Simple wiring query

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wanzap1

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So I'm undertaking a very minor wiring job. It will consist of battery with solar charge to power very simple boat electrics including anchor light, interior lights, nav lights and instruments etc.

Ive researched the wiring and have one specific query.

I'm considering using an eBay 6 gang panel with USB etc - I'm sure you are familiar. These are prewired but come without fuses therefore I'm left with some options:

I could calculate maximum load the size a master fuse that suits and hence have one fuse in line before the control panel. This of course means if it does blow I'm left non the wiser as to there the fault lies.

The optimum solution is to have a fuse for each switch before the panel, but it would involve the hassle of rewiring the panel (not major granted)

Is it acceptable to have a fuseblock after the panel I. E. The live from the panel switch enters the fuse or must they be before the switch panel?

Many thanks
 
The purpose of fuses is to protect the cable downstream of the fuse. Not the cable feeding the fuse. That is protected by the previous fuse upstream. This falls down when we get to the battery which rarely have fuses, hence the requirement for substantial cables of 25mm square cross section or greater.
 
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wanzap1 said:
Is it acceptable to have a fuseblock after the panel I. E. The live from the panel switch enters the fuse or must they be before the switch panel?
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You can put the fuse either before or after a switch. However, as Boater Sam commented, the idea of fuses is to protect the cable, primarily in the event of a short circuit.

However, if you're only powering lights and instruments, you could calculate the maximum current draw and then have one master fuse as close to the battery as possible. It's unlikely that a short in any of the wires to lights, etc, would cause damage before the master fuse blows.

As an alternative, you could also split the supply to the switch panel and have two fuses just before the panel (in addition to a master fuse). One advantage of this (depending on how you arrange your circuits) is that you wouldn't necessarily lose all lighting if a fault occurs. Some boats have the port and starboard cabin lights on different circuits for this reason.
 
I think you've correctly identified one the weaknesses of the one fuse installation. If it blows you don't know which part of the installation has the fault. That's not too bad in itself because you can get out your meter and do some testing, turning off the switches and turning on each in turn until you find the circuit that's causing the problem.

Another weakness is that it's 'one out, they're all out'. So for example if your interior light circuit blows the fuse, out go your intruments and nav lights. For me that would be more of a problem as it might happen at an inconvenient moment when you haven't got time to start circuit testing. I'd think it was too big a risk and so I'd be inclined to put in a fuse per switch, but I put them in the circuits after the panel as you're going to be working with those wires anyway and you wouldn't need to rewire the panel.

But in the scheme of things, this isn't going to sink you or cause an explosion, so it's really down to preference.
 
De.windhoos said:
Get something like this. You also have these with leds, indicating blown fuse. Put it between your switch panel and the consumers
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Yes this was what I was planning, it would be simpler to have this after the panel as it means less wiring and I was wondering if that caused any issues. It seems like it won't cause any major harm and I'll still have a master fuse before the panel for added security / incase the panel itself is at fault.

Thanks for the input.
 
jbweston said:
Well, yes. Even better a modern panel with circuit breakers to do away with the fuses. But I was assuming there was some reason you'd chosen a specific unfused panel.
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I was looking at the unfused panels on eBay with built-in volt meter and USB, they are dirt cheap.
 
I think the chances of a short in wiring pos to negative are quite slim. One exception being any mast head light using mast as negative. So just fit a suitable sized fuse near the positive terminal of the battery for the whole system. IMHO the fuse and holder of those holders in a panel are more likely to cause a bad connection than having a short blowing the fuse.
I use one of those auto fuses 5 amp, with 2 spade connectors and just attach 2 crimp (AMP) connectors to the wires. Wrap the lot in insulation ape or tube to give safety to the whole system. ol'will
 
wanzap1 said:
Yes this was what I was planning, it would be simpler to have this after the panel as it means less wiring and I was wondering if that caused any issues. It seems like it won't cause any major harm and I'll still have a master fuse before the panel for added security / incase the panel itself is at fault.

Thanks for the input.
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Fit a master fuse at the battery, rated for all loads or the cable rating. Then fit a fuse panel, something like the one in post #6.
 
Mudisox said:
If you et a fused system, ensure that you also have a good supply of fuses to replace those that blow. Don't ask....
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In 17 years of owning a boat that's now 50 years old, the only fuses that have blown are those due to my own stupidity. I carry spare fuses, but have only ever needed them when I've interfered with something. Yes, I know I should turn the power off, but sometimes you need it on...

Incidentally, a big +1 for a fuse box with LEDs. It makes replacement so much easier for a small increase in cost. Possibly a better idea still would be blade circuit breakers
 
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wanzap1 said:
Yes this was what I was planning, it would be simpler to have this after the panel as it means less wiring and I was wondering if that caused any issues. It seems like it won't cause any major harm and I'll still have a master fuse before the panel for added security / incase the panel itself is at fault.

Thanks for the input.
Click to expand...
Be aware that If you have multiple consumers on the same switch (for instance cabin lights) using multiple wires (port & sb) you’ll need a fuse block with a common positive. Something like this. This one also has a common negative
 
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