Above50Fsupply-airtemperature,thedmnperswillmodu- latefrom100%opentotheminimumopenpositionFrom50F. to 45F supply-airtemperature,the&tmperswill maintain attheminimumopenpositionBelow45Fthe&lmperswill. becompletelyshutAsthesupply.-airtemperaturerises,the damperswillcomebackopentotheminimumopenposition oncethesupply-airtemperatmerisesto48IF.

If optionalpowerexhaustisinst_dled,astheoutdoor-air damperopensandcloses,thepowerexhaustfanwillbeener- gizedanddeenergized.

If field-installedaccessory COz sensors are connected to the EconoMiSerIV control, a demand controlled ventilation strate-

gy will begin to operate. As the CO2 level in the zone increases above the CO2 set point, the minimum position of the &_mper will be increased proportionally. As the CO2 level decreases because of the inclease in fresh aik the outdoor-air damper will be proportionally closed. Daraper position will follow the high- er demand condition from DCV mode or free cooling mode.

Damper movement from full closed to lifll open (or vice veLsa) will take between 11/2and 21/: minutes.

If free cooling can be used as determined from the appropri- ate changeover command (switch, diy bulb, enthalpy curve,

differential dry bulb, or differential enthalpy), a call for cooling (YI closes at the thermostat) will cause the control to modulate the &tmpeLs open to maintain the supply air temperature set point at 50 to 55 E

As the supply-air temperature diops below the set point

range of 50 to 55 E the control will modulate the outdoor-air dampers closed to maintain the proper supply-air temperature.

HEATING, UNITS WITH ECONOMISERIV -- When the room thermostat calls for heat, the heating controls are ener- gized as described in the Heating, Units Without Economizer section. When the indoor fan is energized, the economizer damper moves to the minimum position. When the indoor fan is off. the economizer dmnper is fully closed.

COOLING. UNITS WITH ECONOMISER2, PREMIER-

LINK TM CONTROL AND A THERMOSTAT -- When free

cooling is not available, the compressoLs will be controlled by the PremierLink control in response to the YI and Y2 inputs from the thermostat.

The PremierLink control will use the following information 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 Sir[ '.

•Enthalpy must be LOW (may be jumpered if an enthalpy sensor not available).

•Economizer position is NOT forced.

Pre-cooling occurs when the is no call fi_m the thermostat except G Pre-cooling is defined as the economizer modulates to provide 70 F supply air

When free cooling is available the PremierLink control will control the compressors and economizer to provide a supply- air tempemtme determined to meet the YI and Y2 c_dls from

the thermostat using the following three routines. The three control routines are based on OAT.

The 3 routines ;ue based on OAT where:

SASP = Supply Air Set Point

DXCTLO = Dilect Expansion Cooling Ix_ckout Set Point PID = Proportional Integral

Routine 1 (OAT < DXCTLO)

YI energized - economizer maintains a SASP = (SATLOI + 3).

Y2 energized - economizer maintains a SASP = (SATLO2 + 3).

Routine 2 (DXCTLO < OAT < 68 F)

•If only YI energized, the economizer maintains a SASP = (SATLOI + 3).

•If SAT > SASP + 5 and economizer position > 80%, economizer will go to minimum position for 3 minutes or until SAT > 68 IF.

•First stage of mechanical cooling will be energized.

•Integrator resets.

•Economizer opens again and controls to current SASP after stage one on for 90 seconds.

•With YI and Y2 energized economizer maintains an SASP = SATLO2 + 3.

•If SAT > SASP + 5 and economizer position >80%, economizer will go to minimum position for 3 minutes or until SAT > 68 E

•If compressor one is on then second stage of mechanical cooling will be energized. Otherwise the first stage will be energized.

•Integrator resets.

•Economizer opens again and controls to SASP after stage one on for 90 seconds.

Routine 3 (OAT > 68)

•Economizer is opened 100%.

•Compressors 1 and 2 are cycled based on YI and Y2

using minimum on and off times and watching the sup-

ply air temperature as compared to SATLOI and SATLO2 set points.

If optiomd power exhaust is installed, as the outdoor-air &tmper opens and closes, the power exhaust fans will be ener- gized and deenergized.

If field-installedaccessory CO2 sensors me connected to the

PremierLink control, a PlD-controlled demand ventilation strategy will begin to operate. As the CO2 level in the zone increases above the CO2 set point, the minimum position of the

&_mper will be increased proportionally. As the COz level decreases because of the increase in fresh air, the outdoor-air

&tmper will be proportionally closed.

HEATING, UNITS WITH ECONOMISER2, PREMIERLINK CONTROL AND A THERMOSTAT -- When the thermostat calls for heating, terminal Wl is energized. The PremierLink control will move the economizer damper to the minimum position if there is a call for G and closed if there is a call for WI without G In order to prevent thermostat from short cy-

cling, the unit is locked into the heating mode for at least 10 minutes when WI is energized. The induced-di'aft motor is then energized and the burner ignition sequence begins.

On units equipped for two stages of heat, when additional heat is needed, W2 is energized and the high-fire solenoid on the main gas valve (MGV) is energized. When the thermostat

is satisfied and WI is deenergized, the IFM stops after a 45-second time-off delay unless G is still maintained.

COOLING, UNITS WITH ECONOMISER2, PREMIER-

LINK CONTROL AND A ROOM SENSOR -- When free cooling is not available, the compressors will be controlled by the PremierLink controller using a PID Enor reduction calcula- tion as indicated by Fig. 46.

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 E

•OAT must be less than SPT.

•Enthalpy must be LOW (may be jumpered if and enthalpy sensor is not available).

•Economizer position is NOT forced.

When free cooling is available, the outdoor-air damper is

positioned through the use of a Proportional Integral (PID) control process to provide a calculated supply-air temperature

37

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Carrier 48TJ016-028 specifications COOLING. Units with ECONOMISER2, Premier, COOLING, Units with ECONOMISER2, Premier
Page 36 Page 38

48TJ016-028 specifications

The Carrier 48TJ016-028 is a notable model in the range of packaged rooftop units designed by Carrier, a leader in heating, ventilation, and air conditioning (HVAC) solutions. Tailored specifically for commercial applications, these units provide a blend of efficiency, durability, and reliability, making them suitable for a variety of settings, including offices, retail spaces, and industrial environments.

One of the standout features of the 48TJ series is its energy-efficient performance. Equipped with high-efficiency scroll compressors, these units offer superior cooling capacity while minimizing energy consumption. This aligns with modern sustainability goals, helping businesses reduce their carbon footprint and operational costs. Additionally, the 48TJ units comply with stringent industry standards, such as the ASHRAE 90.1 energy efficiency guidelines, ensuring that users receive a product that meets modern energy performance benchmarks.

The 48TJ016-028 units also include advanced technologies that enhance performance and user comfort. The inclusion of a sophisticated microprocessor control system facilitates precise temperature regulation, allowing for an optimal balance of cooling and heating based on real-time conditions. Moreover, the user-friendly controls make it easy for facility managers to monitor system performance and make adjustments as necessary.

Another notable characteristic of the 48TJ series is its flexible installation options. These rooftop units are designed for easy integration into existing building structures and can be installed on flat or pitched roofs. Their compact design and lightweight construction simplify the installation process while minimizing structural impacts on buildings.

Durability is paramount in the design of the 48TJ units as well. The cabinets are constructed from high-quality materials with corrosion-resistant coatings, ensuring a long lifespan even in harsh environmental conditions. The systems are also equipped with robust insulation to reduce sound levels and improve overall operating efficiency.

Furthermore, the Carrier 48TJ016-028 units offer various options for customization. Users can choose from different airflow configurations, heating options, and accessories, allowing for tailored solutions that meet specific requirements. Whether you are looking for a unit with enhanced filtration, economizer capabilities, or advanced humidity control, the 48TJ series provides the flexibility needed for diverse applications.

In summary, the Carrier 48TJ016-028 units deliver a compelling combination of energy efficiency, advanced technology, and robust construction, making them an ideal choice for commercial HVAC needs. With their versatile features and customizable options, they stand out as reliable solutions for maintaining comfortable indoor environments.
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