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SunSynk 5kw Battery Backup

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Good day to all,

New to your forum, so hopefully this is posted in the correct section. Wasn’t sure if you have an “intro” thread I need to post in first? If so and I’ve missed it, my apologies.

As with many people on this forum, I have decided to install a battery backup and would appreciate some input with regards to my understanding of these systems. I’m no electrician but don’t want to be mis-lead by installers and thus would like to have a good understanding of how they “should” correctly install this setup.

I have opted to install a SunSynk 5kw inverter with a SunSynk 5.32kw battery as a battery backup only. This has been calculated based on my particular usage +- 10Kw a day (24hrs), which equates to about 500watts/h. Max is about 700watts/h. So, my requirement is for about 2.5kw (max) for the 4/5hr slots expected in the next few months.

Some points to clarify for this particular installation:

·        I live in a block of flats, so I will never install solar panels or use a generator. The installation will only be used as a UPS(Island mode) setup.

·        The Inverter and battery will be installed about 1.5m away from the main DB Box.

·        The Inverter will not feed back to the Grid.

·        I do not have an electric geyser (converted to gas)

·        I do not have an electric stove & hob (converted to gas)

·        The electric geyser used to be connected to a CoJ relay, but this circuit and geyser has been switched off.

·        NB! An Important difference to be noted is: all my current circuit breakers for lights and plugs will be used by the Inverter Battery backup. I do not need to split my loads (essential and non-essential), as all these circuits are deemed essential. All non-essential (heavy loads) are not present on my current DB board anymore.

With this in mind, I have not seen any information in any threads that address installations where the battery backup is fed directly back into the main DB board (no split DB board)?

So, I have done a schematic to try and clarify my thinking as to how this will be installed (see pic below).


However, I require clarification on the following questions:

1.       The battery cables will be 50mm2, so are 160amp fuses the correct size?

2.       Do you install the SunSynk CT coil before or after the Mains switch? I would assume before but just want to make 100% sure?

3.       The recommended wire diameter for the Inv: Load and Grid wires is 6mm2, and the documentation states/suggests 40amp breakers for both Grid and Load? Is this wiring and breaker correct for the installation? This will be put in a separate DB box close to the Inverter, so that the breakers can be switched off and thus disconnect the inverter to the main DB box, if required.

4.       To provide the Inverter with power i.e., Inv: Grid, do you connect the positive and negative wire directly from the mains output? Or from the Earth Leakage output

           a.       E.g.: Mains output -> 40 amp breaker -> Inverter: Grid or

           b.       E.g: Earth Leakage output -> 40amp breaker -> Inverter: Grid

5.       As per the SunSynk documentation (Point 4.12 – second diagram), it’s recommended to do a permanent Ground to Neutral Bond? I understand that this is a highly debated topic and don’t want to debate/argue this to death. So, input would be appreciated for this PARTICULAR installation only. Therefore, would a permanent bond just be to link the DB Neutral and Ground bars in the DB box?

6.       To provide the DB with battery backup power i.e: Inv: Load, do you connect the positive wires, directly into the connected circuit breakers (as per my pic)? And the Neutral to the DB board neutral bar?

If there are any other components that need to be included or excluded, please advise accordingly.

I understand that this is a long-winded post but would appreciate any info, to further my understanding of this topic.



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