JOHNSON CONTROLS
94
FORM100.50-EG12 (918)
4.
Modulating Economizer:
The economizer segment shall be designed to use out-
side air for cooling and ventilation and provide a means of exhausting air from the
air-handling unit. The segment shall consist of parallel acting low-leak dampers. The
return air, outside air and exhaust air dampers shall be sized for 100% of nominal
unit airflow. The exhaust air damper assembly shall have a factory-assembled rain
hood. The rain hood shall have a drip-lip the full width of the hood to channel mois-
ture away from the air being drawn into the unit.
Economizer Leakage
Select One of the Following
1. Damper assemblies are low-leak design. Damper blades are fabricated from a mini-
mum of 16-gauge galvanized steel. Blade edges are covered with vinyl seals.
2. Damper assemblies have a maximum leakage rate of 10 CFM/ft
2
at 1.0 inch wa-
ter gauge (iwg) when tested in accordance with AMCA Standard 500, and have a
longevity of 60,000 damper opening and closing cycles, complying with the require
-
ments of California Title 24.
Select One of the Following Types of Building Pressure Control
1.
No Building Exhaust/Relief:
The unit has no provisions to exhaust building return
air.
2.
Barometric Relief Damper:
Building air exhaust shall be accomplished through
barometric relief dampers installed in the return air plenum. The dampers open rela-
tive to the building pressure. The opening pressure shall be adjustable.
3.
On/Off Fan Powered Exhaust:
A twin double width, double inlet (DWDI) Class II
forward-curved centrifugal exhaust fan shall be provided to exhaust building return
air to relieve building static pressure. The fans shall be constant volume and oper-
ate based on either a building static pressure, or outside air damper position.
4.
Powered Exhaust with Modulating Discharge Damper:
A twin DWDI Class II
forward-curved centrifugal exhaust fan shall be provided to exhaust building return
air to relieve building static pressure. The fans shall operate at a constant volume
and operate based on building static pressure. Exhaust airflow shall be modulated
via a parallel-acting control damper. The exhaust air dampers shall be sized for
100% of the exhaust airflow.
5.
Powered Exhaust with Variable Frequency Drive (VFD):
A twin DWDI Class II
forward-curved centrifugal exhaust fan shall be provided to exhaust building re-
turn air to relieve building static pressure. Exhaust airflow shall be modulated via a
factory-installed and commissioned variable frequency drive (VFD) with the same
nameplate horsepower as the supply fan motor.
6.
Power Return Fan:
Two single width, single inlet (SWSI) plenum fans shall be pro-
vided to draw return air from the building to the single package unit. An access door
shall be provided on at least one side of the unit for fan/motor access. The return fan
shall operate to maintain a constant pressure within the return plenum.
7.
Power Return Fan:
Two SWSI plenum fans shall be provided to draw return air
from the building to the single package unit. An access door shall be provided on
at least one side of the unit for fan/motor access. The return fan shall operate to
maintain a constant pressure within the return plenum. A discharge damper shall be
provided to modulate building exhaust. The damper shall be controlled via building
pressure. The return damper shall linked with the outside air damper to modulate
volumes of return and outside airflows.
Guide Specifications (Cont'd)