VHF Power Supply - switchboard or independent?

[Hardtack]

"The only reason I'd not use the switched busbar is if I thought the quality of the power supply might be affected by something else connected to it - fairly unlikely on a DC battery system and with today's kit."

Agreed.

When we hit the transmit button the VHF immediately puts a load of several amps on the supply cable to the battery. If other hardware demanding a high current (typically a bilge pump) is running simultaneously, then there's the possibility of a so-called "brown out" occurring, and in that situation the VHF transmitter circuit won't be able to draw the current it requires.

A quick and dirty test for this might be to run the bilge pump and, while it's running, press the VHF transmit switch. If you hear the bilge pump's motor slow down then - because of the way electricity works - you'll know the transmitter circuit isn't receiving enough amps either, and something needs attention.

Using a battery supply cable with a generous cross-section reduces this problem considerably, especially if the cable run is a long one. Worth noting, however, that when doing the "quick and dirty" test, terminals common to both circuits which have gone high resistance due to corrosion or mechanical loosening will produce similar symptoms. Under a sustained load, terminals that have gone high R will often feel warm - and sometimes uncomfortably hot - to the touch.

 

[prv]

I reckon i'll be long abandoned when the batteries flood, the water needs to be at least a foot deep in the saloon for that to happen :ambivalence:

I've been in a yacht with the water swilling around the level of the bunks. We weren't even contemplating abandoning ship - after putting the dislodged transducer back in and pumping the water out, we reached our destination, retired to the pub for the evening, and carried on with our Day Skipper course for the remainder of the week. The flooding did knock out all the electronics (non-waterproof and mounted low down under the chart table) so our trad nav was more than just an exercise

Launching the raft with only a foot of water in the cabin is massively premature.

Pete

 

[PaulRainbow]

Launching the raft with only a foot of water in the cabin is massively premature.

Pete

OK, i'll just get it ready then

 

[Hardtack]

Launching the raft with only a foot of water in the cabin is massively premature.

Not necessarily.

Depth of water in the cabin is only a part of the criteria that need examining prior to making a decision to abandon.

If your foot of water in the cabin has taken a couple of hours to accumulate then there shouldn't be a headlong rush to jump off the boat.

If, on the other hand, it's a sudden and uncontrollable ingress which is rising too fast for the pumps to combat, and the point of ingress can't be either traced or plugged, then it may well be time to consider departing.

Incidentally, it's been demonstrated that not many bilge pumps fitted to small yachts will make much of an impression on flooding caused by, say, the failure of a 1 1/2" seacock a couple of feet below the waterline. On a brighter note, it's also been demonstrated that not many bilge pumps fitted to small yachts can shift water as fast as a terrified man with a bucket!

 

[duncan99210]

"Whilst I fully understand the OP thinking about a dedicated, hardwired feed to the fixed VHF he has yet to step into the real world of the UK leisure boater."

I thoroughly enjoyed reading your offering.

Just want to correct one point. Although I've been a professional mariner for most of my working life, I come from seafaring stock and most of my spare time over the past 50 years has been absorbed by sailing and maintaining my own boats and those of others.

My favourite was a 49 foot timber ketch (built in Gosport in 1946) which I owned for many years and lived aboard for much of the time when I was on leave from the Merchant Navy. Also owned one of Van de Stadt's lovely old Excaliburs - very pretty boat with a nice long keel, and in contrast, a Contessa 32 which, although not one of my favourites, was surprisingly quick for such a short waterline. Since I've retired I've downsized a tad but still spend much of my time afloat

So a more accurate statement would be that I "stepped into the real world of the UK leisure boater" in 1964 (which is when I was first ordered to get into a sailing dinghy and figure it out) and I've yet to find a satisfactory way of stepping out of it! (The world of the UK leisure boater I mean - not the dinghy).

But you still haven't addressed the major point I was raising: given that you are seeking to protect the VHF supply where does the tipping point come? Given that most leisure vessels have all of their electronics in what is effectively a single site, how do you go about protecting them all given that an incident that takes out one item will probably take out all, even if the radio is wired separately? Looking at the problem, I cannot see a solution that represents a cost effective way of providing what you are seeking to achieve, that is, continued radio communications in the face of fire or other emergency. Please could you address this?

 

[Hardtack]

But you still haven't addressed the major point I was raising: given that you are seeking to protect the VHF supply where does the tipping point come? Given that most leisure vessels have all of their electronics in what is effectively a single site, how do you go about protecting them all given that an incident that takes out one item will probably take out all, even if the radio is wired separately? Looking at the problem, I cannot see a solution that represents a cost effective way of providing what you are seeking to achieve, that is, continued radio communications in the face of fire or other emergency. Please could you address this?

I suppose the ultimate and boringly facetious answer would be to put the vessel safely ashore, swaddle it in bubble wrap and tarpaulins, and leave it well alone. But in the real world we have to do our best, and in the real world our best is likely to involve unavoidable compromises and solutions that fall short of ideal.

I understand the point you’re making, essentially that on most leisure vessels the instruments necessarily live shoulder to shoulder in a confined space. They certainly do on mine. But I don’t accept the premise that an incident that takes out one item will necessarily take out all. And, as it would probably be impractical to try to protect them all, perhaps we should try to strike a sensible compromise, doing our best to design with damage limitation in mind and, where possible, include a degree of built in redundancy.

The philosophy supporting the dedicated VHF power supply (which is the original topic of this thread) embraces the concept of built in redundancy. That is to say, if a local electrical problem were to disable the switchboard, or result in it being shut down manually to curtail a problem, the VHF would still have power. The counter-argument to that might be that the problem which disabled the switchboard is likely to destroy the VHF anyway, but I really don’t believe that would automatically be the case. And by providing the VHF with its own supply, one at least has a fighting chance of it staying on line when all else has - quite literally - failed.

On the same topic, another contributor to this thread has come up with an interesting solution that I haven’t come across before. His suggestion is to wire the VHF to the switchboard - as most of us do -but also run a parallel, switched emergency supply back to the battery, with the emergency supply switch in the battery compartment. I think that’s an elegant solution because it covers all bases, embraces the relevant legal requirements of all nations, and you end up with two power supplies to your VHF. In other words, potentially valuable built in redundancy.

Aircraft instrumentation engineers have been doing this for safety reasons since the year dot, but in the marine instrumentation world we often seem reluctant to do more than the bare minimum required to keep things working, and if it goes wrong we’ll hopefully muddle through somehow. We all have our own ways of doing things. In my case, I feel it’s often easier to address a potential problem in advance and investigate ways of heading off the difficulty before it can happen.

 

[lw395]

But you still haven't addressed the major point I was raising: given that you are seeking to protect the VHF supply where does the tipping point come? Given that most leisure vessels have all of their electronics in what is effectively a single site, how do you go about protecting them all given that an incident that takes out one item will probably take out all, even if the radio is wired separately? Looking at the problem, I cannot see a solution that represents a cost effective way of providing what you are seeking to achieve, that is, continued radio communications in the face of fire or other emergency. Please could you address this?

You may not be able to protect the vhf supply from serious fire, but a separate supply will protect it from:
Main bus fuses blown
Flat batteries
Batteries switched off due to problems

Whether that protection is worth the outlay and hassle might well be debatable. It might be more worthwhile perhaps on a racing yacht with small batteries, where it doesn't take much to go wrong to get flat batteries. It might also depend on what value you place on VHF instant availability. For instance if you need to call up QHM or port control and might be singlehanded, you might not be wanting to take time to hotwire the VHF to the engine battery.

I'm not convinced myself, but I think the 'what if' discussion can be useful.
Stuff does go wrong on boats. (or is it just the cheapskates I sail with?)

A related thought, how many boats have all the instruments, GPS, VHF etc on one data bus?
What happens if one device locks the bus?
I've been on a boat where a fault in the masthead unit wiring locked up the depth sounder. That could have been awkward.....

 

[Finbar]

This one got me thinking, so I had a look at the Malo approach on my boat. While most things are run from the main panel, there are a set of fuses under the companionway steps for the VHF, and autopilot. These are run through the main battery switch for isolation, but allow for operation if the fuse for the main panel blows, or the panel otherwise self destructs.

one up for the Swedes!

 

[Hardtack]

This one got me thinking, so I had a look at the Malo approach on my boat. While most things are run from the main panel, there are a set of fuses under the companionway steps for the VHF, and autopilot. These are run through the main battery switch for isolation, but allow for operation if the fuse for the main panel blows, or the panel otherwise self destructs.

Yes, the Swedes are good with this sort of stuff and I think the setup you've described represents an intelligent approach. Plus it opens an interesting avenue of thought for refinement and customisation of an existing installation to suit a particular boat / owner / skipper's requirements.

That is to say, if you have a couple of services that you consider mission critical - services that you'd like to protect as far as possible from unavoidable power supply failure - which by its nature may occur in unforeseen circumstances - introduce a small secondary back up panel situated remotely from the primary house circuit panel.

That way, if your main power distribution arrangement should ever go belly up (and unexpected stuff sometimes happens) the services which you consider to be vital and wish to keep on line, still have access to power.

This, incidentally, need not be an expensive exercise unless you choose to employ outside agencies to execute the work. And once the work's done, the result will hopefully sit there for years doing nothing. Rather like your lifejackets, liferaft, EPIRB etc. which cost you a lot more. But on the other hand, its existence provides reassurance and, more importantly, it could save a lot of profanity and inconvenience at sea, should you ever need to use it.

 

[Bru]

This one got me thinking, so I had a look at the Malo approach on my boat. While most things are run from the main panel, there are a set of fuses under the companionway steps for the VHF, and autopilot. These are run through the main battery switch for isolation, but allow for operation if the fuse for the main panel blows, or the panel otherwise self destructs.

one up for the Swedes!

And a black mark too because if you're going to go to the trouble of having a separate feed for vital equipment it needs to have its own separate isolator

An electrical fire at the main panel or associated equipment will necessitate turning off the isolator on the feed to the panel...

 

[prv]

You may not be able to protect the vhf supply from serious fire, but a separate supply will protect it from:
Main bus fuses blown
Flat batteries
Batteries switched off due to problems

Here you seem to be envisaging a separate VHF battery - perhaps a 20Ahr gel pack mounted high up in a locker near the radio. This is an idea I can support - indeed I nearly did it on Ariam, even bought the battery, but in the end there wasn't a good place to put it. For a while I carried the battery in the emergency-gear locker, but eventually put it ashore as unnecessary weight and complication.

Separate VHF wiring though - I just can't see much benefit to running a special length of 2mm² right alongside the existing run of 35mm² that's properly terminated and securely bolted down to quality fittings at each end.

A related thought, how many boats have all the instruments, GPS, VHF etc on one data bus?
What happens if one device locks the bus?
I've been on a boat where a fault in the masthead unit wiring locked up the depth sounder. That could have been awkward.....

As we were sailing out of the Itchen soon after buying the boat, my dad decided to secure one corner of the hatch garage that was slightly loose - and managed to put the new screw straight through the Seatalk cable . That definitely confused the instruments, and actually burned out one of them although I'm still not sure how given that only 12v was available and that's what the signal line spends most of its time at anyway...

Nowadays we actually have four independent navigation systems on board - not so much from a desire for massive redundancy but just because that's how things panned out between different kit for different purposes bought at different times.

• Raymarine network - the main plotter, wind/speed/depth/etc instruments, and a Seatalk GPS glued down on deck just ahead of the windscreen. All in the cockpit except that there is a converter box to NMEA0183 which feeds the Navtex, which can thus be used as a repeater at the chart table if required (mostly just used to add the log reading to the hourly plot when offshore).
• "Chart Nav" - or that's how the circuit is labelled on the panel. This is a Garmin GPS128, a Yeoman plotter built into the chart table, and a numeric repeater in the cockpit. I like to mix the best of plotter and paper navigation, tending towards the former when inshore and the latter when offshore. The two sets of electronics are completely separate as far as the positive busbar built into the fusebox.
• Helm plotter. For most purposes I like to have the main plotter at the forward end of the cockpit, since most of the time I'm not behind the wheel (either the autopilot is steering or another person) and the forward area of the cockpit is the practical centre of the boat under way. But there are times (mostly when coming up the channel in an unfamiliar harbour) when I do want a pilotage aid right there at the helm. So I added a small, relatively cheap, 4" plotter on the binnacle. It's self-contained apart from the power supply, including a built-in antenna.
• Radio and AIS. It's simpler all round to give the radio its own basic GPS receiver - just a black blob on the end of a wire - rather than wiring it to a navigation unit that then has to be switched on and off along with the radio. The radio also incorporates the AIS receiver, but I use a separate Watchmate display to view the data and provide alarms. So this little cluster of instruments is again separate apart from its 12v supply, and while it's not a navigation suite per se, the radio does display a lat and long on its screen which can be plotted on the chart.

Of course, as well as the boat's kit, there's the usual menagerie of iPhones and iPads, several of which have various charting apps installed.

Specifically on the depth sounder - our instruments are the old ST60s so although they can talk to each other, each one is self-contained with its transducer. When my dad blew up the Seatalk bus, I ripped out the connections to everything else and just ran power to the depth-sounder - and really in familiar coastal waters that's all the instrumentation you need.

We do also have a portable sounder (intended for fishermen and runs off AA batteries) stowed away.

Pete

 

[Finbar]

They thought of this one too. There are two fuse blocks, one marked continuous and the other marked interrupted. Interrupted seems to mean going through the main battery switch while continuous is direct to the battery. While the fuse block use blade type automotive fuses, both supplies are protected by higher capacity fuses at the battery, as indeed is the supply to the main panel and the winch.
I prefer to be able to switch everything off when leaving the boat and am set up that way, but the option is there. Mind you the fridge and heater are permanently connected, which led to a learning event when the boar was new to me!

 

[Hardtack]

And a black mark too because if you're going to go to the trouble of having a separate feed for vital equipment it needs to have its own separate isolator

An electrical fire at the main panel or associated equipment will necessitate turning off the isolator on the feed to the panel...

Yes, although the set up that finbar has described has a spurred feed rather than a separate feed.

A separate feed would be routed back to the power source, in which case it should have an isolating switch and circuit protection. Viewed from the perspective of electrical safety, the isolator and protective device would ideally be installed adjacent to the battery so as to protect the power supply cable itself from the consequences of damage and shorting en route to the distribution panel.

I agree with your point though. If you're going to have a back up panel for vital services, run an independent dedicated supply line to it. If not direct from the battery, then from the live (battery side) of the isolator that feeds the main switchboard. In which case you'd install the back up panel's isolator between the main battery isolator (because you've tapped your supply off the isolator's live side) and your secondary back up panel. It's a simple and inexpensive arrangement, although for anyone unfamiliar with wiring installations, a written description of the circuit probably makes it seem rather more complicated than it really is!

That apart, I think the Swedes did well to recognise the value of fitting a small backup distribution board, to support what they or the owner considered to be vital services. Of course, the secondary panel might have been an additional extra requested by the person who commissioned the build but, whoever it was, somebody over there thought things through, visualised a possible scenario, and took preemptive avoiding action.

 

[Hardtack]

"I ripped out the connections to everything else and just ran power to the depth-sounder - and really in familiar coastal waters that's all the instrumentation you need."

Oddly enough, in familiar coastal waters, a depth sounder is the one instrument that I almost never use.

On the other hand, if you want to seriously p**s off a grumpy port captain, try entering a busy commercial harbour without advertising your presence or intentions via the appropriate VHF channel!

 

[Hardtack]

They thought of this one too. There are two fuse blocks, one marked continuous and the other marked interrupted. Interrupted seems to mean going through the main battery switch while continuous is direct to the battery. While the fuse block use blade type automotive fuses, both supplies are protected by higher capacity fuses at the battery, as indeed is the supply to the main panel and the winch.
I prefer to be able to switch everything off when leaving the boat and am set up that way, but the option is there. Mind you the fridge and heater are permanently connected, which led to a learning event when the boar was new to me!

Well there you go! They appear to have thought through the design carefully and got it right!

 

[Bru]

I agree with your point though. If you're going to have a back up panel for vital services, run an independent dedicated supply line to it. If not direct from the battery, then from the live (battery side) of the isolator that feeds the main switchboard. In which case you'd install the back up panel's isolator between the main battery isolator (because you've tapped your supply off the isolator's live side) and your secondary back up panel..

No, no, no! And thrice no I say!

If you're going to go to all the trouble of wiring in an independent supply it needs to be totally independent. Running the backup supply / panel off the main isolator does not achieve that because item one on the "Electrical fire" checklist should be "isolate the supply" (which in many cases, unless secondary ignition has already occurred, will result in the fire going out). So just when you need your backup supply to the vital equipment, you need to turn it off!

The backup supply / panel isolator needs to be on a direct feed from the battery (and as I've already mentioned, if you're going to go down this route you might as well go the whole hog and fit a seperate emergency backup battery as well)

 

[Hardtack]

No, no, no! And thrice no I say!

If you're going to go to all the trouble of wiring in an independent supply it needs to be totally independent. Running the backup supply / panel off the main isolator does not achieve that because item one on the "Electrical fire" checklist should be "isolate the supply" (which in many cases, unless secondary ignition has already occurred, will result in the fire going out). So just when you need your backup supply to the vital equipment, you need to turn it off!

The backup supply / panel isolator needs to be on a direct feed from the battery (and as I've already mentioned, if you're going to go down this route you might as well go the whole hog and fit a seperate emergency backup battery as well)

Yes yes yes! And a thousand times yes I say!

Seriously though, and with all due respect, you appear to have misunderstood or misread what I've said.

So to briefly recap...

On several occasions in this thread I've advocated running an independent back up feed direct from the battery. However, if you re-read the relevant posts you'll find that I have also (under mild duress and I confess a bit reluctantly) conceded to a compromise which entails spurring the secondary feed FROM THE LIVE SIDE of the battery isolator. I'll say that again: the live side of the isolator. This arrangement means that the secondary feed from the isolator is not switched by the isolator. The secondary feed will remain live when the isolator is off, which is what we require.

In other words, all we're doing is tapping an uninterruptible supply from a convenient local point, which in this case is the live (i.e. the battery side) of the house circuits' main isolator. It is effectively the direct supply from the battery which you and I both advocate.

As a secondary supply thus arranged will remain live (which is the entire point of installing the damned thing) when the main isolator is switched off, it will require a dedicated isolator between the live main isolator terminal, from which it has been tapped, and the secondary service panel which it is feeding.

I hope that clarifies things for you.

 

[Lon nan Gruagach]

if a piece of equipment is that important you should:
Have a spare, its all well and good coming up with what ifs to do with its supply, but what if it blows up all of its own accord?
Have spare peripherals, for a radio then a spare antenna (requirement for MCA coding anyway), that could include spare power connection. In that case conectorise the supply and have the option to plug it in somewhere else. if you dont like that then a change over switch mounted away from the main distribution (probably next to the radio) with supplies run one from the main distribution and another via a separate route from what ever back up you like.

 

[Hardtack]

if a piece of equipment is that important you should:
Have a spare, its all well and good coming up with what ifs to do with its supply, but what if it blows up all of its own accord?
Have spare peripherals, for a radio then a spare antenna (requirement for MCA coding anyway), that could include spare power connection. In that case conectorise the supply and have the option to plug it in somewhere else. if you dont like that then a change over switch mounted away from the main distribution (probably next to the radio) with supplies run one from the main distribution and another via a separate route from what ever back up you like.

Yes - I have a pair of panel mounted VHF sets. The more recent is an Icom IC-M323 (DSC ), and the older one is an Icom IC-M56 (the M56 is a pre DSC model). Rather expensive kit to buy new but it's well made and in my experience pretty reliable.

The IC-M56 was already installed on the yacht when I bought it and, because I wanted a DSC unit, I added the IC-M323 later on. As there was some spare real estate on the nav station panel I left the IC-M56 in-situ, partly as a useful backup and also because the pair of them look quite nice on the panel!

 

[Bru]

Yes yes yes! And a thousand times yes I say!

Seriously though, and with all due respect, you appear to have misunderstood or misread what I've said.

So to briefly recap...

On several occasions in this thread I've advocated running an independent back up feed direct from the battery. However, if you re-read the relevant posts you'll find that I have also (under mild duress and I confess a bit reluctantly) conceded to a compromise which entails spurring the secondary feed FROM THE LIVE SIDE of the battery isolator. I'll say that again: the live side of the isolator. This arrangement means that the secondary feed from the isolator is not switched by the isolator. The secondary feed will remain live when the isolator is off, which is what we require.

In other words, all we're doing is tapping an uninterruptible supply from a convenient local point, which in this case is the live (i.e. the battery side) of the house circuits' main isolator. It is effectively the direct supply from the battery which you and I both advocate.

As a secondary supply thus arranged will remain live (which is the entire point of installing the damned thing) when the main isolator is switched off, it will require a dedicated isolator between the live main isolator terminal, from which it has been tapped, and the secondary service panel which it is feeding.

I hope that clarifies things for you.

Edit after re-read

Ah, you've got it I see! I initially missed the bit about the secondary isolator, that is EXACTLY the point I was making!