Wiring and double fuses

4str · 22 July 2008, 14:51

This last weekend an intermittent fault was causing my GPS to shut down when the water got bumpy. I traced the problem to the in line fuse supplied as part of the wiring harness by the manufacturer. Visually there was nothing wrong with the fuse holder, no corrosion and the connections looked like they were well made. But the ohm meter would register a continuity break when I jiggled the fuse holder.

Most of my boat's electric components are fed through a couple of Blue Sea Systems panels with fuses in the panel. All panel switches control only one component. So the GPS was wired with two 2 amp fuses in the system. I have been told by people that I thought knowledgeable that this adds safety to a circuit and is a good thing.

It seems to me that wiring 2 fuses to a circuit adds 3 more contact points to the circuit that can fail. One appropriate amperage fuse in the circuit should be enough, right? I have a radio, depth sounder and a radar that all are wired the same way as the GPS. This just seems wrong to me.

I am a shade tree electrician so I only know enough to get me into trouble. What is boating industry standard for wiring electronics that come with an in line fuse? How is your boat wired?

BruceB · 22 July 2008, 15:52

I have a Blue sea switch panel as well with built in fuses for every circuit. This is sufficient as long as you put the correct size fuse in. I am not sure why you would want to put two fuses of the correct size inline with each other as it would make no difference to when it would pop.
I would take them out and use the Blue sea fuses rated to the correct value.

Cookee · 23 July 2008, 12:58

As a manufacturer we are a big fan of the right stuff, and Blue Sea is definitely the right stuff!

Two fuses is overkill and doubling the opportunity for a fault - your knowledgeable friends aren't helping!

martini · 23 July 2008, 15:12

This is something that has always annoyed me too. You wire in a nice fuse box and keep a load of spare fuses to suit, or even (like I've done on my Arctic) fit a lovely blue sea breaker panel, and where does it get you?

You still got umpteen (usually 2 different sizes) of crappy glass fuses scattered all around in the console, They always corrode and stop working, you have to keep a load spare of these things on board somewhere where they wont get lost or broken

someone pass me the side cutters...

Chris · 24 July 2008, 16:51

I have just fitted the Blue Sea Panel with Breakers instead of fuses, however with this option you have to keep the inline fuses in place as the breakers are rated to 15amps and cannot be changed. The idea is the breakers would prevent your boat going up in flames as they protect the wiring whilst the actual head unit is protected by the 2amp fuse so that you do not risk burning out circuit boards etc because the breakers did not kick in quickly enough.

Chris

BruceB · 24 July 2008, 19:47

The blue sea CB panel comes with standard breakers fitted. You need to change them for the correct sizes which Blue sea sell for this purpose.
The breakers fitted are just realy to fill the holes until you fit ones of the correct sizes.

Chris · 25 July 2008, 17:12

I phoned Blue Sea and they explained that the breakers are not designed to protec the devices, breakers take much longer to trip than the fast blow 2/3amp inline fuses that the manufactures fit just next to the device.

I will definately be fitting the fuses back into my GPS and VHF Looms

4str · 26 July 2008, 01:51

Quote:

Originally Posted by Chris

I phoned Blue Sea and they explained that the breakers are not designed to protec the devices, breakers take much longer to trip than the fast blow 2/3amp inline fuses that the manufactures fit just next to the device.

I will definately be fitting the fuses back into my GPS and VHF Looms

Now the in line fuses in the manufacturer's harnesses make sense to me. You can wire devices with different fuse requirements to one switch: GPS and depth sounder on a "Nav Instruments" switch for example. Its better I think to have one fuse and one device per circuit, but if you have limited real estate...