Carrier ZONECC3Z Installation And Start-up Instructions Manual

Contents

Carrier ZONECC3Z Installation And Start-up Instructions Manual Manual pdf 6 page image

UNDERSTANDING SYSTEM OPERATION(READ BEFORE STARTING SYSTEM)Mode and Damper PositionsThe thermostats determine the system heating or cooling mode.The first call in any zone sets the mode to satisfy that call. It willremain in that mode until all calls in that mode are satisfied and theequipment has been off for the time set by the auto changeovertime dipswitches. (See Timers section.)In normal heating or cooling, the damper of any zone with a callin the current mode will be open and all other zones will be closed.When there is no call, any zone with its fan set to ON will be open,and any zone with its fan set to AUTO will be closed. If any zonefan is set to ON, the blower will be energized.If all fan settings are AUTO, the dampers will remain in their lastposition before the equipment turned off and the blower will beoff. (This normally means one damper open and all others closed.)When dampers are to move, all opening is done first, followed byall closing.StagesIn multi-stage systems, the equipment stage is set by the greatestthermostat call, but may be delayed by the control’s cycle andstaging timers. (See timers explanation below.) The AC Controlsupports only single stage heat and cool. The HP control supportstwo stage cooling, two stage furnace heating, and three stage HPheating (lo HP, hi HP, hi HP + aux heat.)Emergency HeatEmergency heat (aux heat without compressor heat) can beselected for a HP system by either of two ways: First, by selectingEheat using the Eheat override switch on the HP Control, orsecond, selection of Eheat on each of the thermostats, providedthey have the Eheat function. When either of these Eheat selectionsis made, a heating demand provides a W signal without a Y signalto the equipment.NOTE: The second Eheat method requires HP thermostats andthat they all must be set to Eheat.Indicator LEDsThere are 7 indicator LEDs on the AC Control and an additional 3on the HP/2S Control. Their locations are shown on Fig. 8 and 9.Each damper has its own green LED which is ON when thedamper opens due to a calling condition or partially open due to anLAT or HPT limit condition.Each equipment output has its own LED which is on when thatoutput is energized. Y and O outputs are yellow, W outputs are redand the G output is green.In addition, there is a status LED whose operation is describedunder the section Error Codes.TimersTo control excessive equipment cycling or rapid staging up, thecontrol has two timers. The cycle timer prevents the same stagefrom turning on within 10 minutes of the last time it turned on.This allows a stage to turn on for as short or as long as thethermostats request, but will not allow more than six cycles perhour.The staging timer prevents a higher stage from turning on until thenext stage below it has been on for 15 minutes. This minimizes useof electric heat with heat HP systems.There is also a timegaurd timer which will not allow the compres-sor to be turned on until it has been off for five minutes.A changeover timer, which can be set from 0 to 30 minutes, limitsthe control’s ability to switch between heating and cooling. Theopposite mode is prevented from coming on until the first modehas been satisfied for the selected time.Timer OverrideA momentary switch is located near the bottom of the controlcircuit board. Pressing it momentarily overrides all of the systemtimers, allowing the control to immediately jump to the highestcalling stage.Temperature Limits and SensorsBoth the AC and HP controls have a LAT (leaving air temperature)sensor which is to be placed in the downstream air path of theheating /cooling equipment. It is used in both heating and coolingto limit LAT to a safe value. It must be connected. The system willnot operate without it. Its setting is fixed for cooling and isadjustable in four settings for heating. Selection of best setting isdiscussed under LAT Limit Selection.The HP control also has an optional HPT Sensor (heat pumptemperature) which is to be placed downstream of the coil butahead of the electric heater. This sensor measures the temperatureof the air leaving the coil during HP heating. It is not included withthe control, but may be ordered separately as part numberTSATXXSEN01-B. A 10K ohm resistor is factory installed in itsplace when the actual sensor is not used. In the HP control only,dipswitch 11 allows the installer to temporarily disable both theLAT and the HPT sensors. Disabling of these sensors is only to bedone on a temporary basis.UNIT DAMAGE HAZARDFailure to follow this caution may result in unit damage.Operating equipment with sensors disabled can cause perma-nent damage to HVAC equipment.BypassThe purpose of a bypass is to limit noise in the duct system whenthe dampers are excessively restricting it. When a direct bypass(outlet air fed back directly into the return) is used, bypassingdecreases entering air temperature in cooling and increases it inheating. Excessive bypassing will lead to limit trips, either throughthe LAT /HPT sensors or the equipment internal limits.Setting the BypassSetting the bypass is a balance between too much noise (bypasstrip pressure set too high) and excessive bypassing which willcause limit trips, diminishing performance. As a general rule, thebypass should remain closed as much as possible. It should neveropen when all the dampers are open and only open as much asneeded to bring noise to an acceptable level when only one damperis open. (See System Setup for details.)LAT Limit SelectionCycling on internal equipment limits is to be avoided because itoverstresses and can shorten the life of the equipment. Therefore,the LAT limit setting should be selected to trip below theequipment limit. See System Setup for details on how to chooseone of four available LAT limits.Limit Levels and ActionsThe response of the system to the LAT/HPT sensors are shown inTable 2. Cooling and HP limits are not adjustable. Looking atTable 2, there are eight limit level index numbers, 0 through 7.These represent the closeness of the actual LAT/HPT temperaturesto the final shutdown limit. 0 represents no limit challenge while7 indicates a final shutdown of the equipment. Note that progres-sive actions are taken by the control as the LAT/HPT limit isapproached. Each action progressively reduces the limit challengeby increasing airflow. Normally, the system will stabilize at limitlevel 1 or 2 because opening all closed dampers 2 or 4 positions(out of 15) will reduce LAT to a level below its limit.6