Greenheck Fan 470656 manual Operation - Economizer, Option EC-1 Outside Air Temperature Reference

Operation - Economizer

Note

Only models IG-HV and IGX-HV with options EC-1, 2, 3 or 4 use an economizer.

Option EC-1

(Outside Air Temperature Reference)

This option uses one dry bulb temperature sensor field-installed in the inlet of the unit. A second dry bulb temperature sensor is factory-installed in the discharge of the unit.

After a call for cooling, the outside air temperature is compared to the economizer set point. If the outside air temperature is above the economizer set point, the economizer sends the dampers to the minimum outside air position and calls for mechanical cooling. If the outside air temperature is between the economizer set point and 55°F, the economizer sends the dampers to the 100% outside air position. If the outside air

is less than 55°F, the economizer modulates the dampers to achieve a 55°F mixed air temperature.

Option EC-2

(Outside Air Enthalpy Reference)

This option uses one enthalpy sensor field-installed in the inlet of the unit. A dry bulb temperature sensor is installed in the discharge of the unit.

After a call for cooling, the outside air enthalpy is compared to the field-adjustable enthalpy changeover set point. If the outside air enthalpy is less than the set point, the dampers will modulate to provide a 55°F mixed air temperature. If the outside air enthalpy is greater than the set point, the economizer sends the damper to the minimum outside air position and sends a call for mechanical cooling.

Option EC-3

(Differential Temperature Control)

This option uses one dry bulb temperature sensor field-installed in the inlet of the unit. A second dry bulb temperature sensor is field-installed in the return air duct. A third dry bulb temperature sensor is factory- installed in the discharge of the unit.

After a call for cooling the economizer compares the outdoor and return air temperatures. If the outdoor air temperature is greater than the return air dry bulb temperature, the economizer sends the dampers to the minimum outside air position and sends a call for mechanical cooling. If the outside air temperature is less than the return air temperature, the economizer will modulate the dampers to achieve a 55°F mixed air temperature. If the outside air temperature is less than the return air temperature, but a 55°F mixed air temperature cannot be achieved, the programmable room thermostat may call for mechanical cooling.

Option EC-4

(Differential Enthalpy Control)

This option uses one enthalpy sensor, field-installed in the inlet of the unit. A second enthalpy sensor is field- installed in the return air duct. A dry bulb temperature sensor is factory-installed in the discharge of the unit.

After a call for cooling the economizer compares the outdoor and return air enthalpies. If the outdoor air enthalpy is greater than the return air enthalpy, the economizer sends the dampers to the minimum outside air position and sends a call for mechanical cooling. If the outside enthalpy is less than the return air enthalpy, the economizer will modulate the dampers to achieve a 55°F mixed air temperature. If the outside enthalpy is less than the return air temperature, but a 55°F mixed air temperature cannot be achieved, the programmable room thermostat may call for mechanical cooling.

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Model IG / IGX Make-Up Air 45