This article applies to the following CoolMaster products: CoolMaster CoolMasterPro CoolMasterNet HVAC Communication TerminalsHVAC outdoor connection * For Heat Recovery systems the connection is at outdoor units only. * Polarity is not required on the HVAC communication line. Connecting to the line plugSecure the cables in the L1 line plug. Plugging to the CoolMasterInsert the plug in to the CoolMaster L1 socket. Check DIP Switches are set correctlyDip switches setup for VRF HVAC system on L1.