Solar PV supply

[revor]

Have had 2 quotes for solar pv 4kw on the ground some 90 m cabling from the CU. One installer said the inverter would be housed in a box next to the array the other would put it indoors next to the CU. My gut feeling is that the external option is the best as I don't think sending DC 90 m to the house albeit in a ducting is a good idea. Typically what would be the spec of the cable. What do you think.

Thank you

 

[Barx]

Neither is right or wrong to be honest. A lot of inverters can be mounted outside (IP rating) and many are mounted outside. Kept out of the extremes (direct sunlight, frost) there shouldn't be an issue. Likewise, there is no issue with the DC run either. If doing the long DC run, I would probably do it in 6mm cable rather than 4mm. At 90m you would probably just be about ok with 4mm, but better with 6mm. Having the inverter closer to point of connection could save you a bit on the AC run too.

 

[binky]

4mm is fine over that distance, but I would be inclined to keep the DC short and mount the inverter by the panels. DO NOT BE PALMED OFF WITH A CHINESE INVERTER. SMA / Steca / Fronius are the best options.

 

[revor]

Thank you the inverter outside was from an installer who does a lot of external ground mounted arrays whilst the internal inverter was by someone who does mainly domestic roof installations. Hence probably the difference. To clarify would it be 6 mm for DC and 4 mm for AC would they need to be SWA even in a trunking?

 

[binky]

4mm DC, AC , I would suggest 10mm XLPE armoured to avoid cable losses. Put generation meter in IP rated box adjacent to panels and inverter.

Domestic fella probably uses cheap Chinese inverters not rated for outdoors. Any solar farm you care to look at has the inverters close to panels and outdoors, usually mounted to framework so out of hot sun and shltered from rain, but in plenty of fresh air to dissipate heat.

 

[leesparkykent]

Working from memory, 25mm will give you around the recommended 1% maximum volt drop mark.

 

[binky]

doesn't matter so much once it is past the meter - you've clocked the kWhs, I've just double checked on PV-sol and 16mm will be sufficient.

 

[leesparkykent]

More to do with nuisance tripping of the inverter due to over voltage depending on the OP's supply voltage of course.  

 

[binky]

inverters will run upto 260V, so that shouldn't happen.

 

[leesparkykent]

inverters will run upto 260V, so that shouldn't happen.

Shouldn't happen but does. If the grid voltage at the house was near the same voltage as the TX output (depending on how close they are to the TX of course) and an undersized PV

circuit over a span of 90 meters its defiantly achievable. 

 

[binky]

7v is quite a bit of head room

 

[leesparkykent]

7v is quite a bit of head room

16/17A at 90 meters would bring you in at around 7V volt drop with 10mm swa.