How Do I Size Breakers and Fuses for a Given Load?
Transcript is auto-generated.
hi youtubers jeff cote here with uh ask pys our little series where you the boater asked us the pros about questions about electrical and electronics so i've got a question from chip a fellow boater chip asks how do i size breakers or fuses for a given load well that's a short and sweet question that could have a really long answer so i'm going to try to keep it brief because i've done videos that are 45 minutes i'm fusing and i don't want to lose all of you just simply going to lose it you're going to go on another channel so we're going to keep it simple so all right first thing you got to remember is that circuit breakers can be thermal there can be fuses but it's a way to protect both the wire right from whatever source it is it could be from ac which is shore power or it could be from a generator it can be from a battery so it depends ac power is shore and generator or dc is your batteries and so what you're trying to do when you're putting circuit protection is you're protecting both the wire and the appliance or you could have two fuses for each you should have a fuse just for the wire and you could have another fuse for the appliance so you're going to want to make sure that your fuse is especially for the wire is going to protect and will never if the wires ever overloaded the fuse will trip so you know if you've got for example common wire size is a gauge 10 wire size okay the gauge 10 wire size is commonly used for ac 30 amp circuits you can actually put a 30 amp fuse on a number 10 wire and that's fine the wire can handle 30 amps but you would never want to put a 45 amp fuse or 50 amp fuse on a number 10 wire because now the wire is going to be the fuse right if you over size a fuse you're defeating the purpose of the fuse altogether we just had it for instance just recently we had a client um they had a blower an engine blower and their blower specified seven point amp fuse on that boat they installed a 10 amp fuse thinking a fuse is a fuse well fuse is not a fuse right a tire is not a tire a home is not a home they all come in different sizes and you've got to use and this is so critical so we had our technician on that boat so remember blower fuse with 10 amps but yet the manufacturer wants that 1.5 amps literally no joke the blower was turned on my technician was in the engine bay the blower was on fire smoking not a joke and the fuse never tripped why because the fuse was too big so the motor got stuck probably around nine amps not turning literally i saw pictures there's fire all on the ceiling and because simply someone decided to switch a 10 amp fuse instead of a 7.5 use so it's important to remember when you fuse a circuit you're fusing not only the wire but also the appliance and you have to you absolutely have to follow the manufacturer's specifications thank you for watching this video if you've got further questions and you're wondering about your own boat please ask questions below or send us an email with your questions and we'll get to them hopefully as soon as possible if you haven't done so please subscribe to our youtube and get our weekly updates we're posting about four videos a week right now and also thanks for watching
