrum. You could use very light wire for the supply in which case you should use an appropriate sized fuse (1 amp). However on boats we mostly use much heavier wire simply for rubustness in the face of harsh environment corrosion etc.
So most likely you will have heavier wire OK for smallest CB (5 amp). This will not protect the equipment if there is an internal failure (short) with high current. It may have an internal fuse all good, however, if not, most instruments/electronics if you got an internal short will require replacement anyway so who cares if there is a lot of charcoal inside due to a 5amp breaker and heavy supply wire. So in the end you must decide just how much safety you need. I would use 5amp breaker (Ok for many instruments) and leave it at that. good luck olewill

 

[Jim@sea]

I replaced the original equipment switch panel (1984) on my boat (deck light,cabin,masthead, nav lights) with an identical modern switch panel which had circuit breakers, and I was not impressed with the Chinese copy, so as I am replacing all the external stuff which was not original equipment, (VHF, Log, Depth,Stereo etc) I have basically made a separate wiring loom, with a positive wire going to a cut off switch, then to a 6 way "glass" fuse box then with 6 cables out, and with the negative going to a Buz-Bar and 6 cables going out, the lot cost about £40, OK it took a bit of time to do it but I prefer glass fuses as they are as cheap as chips.
I also used the brilliant rubber sleeving which you put on the end of a connection and shrink it with a heat gun, just helps to make the connection more secure.