Engineering Bulletin Tracer® ZN524 Unit Controller for water-source heat pumps December 2009 WSHP-PRB002-EN Introduction General The TracerTM ZN524 water-source heat pump unit controller is a microprocessor-based direct digital controller that controls a range of water source heat pump equipment including: • high-efficiency horizontal and vertical units; • premuim-horizontal and vertical units; and • console water source heat pumps. The Tracer ZN524 is designed to provide accurate and reliable zone temperature control through the use of pre-engineered control algorithms. Based on the unit type, the controller is a factory installed and commissioned, resulting in a highly integrated product. Factory commissioning helps to ensure the highest level of quality and customer satisfaction. Applications The ZN524 unit controller may be applied as part of a Trane Tracer Summit® system, as part of a Trane Tracer Loop controller small building system, a stand-alone device, or as an interoperable controller. In addition, the unit controller may be applied in a peer-to-peer communication environment, where data can be exchanged between similar controllers without requiring a master controller. Inputs/Outputs The Tracer ZN524 unit controller is factory configured to control the unit fan, reversing valve, one or two compressors, and various other end-devices and components. The controller utilizes space temperature and setpoint inputs; fan mode switch input and entering water temperature to condition the space. Other optional inputs include condensate overflow, and occupancy. © 2009 Trane All rights reserved WSHP-PRB002-EN Features and Benefits Factory Installed and Commissioned Controls All Trane controls are factory-commissioned and installed. The ZN524 control board, sensors, power transformer, required wiring, and actuators (when applicable) are installed as part of the normal construction of the unit. Upon completion, each unit receives testing via an automated download/test stand. The computer downloads the proper unit configuration and location ID and proceeds to test the unit both mechanically and electrically. The unit must pass all phases of testing before the automated tester allows the unit to be shipped. This helps to ensure a high quality product is delivered and installation time is reduced. Occupied/Unoccupied Note: Occupied and unoccupied modes are typically coordinated by the Trane Tracer Summit or Tracer Loop Controller The ZN524 unit controller is factory programmed with a set of occupied, occupied standby, and unoccupied setpoints. During unoccupied conditions, when larger space temperature swings can be tolerated, the controller significantly reduces unit run-time, saving operating expense. The controller has a binary input that is configured to be either an input for switching between occupied and unoccupied modes or as a generic input. This feature allows the controller to function as a standalone controller, or allows the unit to be put into an occupied standby mode when used with an occupancy sensor in a building automation system application. The controller can accept both hardwired and communicating occupancy inputs. This gives the user ultimate application flexibility for localized or system-wide time-of-day scheduling. Timed Override The controller includes a timed override function for after- hours operation. This allows the user to request unit operation by the touch of a button on the unit’s space temperature sensor. Additionally, the user can push the cancel button at any time during the override command to place the unit back into unoccupied mode. Random Start The controller inhibits fan and compressor operation for a random period of time at power-up and on the transition to the occupied mode. This avoids a possible system power surge that may occur when multiple units start at the same time. High and Low Pressure Protection The controller has built-in refrigerant high and low pressure protection capabilities. These safeties prevent the unit from operating with high/low refrigeration pressure levels that may occur under abnormal system conditions. Compressor Minimum Timers All unit compressors are subjected to minimum on and off timers to prevent short cycling and therefore maximize compressor life. Condensate Overflow When the condensation reaches a trip point in the drain pan, the condensate overflow switch disables unit operation. This feature prevents water damage to the building. WSHP-PRB002-EN 3 Features and Benefits Fan Status Tracer ZN524 unit controllers provide two methods of monitoring fan status. The first method monitors the fan output status through the Tracer ZN524 unit controller. This method is not considered positive proof of airflow, but is typically acceptable on direct drive fan applications. Tracer ZN524 unit controller also has the ability to accept a binary input from a fan proof switch for belt driven applications or when proof of flow is required by the customer. When fan operation is expected by the controller, but not confirmed by the proof switch, unit operation is disabled if the unit is configured as Fan Status with Diagnostic. If the unit is configured as Fan Status - No Diagnostic, the status of the fan proof switch will be passed to the BAS system and does not have any affect on the operation of the unit. Filter MaintenanceControls Filter maintenance status for the Tracer ZN524 unit controller is based on the cumulative run hours of the unit fan. An adjustable and re-settable timer exists in the controller that, when expired, indicates to the user through Tracer Summit or Rover service tool, that maintenance is recommended for that unit. The unit controller complies to ASHRAE 6289 Filtration Section. Active Dehumidification The Tracer ZN524 unit controller supports active dehumidification through the use of a reheat coil and humidity sensor. This feature allows the user to keep space RH levels within ASHRAE 6289 guidelines to provide comfort as well as minimizing the risk of microbial growth and damage to the building or its furnishings. Interoperability Trane has lead the industry with BACnet interoperability and is now expanding the realm of interoperable solutions by offering LonMark certified unit controllers. The Tracer ZN524 controller is certified to the LonMark Space Comfort Controller (SCC) profile. This allows the ZN524 to be used as a unit controller on other control systems that support LonTalk and the SCC profile (See Table 1, pg. 7). Building owners have more choices and, design engineers have more flexibility to meet the challenges of building automation. Waterside economizer The Tracer ZN524 unit controller supports a two position waterside economizer through the use of an economizer coil. This feature can help comply with ASHRAE 90.1 guidelines and allows the user to reduce energy consumption. Electric/Boilerless Heat The Tracer ZN524 unit controller supports two types of electric heat, Main heat and Boilerless. When used as a main heat source the electric heat can operate concurrently with compressor heat or as the only source of heat. When configured for boilerless, the electric heat only operates when compressor heat has been disabled, typically based on entering water temperature. Manual Output Test A manual output test function is included to assist in the installation and trouble shooting processes. This function allows the user to temporarily override normal unit operation and manually exercise each of the controller’s outputs. This enables the user to quickly verify fan, reversing valve, compressor, and outdoor air damper operation. 4 WSHP-PRB002-EN Features and Benefits Generic I/O Tracer ZN524 unit controller comes equipped with three generic points for use with a Tracer Summit system: • Binary Input (shared with occupancy) • Binary Output • Analog Input (4-20mA shared with humidity sensor and often used with an optional carbon dioxide sensor) The two generic inputs are only for passing information to the BAS system. They do not have any affect on the operation of the unit. The generic binary output is controlled from the BAS system and its state is not affected by unit operation, even under a diagnostic shutdown. WSHP-PRB002-EN 5 Specifications LonMark Space Comfort Controller Profile The Tracer ZN524 unit controller conforms to the LonMark Space Comfort Controller Profile. It provides LonTalk communications via an FTT-10A transceiver. Typical Zone Sensor Description • Space temperature • Setpoint • Fan switch (off and auto) timed override and cancel buttons • Communication jack for use with laptop communication tool • Vertical case with Trane logo Specifications • Power • Dimensions: – 18 to 32 VAC (24 VAC, 300mA nominal); 50 or 60 Hz – Height: 5.25” (133.35 mm) – Width: 5.50” (140 mm) – Depth: 2.25” (57 mm) • Operating Environment Storage – 32 to 140°F (0 to 60°C) – 5 to 95% non-condensing – -40 to 185°F (-40 to 85°C) • Environment 5 to 95% non-condensing • Agency Listings System UL and CUL 916 Energy Management • Agency Compliance – IEC 1000-4-2 (ESD) – IEC 1000-4-4 (EFT) – IEC 1000-4-5 (Surge) – FCC Part 15 – Class A 6 WSHP-PRB002-EN Specifications Table 1. Input/Output summary Type Description Condensate Overflow Occupancy(a) Fan status(b),(c) Binary Inputs Low evaporation temperature Generic (a),(b) High/Low pressure protect (Circuit 1) High/Low pressure protect (Circuit 2) Fan Reversing Valve Electric heat(a),(c) Reheat(a),(c) Compressor(a) Binary Outputs Compressor(b) Isolation valve(a) Isolation valve(b) Waterside economizer (2-position)(c) Outside Air Damper (2-position) Generic(b) Entering water temperature(a) Outside air temperature (a) Discharge Air Leaving Water Temperature (Circuit 1)(c) Analog Inputs Space temperature Space temperature setpoint Fan switch Relative humidity(a),(c) Universal (Generic)(a),(b),(c) (a) Indicates that two or more features can be associated with this point (Only one may be used). (b) Indicates Tracer Summit is required. (c) Indicates optional feature. Table 2 provides an input/output listing for the Tracer ZN524 unit controller. Table 3, p. 8 provides the configuration properties for the unit controller. The content of the lists conforms to both the LonMark Space Comfort Controller Functional Profile 85.00 and the LonMark node object. Table 2. WSHP-PRB002-EN Input/Output listing Input SNVT type Output SNVT type nviRequest SNVT_obj_request nvoStatus SNVT_obj_status nviSpaceTemp(a) SNVT_temp_p nvoFileDirectory SNVT_address nviSetpoint SNVT_temp_p nvoSpaceTemp(a) SNVT_temp_p nviSetptOffset SNVT_temp_p nvoUnitStatus(a) SNVT_hvac_status nviOccSchedule SNVT_tod_event nvoEffectSetpt SNVT_temp_p nviOccManCmd SNVT_occupancy nvoEffectOccup SNVT_occupancy nviOccSensor SNVT_occupancy nvoHeatCool SNVT_hvac_mode nviApplicMode SNVT_hvac_mode nvoSetpoint SNVT_temp_p 7 Specifications Table 2. Input/Output listing (continued) Input SNVT type Output SNVT type nviHeatCool SNVT_hvac_mode nvoDischAirTemp SNVT_temp_p nviFanSpeedCmd SNVT_switch nvoLoadAbsK SNVT_power_kilo nviComprEnable SNVT_switch nvoTerminalLoad SNVT_lev_percent nviAuxHeatEnable SNVT_switch nvoSpaceRH SNVT_lev_percent nviEconEnable SVNT_switch nvoOutdoorTemp SNVT_temp_p nviEmergOverride SNVT_hvac_emerg nvoSpaceCO2 SNVT_ppm nviSourceTemp SNVT_temp_p nvoEnterWaterTemp SNVT_temp_p nviSpaceRH SNVT_lev_percent nvoLeaveWaterTemp SNVT_temp_p nviOutdoorTemp SNVT_temp_p nvoOADamper SNVT_lev_percent nviValveOverride SNVT_havac overid (a) Required points under Space Comfort Controller profile. All other points are optional. Table 3. Configuration properties Configuration property SNVT type nciSndHrtBt(a) SNVT_time_sec SCPTmaxSendTime (49) Send heartbeat nciSetpoints(a) SNVT_temp_setpt SCPTsetPnts (60) Occupancy temperature setpoint nciUnitType(a) SNVT_hvac_type SCPThvacUnitType (169) Unit type nciMinOutTm SNVT_time_sec SCPTminSendTime (52) Minimum send time nciRcvHrtBt SNVT_time_sec SCPTmaxRcvTime (48) Receive heartbeat SCPT reference Description nciLocation SNVT_str_asc SCPTlocation (17) Location label nciBypassTime SNVT_time_min SCPTbypassTime (34) Local bypass time nciRHSpaceSetPt SNVT_lev_percent SCPThumSetPt (36) Space RH setpoint nciManualTime SNVT_time_min SCPTmanOvrTime(35) Manual Override Duration for Water Valve (a) Required points under Space Comfort Controller profile. All other points are optional. Literature Order Number WSHP-PRB002-EN Date December 2009 Supersedes WSHP-PRB002-EN (April 2002) www.trane.com For more information, contact your local Trane 8 office or e-mail us at email@example.com Trane has a policy of continuous product and product data improvement and reserves the right to change design and specifications without notice. Only qualified technicians should perform the WSHP-PRB002-EN installation and servicing of equipment referred to in this literature.