1 Pole + Neutral VS 2 Pole MCB's

[Andrew_van_Zyl]

Hi folks
Any difference between the two (assuming both have overload protection)?
Thanks in advance
AvZ

[GCE]

You would not use an SPN on 2 live wires or output of a safety transforming.

My feeling is SPN should not be used on an inverter so as to provide overload protection on both legs of the output

SPN is fine anywhere you want protection on live and need to disconnect the neutral

[Isetech]

You would not use an SPN on 2 live wires or output of a safety transforming.

My feeling is SPN should not be used on an inverter so as to provide overload protection on both legs of the output

SPN is fine anywhere you want protection on live and need to disconnect the neutral

Why would you want to do that if the neutral on the output of the inverter is bonded to ground? I use the SPN on the input and output of the inverters we install.

The only thing we will be changing in the future is the protection size and wire. Instead of using a 32 amp SPN, we will be fitting 40 amp (I dont know if you get 40 amp SPN). I will also be installing 10 mm wire from the DB to the inverter and 10mm back to the essential sub DB for 5 kva units. IF we install 8 KVA units, which are becoming more popular because they can be used with the new bigger panels, I will probably need 16 mm wire.

[GCE]

Why would you want to do that if the neutral on the output of the inverter is bonded to ground? I use the SPN on the input and output of the inverters we install.

The only thing we will be changing in the future is the protection size and wire. Instead of using a 32 amp SPN, we will be fitting 40 amp (I dont know if you get 40 amp SPN). I will also be installing 10 mm wire from the DB to the inverter and 10mm back to the essential sub DB for 5 kva units. IF we install 8 KVA units, which are becoming more popular because they can be used with the new bigger panels, I will probably need 16 mm wire.

There will be times when it is not bonded depending on the set up for short periods of time

[Isetech]

There will be times when it is not bonded depending on the set up for short periods of time

That is why it is important to understand the inverter type and installation criteria. IF we install an Axpert type of inverter the output is always bonded. Now as we move into the Hybrid bi directional type, its is going to be interesting to see what happens when we run the tests in the workshop.

[AndyD]

SP+N breakers also have a staggered break sequence where neutral contact breaks last and makes first. This can also cause interesting problems under certain fault conditions when the neutral isn't bonded to earth.