AC cable size for 3 x 5kW parallel Deye inverters?

[Eric007]

What size of AC cables should I use? The inverters are capable of delivering a bit more that 5 kW each for limited time, should I use larger cables to take this into account?

[Jacques Ester]

I would not use anything less than 6mm for each.

[Eric007]

Will then using 3 x 6mm2 = 25mm2 be sufficiently safe?

Edited August 28, 2023 by Eric007

[Jacques Ester]

3 phase or Single phase installation?

[Eric007]

2 hours ago, Jacques Ester said:

3 phase or Single phase installation?

Single phase...

[Jacques Ester]

I would rather install 3 MCB's to supply & isolate each inverter. If you want to supply all 3 with one cable I would not go smaller than 16mm. This will easily handle 63Amps which is any normal house supply breaker rating and cable size.

[PsyCLown]

2 hours ago, Jacques Ester said:

I would rather install 3 MCB's to supply & isolate each inverter. If you want to supply all 3 with one cable I would not go smaller than 16mm. This will easily handle 63Amps which is any normal house supply breaker rating and cable size.

I agree with this, I'd also rather install 3 breakers (one per inverter) and what I did with my install is a main isolator which feeds these 3 separate breakers so you can easily isolate power to all inverters at once if need be.

6mm per inverter should be good and more than sufficient. If you decide to go with an isolator then at least 16mm to provide power to the isolator.

 

For interest sake, what is your main feed from Eskom? Mine is 60A with 16mm cable, if you're also on 16mm feed from Eskom then I would not bother with going for a larger cross sectional cable.

[Steve87]

The calculation should be that each machine with AC passthrough can go to 8kW. 8 kW is +-40A so multiply that by 3 for 3 inverters on a single phase supply feed. So 40x3 =120A cable AC cable. 

Which also means you need more than a 120A Grid supply. Begs the question if you have this place. If not I wouldn't bother with the 35mm2 cable. But place that on your Load side.

The ATESS range of inverters has the same issue. It needs a Grid port cable thickness to carry its rated load & charge the battery at peak charge rates as a grid charger. The HPS100 (100kW) inverter requires a 120mm2 AC cable. Most Eskom Supply lines are at 35mm2 for most of these deployments. So what do we do? Match the Grid cable size & derate the Machines Grid output. However, on the load side they ask for 70mm2 cable. Now that you can install as it's possible to generate that sort of energy as a base line requirement. 

Edited August 28, 2023 by Steve87

[Eric007]

55 minutes ago, PsyCLown said:

I agree with this, I'd also rather install 3 breakers (one per inverter) and what I did with my install is a main isolator which feeds these 3 separate breakers so you can easily isolate power to all inverters at once if need be.

6mm per inverter should be good and more than sufficient. If you decide to go with an isolator then at least 16mm to provide power to the isolator.

 

For interest sake, what is your main feed from Eskom? Mine is 60A with 16mm cable, if you're also on 16mm feed from Eskom then I would not bother with going for a larger cross sectional cable.

I will check the cable size. My feed from Eskom is limited to 63A but I'm going to ask for 80A (I actually asked municipality to quote me on upgrading to 3phase but it was far too much!).

[Scorp007]

1 hour ago, Steve87 said:

The calculation should be that each machine with AC passthrough can go to 8kW. 8 kW is +-40A so multiply that by 3 for 3 inverters on a single phase supply feed. So 40x3 =120A cable AC cable. 

Which also means you need more than a 120A Grid supply. Begs the question if you have this place. If not I wouldn't bother with the 35mm2 cable. But place that on your Load side.

The ATESS range of inverters has the same issue. It needs a Grid port cable thickness to carry its rated load & charge the battery at peak charge rates as a grid charger. The HPS100 (100kW) inverter requires a 120mm2 AC cable. Most Eskom Supply lines are at 35mm2 for most of these deployments. So what do we do? Match the Grid cable size & derate the Machines Grid output. However, on the load side they ask for 70mm2 cable. Now that you can install as it's possible to generate that sort of energy as a base line requirement. 

It might be worse than what you indicated. The maximum pass through on a 8kW Sunsynk is 53A. 

I seem to remember the 5kW is 35A.

@PsyCLown

Depending on the spec of the isolator it might not be good to break the current of all 3 inverters. It is called an isolator to isolate after you have switched them off and they are under no load. 

@Jacques Ester

3 x 5kW inverters with a pass through of 35A each gives 105A. This is more than the main supply from Eskom in most cases at 63A. So having only 63A the 16mm could be OK? 

Edited August 28, 2023 by Scorp007

[TaliaB]

1 hour ago, Eric007 said:

I will check the cable size. My feed from Eskom is limited to 63A but I'm going to ask for 80A (I actually asked municipality to quote me on upgrading to 3phase but it was far too much!).

If you have a 63A incomer you have a 16mm² 3 core Swa cable from your kiosk on the sidewalk. Most residential feed is supplied by 16mm² 3 core Swa cable protected by a 80 amp curve D breaker in the kiosk. The max current for a 16mm² Swa cable is 94 amps. There would be a risk running 3 x 5kw inverters in parallel from single phase supply cable as there is a possibility to go beyond the 94 amps unless you derate the input breakers per inverter from 40 amp to 30 amp with main switch as 80 amp curve C ensuring that you don't trip the breaker in the kiosk in overload or short curcuit situation.

 

 

 

 

[Jacques Ester]

This is the reason I said 16mm cable. There is no need fitting anything bigger if the main supply cable cant handle it. The load side is a different story.

[TaliaB]

The only safe way to do this installation with 3 x 5kw inverters is with 3 phase each inverter on its own phase with 40 amp input mcb's. Single phase will be a risk and not advised. 

[PsyCLown]

16 hours ago, Scorp007 said:

@PsyCLown

Depending on the spec of the isolator it might not be good to break the current of all 3 inverters. It is called an isolator to isolate after you have switched them off and they are under no load. 

So isolator should only be turned off once power to it has been disconnected?

A circuit breaker can be turned off under load though?

15 hours ago, TaliaB said:

If you have a 63A incomer you have a 16mm² 3 core Swa cable from your kiosk on the sidewalk. Most residential feed is supplied by 16mm² 3 core Swa cable protected by a 80 amp curve D breaker in the kiosk. The max current for a 16mm² Swa cable is 94 amps. There would be a risk running 3 x 5kw inverters in parallel from single phase supply cable as there is a possibility to go beyond the 94 amps unless you derate the input breakers per inverter from 40 amp to 30 amp with main switch as 80 amp curve C ensuring that you don't trip the breaker in the kiosk in overload or short curcuit situation.

 

Interesting, I actually had to check this morning and my property has an old CBI single pole 60A breaker outside and inside I have since upgraded to a newer 2 pole 63A CBI breaker (was originally the old, single pole 60A CBI breaker which I was told is no longer compliant as mains should be 2 pole for single phase).

Not really the end of the world as I have access to both breakers to reset them should either trip.

My cable also does not seem to be armored cable, looks to be normal GP wire. This is in Gauteng though, so perhaps the infrastructure was built differently to how it was in Cape Town?

 

 

@Eric007 Do you actually need 15KW of inverter power? Would 2 not suffice and then keep some of the breakers on feed?

[Scorp007]

34 minutes ago, PsyCLown said:

So isolator should only be turned off once power to it has been disconnected?

A circuit breaker can be turned off under load though?

 

Interesting, I actually had to check this morning and my property has an old CBI single pole 60A breaker outside and inside I have since upgraded to a newer 2 pole 63A CBI breaker (was originally the old, single pole 60A CBI breaker which I was told is no longer compliant as mains should be 2 pole for single phase).

Not really the end of the world as I have access to both breakers to reset them should either trip.

My cable also does not seem to be armored cable, looks to be normal GP wire. This is in Gauteng though, so perhaps the infrastructure was built differently to how it was in Cape Town?

 

 

@Eric007 Do you actually need 15KW of inverter power? Would 2 not suffice and then keep some of the breakers on feed?

It will depend on the kiosk. Some are built with normal GP wire from meter and MCB to a terminal strip at the bottom of the kiosk. Here the SWA cable is joined and goes underground to a connection point at the border of the property. From here the consumer cable is joined going to the connection on the side of the house and at times there is a steel box built into to wall. From here it then goes via conduit to the DB. 

Depending on the standard arrangement it could differ from time to time and between munics.

Example  of our kiosks. 

Edited August 29, 2023 by Scorp007
Added pic of kiosk.

[Eric007]

6 hours ago, PsyCLown said:

So isolator should only be turned off once power to it has been disconnected?

A circuit breaker can be turned off under load though?

 

Interesting, I actually had to check this morning and my property has an old CBI single pole 60A breaker outside and inside I have since upgraded to a newer 2 pole 63A CBI breaker (was originally the old, single pole 60A CBI breaker which I was told is no longer compliant as mains should be 2 pole for single phase).

Not really the end of the world as I have access to both breakers to reset them should either trip.

My cable also does not seem to be armored cable, looks to be normal GP wire. This is in Gauteng though, so perhaps the infrastructure was built differently to how it was in Cape Town?

 

 

@Eric007 Do you actually need 15KW of inverter power? Would 2 not suffice and then keep some of the breakers on feed?

Thnx. I have 6 flats on my property and wanted to provide a backup power. I'm not thinking of feeding the Eskom grid, not for now at least. The 3rd inverter is a backup if one fails. With 2, if one fails, a single inverter will be far too little and will most likely trip on overload. So I consider to add the 3rd one... Don't know if it make sense?  

For now I purchased only 2 inverters + 24 x 550W panels (12 each) but when installing the AC cables I wanted to make provision for 3rd inverter in the future, therefore my original question about the cable size. Am I overkilling?  

[Scorp007]

41 minutes ago, Eric007 said:

Thnx. I have 6 flats on my property and wanted to provide a backup power. I'm not thinking of feeding the Eskom grid, not for now at least. The 3rd inverter is a backup if one fails. With 2, if one fails, a single inverter will be far too little and will most likely trip on overload. So I consider to add the 3rd one... Don't know if it make sense?  

For now I purchased only 2 inverters + 24 x 550W panels (12 each) but when installing the AC cables I wanted to make provision for 3rd inverter in the future, therefore my original question about the cable size. Am I overkilling?  

2 inverters will provide 70A in bypass which is what your current munic supply is. I belief if the 3rd one is seen as a back up and only 2 in use then it could be OK but limit each to 40A from the DB as @TaliaB suggested earlier.

6 flats on a 63A main MCB is also cutting it close to a risk of tripping any moment.

Edited August 29, 2023 by Scorp007