LENNOX 24K58 Standard Economizers Raider Rooftop Units with ZC 092-150 Instruction Manual

LENNOX 24K58 Standard Economizers Raider Rooftop Units with ZC 092-150

Product Information

Horizontal Economizers

The Horizontal Economizers are accessories used with ZC, ZG, ZH 092-150 units to improve energy efficiency. The economizer system includes various components such as an economizer damper assembly, outdoor air damper, return air damper, gravity exhaust damper, horizontal blank-off panel, economizer actuator, economizer control module, outdoor air temperature sensor, mixed air sensor, and necessary hardware.

The economizer system is designed to modulate dampers and maintain a mixed air temperature of 55°F (R1) based on different conditions such as outdoor air temperature, humidity, and enthalpy. The system provides free cooling when the outdoor air conditions are suitable, helping reduce energy consumption and improve indoor air quality.

Product Usage Instructions

Installation of Economizer

1. Disconnect all power sources to the unit.
2. Remove the filter door panel, return chamber panel, and blower access panel from the unit.
3. Remove the panel covering the horizontal return air opening on the unit and reinstall it on the base of the unit to cover the bottom return opening.
4. Install the damper assembly into the unit where the return chamber panel was. The economizer should sit inside the unit and rest on the base rail.
5. Screw the left side flange of the economizer to the HVAC unit using the provided (4) #10-14 x 3/4 screws with washer.
6. Align the holes in the base flange of the economizer with the holes in the base rail of the HVAC unit. Secure it in place using (2) #10-16 x 5/8 screws.
7. Install the provided blank-off above the economizer to cover the top part of the horizontal return air opening. Screw it in place.
8. Install the economizer hood over the economizer and screw it in place on both sides and top flanges.
9. Install the field-supplied horizontal return duct as per the unit instructions. Ensure a water-tight seal by caulking or gasketing the seam.
10. Relocate the economizer control module from its shipping location to the control box.
11. The installation process should be performed by a qualified installer, service agency, or the gas supplier to ensure proper installation, adjustment, and safety.

Important Safety Instructions

• Improper installation, adjustment, alteration, service, or maintenance can cause property damage, personal injury, or loss of life. Therefore, installation and service must be performed by a qualified professional.
• Take care when servicing the unit to avoid accidental contact with sharp metallic edges that can cause injury.

Shipping and Packing List

Package 1 of 1 contains

• 1 – Economizer damper assembly
  • 1 – Outdoor air damper
  • 1 – Return air damper
  • 1 – Gravity exhaust damper
  • 1 – Horizontal blank-off panel
  • 1 – Economizer actuator
  • 1 – Economizer control module
  • 1 – Outdoor air temperature sensor
• 1 – Hardware bag
  • 1 – Mixed air sensor
  • 3 – #10-14 × 3/4″ screws with washer
  • 11 – #10-16 × 5/8″ screws
• 1 – Side economizer panel
• 1 – Wiring diagram label
• Order Of Installation
  • Economizer
  • Mixed air sensor
  • Optional OA and RA sensors
  • Power Exhaust fans (optional)
  • Side economizer panel

WARNING: Improper installation, adjustment, alteration, service or maintenance can cause property damage, personal injury or loss of life. Installation and service must be performed by a qualified installer, service agency or the gas supplier.

Application

The standard economizer is used with ZC,ZG,ZH 092-150 units in horizontal air discharge applications. Economizer dampers will modulate to maintain 55oF (13oC) supply air when outdoor air is suitable. The mixed air temperature sensor measures the supply air sensible temperature.An outdoor air sensor is used to determine whether outdoor air is suitable for free cooling. The outdoor air sensor is factory-installed in all economizers. Other outdoor and return air (OA and RA) sensor options are available to determine whether outdoor air is suitable for free cooling. See Table 1 and the instructions provided with optional senors.

TABLE 1

Sensors| Dampers modulate to maintain 55 o F mixed air (R1) when:
---|---
*Single OA Sensible| OA temperature is lower than free cooling setpoint
Single OA Enthalpy| OA temperature and humidity is suitable for free cooling
Differential Enthalpy

– 1 in OA & 1 in RA

| OA temperature and humidity is lower than RA temperature and humidity.

• Single OA sensible sensor is shipped standard on economizer

INDOOR AIR QUALITY SENSOR

An IAQ sensor is used when demand control ventilation (DCV) is specified. Damper minimum position can be set lower than traditional minimum air requirements resulting in cost savings. The IAQ sensor allows the economizer control module to open dampers to traditional ventilation requirements as room occupancy (CO2) increases. For proper operation, the IAQ sensor must provide a 2-10VDC, 100 ohm impedance signal. Connect sensor leads to AQ and AQ1 terminals on the economizer control module located in the filter section.

CAUTION

• Danger of sharp metallic edges. Can cause injury.
• Take care when servicing unit to avoid accidental contact with sharp edges.

Install Economizer

1. Disconnect all power sources to the unit
2. Remove the following panels from the unit;
   • Filter door panel
   • Return chamber panel
   • Blower access panel
   • When filter access door and return chamber panels are removed there will be a cross support still in the unit stretching from side to side of the return chamber.
3. Remove panel covering the horizontal return air opening on unit and reinstall on base of unit, covering bottom return opening. See unit instructions for details.
4. Install damper assembly into unit where return chamber panel was. Economizer will sit inside of unit, and will rest on base rail.
5. Screw left side flange on the economizer to HVAC unit using provided (4) #10-14 x 3/4” screws with the washer.
6. Align the holes in the base flange of the economizer intothe holes in the base rail of the HVAC unit. Secure in place using (2) #10-16 x 5/8” screws.
7. When the economizer is installed it will not cover the entire horizontal return air opening in the unit. Install provided blank-off above the economizer covering the top part of the horizontal return air opening. Screw in place.
8. The Economizer hood is shipped assembled. Install over economizer and screw in place on both sides and top flanges. See Fig 6.
9. Install field supplied horizontal return duct per unit instructions. Caulk or gasket seam to ensure water tight seal. See Fig. 6.

Economizer Wiring

1. 1. The economizer control module is located next to the actuator for shipping. Relocate the module to the unit control box, see Figure 7A.
2. 2. Route the control wires to unit terminal block (TB1) and connect these wires to TB1 as following (see Figure 5A):
   • Connect all female terminals to TB1 – Pink (24V) to R: Grey (GND) to ground; Yel (Cool 1) to Y1; and Blue (Cool 2) to Y2.
   • Disconnect the factory-installed terminals at TB1, Y1 and Y2. Connect these terminals to control male terminals Y1 and Y2
3. Attach the control harness jack (J142) to prewired harness plug (P142).
4. At economizer/filter compartment, attach economizer plug (P10) to prewired harness jack (J10). See Figure 7.
5. Connect any optional sensors as shown in Figure 7.
6. If optional power exhaust is used, wire it according to instructions provided with power exhaust. See Figure 7.
7. Apply wiring diagram to the control panel. See Figure 9

Install Mixed Air Sensor

1. Remove the mixed air sensor from the economizer parts bag. The sensor has a small ring terminal. See Fig. 7.
2. Locate the 2 mixed air sensor wires in the unit from plug J3. The mixed air sensor wire color is white. Attach these 2wires to the mixed air sensor wires.
3. Mount the mixed air sensor to the indoor fan through the existing screw on the blower. See Fig. 8.
4. Secure wires in place so they don’t interfere with unit operation.
5. Replace all panels.

Economizer Side Panel

1. Install economizer side panel to the right side of the economizer,see Fig. 5 and 6. Screw panel to economizer on left side,and into door bracket on right side of panel.
2. Caulk all seams and gaps along sides and bottom of the economizer and economizer side panel sheet metal. Allow time for caulk to cure prior to placing unit into operation.
3. Reinstall unit’s filter access door.

TABLE 2: ECONOMIZER CONTROL MODULE LEDs

more fresh air

FREE COOLING CHANGEOVER

Note:  The following conditions assume unit is operating during occupied period.

Single Outdoor Air Temperature Sensing:

• The temperature sensor shipped with the economizer is used to determine outdoor air suitability for free cooling. The sensor has a fixed changeover and cannot be adjusted. Set the A,B,C,D setting on economizer control module to the “D” setting.
• The sensor will allow economizer to go to free-cooling mode when the temperature falls below 55oF, and will then disable free-cooling when temperatures rise above 70oF.

Single Enthalpy Sensing:

Note:  The following conditions assume unit is operating during occupied period.

Single Outdoor Air Enthalpy Sensing:

• The enthalpy sensor is an optional accessory. The temperature sensor shipped with the economizer will be removed and discarded, and the enthalpy sensor field installed. The enthalpy sensor is used to determine outdoor air suitability for free-cooling, see Table 3.
• Free cooling will be enabled when the outdoor air enthalpy is lower than the free cooling setpoint. Table 3 shows the free cooling setpoints which are adjustable on the economizer control module.

For example: At setting A (Table 3), free cooling will be enabled when outdoor air enthalpy is lower than 73oF and 50% RH. If indoor air is too warm or humid, lower the setpoint to B. At setting B, free cooling will be enabled at 70oF and 50% RH.

Differential Enthalpy Sensing:

Outdoor air and differential enthalpy sensors are optional accessories. Two enthalpy sensors can be used to compare outdoor air to return air. When outdoor air is cooler than return air and free cooling setpoint, outdoor air is suitable for free cooling. Adjust the free cooling setpoint to “D” in this application. Table 3 shows the free cooling setpoints for enthalpy sensors.

For example: At setting D (Table 3), free cooling will be enable when outdoor air enthalpy is lower than return air enthalpy AND free cooling setpoint 63°F / 50% RH. If indoor air is too cool or dry, increase the setpoint to C.

When return air is cooler than outdoor air, the damper will be modulated to the minimum position.

DAMPER MINIMUM POSITION SETTING

NOTE:  24 volts must be provided at unit 24 volt leads R and OC to enable economizer operation (allowing minimum fresh air). Typically a separately ordered thermostat or energy management system with an occupied/unoccupied output is connected between R and OC leads. The thermostat will provide 24 volts to the economizer control during the occupied time period to enable the economizer. If a device is not used to enable the economizer, install a jumper between R and OC leads R and OC to maintain minimum position continuously.

Make wire connections to leads R and OC as shown in literature provided with thermostat or energy management system.

1. Set thermostat to occupied mode if the feature is available.Make sure the jumper is in place between leads R and OC if using a thermostat which does not have the feature.
2. Rotate MIN POS SET potentiometer to approximate desired fresh air percentage. Use care when adjusting minimum potentiometer to avoid damaging the potentiometer.
   • Note:  Damper minimum position can be set lower than traditional minimum air requirements when an IAQ sensor is specified.
3. Measure outdoor air temperature. Mark the point on the bottom line of chart 1 and label the point “A” (40oF, 4oCshown).
4. Measure return air temperature. Mark that point on the top line of chart 1 and label the point “B” (74oF, 23oC shown).
5. Measure mixed air (outdoor and return air) temperature. Mark that point on the top line of chart 1 and label point “C”(70oF, 21oC shown).
6. Draw a straight line between point A and B.
7. Draw a vertical line through point C.
8. Draw a horizontal line where the two lines meet. Read the percent of fresh air intake on the side.
9. If fresh air percentage is less than desired, adjust the MINPOS SET potentiometer clockwise (further open). If fresh air percentage is more than desired, adjust MIN POSSET potentiometer counterclockwise (less open). Repeat steps 3 through 8 until calculation reads desired fresh air percentage.

DCV SET AND DCV MAX SETTING

• The DCV SET potentiometer is factory-set at approximately 50% of the potentiometer range. Using a standard 1-2000ppm CO2 sensor, dampers will start to open when the IAQ sensor reads approximately 1000ppm. Adjust the DCV SET potentiometer to the approximate setting specified by the controls contractor. Refer to Fig. 9.
• The DCV MAX potentiometer is factory-set at approximately 50% of the potentiometer range or 6VDC. Dampers will open approximately half way when CO2 rises above setpoint. Adjust the DCV MAX potentiometer to the approximate setting specified by the control contractor. Refer to Fig. 10.

Note:  DCV Max must be set higher than economizer minimum position setting for proper demand control ventilation.

Economizer Operation

• When the outdoor air is suitable, dampers will modulate between minimum position and full open to maintain 55oF (12oC) supply air.
• See Table 4 for economizer operation when outdoor air is suitable. See Table 5 for economizer operation when outdoor air is NOT suitable.

IAQ Sensor

During the occupied period, dampers will open to DCV MAX when IAQ reading is above setpoint (regardless of thermostat demand or outdoor air suitability). DCV MAX will NOT override damper full-open position. The DCV MAX setting may override damper free cooling position when occupancy is high and outdoor air temperatures are low.

Note:  If mixed air sensor senses mixed air temperature below 45oF (7oC), dampers will move to minimum position until mixed air temperature rises to 48oF (9oC)

TABLE 4: ECONOMIZER OPERATION

OUTDOOR AIR IS SUITABLE FOR FREE COOLING — FREE COOL LED

• IAQ sensor can open damper to DCV max.
• Damper position when no occupied/unoccupied signal is available from building thermostat or energy management system.

TABLE 5: ECONOMIZER OPERATION

OUTDOOR AIR IS NOT SUITABLE FOR FREE COOLING — FREE COOL LED

• IAQ sensor can open damper to DCV max.
• Damper position when no occupied/unoccupied signal is available from building thermostat or energy management system.

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