McDaniel Metals DNECONGS3672B Installation Manual

DNECONGS3672B INSTALLATION AND OPERATION GUIDE

DOW

to cool the space. (Go to step 5.)

Outdoor air dampers open to minimum position and the 4.
compressor engages to provide mechanical cooling.
When the thermostat is satisfi ed the outside air dampers 5.
return to a closed position.

ECONOMIZER 101

Economizers are designed to provide “free” air conditioning

when outside conditions are appropriate. When the outside air
is cool and dry enough, the economizer automatically opens to
introduce the cool air to the interior space, thereby eliminating
the need to run the air conditioning compressor.
If the outside air becomes too warm or humid, the economizer
automatically closes the fresh air damper and the compressor
engages to begin cooling the space mechanically.
If a two stage thermostat is used it is possible to use a
combination of economizer and mechanical cooling to condition
the space.
The economizer can also be set to allow a minimum amount of
fresh air to enter the space when the equipment’s indoor blower
is operating.
Economizers are valuable tools to enhance indoor air
quality, save energy and prolong the life of the air conditioning
equipment.

SEQUENCE OF OPERATION

This sequence assumes employment of a single enthalpy

economizer using a two stage thermostat.

Figure 1

INSTALLATION

Open carton and inspect contents for shortages and damage.1.
Remove fi lter access and bottom evaporator access panel 2.
from package unit. Keep the screws from the bottom panel.
Slide internal damper rack into the opening until the outside 3.
fl anges of the assembly nest inside of the posts framing the
opening. (Figure 1)

A call for cooling comes from room thermostat.1.
The enthalpy sensor determines if the atmospheric condi-2.
tions are conducive for using outside air for cooling. If YES,
go to step 3. If NO, or if outdoor air temperature rises above
enthalpy set point, go to step 4.
The outside air dampers open and modulate to maintain a 3.
mixed air temperature (outside air + indoor air) of 53 degrees
F. If the outdoor air is insuffi cient to satisfy the thermostat
alone and a second stage of cooling is required, the com­pressor starts and works in conjunction with the economizer

Figure 2

Rev 2

4. Plug 6-pin economizer plug into matching 6-pin plug in the
unit.

CONTENTS

NOTE: Ensure neither the wire nor the plugs interfere with the

movement of the dampers during operation.

Assemble hood kit per the instructions on page 4.5.
Secure hood kit to the unit with the screws removed in Step 2.6.
Refer to psychrometric chart included with controller check 7.
out literature to determine the A, B, C, or D setting for the
controller. The factory setting is the D position.
Use the Minimum Set Point Equation below to determine the 8.
minimum position setting on the controller. The factory setting
is closed or full CCW.
Replace fi lter access panel on unit.9.

MINIMUM SET POINT EQUATION

(To X OA) + (Tr X RA) = Tm
To = Outdoor air temperature
OA= Percent of outdoor air
Tr = Return air temperature
RA= Percent of return air
Tm= Resulting mixed air temperature

1 Damper rack w/ economizer controls
1 Hood Kit
1 Fresh Air Mist Eliminator
1 Screw package and control jumpers
1 Installation/Component Manual

ACCESSORIES / CAPABILITIES

Dual Enthalpy - Requires an additional C7400 enthalpy
control installed in the return air duct.

Demand Control Ventilation - Requires a CO2 sensor.
Power Exhaust - PE3672(2/4) power exhaust used in

applications where barometric relief is not suffi cient.
Remote Minimum Positioner - For applications requiring

minimum position adjustments inside the conditioned space.

Example:

Fresh air required is 10% outdoor air.
Outdoor air temperature is 60 degrees F.
Return air temperature is 75 degrees F.
(0.1 X 60) + (0.9 X 75) =

6.0 + 67.5 = 73.5
Mixed air temperature will be 73.5 degrees F when
the OA is 60 degrees F and the RA is 75 degrees F
with 10% outdoor air.

Important Notes

The economizer will open to minimum posi-•
tion in heating unless the MAT drops below
45F at which point the fresh air dampers will
close completely. See the enclosed brochure
for additional information.
Please see enclosed brochure for Honeywell •
component trouble shooting instructions.
The fresh air mist eliminator should be •
fl ushed periodically with warm soapy water.
A two stage thermostat is recommended with •
this accessory.
If Power Exhaust of Demand Control Ventila-•
tion are not included in the system please
ensure the DCV Set and DCV Max pots are
turned full counterclockwise.