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The Pitot tube should be connected to a magnehelic gauge or other manometer capable of reading from 0 to 0.25 in. (0-62 Pa) of water, preferably to 3 digits of resolution. The tube coming out of the top of the pitot is connected to the high pressure side of the gauge. The tube coming out of the side of the pitot is connected to the low pressure or reference side of the gauge. Insert the Pitot tube into the duct; pointing the tip into the airflow. For general balancing it is sufficient to move the pitot tube around in the duct ing. The value read on the gauge is called the velocity pressure. The Pitot tube comes with a chart that will give the air flow velocity based on the velocity pressure indicated by the gauge. This velocity will be in either feet per minute or meters per second. To determine the actual airflow, the velocity is multiplied by the cross sectional areas of the duct being measured. This is an example for determining the airflow in a 6" duct. The Pitot tube reading was 0.025 inches of water. From the chart, this is 640 feet per minute. The 6" diameter (D) duct has cross sectional area (A) of A = 3.14 x (D/24) 2 A = 3.14 x (6/24) 2 A = 0.196 or about 0.2 ft2 The airflow is then: 640 ft/min x 0.2 ft2 = 128 cfm For your convenience, the cross sectional area of some common round duct is listed below: DUCT DIAM. (inches) CROSS SECTION AREA (sq ft.) 5 0.14 6 0.20 7 0.27 8 0.35 The accuracy of the airflow reading will be affected by how close to any elbows or bends the readings are taken. Accuracy can be increased * Pitot tube should be kept at least 12” away from fans elbows and dampers to ensure accurate reading. * A calibration decal is included to place over electronic balanc- ing system adjustments after it has been balanced. • The balancing procedure consists of measuring the exhaust air leaving the system and the supply air entering the system and ensuring that these Place pitot tube a minimum of 18" from blower elbows. Note: Duct connections may vary, depending on model. and take an average or typical reading. Repeat this procedure in the other (supply or return) duct. Determine which duct has the highest air- flow (highest reading on the gauge). Reduce this airflow using either the electronic balancing system (if applicable) or damper. The flows should now be balanced. Actual airflow can be determined from the gauge read- by taking an average of multiple readings as outlined in the literature supplied with the Pitot tube. two are equal. A deviation of 10% or less is acceptable. In such cases, it is recommended to have a greater amount of exhaust air than supply air as so to increase the supply air’s temperature. AIR FLOW BALANCING (CONT'D) AIRFLOW STATION (GRID) METHOD B 2 Before taking the reading, make sure that the magnehelic gauge is level and at 0. Refer to the flow measuring station’s chart to determine your unit’s airflow velocity. 3 Adjust the “Supply Air Out” damper until you reach the desired velocity. Follow the previous steps to adjust the “Exhaust Air Out” damper, if needed. Fan+- Use slot screwdriver to adjust speed/airflow 1 For this flow measuring station, cut the duct and place the flow measuring station between each station. Make sure that the flow measuring station’s air direction arrow points in the direction of the airflow. Secure the flow measuring station with duct tape. • To avoid airflow turbulence and incorrect readings, the airflow 18” (457 mm) 18” velocity should be (457 mm) measured on steel Measure here ducting a minimum of 18” (457 mm) from the Measure here unit or elbow and before any transition. ADJUSTING AIRFLOWS ELECTRONIC BALANCING MOTORS [HRV 150D & 200D only] - Motors will be factory set at their full potential depending on speed selected. When unit is installed you will need to balance the motors for proper operation. Insert screwdriver and turn clockwise to slow down the motor, you will notice the motor changing speeds while performing this operation. Set to desired cfm. MAINTENANCE CAUTION MAKE SURE UNIT IS UNPLUGGED BEFORE ATTEMPTING ANY MAINTENANCE WORK The following components should also be inspected regularly and well maintained. PRACTICAL TIPS • To prevent electrical shock, check that the unit is unplugged before doing any repairs or maintenance. • A yearly inspection is recommended to ensure the efficiency and trouble- free use of your system. Run through the system and verify the different operating modes. FILTERS The filters (2) need to be checked and cleaned every three months or when they appear dirty. Wash in warm sudsy water (mild detergent) or use a soft brush vacuum. The filters should be replaced when they can no longer be cleaned properly. Filters need to be checked regularly The motor - The motors are factory balanced and lubricated for life. They require no maintenance. The unit - The inside of the unit should be vacuumed yearly. Be careful not to damage any of the mechanical components and electrical connections. The drain pan and...

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