As a quick refresher on Normally Open (NO) / Normally Closed (NC) Relays that are found as the control outputs on the Compressor Controller:
On Compress Controllers Version 2:
And Compressor Controller Version 3:
The Compressor Controller is equipped with both NC and NO relay outputs, with the center connection as common, this allows it to work with virtually any type of configuration.
NO = Normally open (open = open circuit = not creating a path for the current)
NC = Normally closed (closed = short circuit = creating a path for the current)
C = Common