Carrier 48TM016-028 Installation, Start-up And Service Instructions Manual

Also see for 48TM016: User's information manual

Contents

42Routine 3 (OAT > 68)• Economizer is opened 100%.• Compressors 1 and 2 are cycled based on Y1 and Y2using minimum on and off times and watching the sup-ply air temperature as compared to SATLO1 andSATLO2 set points.If optional power exhaust is installed, as the outdoor-airdamper opens and closes, the power exhaust fans will be ener-gized and deenergized.If field-installed accessory CO2 sensors are connected to thePremierLink™ control, a PID-controlled demand ventilationstrategy will begin to operate. As the CO2 level in the zoneincreases above the CO2 set point, the minimum position of thedamper will be increased proportionally. As the CO2 leveldecreases because of the increase in fresh air, the outdoor-airdamper will be proportionally closed.HEATING, UNITS WITH ECONOMI$ER2, PREMIERLINKCONTROL AND A THERMOSTAT — When the thermostatcalls for heating, terminal W1 is energized. The PremierLinkcontrol will move the economizer damper to the minimumposition if there is a call for G and closed if there is a call forW1 without G. In order to prevent thermostat from short cy-cling, the unit is locked into the heating mode for at least10 minutes when W1 is energized. The induced-draft motor isthen energized and the burner ignition sequence begins.On units equipped for two stages of heat, when additionalheat is needed, W2 is energized and the high-fire solenoid onthe main gas valve (MGV) is energized. When the thermostatis satisfied and W1 is deenergized, the IFM stops after a45-second time-off delay unless G is still maintained.COOLING, UNITS WITH ECONOMI$ER2, PREMIER-LINK CONTROL AND A ROOM SENSOR — When freecooling is not available, the compressors will be controlled bythe PremierLink controller using a PID Error reduction calcula-tion as indicated by Fig 47.The PremierLink controller will use the following informa-tion to determine if free cooling is available:• Indoor fan has been on for at least 30 seconds.• The SPT, SAT, and OAT inputs must have valid readings.• OAT must be less than 75 F.• OAT must be less than SPT.• Enthalpy must be LOW (may be jumpered if andenthalpy sensor is not available).• Economizer position is NOT forced.When free cooling is available, the outdoor-air damper ispositioned through the use of a Proportional Integral (PID)control process to provide a calculated supply-air temperatureinto the zone. The supply air will maintain the space tempera-ture between the heating and cooling set points as indicated inFig. 48.The PremierLink will integrate the compressors stages withthe economizer based on similar logic as the three routines list-ed in the previous section. The SASP will float up and downbased on the error reduction calculations that compare spacetemperature and space set point.When outdoor-air temperature conditions require the econo-mizer to close for a compressor stage-up sequence, the econo-mizer control integrator is reset to zero after the stage-upsequence is completed. This prevents the supply-air tempera-ture from dropping too quickly and creating a freeze conditionthat would make the compressor turn off prematurely.The high space set point is used for DX (direct expansion)cooling control, while the economizer space set point is acalculated value between the heating and cooling set points.The economizer set point will always be at least one degreebelow the cooling set point, allowing for a smooth transitionfrom mechanical cooling with economizer assist, back toeconomizer cooling as the cooling set point is achieved.The compressors may be used for initial cooling then thePremierLink controller will modulate the economizer using anerror reduction calculation to hold the space temperaturebetween the heating and cooling set points. See Fig. 48.The controller uses the following conditions to determineeconomizer cooling:• Enthalpy is Low• SAT reading is available• OAT reading is available• SPT reading is available• OAT ≤ SPT• Economizer Position is NOT forcedIf any of the above conditions are not met, the economizersubmaster reference (ECSR) is set to maximum limit and thedamper moves to minimum position. The operating sequenceis complete. The ECSR is recalculated every 30 seconds.If an optional power exhaust is installed, as the outdoor-airdamper opens and closes, the power exhaust fans will beenergized and deenergized.If field-installed accessory CO2 sensors are connected tothe PremierLink control, a PID-controlled demand ventilationstrategy will begin to operate. As the CO2 level in the zoneincreases above the CO2 set point, the minimum position of thedamper will be increased proportionally. As the CO2 leveldecreases because of the increase in fresh air, the outdoor-airdamper will be proportionally closed.6869707172737475SPACE TEMPERATURETIMETEMPERATURE CONTROLSET POINTTEMPERATURENOTE: PremierLink control performs smart staging of 2 stages of DXcooling and up to 3 stages of heat.Fig. 47 — DX Cooling TemperatureControl Example6869707172737475SPACE TEMPERATURETIMETEMPERATURE CONTROLCOOL SETPOINTTEMPERATUREHEAT SETPOINTFig. 48 — Economizer TemperatureControl Example