16A cable into 32A socket

[laika]

We arrived at our new berth to discover that the closest power outlet is one of the bigger 32A types. The marina staff suggested we plug into another empty 16A socket while we got ourselves an adaptor.

My connectors arrived from ebay last night and I was about to rig up the converter but had a small doubt. I have a 16Amp RCD on the boat side. I'm using 2.5mm blue arctic. There's obviously 16 amp connectors inline but those plugs are pretty chunky and they're nice gewiss IP67 ones..

I'm not doing anything too dodgy here am I?

 

[prv]

I guess in theory there ought to be a 16amp fuse or breaker immediately after the 32amp plug, but I don't think I've ever seen such a thing in practice. The risk seems pretty small. I would just make up the adaptor.

One of my mates does power distribution for shows and events. He used to have, as a sort of joke, a "63amp 3-phase to Nokia phone charger" adaptor. There was enough space inside the huge 3-phase plug to fit the whole phone charger, with its domestic 13a pins wired to one of the phases in the plug and the tiny low-voltage cord coming out of the other end. He'd plug it into a spare outlet on a 3-phase distro near the amp racks and leave his phone to charge

Pete

 

[nigelmercier]

My home berth has a 32A socket into which I plug an adaptor to 16A. If there was a short, the 32A MCB would trip before the cable was damaged; if too much current, my MCB would trip. It has never concerned me unduly, but I probably wouldn't leave it connected while I was away.

 

[davidpbo]

The fuse/breaker is supposed to protect the cable downstream of it.

I think the correct way to do it would be to go 32A plug with appropriately sized cable to 16A fuse then to a 16 Amp socket outlet but making that safe and watertight would not be easy. I doubt many people have a problem with a 32A plug to 16A socket with a short 2.5mm cable in between providing there is a 16A fuse or breaker in the circuit.

 

[David2452]

We have similar issues in South Dock as they have upgraded to 32a on many posts. On boats able to make use of the 32a I have upgraded to 4 or even 6mm2 cable, not just the shore power cable but the inlet socket and as far as the consumer unit, upgrading the G.I. or I.T. as required. For smaller vessels and cruising boats who would normally only use 16a I made adaptors. These were a 32a plug with 4mm2 cable to a small IP66 enclosure containing a 16a fuse, then 2.5mm2 cable to a 16a trailing socket, may seem over the top but it's the right way to do it.

 

[laika]

Thanks all: It's as I thought.

Wasn't too chuffed to find the boat unplugged last night. Someone had come into the berth two over from us where we'd been directed by marina staff to plug our 16amp plug in and despite the other side of the same outlet being free, had decided to take out our cable and chuck the end back onto our deck. Although I probably wouldn't go away for a week and leave the fridge on, I'm sure some people do and I doubt in that case the batteries would have been happy.

 

[laika]

These were a 32a plug with 4mm2 cable to a small IP66 enclosure containing a 16a fuse, then 2.5mm2 cable to a 16a trailing socket, may seem over the top but it's the right way to do it.

Has anyone tried the inline RCDs you can get? Draper 16A one seems to crop up in google searches. IP55. Seems less hassle than a stash of fuses and if your power trips a dozen times you've easily made your money back.

Meantime I've wired things up the amateur way (sans fuse, relying on the RCDs at either end)

 

[sailorman]

Has anyone tried the inline RCDs you can get? Draper 16A one seems to crop up in google searches. IP55. Seems less hassle than a stash of fuses and if your power trips a dozen times you've easily made your money back.

Meantime I've wired things up the amateur way (sans fuse, relying on the RCDs at either end)

An RCD protects earth leakage
An mcb protects over load ( ie fuse)

 

[VicS]

Has anyone tried the inline RCDs you can get? Draper 16A one seems to crop up in google searches. IP55. Seems less hassle than a stash of fuses and if your power trips a dozen times you've easily made your money back.

Meantime I've wired things up the amateur way (sans fuse, relying on the RCDs at either end)

As Sailorman indicates RCDs and fuses ( or mcbs) have different purposes.

If you are going to fit anything "in line" it should be a 16amp fuse or mcb as close as possible to the supply .

 

[nigelmercier]

I guess one way to do it is to fit a 20A fuse in the 32A plug.

 

[Bertramdriver]

Just changed my set up to a 32 amp socket aboard with an 16 amp RCD before the distribution board. All currently plugged into a boatyard 13 amp outlet. Overkill?

 

[GrahamM376]

My home berth has a 32A socket into which I plug an adaptor to 16A. If there was a short, the 32A MCB would trip before the cable was damaged; if too much current, my MCB would trip. It has never concerned me unduly, but I probably wouldn't leave it connected while I was away.

We sometimes have to use a converter, a 150mm cable with 32A plug & 16A socket and, as you say, the onboard MCB & RCD will handle any problems. Don't understand why there should be any worries provided shore lead is suitable for the boat load, which is limited by on board MCB.

 

[sailorman]

We sometimes have to use a converter, a 150mm cable with 32A plug & 16A socket and, as you say, the onboard MCB & RCD will handle any problems. Don't understand why there should be any worries provided shore lead is suitable for the boat load, which is limited by on board MCB.

Quite so

 

[prv]

We sometimes have to use a converter, a 150mm cable with 32A plug & 16A socket and, as you say, the onboard MCB & RCD will handle any problems. Don't understand why there should be any worries provided shore lead is suitable for the boat load, which is limited by on board MCB.

The theoretical risk is that the cable is damaged (run over by a heavy trolley, stretched by the motion of the boat, pinched between a shifting warp and the horn of a cleat, etc) in such a way that it suffers a partial short. Drawing more than the cable can carry, but less than it takes to trip the 32a breaker (which probably doesn't trip at exactly 32 amps).

I agree the risk seems remote.

Pete

 

[davidpbo]

If it is your permanent birth it would be worth asking the marina what the 32A socket is fused at. It may be 16A especially if they have changed the sockets without uprating the wiring.

If they have competent people it may also be worth asking them to down rate the breaker to 16A.

 

[sailorman]

If it is your permanent birth it would be worth asking the marina what the 32A socket is fused at. It may be 16A especially if they have changed the sockets without uprating the wiring.

If they have competent people it may also be worth asking them to down rate the breaker to 16A.

re read#12, what is supplied from the marina pillar has nothing to do with thew price of eggs

 

[prv]

re read#12, what is supplied from the marina pillar has nothing to do with thew price of eggs

It does, however, have a lot to do with the current potentially available to flow through the cable.

Pete

 

[sailorman]

It does, however, have a lot to do with the current potentially available to flow through the cable.

Pete

it would still be protected by an RCD in the pillar

 

[GrahamM376]

It does, however, have a lot to do with the current potentially available to flow through the cable.

Pete

Unless the marina is breaking all regs. it doesn't matter. The supply point in the marina should have MCBs for each socket and an RCD protecting the lot, usually 2 or 4 sockets. Any short or imbalance such as leakage to ground on the shore lead or boat would isolate the shore lead instantly.

ADD - Don't forget the household ring main has 32A breakers and no-one worries about plugging a 0.5mm cable in.

 

[oldvarnish]

As a matter of interest, can anyone tell me what kinds of things people have on their boats that would require 32A, which is nearly 8KW??