wonkywinch
Well-Known Member
Think we're just at cross purposes here. I understand that but was speaking figuratively about a 63A device in isolation, not the specific set up the OP has.
Shore power circuit breaker size
- Thread starter Parmesan
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Alex_Blackwood
Well-Known Member
With you on that one
It's an RCD not a MCB. As per#8 I would fit a 16amp RCBO in it's place.
Boathook
Well-Known Member
Replace the whole lot with a double pole master switch and double pole RCBO's suitably rated for the circuits. Possibly 16 and 6 amp.
VicS
Well-Known Member
With you on that one
Why?
Why change anything if all that is required is power for a kettle or fan heater and a battery charger?
I am sure that by now the OP has realised his misunderstanding of the 63 amp rating of the RCD, which was his initial concern.
st599
Well-Known Member
Is the suggestion about moving to double pole not more to do with visiting foreign ports. In countries which use double pole protective devices, there's less care taken with phase and neutral.
PaulRainbow
Well-Known Member
If he turns a kettle and fan heater on at the same time it will trip the shore power marina side. Swapping the 32A MCB for a 16A one should cause the onboard MCB to trip. Bit more convenient and safer than relying on the marina trips.
VicS
Well-Known Member
I had not noticed that he said it was 32ampIf he turns a kettle and fan heater on at the same time it will trip the shore power marina side. Swapping the 32A MCB for a 16A one should cause the onboard MCB to trip. Bit more convenient and safer than relying on the marina trips.
! Agreed that should be swapped out for a 16 amp one. ( unless cabled and fitted with connectors for a 32 amp supply)
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Dockhead
Well-Known Member
Nothing wrong with 32A shore power circuit protection, if the whole circuit, including cabling from shore power inlet to main panel, and the connections, and the shore power cable, is rated for that. In fact that's the correct way to do it.
My shore power circuit is protected with a 32A RCD and breaker. All the cabling is rated for that and the boat-end connector is rated for that. The shore power cable is rated for that.
If the pedestal is less, it has its own breaker with appropriate rating. It's rare to find more than 16A rated supply in this hemisphere, but it exists. I use commercial harbours occasionally and have adapters for larger supplies, and so occasionally get a 32A supply.
Branches in your boat's electrical system are each protected by its own breaker sized to protect THAT BRANCH.
N.B. that those breakers don't protect the devices you connect -- just the wiring and connections.
That's how overcurrent protection works.
My shore power circuit is protected with a 32A RCD and breaker. All the cabling is rated for that and the boat-end connector is rated for that. The shore power cable is rated for that.
If the pedestal is less, it has its own breaker with appropriate rating. It's rare to find more than 16A rated supply in this hemisphere, but it exists. I use commercial harbours occasionally and have adapters for larger supplies, and so occasionally get a 32A supply.
Branches in your boat's electrical system are each protected by its own breaker sized to protect THAT BRANCH.
N.B. that those breakers don't protect the devices you connect -- just the wiring and connections.
That's how overcurrent protection works.
Dockhead
Well-Known Member
If he's got kettle and fan heater on the same ring main branch circuit, then the branch circuit breaker will deal with that, no?If he turns a kettle and fan heater on at the same time it will trip the shore power marina side. Swapping the 32A MCB for a 16A one should cause the onboard MCB to trip. Bit more convenient and safer than relying on the marina trips.
On my boat, the ring main circuit is protected with a 16A breaker.
If he's got 32A rated wiring from shore power inlet to main panel, why would he worry about the pedestal? The pedestal can take care of itself, no?
In any case, I feel it's a good idea to monitor volts and amps in the AC system to keep an eye on all this. I have two cheap Chinese V/A meters on my instrument panel which display values for shore power/generator and then for the main panel, which may be different from one another as there is a charger/inverter between them. I find this very useful -- might be a good tip for someone. I actually wish I had a third one for the ring main circuit.
PaulRainbow
Well-Known Member
Only if the boat is plugged into a 32A supply.
It doesn't matter how your boat is wired, what matters for the OP is how his boat is wired.
His RCD is rated at a max current of 63A, so offers no over current protection, that is provided by the MCBs. He has two socket outlets protected by a 32A MCB, connected to a 16A supply, so again, no over current protection, relying on shoreside equipment for that. This is incorrect.
The pedestal breakers should only be considered as last ditch protection, to protect against faults between the pedestal and the onboard protection, or in the case of faulty protection onboard. They are not there for routine over current protection for the boat.
So fitting a 32A MCB for the socket outlets is incorrect then.
FYI the pedestal beside my boat has 2x32A outlets, as does every hammerhead in my marina.
So a 32A MCB for two outlets, connected to a 16AS supply is wrong.
Thanks for the lesson, but the OPs MCB is incorrect.
PaulRainbow
Well-Known Member
No, it will not. See post #26
"If he turns a kettle and fan heater on at the same time it will trip the shore power marina side. Swapping the 32A MCB for a 16A one should cause the onboard MCB to trip. Bit more convenient and safer than relying on the marina trips."
Again, no. See above.
Dockhead
Well-Known Member
With great respect for your expertise in the field, I would politely disagree with this. Each OCP device is intended to protect particular parts of the circuit. Branch circuits are protected by their own OCP devices. The boat's shore power supply is protected by the feedline OCP device. The pedestal is protected by its own breaker. They are all specified for the capacity of THAT CIRCUIT, and are not intended to protect OTHER CIRCUITS, or indeed any connected devices.
What if you are plugged into one of those common 6A French pedestals? Or a 10A Swedish one? Are you supposed to get out your tools and change your main circuit breaker to 6A, or 10A? Of course not. It's perfectly fine to plug a boat with a 16A (or 32A) main breaker into a 6A pedestal, just like it's perfectly fine to use a boat with a 32A main breaker with a 16A pedestal. Because your shore power circuit is designed for 16A or 32A or whatever and is not intended to protect the pedestal. A pedestal has to take care of itself regardless of what's plugged into it. Your main breaker takes care of your shore power connection circuit, not the pedestal.
It's the operator's job not to overload the pedestal and have to go out in the rain in a bathrobe with a torch to find the bloody pedestal breaker. For this, Victron charger/inverters with "Power Boost" are immensely valuable, especially when connected to a very small capacity pedestal like the French ones. You can set the maximum draw from shore power, to suit the pedestal, and prevent overloading it. And the Victron will boost the pedestal power as required to support higher loads, with inverted battery power.
Maybe the OP never connects to a shore power supply capable of delivering more than 16A. In that case, it's fine if he WANTS to change his main breaker to 16A, but that would be optional if his shore power circuit is rated for 32A. In my case I do sometimes plug into a bigger capacity shore power supplies. I have an adapter for the 63A 400V 3-phase shore power connectors which are common in commercial harbors, which taps 230V single-phase power off one of the legs, and I happily draw 32A from this, similar to what I can get from my generator (which produces 30A of single phase power). I have a lot of electrical equipment on my boat so this is nice to have. The OP's case may be different, of course.
PaulRainbow
Well-Known Member
Just nonsense, i can't be bothered with it.
Dockhead
Well-Known Member
OK, out of respect for you, I looked it up.
BS Standard 7671, Regulation 433.1.1, says: “the rated current or current setting of the protective device (In) does not exceed the lowest of the current-carrying capacities (Iz) of any of the conductors of the circuit.” and "a device for protection against overload shall be placed at the point where the reduction in current-carrying capacity occurs.”
Shore power supply from the distribution panel inside the pedestal to the boat's main panel is a single circuit according to this definition. It's required by standards to be protected AT THE POINT THE REDUCTION OF CAPACITY OCCURS. That point is inside the 16A rated pedestal, not inside the boat, if everything in the boat is rated for 32A.
It is most definitely NOT a requirement in any of the standards, that the boat's shore power breaker should be sized according to the pedestal it's plugged into. Otherwise, it would be a violation to plug your boat into a 6A French pedestal, but you know very well that you can.
It's no more a problem to plug a 32A boat into a 16A pedestal, than it is to plug a 16A boat into a 6A pedestal.
There is 32A single phase power in some UK marinas. You need the larger blue IEC plug for that. And you see 10A single phase pedestals from time to time. Do you seriously believe that you need different breakers at your main panel, depending on which you are plugged into? You don't, I can assure you.