Fuse for VHF

JumbleDuck said:
The bike hire man with "Ar Bata"? I met him once - hired a bike from him in fact.
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That’s the chap, top marks for remembering his boat name. I once bought a fishfinder for him at the London boat show, I had a boat in Ardrossan at the time and delivered the ff to him in Millport.
 
prv said:
“VHF is usually sometimes wired directly to a main power source, ie battery, to lessen the impact of a failure in the main electrical system because in the 80s 7 amps while transmitting was a heavy drain and yacht electrics could be iffy, and manufacturers wanted to minimise support issues due to poor performance so they told people to wire direct.“

If your boat’s electrical system was dodgy enough to warrant special wiring for the VHF “just in case it fails in an emergency”, why not apply the same principle to the nav lights? The bilge pumps? The autopilot, so that you have your hands free to deal with the problem? The depth sounder so you don’t run aground unexpectedly? Yet nobody ever does these (bilge pumps are sometimes wired separately, but that’s so they work when the boat’s unoccupied - “works in emergency” is never given as the explanation), it’s always the VHF, which is unlikely to be the thing you urgently want to use in the event of electrical problems anyway.

It’s just another of those PBO cargo-cult things.

Wire your VHF to your distribution board with an appropriate fuse or breaker, and if your boat’s wiring is so unreliable that you think the VHF might not work, fix that instead of going around it.

Pete
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That is a big generalization and a disservice to the industry .

From the early 80's we supplied very robust switch gear. Westerly were fitted with very comprehensive switch panels, all circuit breaker, battery status, VSR, low voltage power lock-out to fridge integral mains multi-stage charger, but they still wired the VHF to the battery. While Sealine besides the above included twin engine VSR , build in AC shore supply distribution and auto shore / gen change-over, but used a breaker on the panel for VHF.

Nothing to do with 7 amp, well it may have been in the 60's, by the 80's it was just convention to many builders and VHF had been a option, not a standard item..

Brian
 
I recall at one point having offshore racing regs which required the VHF to have its own power. My first offshore boat had a little 12V battery which could be switched to supply the VHF and IIRC the Decca navigator.
I assume the point was you might want to use the VHF to ask for assistance in the event of an electrical problem?
Like maybe the 1-Both-2 switch exploding? :-)
 
Jamie Dundee said:
That’s the chap, top marks for remembering his boat name. I once bought a fishfinder for him at the London boat show, I had a boat in Ardrossan at the time and delivered the ff to him in Millport.
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I wonder how many others of the old u.r.s. gang are around. The chap who was going to convert a knackered old racer to a top-notch cruiser is here under a similar username. The project went much as everyone predicted ...
 
If it's wired directly to the battery it still needs a fuse and that needs to be at the battery, not often so easy to get to in a hurry. You need to run new cable all the way to the radio, rather than use existing, heavy, cables. If the battery that you connect it to fails, no radio, without connecting to another battery, are the cables long enough to reach another battery ?

If it's wired to a fuse at the electrical panel, this is usually close to where you mount the VHF, certainly closer than the battery. You don't need to fit a separate switch, as the VHF has it's own (unless it's a black box VHF). The panel will be supplied from the isolator with nice thick cable and short, lighter, cables to the set itself. The fuse would be easy to change. If the domestic battery were to fail it would simply be a matter of turning a switch or two to change over to the engine battery and restore the power to the VHF.

If the boat wiring is so unreliable that you're worried that the thick cables going to the panel are likely to fail, you do (as mentioned) need to look at your wiring.
 
The reason the radio is wired directly to the battery (through an inline fuse and optional additional switch) is because if you have an electical fire or major fault and have to isolate the engine or domestic wiring circuits, you still have a functioning radio to call for help. Nothing to do with integrity of wiring, the fault could be caused by accident damage.
 
salar said:
The reason the radio is wired directly to the battery (through an inline fuse and optional additional switch) is because if you have an electical fire or major fault and have to isolate the engine or domestic wiring circuits, you still have a functioning radio to call for help. Nothing to do with integrity of wiring, the fault could be caused by accident damage.
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I disagree with the logic.

If you have a fault battery and have to isolate it, no VHF.

If you have an electrical fire that takes out the whole installation, it's a rubbish installation, with inadequate circuit protection.

Major fault where ? In the heavy cable to the isolator, the isolator itself, or the heavy wire from the isolator to the panel, because those are the only components between the battery and the VHF. If the cables fail, it's another rubbish installation. If the isolator fails and you don't have a backup system, it's yet another rubbish installation.

I always fit battery cables to the domestic isolator, min of 35mm, so highly unlikely to fail. from the isolator it's a minimum of 10mm, up to 35mm, so very robust, more so than running thin cables all the way to the battery. OK, the isolator could fail, but if it did i will have fitted an emergency switch.
 
PaulRainbow said:
I disagree with the logic.

If you have a fault battery and have to isolate it, no VHF.

If you have an electrical fire that takes out the whole installation, it's a rubbish installation, with inadequate circuit protection.

Major fault where ? In the heavy cable to the isolator, the isolator itself, or the heavy wire from the isolator to the panel, because those are the only components between the battery and the VHF. If the cables fail, it's another rubbish installation. If the isolator fails and you don't have a backup system, it's yet another rubbish installation.

I always fit battery cables to the domestic isolator, min of 35mm, so highly unlikely to fail. from the isolator it's a minimum of 10mm, up to 35mm, so very robust, more so than running thin cables all the way to the battery. OK, the isolator could fail, but if it did i will have fitted an emergency switch.
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You haven't taken into consideration the many other scenarios that could expose wiring and cause a risk, such as accidental damage which I mentioned. Collosion, mast breakage, dropping something sharp/heavy over wiring, localised unrelated fire such as in the galley, loads of other scearions I can think of where I would want to reduce risk of electrical shorts by isolating a battery while I do a damage assessment. That's my logic, if you have another logic feel free to wire your VHF to your main distruibition panel. But make sure you have a handheld VHF available ;)
 
salar said:
The reason the radio is wired directly to the battery (through an inline fuse and optional additional switch) is because if you have an electical fire or major fault and have to isolate the engine or domestic wiring circuits, you still have a functioning radio to call for help. Nothing to do with integrity of wiring, the fault could be caused by accident damage.
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Does not help if the fault/fire takes out your direct wire from battery to VHF.

Brian
 
JumbleDuck said:
I wonder how many others of the old u.r.s. gang are around. The chap who was going to convert a knackered old racer to a top-notch cruiser is here under a similar username. The project went much as everyone predicted ...
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I suspect a fair few are sailing the great oceans in the sky by now. I believe Graham Frankland did eventually get to ’sail away’ as he’s now an offshore member of NWCC. I always have a chuckle when people say “when you’ve been around forums a bit longer.....”
 
salar said:
You haven't taken into consideration the many other scenarios that could expose wiring and cause a risk, such as accidental damage which I mentioned. Collosion, mast breakage, dropping something sharp/heavy over wiring, localised unrelated fire such as in the galley, loads of other scearions I can think of where I would want to reduce risk of electrical shorts by isolating a battery while I do a damage assessment. That's my logic, if you have another logic feel free to wire your VHF to your main distruibition panel. But make sure you have a handheld VHF available ;)
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There are just as many scenarios that would take out your dedicated supply, in fact every single thing you mention above could happen to your dedicated wire, although i think you might have made a few unlikely scenarios up there :) Can't quite see how a broken mast is going to take the domestic system down and having lost the mast, what will you be using as an antenna to transmit via ? Unless you have an emergency VHF antenna.

I can isolate my domestic supply and transfer supply to the engine battery with a turn of a couple of switches. If a domestic battery shorts a cell i just isolate it and switch the emergency switch on, you're crawling around swapping wires on a red hot, gassing, battery, where a spark covers you in acid and broken battery case shards.
DCS handheld clipped to life jacket, just in case ?
 
Thanks for the replies, chaps. The thread certainly went in interesting directions. :oops:

I've had a look at the fuse and there's no distinguishing marks on it so I think I'll just use the equivalent blade fuse. Cheers!
 
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