AC cable size

[hduz5]

Hi,

I'm looking at installing a 3.96kwp system on a barn roof. Looking at an SB 3800 inverter.

The inverter will be sited within 10m of the array, in the barn. The consumer unit is 100m run away from the inverter. Looking at volt drop calculator suggest I need 10mm SWA. Does this seem correct? I'm pretty new to all of this and would greatly appreciate any advice.

Cheers

 

[BruceB]

No way with 10mm SWA I suggest if you want to meet the <1% voltage drop requirement.
The Sunny Design software will work it out for you.

Regards
Bruce

 

[MCS Renewables]

It depends on how accurate your 100 metres is for 25mm or 35mm .

At 100 metres 25mm fails at real power loss of 1.04% (2.39V) so you would need 35mm.

 

[SolarCity]

More like 35mm

 

[JulianC]

If 25mm gave me 1.04% loss, I'd be happy with that. The world won't suddenly end if your AC volt drop is greater than 1.00000000001%

 

[Markc]

JCDC - LOL you never know! It just might!

There has been comments on here that voltdrop of cable is calculated at 90 degree operating temperature and a PV installation is unlikely to be operating a full capacity so cable calc could be worked as a rule of thumb. I on the other hand prefer to support my designs using the only information available to me and by using a cable calc program. Until this takes the operating temperature into account then I going to run with what that says.

I have a 4kW ground mount starting in early May which is 52mts away from mains. Cable calc worked 1% to need 16mm 3 core over that distance so the 10mm over 100mts is going to be to small, but thats just my opinion.

 

[earwig]

I had a similar job. Surveyed for a ground mount with swa length of 60 meters. Checked the guidance which accepts 1% loss is not practical in certain circumstances. Went with regs volt drop of 11.5v and felt confident to quote on 10mm, volts drop calc on 16 amp well inside this. I don't see a problem with this but I'm open to comments.

 

[andyemms]

Just been to look at a job like this today. I would be confident if the 100m length had been in 25mm but the existing is in 10mm and they dont want to change it. I won't be putting my name to this one!