Boat cable size

[Tobenn]

Hi,
I'm planning to fit shore power supply to my boat using a 3 pin input connector, a consumer unit RCDO sockets and cabling. The shore power on offer is 16 amps and I note that 1.5mm cable is ok for approx 15 amps. Do you think that 1.5mm cable is sufficient or should I go up a bit higher? ( I'm asking because I have 1.5mm cable in stock, but would have to purchase any higher rated cable! )

 

[JohnW2]

I'm planning to fit shore power supply to my boat using a 3 pin input connector, a consumer unit RCDO sockets and cabling. The shore power on offer is 16 amps and I note that 1.5mm cable is ok for approx 15 amps. Do you think that 1.5mm cable is sufficient or should I go up a bit higher? ( I'm asking because I have 1.5mm cable in stock, but would have to purchase any higher rated cable! )

1.5mm² flexible cable is rated at 16A.

Kind Regards, John

 

[davelx]

Hi,
I'm planning to fit shore power supply to my boat using a 3 pin input connector, a consumer unit RCDO sockets and cabling. The shore power on offer is 16 amps and I note that 1.5mm cable is ok for approx 15 amps. Do you think that 1.5mm cable is sufficient or should I go up a bit higher? ( I'm asking because I have 1.5mm cable in stock, but would have to purchase any higher rated cable! )

Don't forget galvanic isolation on the earth conductor to avoid erosion of the boat metalwork/anodes:

http://www.piratescave.co.uk/sterli...?src=froogle&gclid=CPfJhp3k28kCFUm3GwodLxUOPQ

 

[Robin0577]

Oddly, section 708 (caravan parks) of BS7671 specifies a minimum of 2.5mm2 for a cable connecting a caravan to a site supply, yet section 709 (marinas) mentions no such requirement for a cable connecting shore power to a boat, so I guess 1.5mm2 would be OK provided the length is not excessive.

 

[Tobenn]

Thanks to all, looks like 1.5mm is acceptable in this instance. It is a short run of around 10 feet max. I will check galvanic isolation and also BSS which is the mot for boats. Thanks again.

 

[ericmark]

It seems there are two methods of galvanic protection one is the isolation transformer the other is the diode in the earth wire. The latter must have a TT supply to ensure earth voltage does not exceed the 3 volt threshold of the diodes used, it is also against ESQCR regulations to use a TN-C-S supply. I looked into isolation transformers when my son had a narrow boat and the costs were silly. I found I could get a 230 - 110 step down transformer and a 110 - 230 step up transformer for less money than an isolation transformer which seems crazy.

The other point is most earth electrodes are copper coated steel. For a steel boat you really don't want that copper coating. For an aluminium boat really isolation transformer is a must.

Also remember with boats and caravans the RCBO must be double pole at least for the RCD function.

 

[Tobenn]

Thanks Eric
Perhaps I should have said that I have no control over the supply or the type of earthing system, this is the responsibility of the marina owner. I appreciate your points may have been for information though. I now wonder if I need galvanic isolation at all, the boat is glass fibre and none of the appliances connect to any part of the boat that touches the water. I can see the need if it is a steel hulled narrowboat using the hull as a common connector but not in my case. I certainly do plan on a double pole RCBO though, 30mA trip and current rating of around 5 amps with curve type A or B so a short will trip out at around 50 amps max.

 

[davelx]

Thanks Eric
Perhaps I should have said that I have no control over the supply or the type of earthing system, this is the responsibility of the marina owner. I appreciate your points may have been for information though. I now wonder if I need galvanic isolation at all, the boat is glass fibre and none of the appliances connect to any part of the boat that touches the water. I can see the need if it is a steel hulled narrowboat using the hull as a common connector but not in my case. I certainly do plan on a double pole RCBO though, 30mA trip and current rating of around 5 amps with curve type A or B so a short will trip out at around 50 amps max.

Does the boat have an inboard engine/prop shaft/prop? If so, can you guarantee that it is all isolated, from the appliances/mains earth and will continue to be so isolated. If so, then I guess you could skip the galvanic isolation.

 

[ban-all-sheds]

Boat cable size

185.2m, isn't it?

 

[Ian2008]

BS EN ISO 13297 ac instalations in boats insist that the engine etc are bonded. So a galvanic isolator Is a must. You only need to be moored next to a boat with a bad instalation and be pluged into the same point to have your prop, rudder and other underwater metalwork eaten away surprisingly fast.

 

[Tobenn]

Very droll, Ban-all-sheds, you are spot on. Ian ( not of Evening Tide? ) by bonding the engine, do you mean connecting the engine block to the shore power earth? I'm finding it difficult to view 13297 online without paying an arm and a leg.

 

[ericmark]

I remember looking at RCD protection. I thought RCD mean Residual current detection, but it seems I was wrong and it means recreational craft directive. There are many items which are rather special with boats. And it would seem the maria owners have not got a clue as to what they should provide. I would hope in the maria the outboard is out of the water so not a problem. However it is rather specialised and one has to be careful.

 

[Ian2008]

That's right. The engine block etc need to be bonded to the met.

 

[ericmark]

I had been thinking of an outboard engine which would lift up out of the water and in real terms see no reason to earth an outboard engine it would be like earthing window frames in the home.

However as we go to inboard engines some consideration is required. The first question is what is on the engine and how it it wired. With an inverter generator bolted onto the engine then very likely an earth is essential, however with other great lengths are gone to isolate the engine electrics with insulated return systems, in this case one would not earth the engine.

What we have to consider is the dangers both with earthing items and with not earthing items. For extra low voltage we have SELV, FELV and PELV and the difference is all to do with earthing. PELV must be earthed, SELV must NOT be earthed, and FELV can be either. Job one is to decide which category items fall into. With 200 amp starting current fitting earth wires where they should not be can cause fire I had this problem with wagons where the drivers added earth wires for their CB radios with insulated return systems. I have also had wet liners get eaten way due to incorrect earth systems.

It is specialised and you have to accept that fact. We will normally use 6mm² earth wires but on a boat using 165mm² earths is not unknown where it may take starter current. Also finding throttle cables and the like welded inner to outer where they have taken a starter current is not unknown.

We simply don't have enough information to advise and personally I would want to be on the boat before I advised on how to do the job. With my sons we decided that using a class II battery charger as the only shore connection was the best option. No earth was connected to the boat. We would have liked an isolation transformer but the cost was silly and we had a 3kVA inverter with 6kVA peak and 420 AH of battery plus often shore power limited to 4 amp. Each boat is different but really you need to ask people involved with boats as they are special.

 

[stillp]

I'm finding it difficult to view 13297 online without paying an arm and a leg.

Many public libraries have online access to British Standards.