York HFC-410A manual Duct Considerations, Unit Orientation, Horizontal Applications, Economizer

FORM 100.50-EG5 (108)

persons. Erecting a fence around the unit is common practice.

•Roof curb – YORK offers optional roof curbs designed specifically for the Eco2 footprint. This curb comes as an open condenser model and is shipped disassembled and requires field assem- bly and installation. For bottom supply and return openings, the curbs have matching connections to ease installation. A pipe chase that matches the rooftop unit pipe chase is also included in the curb footprint for through-the-curb utility connections. The curb should be located according to the loca- tion recommendations above, and properly sealed to prevent moisture and air leakage into and out of the duct system. Flexible collars should be used when connecting the duct work to prevent unit noise transmission and vibration into the building.

Duct work should be supported independently of the unit.

TABLE 1 – SUPPLY-AIR DUCT-CONNECTION CONFIGURATIONS

Unit Configuration			Supply Air
		Bottom		Left	Right
	Cooling only				
50-65 Tons	Cool/gas heat 375-750 MBH				N/A
	Cool/gas heat 1,125 MBH			N/A	N/A
TABLE 2 – RETURN-AIR DUCT-CONNECTION CONFIGURATIONS
	Unit Configuration		Return Air
			Bottom	Left	Rear
	No exhaust				
50-65 Tons	Barometric relief damper				N/A
	Powered exhaust fan				N/A

DUCT CONSIDERATIONS

Unlike competitive units where air can leave the rooftop unit stratified across the width of the unit, the Eco2 unit sufficiently mixes airflow to ensure consistent air tem- perature from the unit. No special Tee considerations are required and the unit may be oriented either way.

UNIT ORIENTATION

For applications with multiple rooftop units located in close proximity on the roof, the orientation of the unit may be important to reduce the potential for re-entrain- ment of outside airflow. Regardless of the outside air and exhaust air openings on a unit, all rooftop applications can permit recirculation of exhaust air to the return, if applied improperly.

HORIZONTAL APPLICATIONS

The spectrum of applications for roof top units in today’s market is continuing to grow wider by the day. Flexibil- ity in unit design and construction is a must in today’s market in order to insure safe and sound applications of HVAC equipment. The Eco2 has been designed for spe- cific application of horizontal supply and return airflow taking the guess work out of unit application by building a unit specific to these needs. If the application calls for horizontal supply and return air, YORK can ship it from the factory as a horizontal unit. This option elevates the need for field modification of equipment, saving time and money. The Eco2 can support a left discharge on all units except 1,125 MBH gas, and/or right discharge on all cooling-only units. Return air can be brought through the end or side return air inlet making the unit specific to building needs.

ECONOMIZER

The economizer section is used for ventilation of the conditioned space to maintain indoor air quality, and also to reduce energy consumption by using outdoor air cooling in lieu of mechanical cooling. If outdoor air is appropriate for cooling, but not sufficient for the cooling demand, mechanical cooling will stage on as necessary until the cooling load is met.

Dual (comparative or differential) enthalpy operation is the most accurate and efficient means of economizer operation. The unit controller monitors the return and outside air energy content, and selects the lower of the two for operation.

NOTE:
This diagram is provided as a visual reference of the Eco2 discharge & return air openings & locations for all sizes. Please refer to the dimensional
data for exact size & location of panels and openings.	LD08045

JOHNSON CONTROLS 9