Max Cable Run

[LA3222]

Long story short, I have an invertor on the side of the house and am in the process of building a garden room at the bottom of the garden. The cable run from one t'other would be about 100m. I want to stick another 3.64kWp onto the roof but don't want to add another invertor there. Is it feasible to add them to existing invertor and if so, how large would the cable need to be to keep the voltage drop within limits?  

[JohnMo]

Doing distance in AC is problematic, doing it DC is easy. Adding to the existing inverter is a different issue. You really need to treat it as different string, not add to existing.  Other issue is max amps the existing inverter can handle.

 

I have just done 3.6kW about 70m and had to split into two strings otherwise the cable became big/expensive. Each string was 260V DC, and used 6mm2, 4 core armoured cable.

[LA3222]

15 minutes ago, JohnMo said:

Doing distance in AC is problematic, doing it DC is easy. Adding to the existing inverter is a different issue. You really need to treat it as different string, not add to existing.  Other issue is max amps the existing inverter can handle.

 

I have just done 3.6kW about 70m and had to split into two strings otherwise the cable became big/expensive. Each string was 260V DC, and used 6mm2, 4 core armoured cable.

Cheers for the reply bud. I need to do some thinking about the setup- I was already thinking along the lines of a separate string. I can't recall what I put out there but I think it's a 3.6kW invertor with around 2.2kWp currently connected to it (small bit of roof). The ones on the garden room are going to be an East/west ish split whilst the others are south east ish but with an overhang shading slightly. In short, I don't expect to ever have all panels kicking out max power at the same time so with my fag packet thinking at the minute, they will be within the capacity of the invertor.

 

The part of the puzzle I am trying to understand better is the wiring from a to b. Sounds like it's a non issue, I will look in more detail at the setup at the invertor end.

[ProDave]

New 3.68kW panels will be 2 strings and will be the max your inverter can take.

 

Then put the original panels on a separate inverter that does not need to be as big.

 

And don't forget to ask permission from your DNO first to have more than 3.68kW

[Dillsue]

If the garden room panels are on an east/west split the you'll probably want the east and west arrays on separate strings so you'll need 2 spare mppt inputs on the inverter and 2 loops of cable running down to the garden room.

 

The mix of directions and shading would make your set up an ideal candidate for optimisers/microinverters