Fuse size

W

wellcraftv20step

Senior Member
I opened the cover to my fuse panel last week and couldn't believe what a mess , previous owner had it wired in a way that if any one fuse were to blow every accessory below it would be dead as well, I recently saw a thread on here that was a carbon copy of mine. So I replaced the entire block no big deal . Funny thing though wen I asked the po what he did for a living he said he was a union electrician! So anyway my question is this, what size fuse should I be using for my Apelco VHS radio and for the light on my compass
 
Look on the label of the device, there is usually a power consumption rating there. Or look in the book that came with the device or look on the net, most products have instruction manuals listed.

Find out what watt bulb you are using.

If needed convert Amps to Watts.
Amps x Volts = Watts
Watts divided by Volts = Amps

Total these numbers, add 20 % to this = minimum fuse size.

Best guess, 2 amp. Unless the wire feeding the devices is long or undersized for that fuse size. Then you will need to derate the fuse size accordingly.
It is easy to create a heating cable and not blow a fuse by using too small of a wire combined with too much length of wire and too large of a fuse.

Most cheap digital volt meters that read AC/DC also read up to 10 amps DC by connecting in line the meter with the load (bacically temporarly taking the place of the fuse), this will give you the current draw taking place at the time.
Problematically this only gives the reading of what is actually being consumed at that time, not what the device is capable of.
 
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By the way.

I've witnessed actual licensed electricians getting their *** handed to them in a hat trying to do 12 volt work.
 
tsubaki said:
By the way.

I've witnessed actual licensed electricians getting their *** handed to them in a hat trying to do 12 volt work.
Click to expand...

Yep. I used to work for a power and light company here in NJ. Was surrounded by guys that daily work with 34,000 volt lines. Hot sticking it all the way. Completely clueless if you asked them a question about 12V DC.

I'm guessing that the PO of the boat was trying to wire the boat like a home distribution box. One main breaker (fuse) feeding the individual breakers (fuses) that go out to the different receptacles (items being powered). Just a guess, but seems logical given Wellcraftv20step's description of how it was wired.
 
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