GREYSTONE AIR4 Series Room Air Quality Transmitter Instruction Manual

GREYSTONE AIR4 Series Room Air Quality Transmitter

INTRODUCTION

In recent years, indoor air quality has been equated to CO2 levels for Demand Controlled Ventilation (DCV) applications in an effort to improve building health and reduce energy costs. The benefits of healthy and “green” buildings are well known today and progress in controlling ventilation rates to optimum values is still being made. One area that has received significant study and attention is the measurement of indoor air quality pollutants.

The traditional measurement of CO2 levels is often seen as limiting when compared to the total amount of volatile organic compounds (VOCs) present in the air that have a detrimental effect on the human perception of air quality. These indoor VOCs are hydrocarbons that originate mainly from bio-effluents (odors from human respiration, perspiration and metabolism) and vapors generated from building materials and Figure 1

TYPICAL INDOOR AIR VOC CONTAMINANTS

Contamination Source| Emission Source| VOCs
HUMAN BEING| Breath

Skin Respiration and Perspiration Flatus

Cosmetics Household Supplies Combustion

| Acetone, Ethanol, Isoprene Nonanal, Decanal, a-Pinene Methane, Hydrogen Limonene, Eucalyptol Alcohols, Esters, Limonene Unburnt Hydrocarbons
OFFICE EQUIPMENT BUILDING MATERIAL FURNITURE  CONSUMER PRODUCTS| Printers, Copiers, Computers Paint, Adhesive, Solvent, Carpet PVC (Poly Vinyl Chloride)| Benzene, Styrene, Phenole

Fromaldehyde, Alkanes, Aldehydes, Ketones Toluene, Xylene, Decane

furnishings. There are thousands of unique VOCs that may be present in indoor air that affect the air quality. The table above (Figure 1) lists some of the more common VOCs and their source. It is generally understood that the root cause of indoor air quality problems lies with the presence of these VOCs. Unfortunately, it has been difficult to accurately measure VOCs due to the lack of suitable VOC sensing devices. Early VOC sensors suffered from long- term stability problems, drift and an output signal that was difficult to define and apply in a reliable way. CO2 sensors have long served as an adequate air quality indicator with a defined range ppm output signal that is easy to set thresholds to. The American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) Standard 62.1 (Ventilation for Acceptable Indoor Air Quality) is generally used in DCV applications because minimum ventilation rates are clearly defined based on occupancy and CO2 sensors are then generally used to determine occupancy.
This system has worked for DCV system designers due to it’s straight-forward design, predictable results and energy saving results. However, the control of indoor air quality based on CO2 levels alone is not optimal because it ignores other air contaminants that are often present. Ventilation should react on demand toward all sources of contamination, not only CO2.

THE IAQ SENSOR

The Indoor Air Quality Sensor uses an advanced MEMS metal oxide semiconductor sensor to detect poor air quality. The sensor reacts quickly to detect a broad range of VOCs such as smoke, cooking odors, bio-effluence, outdoor pollutants and from human activities. The sensor captures all VOC emissions that are completely invisible to CO2 sensors.
Extensive studies and research have shown that there is direct correlation between CO2 levels and VOC levels and the Air Quality Sensor has been calibrated to provide a “CO2-equivalent” ppm measurement value, thereby achieving full compatibility to existing HVAC CO2 ventilation standards.

NOTE: The sensor does not measure CO2 levels directly, it measures VOCs and provides a CO2 equivalent reading. The sensor also includes control algorithms that correct sensor drift and aging and therefore provides a long- term consistent DCV solution while overcoming the deficiencies of CO2 measurement by detecting the true root-cause of ventilation demand, VOCs. The IAQ sensor emulates the human perception of air quality much more than a CO2 sensor and even detects odorless, potentially hazardous substances such as carbon monoxide. The CO2-equivalent sensor output value was developed over a period of several years to allow the IAQ sensor to be optimized for Demand Controlled Ventilation applications. The long-term IAQ sensor performance was monitored in various locations including offices, cafeterias, schools, production facilities, apartments and homes in direct comparison to infrared- absorption CO2 sensors. The data shows consistent results between measured CO2 values and the IAQ CO2-equivalent values and also highlight the poor air quality events detected by the IAQ sensor that the CO2 sensor misses. A sample chart showing CO2 measurements vs. IAQ measurements is shown in Figure 2.

IAQ SENSOR FEATURES

• Measures total VOCs
• High sensitivity and fast response
• Stable long-term operation
• 0 to 2000 ppm CO2 equivalent output signal
• LCD to display air quality information
• Internal menu for easy setup
• Analog stepped output for damper control
• Linear output for logging and control
• Selectable 0-5 or 0-10 Vdc signal
• ri-color LED to indicate IAQ level
• Optional relay output with adjustable setpoint
• Optional override switch output
• Optional resistive temperature sensors

BEFORE INSTALLATION

Read these instructions carefully before installing and commissioning the device. Failure to follow these instructions may result in product damage. Do not use in an explosive or hazardous environment, with combustible or flammable gases, as a safety or emergency stop device or in any other application where failure of the product could result in personal injury. Take electrostatic discharge precautions during installation and do not exceed the device ratings.

MOUNTING

The IAQ room transmitter installs directly on a standard electrical box and should be mounted five feet from the floor of the area to be controlled. Do not mount the sensor near doors, opening windows, supply air diffusers or other known air disturbances. Avoid areas where the detector is exposed to vibrations or rapid temperature changes. Figure 3 The cover is hooked to the base at the top edge and must be removed from the bottom edge first. Use a small Phillips screwdriver to loosen the security screw as shown in Figure 3. (Complete removal of this screw is not required). Use the screwdriver to carefully pry each bottom corner if necessary. Tip the cover away from the base and sit it aside as shown in Figure 4. The PCB must be removed from the base to access the mounting holes. Follow usual anti-static procedures when handling the PCB and be careful not to touch the sensors. The PCB is removed by pressing the enclosure base to unsnap the latch near the bottom edge, then the PCB can be lifted out of the base as shown in Figure 4. Sit the PCB aside until the base is mounted on the wall. For added protection, place the PCB in the supplied anti-static bag. Mount the base by screwing to an electrical box or directly to the wall as shown in Figure 5. The mounting hole locations are shown on page 7. After the base is screwed to an electrical box or the wall using the appropriate holes, remove the PCB from the anti-static bag, feed connection wires through center hole and place the top of PCB into the PCB holders on backplate and snap bottom of PCB into place as shown in Figure 5. Make wire connections as per the Wiring Illustrations on Page 3 and install decorative cover by placing the top of the cover into the cover holder on the top of the backplate and snapping the bottom into place as shown in Figure 5. Tighten security screw with a Phillips screwdriver.

WIRING

Deactivate the 24 Vac/dc power supply until all connections are made to the device to prevent electrical shock or equipment damage. Follow proper electrostatic discharge (ESD) handling procedures when installing the device or equipment damage may occur. Use 18-22 AWG shielded wiring for all connections and do not locate the device wires in the same conduit with wiring used to supply inductive loads such as motors. Connect the cable shield to ground at the controller only. Make all connections in accordance with national and local codes. Connector layout is shown in Figure 6. Diagram shown includes all options. If option is not ordered, connector will not be present. Connect the positive dc voltage or the hot side of the ac voltage

to the terminal marked POWER. The power supply common is connected to the terminal marked COMMON as shown in Figure 7. The device is reverse voltage protected and will not operate if connected backwards. This device has a half- wave type power supply so the power supply common is the same as the output signal common. Therefore, several devices may be connected to one power supply and the output signals all share the same signal common. Use caution when grounding the secondary of an ac transformer or when wiring multiple devices to ensure that the circuit ground point is the same on all devices and the controller.

Ensure the controller Analog Input (AI) matches the IAQ voltage output signal type before power is applied. The voltage signals have a minimum load rating. Follow the ratings in the Specification section or inaccurate readings may result.

Connect the LINEAR output signal to a 0-5 or 0-10 Vdc analog input port on the controller as shown in Figure 7. The device is factory configured for 0-5 Vdc output signal but may be changed to 0-10 Vdc via the menu. Changing the output signal may be done during set up of the device. This linear output signal represents the 0-2000 ppm CO2-equivalent value. The ASO (Analog Stepped Output) output signal is a second voltage signal that represents the three air quality levels of GOOD, FAIR and POOR. Each level may be set independently via the menu to any value between 0 and 10 Vdc. The factory default is GOOD = 2.5 V, FAIR = 5.0 V and POOR = 7.5 V. This signal can also be connected to a controller analog input, or it can be connected directly to a 0-5 or 0-10 Vdc input of a damper actuator for direct ventilation control as shown in Figure 8. In this way, the Indoor Air Quality Sensor can be used as a stand-alone device. Since all steps are completely adjustable, the device can also drive a reverse acting actuator. The optional override switch output is a digital output signal that is controlled by the front panel override button. The signal is available on the OVERRIDE terminal and will short the OVERRIDE terminal to COMMON when activated as shown in Figure 9. This signal typically connects to a low voltage digital input of the controller to indicate room occupancy or override when the button is pressed. This output uses a FET to create the pull-down to common so respect the device ratings. An optional resistive temperature sensor may also be included in the device and is connected to the TEMP terminals as shown in Figure 10. Various thermistors or RTDs may be installed on the pcb to suit the application. These terminal would connect to a thermistor or RTD sensor input on the controller.
Another optional signal is the relay output available on the RELAY terminals. The relay output terminals are completely isolated from other connections and are NOT connected to the signal COMMON terminal as shown in Figure 11. This signal can be used to directly control an alarm, a ventilation fan or may be connected to a digital input of the Building Automation System for status monitoring. Respect the relay contact specification.

SET-UP

Verify that the Air Quality Sensor is properly wired and all connections are tight. Apply power to the device and note that the LCD will display the software version number for a few seconds and then the device will enter Warm Up mode. The Warm Up mode will last for five minutes and the LCD will count down the time. The status LED will cycle through the three colors (green / red / blue). This time is required to allow the device and sensor to reach normal operating temperature. After the five minutes has expired the device will enter normal operation and the LCD will indicate the IAQ status and ppm value.

OPERATION

In normal operation, the Air Quality Sensor will detect a broad range of reducing gases such as CO and VOCs and translate the measurement into a parts per million (ppm) CO2 equivalent value. This value is displayed on the LCD in either ppm or % as set in the menu. The air quality value is also displayed as either GOOD, FAIR or POOR and these values can also be set via the menu. The GOOD, FAIR and POOR air quality levels control the Analog Stepped Output (ASO) signal. The ASO output signal comprises of three independently set voltage levels that can be used to directly control a damper actuator for three positions. The levels are set via the menu and each level can be set anywhere from 0-10 Vdc. The GOOD, FAIR and POOR air quality levels will also be displayed on the tri-color front panel LED. The LED colors are displayed as GOOD = green, FAIR = blue and POOR = red. If required, the  LED operation can be disabled via the menu. The air quality value is also sent to the LINEAR output as a 0-5 or 0-10 Vdc signal to represent the 0-2000 ppm CO2 equivalent. This signal can interface to any voltage analog input for logging or control purposes. The linear output scaling and ASO operation is shown below. Note that the ASO GOOD/FAIR trip level = 1000 ppm and the FAIR/POOR trip level = 1500 ppm. The ASO output levels are GOOD = 2.5 V, FAIR = 5.0 V and POOR = 7.5 V.

If the device is equipped with the optional relay, then the normally open relay will close when the air quality exceeds a pre-set trip point. The trip point and hysteresis value can be programmed via the menu such that the relay closes when IAQ > Relay Setpoint and opens when IAQ < Relay Setpoint – Hysteresis. By default, the relay has a one minute minimum on and off time to prevent short cycling. This feature may be disabled via the menu. The menu may also be used to test the relay function and change the relay action to normally closed (N.C.). The relay can be used to control an alarm, fan directly or to signal a digital input. If the device has the optional Override function installed, then a front panel pushbutton can be used to generate an override signal output. The override signal can be configured for either Momentary, Latch or Toggle operation via the menu. This signal can be connected to a digital input of the controller. Various optional resistive temperature sensors may also be included on the pcb and are available at the TEMP output. This is a two-wire resistive output signal and the temperature value is not displayed on the LCD. Other features and configuration are described in the Setup Menu section.

NOTE: The air quality sensor requires a continuous burn-time of at least 3 weeks before the sensor algorithms provide accurate measurements. During this perios the product-to-product readaings may show large variations. The sensor may also indicate very high PPM readings during the initial burn-in phase.
The air quality sensor is meant to provide accurate measurements of INDOOR air quality. Diesel exhaust is not a component of indoor air quality and the sensor should not be used in such an application.

START-UP

The menu may be accessed any time after the initial warm-up period. The menu is controlled by using the three buttons on the PCB labeled UP, DOWN and MENU. All values entered are saved in non-volatile memory and will be restored correctly in case of a power failure. The menu has several items as shown below. To enter the menu, press and release the