Assessments - 4, GPA: 4.3
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In the balanced airflow system, the HRV exhaust removes stale room air (eg. from lunch room, storage or copy area) and returns to the space an equal amount of fresh outdoor air. Many buildings have a ceiling return air plenum as in Figure 4B. Fresh air from the HRV can be introduced directly into the ceiling space but this should occur near the air handler’s intake. By operating the HRV on a 24 hour/7 day battery backed timer the unit can be set to operate only when occupancy or indoor conditions require the air exchange. In installations where it is satisfactory to provide general exhaust from the space, the air to be exhausted may be taken directly from the return air plenum to the HRV as it is drawn back to the air handler. Fresh air supplied by the HRV is then introduced directly into the return air plenum but at a location closer to the air handler. The air handler would have a constant running blower to effectively distribute the fresh air and remove the stale air. Balancing dampers would be located in both the HRV supply and exhaust ducts between the return air plenum and the HRV. ELECTRICAL CONNECTIONS It is recommended that a licensed electrician make all electrical connections. It is very important that the unit be properly grounded. It is recommended that a separate 15 amp/120 volt circuit be used. WARNING: In order to prevent electric shock when cleaning or servicing the HRV, it is extremely important to confirm the polarity of the power line that is switched by the safety (disconnect) switch whose control arm is located on the outside electrical control box area. The hot line (black) is the proper line to be switched. To confirm the proper polarity, use a voltmeter or test lamp to make sure there is no-power after the switch when the door is open. Check between that point and ground (on the cabinet). This must be done as occasionally some buildings are improperly wired. Always make sure the HRV Is properly grounded. AIR FLOW BALANCING It is necessary to have volume balanced air flows in an HRV. The volume of air brought in from the outside must equal the volume of air exhausted by the HRV. If the air flows are not properly balanced, then; ♦ The HRV may not operate at its maximum efficiency • A negative or positive air pressure may occur in the building • The HRV may not defrost properly. ♦ Failure to balance HRV may void warranty An excessive positive pressure may drive moist indoor air into the external walls of the building where it may condense (in cold weather) and degrade structural components. An excessive negative pressure may have several undesirable side effects. In some geographic locations, soil gases such as radon and methane may be drawn into the building through basement/ground contact areas. Radon is currently believed to be a serious medical concern. As well, an excessive negative pressure may cause the backdrafting of vented combustion equipment if an adequate combustion air supply is not provided. Read the Application Warning at the start of this manual Procedure: A. To balance the air flows requires an accurate flow measure of the fresh entering air and the exhaust stale air. The air flows can be measured with a calibrated measuring instrument such as a flow orifice or by measuring the air velocity across the duct with a pitot tube or hot wire anemometer. The flow measurements should be made in a straight section 10 duct diameters from an elbow or restriction. B. Prior to balancing, make sure: 1. All sealing of the ductwork system has been completed. 2. All of the HRV components are in place and functioning properly. 3. Balancing dampers are fully open. 4. Unit is on HIGH speed. 5. If directly connected to a furnace or air handler, have that units blower on before balancing the HRV. 6. Air flows in branch lines to specific areas of the building should be adjusted first prior to balancing the unit. A smoke pencil used at the grilles is a good indicator of each branch line's relative air flow. 7. After taking readings of both the stale air to the HRV duct and the fresh air to the building duct, the duct with the lower CFM (L/s) (velocity) reading should be left alone, while the duct with the higher reading should be dampered back to match the lower reading. 8. Return unit to appropriate fan speed for normal operation. 6 THE INTEGRATED HVAC SYSTEM ECONOMIZER FIG. 4 - A BALANCING DAMPERS A - Fresh Air Supply B - Stale Air Exhaust 7 VARIOUS INSTALLATION TYPES FIG. 5-A Saddle Installation Hang unit with suspended rods and *U* channel members. Vibration Isolators (Supplied by otters) Threaded rod and U channel (Supplied by others) * NOTE: When installing your LIFE BREA TH® HRV, flexible du...
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