Required cable type and size for 20KW inverter

[masonc]

I'm interested to see what cable would be used in the UK as the AC output cable from an SMA STP20000TL-EE inverter to the disconnect and panel. In the US, it would be #8 in conduit, but I like the multicore cable approach and I want to see if I can satisfy both BS and NEC standards.
The inverter Imax is 29A, under the NEC it would require a cable rated for at least 36.25A. Additionally, the cable has to be rated for outdoor applications.
Please let me know what is required under UK standards.
Chris Mason
Comet Solar

 

[SolarCity]

Depends on the cable length.

 

[Worcester]

There are two requirements:
1) Current carrying capacity (See BS7671 depends upon type of cable and how installed)
and
2) Voltage Drop - once again BS7671 PLUS the PV design requirement of a voltage drop of less than 1% so that the inverters don't overvoltage.

So a 50kW system could be on anything from 25mm2 5 core SWA to 125mm2 4 core SWA depending upon the installation environment.

 

[masonc]

"25mm2 5 core SWA to 125mm2 4 core SWA"
So SWA would be normal? I would have thought that would be overkill for wiring the inverter to the AC Disconnect to the panel. What other cable is acceptable? I don't have a copy of BS7671 (unless anyone can send me one).

 

[Gavin A]

all depends on the mounting method / cable run doesn't it.

this is one of those how long is a piece of string questions without the necessary information, but outdoor would mean not standard 4 core and earth, and tbh I just prefer to use SWA outdoors as it's going to be more durable, and the cost difference is minimal really in the grand scheme of a 20kW solar installation.