HVAC airflow measurement with in-situ calibration
In-situ calibration of a flow measurement device in a forced air HVAC system. A flow measurement that is obtained by a flow measurement device that is temporarily installed in the HVAC system is used to calibrate a flow measurement device that is permanently installed in the HVAC system. The calibration described herein can be aided by a technician installing or servicing the HVAC system.
1 . A method of calibrating a flow measurement device, the method comprising:
obtaining a first flow measurement by a first flow measurement device of a forced air HVAC system;
calibrating a second flow measurement device of the forced air HVAC system in-situ,
wherein the first flow measurement is obtained while the first flow measurement device and the second flow measurement device are installed in series in the forced air HVAC system to measure a volumetric or mass of air flow through the HVAC system and the forced air HVAC system is operating, wherein the calibrating of the second flow measurement device is based on a difference in the first flow measurement and a second flow measurement by the second flow measurement device; and
removing the first flow measurement device after calibrating the second flow measurement device.
2 . The method of claim 1 , wherein the first flow measurement device is temporarily installed at a first location of the forced air HVAC system, and the second flow measurement device is permanently installed at a second location of the forced air HVAC system.
3 . The method of claim 2 , wherein the first location is at a return side of the forced air HVAC system, and the second location is at a supply side of the forced air HVAC system.
4 . The method of claim 2 , where the first location is a filter slot of the forced air HVAC system or a filter grille of the forced air HVAC system.
5 . The method of claim 2 , where the second location is a supply duct of the forced air HVAC system.
6 . The method of claim 2 , where the second location is a return duct of the forced air HVAC system upstream of the first location such that the second flow measurement device creates negligible interference with the first flow measurement device.
7 . The method of claim 1 , wherein the first flow measurement device transmits the first flow measurement to a receiving device separate from the first flow measurement device; and wherein the second flow measurement device obtains a second flow measurement and transmits the second flow measurement to the receiving device.
8 . The method of claim 7 , comprising using the receiving device to calibrate the second flow measurement device.
9 . The method of claim 7 , wherein the receiving device comprises a mobile phone, a tablet computer, a laptop computer, or a personal computer.
10 . The method of claim 4 , wherein the first flow measurement device comprises a flow grid having a pressure drop approximately equal to a pressure drop of a filter that is installable in the filter slot or the filter grille.
11 . The method of claim 1 , wherein the second flow measurement device comprises an averaging pitot tube array.
12 . The method of claim 1 , wherein when the difference in the first flow measurement and the second flow measurement is greater than at least 75%, the second flow measurement device is replaced.
13 . The method of claim 1 , wherein the forced air HVAC system comprises a residential forced air HVAC system.
14 . A method comprising:
in a forced air HVAC system in which a first flow measurement device is installed at a first location and a second flow measurement device is installed at a second location in series with the first flow measurement device to measure a volumetric or mass of air flow through the HVAC system, obtaining a first flow measurement using the first flow measurement device and obtaining a second flow measurement using the second flow measurement device;
comparing the first flow measurement and the second flow measurement;
calibrating the second flow measurement device in-situ or replacing the second flow measurement device based on a determined difference between the first flow measurement and the second flow measurement; and
removing the first flow measurement device after calibrating the second flow measurement device.
15 . A system comprising:
a forced air HVAC system with a blower, a supply duct in fluid communication with the blower and receiving air therefrom, and a return duct in fluid communication with the blower and returning air thereto;
a first flow measurement device that is temporarily installable in the return duct at a first location, the first flow measurement device includes a first wireless data transmitter;
a second flow measurement device that is permanently installed in the supply duct at a second location, the second flow measurement device includes a second wireless data transmitter; and
a receiving device in wireless communication with the first wireless data transmitter and with the second wireless data transmitter, the receiving device includes a data processor that is in communication with a storage device that includes instructions which, when executed by the data processor, configure the data processor to calibrate the second flow measurement device in-situ using one or more flow measurements obtained by the first flow measurement device,
wherein the first flow measurement device and the second flow measurement device are installed in series in the forced air HVAC system to measure a volumetric or mass of air flow through the HVAC system,
wherein calibrating the second flow measurement device in-situ is based on a difference in the one or more flow measurements by the first flow measurement device and a flow measurement by the second flow measurement device.
16 . The system of claim 15 , where the first location is a filter slot or a filter grille.
17 . The system of claim 15 , wherein the receiving device comprises a mobile phone, a tablet computer, a laptop computer, or a personal computer.
18 . The system of claim 16 , wherein the first flow measurement device comprises a flow grid having a pressure drop approximately equal to a pressure drop of a filter that is installable in the filter slot or the filter grille.
19 . The system of claim 15 , wherein the second flow measurement device comprises an averaging pitot tube array.
20 . The system of claim 15 , wherein the forced air HVAC system comprises a residential forced air HVAC system.
21 . The system of claim 15 , wherein the forced air HVAC system further comprises a heating coil and a cooling coil; and the blower, the heating coil and the cooling coil are located in a flow path between the first flow measurement device and the second flow measurement device.