Download Installation, Start-Up and Service Instructions MicroMetl

Large Rooftop Units
13 to 25 tons
1077-0303 Economizer Package
MicroMetl
Installation, Start-Up and
Service Instructions
Part Numbers 1077-0303
GENERAL
! WARNING
IMPORTANT: Read these instructions com-
pletely before attempting to install the acces-
sory Economizer.
The accessory Economizer package uses microprocessor-based controls to sequence mechanical cooling with
cool outdoor air (free cooling) to satisfy the cooling load
and minimize energy consumption. Free cooling can be
used alone or in conjunction with mechanical cooling.
The standard Economizer uses an enthalpy sensor or
dry bulb to sense Outdoor Air. This sensor determines
the availability of free cooling.
When free cooling is available, the economizer sequences free cooling with up to two stages of mechanical cooling to maintain comfort in the space. When free
cooling is not available, it modulates to an adjustable
minimum position set point to maintain a supply of fresh
air entering the building.
Optional barometric relief dampers provide natural
building pressurization control. An optional power exhaust system is available for jobs requiring greater relief.
PACKAGE USAGE AND CONTENTS
UNIT SIZE
13 to 25 ton
PACKAGE
NO.
1077-0303
QTY.
CONTENTS
1
Economizer Assembly
1
Frame Top
14
Screws
1
Discharge Air thermistor
1
Snap Bushing
1
Wire Tie
2
Seal Strip
Note: Economizer package does not include a transformer
Copyright 2003 MicroMetl Corporation
Turn off unit power. Electrical shock and personal
injury could result. 24 Volt AC connection required.
Install economizer damper assembly as follows:
1. If base unit is installed and in operation, turn off all
power to unit.
2. Remove filter access panel. Remove 25% air /
economizer hood. See Fig. 1.
3. Remove 25% outdoor air damper section. Save
screws. See Fig.2.
4. Remove shorting plug located in the left front of
return air compartment at back of unit control box.
See Fig. 2.
5. Remove Economizer damper assembly from shipping carton. See Fig. 3.
6. Install seal strip on left and right sides of Economizer
opening.
7. Slide Economizer assembly into unit opening as
shown in Fig. 4.
8. Complete assembly of damper section into unit (
Fig. 5). For end view of installed Economizer, see
Fig. 6. Ensure that Economizer bottom flange is
positioned on basepan before installing 2 screws
connecting bottom flange to unit basepan.
9. Using 4 screws removed at Step 3, secure the
damper assembly to the unit. See Fig. 5.
10. Plug Economizer wiring assembly into the receptacle
at the back of unit control box where shorting plug
was removed. See Fig. 7.
11. Install frame top above damper assembly.
See Fig. 5.
12. Install discharge air thermistor in fan section in
two holes provided on fan housing. Route wiring
to Economizer controller through knockout hole in
panel. Use bushing provided. Use wire tie to keep
wiring away from fan blades.
13. Reinstall 25% air / economizer hood. Refer to base
unit installation instructions. See Fig. 8.
Form No. 1935-10P
Fig. 1 - Base Unit Details
Fig. 4 - Slide Economizer Assembly into Unit
Fig. 2 - Standard 25% Outdoor - Air Section Details
Fig. 5 - Economizer Assembled in Unit -- End View
ACTUATOR
WITH LOGIC
ECONOMIZER
FLANGE AND
SCREWS (HIDDEN)
Fig. 3 - Economizer Shipping Packaging
Fig. 6 - Economizer Assembled in Unit
2 - 1077-0303 Economizer Package
Ventilation Air (Minimum Position Set Up) -- If ventilation air is not required, proceed to Step 5. If ventilation
air is required, perform the following:
Fig. 7 - Economizer Plug
1. The indoor fan must be on to set the ventilation air.
Either put the thermostat in the continuous fan mode
or jumper the R and G terminals at the rooftop unit
connection board.
2. Locate the minimum position (MIN POS) potentiometer. Turn the potentiometer full CCW to fully close the
outdoor air dampers. Turn the potentiometer gradually clockwise (CW) to the desired position.
3. Replace the filter access panel. See Fig. 1. Ensure
the filter access panel to securely
engaged.
4. Calculate the minimum airflow across the
Economizer.
a. Calculate % of outside air using the following formula.
% Outdoor air through Economizer
Mixture Temp - Return Air Temp
% Outdoor air =
Outdoor Temp - Return Air Temp
b. Multiply total CFM by percentage outdoor air, this gives outdoor air volume in CFM.
5. Turn on base unit power.
! WARNING
Personal Injury Hazard. Avoid possible injury by
keeping finger away from damper blades.
Fig. 8 - Outdoor-Air Hood Details
3 - 1077-0303 Economizer Package
WIRING DIAGRAM FOR 1077-0303 ECONOMIZER
1
The HVAC unit is shipped with a jumper plug attached to the Economizer harness. Remove the jumper plug and
save for future use if economizer is removed. Connect the male side of plug to the female side in HVAC unit
(Fig. 7).
2
Factory installed 620 OHM, 1 watt, 5% resistor should be removed only when using differential enthalpy or dry
bulb.
3
Field mount discharge sensor in indoor blower compartment.
4
Connect optional indoor air quality sensor to "AQ" and "AQ1" terminals.
5
Connect optional power exhaust low voltage activation wires to "EF" and "EF1" terminals.
6
Connect optional remote minimum position potentiometer to "P" and "P1".
7
If a fixed dry bulb sensor is used, the white wire from the "SO" terminal will house a 620 OHM resistor.
8
Connect optional low ambient lockout switch between terminal 3 and plug pin 6.
4 - 1077-0303 Economizer Package
MICROMETL INTEGRATED ECONOMIZERS
The purpose of an economizer is to use outdoor air
for cooling , whenever possible, to reduce compressor
operation.
The economizer system initially responds to a
signal from the cooling thermostat and functions as a
true first stage for cooling, while providing maximum
fuel economy. The economizer is automatically locked
out during the heating mode and holds the outdoor air
damper at the minimum position settings.
During the occupied period, the discharge switch
provides a signal to the actuator during free cooling or
economizer mode. The signal opens the economizer
damper until the discharge temperature drops below
50° F. At this time the signal causes the motor to drive
the damper back to minimum position. As the discharge
temperature climbs to 60°F the motor will drive back
open. During the occupied period, the actuator will not
close past the minimum position.
During the unoccupied period, the actuator will
override minimum position setting and drive fully closed.
On a loss of power, the actuator will spring return fully
closed.
When in heating operation, or when outdoor air
temperature or enthalpy conditions are high, economizer
operation is locked out, and actuator is held at minimum
position.
The staging relay is used when the first stage
compressors must provide mechanical cooling when
assisting the economizer.
The staging relay can be omitted when the second
stage compressors can be used to assist the economizer
with mechanical cooling.
If the fully open actuator cannot satisfy the space
demand, mechanical cooling is sequenced on.
5 - 1077-0303 Economizer Package
Minimum Position Adjustment
The minimum position potentiometer keeps the outdoor air damper from closing completely during system operation
to provide ventilation.
1.) Make sure the factory installed jumper is in place across terminals P and P1.
2.) If remote control of dampers is desired, connect the remote potentiometer to P and P1 and turn it fully clockwise
before adjusting the minimum position.
3.) Connect 24V AC to system and adjust the potentiometer on the face of the logic module with a screwdriver for
desired minimum position.
Enthalpy Changeover Setpoint (1008-0100)
Single Dry Bulb: The dry bulb changeover setpoint is set to
return the outdoor air damper to minimum position when the
temperature rises above it's setpoint. The setpoint scale
markings, located on the W7212, are A,B,C,D as shown below. The factory installed 620-ohm jumper must be in place
across terminals + and SR unless using differential dry bulb.
D setting
mA Signal
1011121314151617181920
Single enthalpy: The enthalpy changeover setpoints is set to
return the outdoor air damper to minimum position when the
enthalpy rises above its set point. The enthalpy setpoint scale
markings, located on W7212 are A,B,C,D as shown below.
The factory-installed 620-ohm jumper must be in place across
terminals + and SR unless using differential enthalpy.
Adjustable Dry Bulb Changeover Setpoint
(1009-0100)
C setting
B setting
A setting
405060708090100
EXAMPLE FOR DETERMINING
ADJUSTABLE DRY BULB CONTROL SETTING
(1009-0100)
Differential Changeover Setting
Differential enthalpy control utilizes two enthalpy sensors
connected to one W7212 Economizer Control.
The enthalpy setpoint scale markings, located on the
W7212, are A,B,C,D. Turn the setpoint potentiometer
fully clockwise past the D setting. The economizer
will select the air with lower enthalpy for cooling; i.e., if
outdoor air has lower enthalpy than return air, then the
outdoor air damper will be opened to bring in outdoor air
for free cooling. The differential enthalpy contacts to SR
and + on the W7212 logic.
NOTE: The C7650A adjustable dry bulb can also be used
for differential change over. Only the temperature of the
outdoor air and return air will be compared and the best
selected for free cooling.
CAUTION
Exercise care when adjusting
the changeover set point and
minimum position setting.
EXCESSIVE FORCE MAY
DAMAGE THE CONTROLS
6 - 1077-0303 Economizer Package
MicroMetl
Call Toll-Free: 1-800-662-4822
Fax: 1-317-543-5986
MicroMetl West
Call Toll-Free: 1-800-884-4662
Fax: 1-775-356-9184
MMC 3035 N. Shadeland Ave., Suite 300 Indianapolis, IN. 46226 MMC West 202 South 18th St.
Sparks, NV. 89431
Manufacturer reserves the right to discontinue, or change at any time, specifications, designs and prices without notice and without incurring obligations.
Form No. 1935-10P
Copyright MicroMetl Corporation 2003. All rights reserved.
7 - 1077-0303 Economizer Package