Carrier 48TM016-028

Routine 3 (OAT > 68)

• Economizer is opened 100%.

• Compressors 1 and 2 are cycled based on Y1 and Y2

using minimum on and off times and watching the sup-

ply air temperature as compared to SATLO1 and

SATLO2 set points.

If optional power exhaust is installed, as the outdoor-air

damper opens and closes, the power exhaust fans will be ener-

gized and deenergized.

If field-installed accessory CO2sensors are connected to the

PremierLink™ control, a PID-controlled demand ventilation

strategy will begin to operate. As the CO2level in the zone

increases above the CO2set point, the minimum position of the

damper will be increased proportionally. As the CO2level

decreases because of the increase in fresh air, the outdoor-air

damper will be proportionally closed.

HEATING, UNITS WITH ECONOMI$ER2, PREMIERLINK

CONTROL AND A THERMOSTAT — When the thermostat

calls for heating, terminal W1 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

W1 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 W1 is energized. The induced-draft 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 W1 is deenergized, the IFM stops after a

45-second time-off delay unless G is still maintained.

COOLING, UNITS WITH ECONOMI$ER2, 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 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 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

into the zone. The supply air will maintain the space tempera-

ture between the heating and cooling set points as indicated in

Fig. 48.

The PremierLink will integrate the compressors stages with

the economizer based on similar logic as the three routines list-

ed in the previous section. The SASP will float up and down

based on the error reduction calculations that compare space

temperature 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-up

sequence is completed. This prevents the supply-air tempera-

ture from dropping too quickly and creating a freeze condition

that 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 a

calculated value between the heating and cooling set points.

The economizer set point will always be at least one degree

below the cooling set point, allowing for a smooth transition

from mechanical cooling with economizer assist, back to

economizer cooling as the cooling set point is achieved.

The compressors may be used for initial cooling then the

PremierLink controller will modulate the economizer using an

error reduction calculation to hold the space temperature

between the heating and cooling set points. See Fig. 48.

The controller uses the following conditions to determine

economizer cooling:

• Enthalpy is Low

• SAT reading is available

• OAT reading is available

• SPT reading is available

•OAT≤ SPT

• Economizer Position is NOT forced

If any of the above conditions are not met, the economizer

submaster reference (ECSR) is set to maximum limit and the

damper moves to minimum position. The operating sequence

is complete. The ECSR is recalculated every 30 seconds.

If an optional power exhaust is installed, as the outdoor-air

damper opens and closes, the power exhaust fans will be

energized and deenergized.

If field-installed accessory CO2sensors are connected to

the PremierLink control, a PID-controlled demand ventilation

strategy will begin to operate. As the CO2level in the zone

increases above the CO2set point, the minimum position of the

damper will be increased proportionally. As the CO2level

decreases because of the increase in fresh air, the outdoor-air

damper will be proportionally closed.

SPACE TEMPERATURE

TIME

TEMPERATURE CONTROL

SET POINT

TEMPERATURE

NOTE: PremierLink control performs smart staging of 2 stages of DX

cooling and up to 3 stages of heat.

Fig. 47 — DX Cooling Temperature

Control Example

SPACE TEMPERATURE

TIME

TEMPERATURE CONTROL

COOL SETPOINT

TEMPERATURE

HEAT SETPOINT

Fig. 48 — Economizer Temperature

Control Example