====== SUM() Function ======

The SUM() function is used to sum up the values of a similar variable name from multiple devices, optionally in a particular device profile.

Usage:

''SUM('variable_name', 'profile_name')'' - see below for description.

===== Examples =====

''SUM('INC1_AE','Inverters')'' 

Return the sum of all variables with the name INC1_AE with a device profile name of 'Inverters'

''SUM('watts')'' 

Return the sum of all variables called 'watts' for all devices that the user has access to