York ECO R-22 - Manual (Page 10)

YORK INTERNATIONAL 10
The curb should be located according to the location
recommendations above, and properly sealed to pre-
vent moisture and air leakage into and out of the duct
system. Flexible collars should be used when connect-
ing the duct work to prevent unit noise transmission
and vibration into the building.
Duct work should be supported independently of the
unit.
ACOUSTICAL CONSIDERATIONS
The eco 2 unit is designed for lower sound levels than
competitive units by using flexible fan connections, fan
spring isolators, double-wall construction, and lower
speed and horsepower fans. For VAV applications,
VFDs are used instead of inlet guide vanes. Additional
sound attenuation can be obtained using compressor
sound blankets and field-supplied sound attenuators
when necessary.
Even with these equipment design features, the acous-
tical characteristics of the entire installation must never
be overlooked. Additional steps for the acoustical char-
acteristics of a rooftop installation should be addressed
during the design phase of a project to avoid costly al-
terations after the installation of the equipment. During
the design phase of a project, the designing engineer
should consider, at a minimum, the impact of the equip-
ment location, rooftop installation, building structure, and
duct work.
SELECTION PROCEDURE
Given:
Total Cooling Load 920 mbh
Sensible Heat 610 mbh
Required Heating Capacity 875 mbh
Design Cooling Ambient Temp. 95°F
Indoor Air Temperature 80°F db/67°F wb
Supply Air Flow 24,000 cfm
External Static Pressure 2.25 in. w.c.
Electrical Service 460V/3ph/60 Hz
Unit Configuration/Options: 0-100% modulating econo-
mizer, barometric relief, premium efficiency supply fan
motor and VFD, and two-inch pleated filters, bottom
supply, bottom return.
Select Unit:
1. Determine the internal static pressure drop of the
cabinet by referencing Table 17.
Wet evaporator coil 0.58
Bottom return opening 0.15
Two-inch pleated filters 0.12
Mod. econ. dampers 0.56
Total 1.41 IWG
2. Determine the total static pressure by adding the
internal to the external static pressure.
TSP = 1.41 IWG + 2.25 IWG = 3.66 IWG total static pressure
3. Determine the BHP of the supply fan from Table 15
using the supply air flow and total static pressure.
From the table, we interpolate to get 26.3 BHP at
724 rpm.
4. Determine the motor heat gain of supply air flow by
first calculating the motor energy and converting it
into Btuh.
Motor Energy
Motor kW = BHP x .746/efficiency
Motor kW = 26.3 x 0.746/0.94
Motor kW = 20.9 kW
Motor Heat Rejection (MHR)
MHR = 2545 x BHP/efficiency
MHR = 2545 x 26.3/0.94
MHR = 71.2 mbh
5. Calculate actual required total cooling capacity by
adding specified cooling capacity to motor heat
rejection.
Required Total Cooling Capacity
920 mbh + 71.3 mbh = 991 mbh
Required Sensible Cooling Capacity
610 mbh + 71.3 mbh = 681 mbh
Application Data
(continued)