Tare (night power consumption) in inverter database.

It appears that some inverters (example PVI-CENTRAL-250-US 480V [CEC 2011]) in the inverter database use a different sign convention for night consumption than others.

To be consistent with most of the entries, tare consumption should be positive. In the example given it is negative, meaning that the inverter generates power at night, rather than consuming it.

I did not see this mentioned elsewhere in the support forum, so I bring it up here.

Hi Steve,

Thanks for pointing out this potential error in the inverter library. It turns out that of the 1400 inverters in the library, 120 have negative night-time power loss values. We're looking into that now.

In the meantime, I can suggest two workaround solutions. The first, and perhaps safest, is to use the "Inverter Datasheet" option to model those inverters, and type the data sheet specifications by hand. The second solution is to edit the SAM library file and change the negative night-time loss value to a positive one. To do that, go to the libraries folder in your SAM installation folder (by default in Windows, it's c:\SAM\2014.1.14\exelib\libraries), and open the SandiaInverters.samlib file with a text editor. You can change the value of pv.inv.sandia.pnt for each of the inverters with a negative value -- just be careful not to add any lines to the file or to change the value of other parameters.

Best regards,
Paul.

Those negative inverter night-time losses are a mistake -- they should be positive numbers. We will change that and issue an update in the next week or so. The update will also include new inverters added to the database since we released SAM 2014.1.14 in January. I will post a reply here when we release the update.

Best regards,
Paul.