Victron Isolation Transformer Overcurrent Protection

Came across this multi function breaker which looks quite interesting. Can't see any indicate of a CE mark or UK equivalent though!! 






 

Hello Rob,

With a 20 amp IT Transformer it is very unlikeley that the shore supply will have more than a 16amp MCCB and thus no chance of overloading.

Minimise wiring from inboard shore connection to distribution board

An RCD downstream of the IT will protect those on board

MCCBs in the consumer unit will protect the downstream wiring.

You may be thinking of installing too many protection devices - and points of failure!

The UK IET (was Institute of Electrical Engineers) will be publishing their guide to boat wiring later this year which reflects my comments above.



 

Balliol Fowden wrote:

Bullet points from my last ramble which is now lost in cyberspace:


4.     If you are on say a 20 amp IT you should have a 20 amp main breaker /fuse, which is better on the output side of the IT (keeps it within the ship’s earth cocoon) and before the main distribution board with ship’s RCD and individual circuit mcb’s. That will prevent you from drawing more than 20 amps. On that basis you will not be able to overload a 20 amp IT or a suitably sized (2.5mm) shore cable.

It’s a bit of a bxxxxr that you can’t seem to scroll down and check the last response!

Balliol.



 

Thanks for this and for your efforts.

On this last point (and maybe I'm overthinking this) I had thought it made sense to have overcurrent protection on the incoming side of the IT rated to the max IT amperage. I've done measurements with a clamp meter and found there is an efficiency loss in the IT. So, if I'm drawing the max amperage on the ship side of the IT, then the shore power side would be over the max draw. I suppose for completeness having protection on both sides would not cause harm.

I'm definitely overthinking this.

Cheers,
Rob

Bullet points from my last ramble which is now lost in cyberspace:

1.   Your shore bollard may have an RCBO (Residual Current device Breaker with Ocercurrent protection). I.e combined mcb and RCD. The looks the same as an RCD.

2.   You can fit an in-line RCD if you don’t trust the shore one, to protect personnel should your shore cable become damaged. This should be as close to the shore bollard as possible.

3.    Victron presume that the shore supply is suitably protected.

4.     If you are on say a 20 amp IT you should have a 20 amp main breaker /fuse, which is better on the output side of the IT (keeps it within the ship’s earth cocoon) and before the main distribution board with ship’s RCD and individual circuit mcb’s. That will prevent you from drawing more than 20 amps. On that basis you will not be able to overload a 20 amp IT or a suitably sized (2.5mm) shore cable.

It’s a bit of a bxxxxr that you can’t seem to scroll down and check the last response!

Balliol.


 

Paul Hayes wrote:

Rob Davison wrote:

A question about protecting a Victron isolation transformer from overload.

In the spec sheet for all models it says "Input Circuit Breaker: Yes"

In the manual it does not talk about overcurrent protection, or what happens if the unit gets overloaded. Only mention is about a soft start protection for high inrush current as well as thermal protection.

Does anyone know what happens if the unit is overloaded? In the model I have, I can't see any kind of reset inside the device. I'm assuming that something will go 'pop' and will require repair.

Would it be sensible to install overcurrent protection in the form of a circuit breaker rated to match the transformer between the shore connection and the transformer? At least in our mooring there is an appropriately rated RCD in the bollard, but it's my understanding that and RCD does not provide overcurrent protection. 

 

Hi
In the electricity supply post, you will find that there may be an RCD, but there will be an MCB, which is the equivalent to a fuse.

The MCB limits the amount of current in Amps that is allowed to flow to your boat.  They are often rated at 16A.ps, but 32, 10, 6A are not unknown.

If you pull more than the rated Ampage, the MCB (Miniature Circuit Breaker) will trip to the "off" position and disconnect the supply.

An RCD (Residual Current Device) monitors the flow of electricity through both the phase (Live) and Neutral conductors (brown and blue wires). If there is any imbalance between the two conductors, it will trip to "off" cutting the supply.

Over loading the MCB can be as simple as putting an electric kettle on, whilst another appliance is in use, and the total amount of Amps required for both adds up to the rating of the MCB, say 16A.

It can also be the case that if there's an insulation fault and the Phase (love) wire comes into contact with either Earth or Neutral, the current surge (Amps) will increase above the MCB rating and it's contacts will open shutting off the supply.

Personally I think that both an RCD and MCB equipment should be installed as close to the point that the shore supply enters into the boat as is practical.

In your case, before the Isolation transformer.

After the Isolation transformer your transformed supply should then enter a Distribution Board, for distributing around the boat through MCBs.

The UK system uses on the whole, single pole switching MCBs, whilst European generally utilise double pole protection devices.

I've seen a number of well known UK barge builder boat s where the incoming supply route utilises the RCD located in the Distribution Board. It's not immediately obvious for the untrained eye to see what is going on without the use of test equipment.

I hope that this helps and has not made the fog thicker.

Paul Hayes 


Hello Both,

Struggling a bit  with the new format

I don't think your transformer needs both an MCCB and RCD upstream - nor do the new (unpublished ) IET guidelines which will be published year.

Nearly all shore side pedastals  will have an MCCB which will usually be below  your transformer capacity.

It is unlikely that you will need an RCD in the short run between shore and transformer output so an an RCD on the input to your distribution board  will be adequate to protect yo and your crew.  Your distribution MCCBs will protect the downstream circuits from over current.

When the IET wiring guidance for small ships is published I will ensure we are all aware!



 

I should know better but I have just typed a reply to Rob’s post on my IPad, then went to “view history” to check that I had answered the right question and lost my response. Grrrrrrr! 

Rob Davison wrote:

A question about protecting a Victron isolation transformer from overload.

In the spec sheet for all models it says "Input Circuit Breaker: Yes"

In the manual it does not talk about overcurrent protection, or what happens if the unit gets overloaded. Only mention is about a soft start protection for high inrush current as well as thermal protection.

Does anyone know what happens if the unit is overloaded? In the model I have, I can't see any kind of reset inside the device. I'm assuming that something will go 'pop' and will require repair.

Would it be sensible to install overcurrent protection in the form of a circuit breaker rated to match the transformer between the shore connection and the transformer? At least in our mooring there is an appropriately rated RCD in the bollard, but it's my understanding that and RCD does not provide overcurrent protection. 
 

Hi
In the electricity supply post, you will find that there may be an RCD, but there will be an MCB, which is the equivalent to a fuse.

The MCB limits the amount of current in Amps that is allowed to flow to your boat.  They are often rated at 16A.ps, but 32, 10, 6A are not unknown.

If you pull more than the rated Ampage, the MCB (Miniature Circuit Breaker) will trip to the "off" position and disconnect the supply.

An RCD (Residual Current Device) monitors the flow of electricity through both the phase (Live) and Neutral conductors (brown and blue wires). If there is any imbalance between the two conductors, it will trip to "off" cutting the supply.

Over loading the MCB can be as simple as putting an electric kettle on, whilst another appliance is in use, and the total amount of Amps required for both adds up to the rating of the MCB, say 16A.

It can also be the case that if there's an insulation fault and the Phase (love) wire comes into contact with either Earth or Neutral, the current surge (Amps) will increase above the MCB rating and it's contacts will open shutting off the supply.

Personally I think that both an RCD and MCB equipment should be installed as close to the point that the shore supply enters into the boat as is practical.

In your case, before the Isolation transformer.

After the Isolation transformer your transformed supply should then enter a Distribution Board, for distributing around the boat through MCBs.

The UK system uses on the whole, single pole switching MCBs, whilst European generally utilise double pole protection devices.

I've seen a number of well known UK barge builder boat s where the incoming supply route utilises the RCD located in the Distribution Board. It's not immediately obvious for the untrained eye to see what is going on without the use of test equipment.

I hope that this helps and has not made the fog thicker.

Paul Hayes 
 

A question about protecting a Victron isolation transformer from overload.

In the spec sheet for all models it says "Input Circuit Breaker: Yes"

In the manual it does not talk about overcurrent protection, or what happens if the unit gets overloaded. Only mention is about a soft start protection for high inrush current as well as thermal protection.

Does anyone know what happens if the unit is overloaded? In the model I have, I can't see any kind of reset inside the device. I'm assuming that something will go 'pop' and will require repair.

Would it be sensible to install overcurrent protection in the form of a circuit breaker rated to match the transformer between the shore connection and the transformer? At least in our mooring there is an appropriately rated RCD in the bollard, but it's my understanding that and RCD does not provide overcurrent protection.