Hardtack
Member
In another currently active thread there’s been a brief but illuminating discussion over whether the power supply for a vessel’s radio communications equipment should be collected from the switchboard busbar and / or battery isolator feed, or alternatively run directly from the battery via the radio’s own dedicated supply cable and fuse.
It’s a contentious issue and opinions tend to be polarised and robustly defended. Moreover, the disagreement is on a global scale, because whilst the UK’s maritime regulating agencies are non-specific about the method used on most privately operated vessels, the relevant legislation of other nations insists that the power for a marine VHF radio installation must be routed via an independent power supply cable and circuit protection device, with the radio’s dedicated power supply cable running direct to the battery.
So if you’ll be patient and bear with me for a minute or so, I’ll explain the philosophy which I support - it’s the one which is widely regarded as good practice when the issue is viewed objectively from the perspective of vessel and crew safety. More specifically, I’ll do it by attempting to illustrate just one compelling reason for not taking a VHF's power supply from the vessel’s general services switchboard.
So here’s a scenario to consider - and unfortunately it’s not without precedent...
You’re sailing happily along fifty miles offshore with the ocean all to yourself when your nostrils are assailed by an acrid burning smell. Following your nose you discover smoke and flames issuing from the vicinity of the services switchboard. The cause of the problem is almost certainly an electrical fault - and the offending wiring is behind the switchboard, which has been beautifully installed in the nav station panelling.
It shouldn’t take long to grab a fire extinguisher, gain access to the seat of the conflagration and start fighting your fire. But before you get this far you’ve very probably made a dive for the battery isolator switch and shut down power to the now melting switchboard.
On ripping open the switchboard fascia you’re confronted by tongues of flame, charred wiring, and melting plastic. The fire is rapidly expanding and consuming anything flammable in its path. Your extinguisher keeps you busy for a minute but the fire is tenacious and spreading fast into inaccessible territory.
You’re going to need outside assistance but summoning help presents you with a dilemma...
You can’t use your VHF because you’ve sensibly turned off your battery power at the isolator switch. And now it gets worse. Needs must, so you turn on the power again - only to discover that the VHF still won’t work because, among the red hot smouldering mess behind the distribution switchboard, your VHF’s fire ravaged power cable has gone open circuit.
Remember, if you will, that you’re a long way offshore on a now blazing vessel, your VHF is out of commission and there’s no other vessel within visual range.
It’s a bit late to be wise in hindsight now, but at about this point you might start wishing that your VHF had its own power supply and fuse, connected directly to the battery bank - and thus entirely independent of anything to do with the battery isolator switch or switchboard...
To reiterate, so far as I am aware there is currently no legal requirement in the UK for a privately owned pleasure vessel to have an independent power supply circuit for its VHF (or an emergency back-up battery supply either). In the interests of safety, however, and regardless of a lack of definitive legislation on the point, it is generally considered good practice to do so.
Other nations’ maritime regulations differ. Some address this specific point and insist that the ship’s radio equipment power supply must be an independent, stand alone installation. Here in the UK, where we rightly and robustly resist anything that smells of over-regulation, the method of routing power to a marine VHF set is - at present - left to the owner, who is expected to exercise discretion and common sense.
Food for thought?
It’s a contentious issue and opinions tend to be polarised and robustly defended. Moreover, the disagreement is on a global scale, because whilst the UK’s maritime regulating agencies are non-specific about the method used on most privately operated vessels, the relevant legislation of other nations insists that the power for a marine VHF radio installation must be routed via an independent power supply cable and circuit protection device, with the radio’s dedicated power supply cable running direct to the battery.
So if you’ll be patient and bear with me for a minute or so, I’ll explain the philosophy which I support - it’s the one which is widely regarded as good practice when the issue is viewed objectively from the perspective of vessel and crew safety. More specifically, I’ll do it by attempting to illustrate just one compelling reason for not taking a VHF's power supply from the vessel’s general services switchboard.
So here’s a scenario to consider - and unfortunately it’s not without precedent...
You’re sailing happily along fifty miles offshore with the ocean all to yourself when your nostrils are assailed by an acrid burning smell. Following your nose you discover smoke and flames issuing from the vicinity of the services switchboard. The cause of the problem is almost certainly an electrical fault - and the offending wiring is behind the switchboard, which has been beautifully installed in the nav station panelling.
It shouldn’t take long to grab a fire extinguisher, gain access to the seat of the conflagration and start fighting your fire. But before you get this far you’ve very probably made a dive for the battery isolator switch and shut down power to the now melting switchboard.
On ripping open the switchboard fascia you’re confronted by tongues of flame, charred wiring, and melting plastic. The fire is rapidly expanding and consuming anything flammable in its path. Your extinguisher keeps you busy for a minute but the fire is tenacious and spreading fast into inaccessible territory.
You’re going to need outside assistance but summoning help presents you with a dilemma...
You can’t use your VHF because you’ve sensibly turned off your battery power at the isolator switch. And now it gets worse. Needs must, so you turn on the power again - only to discover that the VHF still won’t work because, among the red hot smouldering mess behind the distribution switchboard, your VHF’s fire ravaged power cable has gone open circuit.
Remember, if you will, that you’re a long way offshore on a now blazing vessel, your VHF is out of commission and there’s no other vessel within visual range.
It’s a bit late to be wise in hindsight now, but at about this point you might start wishing that your VHF had its own power supply and fuse, connected directly to the battery bank - and thus entirely independent of anything to do with the battery isolator switch or switchboard...
To reiterate, so far as I am aware there is currently no legal requirement in the UK for a privately owned pleasure vessel to have an independent power supply circuit for its VHF (or an emergency back-up battery supply either). In the interests of safety, however, and regardless of a lack of definitive legislation on the point, it is generally considered good practice to do so.
Other nations’ maritime regulations differ. Some address this specific point and insist that the ship’s radio equipment power supply must be an independent, stand alone installation. Here in the UK, where we rightly and robustly resist anything that smells of over-regulation, the method of routing power to a marine VHF set is - at present - left to the owner, who is expected to exercise discretion and common sense.
Food for thought?
Last edited:
