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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