Daikin IM 986-2 VHC Installation & Maintenance Manual

Contents

Page 32 of 48 / IM 986-2MicroTech III Controller With BACnetCommunication Module for NativeBACnet CommunicationsMcQuay water source heat pumps are available witha factory mounted and tested McQuay BACnet com-munication module The module is factory programmedand tested with all the logic required to control the unit,and is designed to communicate over a BACnet MS/TPcommunications network to a building automation sys-tem (BAS) The module operates the compressor, fan,and reversing valve as required to maintain the spacetemperature within the current setpoints Data regardingequipment status, water and air temperatures, and faultconditions can be monitored by any BAS Setpoints andother system preferences may be changed remotely us-ing a front end workstation or service tool softwareThe module makes operational data and commandsavailable on a communications network using BACnetobjects and properties Each heat pump controller con-nects to the communication network using a BACnetMS/TP communication network, which is a simpletwisted-pair communications connection that operates atup to 76 8 Kbps DIP switches on the controller enablethe MS/TP MAC address to be set in the range 0-127 Astatus LED on the unit indicates communication activityon the MS/TP communication networkFigure 47: MicroTech III BACnet Water Source Heat PumpSnap-in Communication ModuleEach BACnet-compliant unit includes discharge airand leaving water temperature sensors, as well as allequipment protection sensors, signals, and switchesWall-mounted room sensors are available to controlheating and cooling operation Sensors are availablefor status override; wall-mounted sensors with tenantsetpoint adjustment lever and timed-override button;wall-mounted sensors with LED status, timed-overridebutton, tenant setpoint adjustment buttons, password-protected field service access to operational data, andoptional humidity sensor; and wall-mounted sensorswith LCD and programmable operationEach BACnet-compliant controller has the followingoperating features: Start-up – The unit will not operate until all theinputs and safety controls are checked for normalconditions Fan operation – Fan operation can be customized insoftware to run continuously during occupied mode,or to cycle ON or OFF appropriately on a call forheating and cooling Cooling mode – On a call for cooling, the compres-sor and fan start immediately Compressor run-time is calculated as a percent of full cycle time(17 minutes) using proportional-integral control tomaximize efficiency. Heating mode – On a call for heating, the com-pressor and fan start immediately, and compressorrun-time is calculated as a percent of full cycle time(17 minutes) using proportional-integral control tomaximize efficiency. Short Cycle Protection and Random Start – A startdelay of 180 seconds plus the compressor’s MACaddress in seconds prevents short-cycling andsimultaneous start-up A minimum 2-minute on timeand 5-minute off time for the compressor furtherensures short-cycle protection Occupied Mode – A simple software control signalfrom the building automation system or a wall-mounted unit puts the unit into occupied modeThe unit controls compressor and fan operation tomaintain occupied setpoints High and low limitsfor occupied setpoints are software configurable. Unoccupied Mode – A simple software controlsignal from the building automation system or awall-mounted unit puts the unit into unoccupiedmode for night setback operation The unit controlscompressor and fan operation to maintain unoccu-pied heating and cooling setpoints, which are alsosoftware configurable.