RA3.9 contains procedures for:
(a) Measurement of WHF airflow rate to confirm compliance with the airflow rate requirements specified in the performance standards set forth in Standards section 150.1(b).
(b) Measurement of WHF Watt draw.
(c) Calculation of WHF efficacy (w/cfm) utilizing simultaneous measurement of WHF Watt draw and airflow rate.
The instrumentation for the diagnostic measurements shall conform to the following specifications:
All pressure measurements shall be performed with measurement systems (i.e., sensor plus data acquisition system) having an accuracy of ± 1% of pressure reading or ± 0.2 Pa (.0008 inches water) (whichever is greater).
All measurements of WHF airflow rates shall be made with an airflow rate measurement apparatus (i.e., sensor plus data acquisition system) having an accuracy of ± 7% of reading or ± 5 cfm whichever is greater.
All measurements of WHF watt draws shall be made with true power measurement systems (i.e., sensor plus data acquisition system) having an accuracy of ± 2% of reading or ± 10 watts whichever is greater.
WHF airflow rate shall be measured using one of the apparatuses listed in Section RA3.9.3. The apparatus shall produce airflow rate measurements that conform to the accuracy requirements specified in Section RA3.9.2 for measurements of residential WHFs.
The airflow rate measurement apparatus manufacturers shall publish in their product documentation, specifications for how their airflow measurement apparatuses are to be used for accurately measuring WHF airflow rates.
The airflow measurement apparatus manufacturers shall certify to the Energy Commission that use of the apparatus in accordance with the specifications given in the manufacturer's product documentation will produce measurement results that are within the accuracy required by Section RA3.9.2.
For the airflow measurement apparatuses that are certified to the Commission as meeting the accuracy required by Section RA3.9.2, the following information will be posted on the Energy Commission website, making the information available to all people involved in the airflow verification compliance process:
(a) The product manufacturers' model numbers for the airflow measurement apparatuses.
(b) The product manufacturers' product documentation that gives the specifications for use of the airflow measurement apparatuses to accurately measure WHF airflow.
A manufacturer's certification to the Commission of the accuracy of the airflow measurement apparatus, and submittal to the Commission of the product documentation that specifies the proper use of the airflow measurement apparatus to produce accurate airflow rate measurements shall be prerequisites for allowing the manufacturer's airflow measurement apparatus to be used for conducting the system airflow verification procedures in Section RA3.9 for demonstrating compliance with Part 6.
The apparatus for measuring the system airflow rate shall consist of a building pressurization and airflow measurement device (subsequently referred to as a fan flowmeter) that meets all applicable instrumentation specifications in Section RA3.9.2, and a static pressure measurement device that meets the specifications in Section RA3.9.2.1. The fan flowmeter shall be attached at the inlet to a WHF from the conditioned space. The fan flowmeter shall be attached at a point where all the airflow through the system will flow through it. All WHF dampers shall be in their normal operating condition. The static pressure probe(s) shall be fixed to locations inside and outside the dwelling such that they will not be moved during this test.
A powered and pressure balanced flow capture hood (subsequently referred to as a Powered Flow Hood) that has the capability to balance the flow capture static pressure difference between the room and the flow capture hood enclosure to 0.0 ± 0.2 Pa (.0008 inches water) and meets the applicable instrumentation specifications in Section RA3.9.2 may be used to verify the system airflow rate at the WHF inlet if the powered flow hood has a flow capture area at least as large as the WHF inlet in all dimensions. The fan adjustment needed to balance the flow capture static pressure difference between the room and the flow capture hood enclosure to 0.0 ± 0.2 Pa (.0008 inches water) shall be provided by either an automatic control or a manual control operated in accordance with the apparatus manufacturer's instructions specified in the manufacturer's product documentation. All WHF dampers shall be in their normal operating position. Measurement(s) shall be taken at the inlet of the WHF.
A traditional flow capture hood meeting the applicable instrumentation specifications in Section RA3.9.2.2 may be used to verify the system airflow rate at the WHF inlet if the device has a capture area at least as large as the WHF inlet grille in all dimensions. All WHF dampers shall be in their normal operating position. Measurement(s) shall be taken at the inlet of the WHF.
The air handler watt draw shall be measured using one of the following apparatuses.
The apparatus for measuring the WHF watt draw shall consist of a wattmeter meeting the applicable instrumentation specifications in RA3.3.1. The measuring device shall be attached to measure the WHF watt draw. All WHF dampers shall be in their normal operating condition.
When required to measure fan watt draw on WHF equipment that is wired directly to an electrical junction box, it is recommended to use portable true power clamp-on meters to provide flexibility for isolating the correct fan wires serving the WHF.
The apparatus for measuring the WHF watt draw shall consist of a utility revenue meter meeting the applicable instrumentation specifications in RA3.9.2.3 and a stopwatch that provides measurements in units of seconds. All WHF dampers and access panels shall be in their normal operating condition.
The apparatus for measuring the WHF watt draw shall consist of a digital utility revenue meter meeting the applicable instrumentation specifications in RA3.3.1 that provides direct digital display of the watt draw. All WHF dampers and access panels shall be in their normal operating condition.
When required for compliance, the installed WHF airflow shall be diagnostically tested using one of the methods specified in this section.
The measured airflow rate shall be expressed in cubic feet per minute of standard air (standard air has a density of 0.075 lb/ft³). When the airflow measurement is made at altitudes significantly different from sea level or at temperatures significantly different from 70°F, the airflow indicated on the device gauge may differ from the standard CFM by as much as 15 percent. Corrections from indicated to standard CFM shall be made using the procedure specified by the airflow measurement device manufacturer.
When multiple WHFs are used to comply with the required WHF airflow rate for the dwelling unit, all WHFs in the dwelling unit shall be operated simultaneously and the sum of the airflow rate measurements of the simultaneously operating WHFs for the dwelling shall be determined.
When flow capture hood devices are used, the capture area shall be at least as large as the WHF inlet grille in all dimensions.
WHF airflow shall be measured with the dwelling unit window openings configured such that when the WHF(s) are operating, a dwelling unit pressure of negative 10 Pa ± 5 Pa with reference to (WRT) outside is attained. This is the WHF operating pressure (WHF-OP).
(a) Open the window(s) that are typically opened during WHF operation.
(b) Place a pressure sensing probe/tube in the attic. If necessary, use a suitable means such as cardboard sheets and tape to facilitate sealing off the access opening between the attic and the dwelling unit's conditioned space to allow the pressure sensing probe/tube to be inserted into the attic space without crimping or restricting the pressure sensing probe/tube. There shall be no leakage of air from the attic through the attic access opening into the dwelling unit during this verification procedure.
(c) Attach the attic pressure sensing tube to a digital pressure gage such that it will measure the pressure difference between the dwelling unit conditioned space and the attic.
(d) Turn on all WHFs required to meet the dwelling unit WHF airflow rate required for compliance. If applicable, adjust multiple WHFs or variable speed WHFs to operate at a total airflow rate greater than or equal to the WHF airflow rate required for compliance.
(e) Adjust the dwelling unit window openings to bring the dwelling unit to the WHF-OP of negative 10 Pa ± 5 Pa WRT outside.
(f) Measure and record the pressure difference (Pa) between the attic and the dwelling unit conditioned space (Pattic) while the dwelling unit is at the WHF-OP.
(g) Turn off the WHF.
(h) Do not change the window openings. The same dwelling unit window opening configuration used to establish the WHF-OP used for the measurement in step (f) shall be used for the pressure matching procedure specified below.
(i) Attach the fan flowmeter to the inlet grille of the WHF. The fan flowmeter's capture enclosure or ductwork shall cover the WHF intake grille completely.
(j) Turn on all WHFs that were used during the measurement in step (f). The speed of the WHFs shall be the same as used for the measurement in step (f).
(k) Turn on the fan flowmeter. Adjust the fan flowmeter speed until the pressure difference (Pa) between the attic and the dwelling unit conditioned space matches Pattic determined in step (f).
(l) Record the flow through the fan flowmeter. When multiple WHFs are used to meet the required airflow, repeat steps (g) through (l) for each WHF, then sum the airflow measurements for all WHFs to arrive at the total WHF airflow for the dwelling unit.
The WHF airflow measurement shall be performed using the following procedures:
(a) Open the window(s) that are typically opened during WHF operation.
(b) Turn on all WHFs required to meet the dwelling unit WHF airflow rate. Adjust multiple or variable speed WHFs to operate at an airflow rate that will be greater than or equal to the rate required for compliance.
(c) Adjust the dwelling unit window openings to bring the dwelling unit to the WHF-OP of negative 10 Pa ± 5 Pa WRT outside.
(d) Measure the airflow rate(s) at the inlet grille(s) in accordance with RA3.9.3.2 with a calibrated powered flow hood to determine the total WHF airflow for the dwelling unit.
No part of the WHF intake shall be blocked or masked off to accommodate an undersized hood.
Operation of the powered flow hood shall conform to the specifications in the manufacturer's product documentation.
The WHF airflow measurement shall be performed using the following procedures.
(a) Open the window(s) that are typically opened during WHF operation.
(b) Turn on all WHFs required to meet the dwelling unit WHF airflow rate. Adjust multiple or variable speed WHFs to operate at an airflow rate that will be greater than or equal to the rate required for compliance.
(c) Adjust the dwelling unit window
openings to bring the dwelling unit to the WHF-OP of negative 10 Pa ± 5 Pa WRT
outside.
(d) Measure the airflow rate(s) at the inlet grille(s) with a calibrated traditional flow capture hood to determine the total WHF airflow for the dwelling unit.
No part of the WHF intake shall be blocked or masked off to accommodate an undersized hood.
Operation of the flow hood shall conform to the specifications in the manufacturer's product documentation.
When multiple WHFs are used to comply with the required WHF watt draw for the dwelling unit, all WHFs in the dwelling unit shall be operated simultaneously and the sum of the watt draw measurements of the simultaneously operating WHFs for the dwelling shall be determined.
When required for compliance, the WHF watt draw shall be measured using one of the following methods:
The WHF watt draw measurement shall be performed using the following procedures.
(a) The WHF(s) shall be operating at the WHF-OP used for the airflow rate measurement procedures specified in Section RA3.9.4.1.
(b) Measure the watt draw(s) to determine the total WHF watt draw for the dwelling unit.
When measuring watt draw of units that are wired directly to an electrical junction box, it is recommended to use portable true power clamp-on meters to provide flexibility for isolating the correct fan wires.
The WHF watt draw measurement shall be performed using the following procedures.
(a) Turn off every circuit breaker except the one exclusively serving the WHF(s).
(b) The WHF(s) shall be operating at the WHF-OP used for the airflow rate measurement procedures specified in Section RA3.9.4.1.
(c) Record the Kh factor on the revenue meter, count the number of full revolutions of the meter wheel over a period exceeding 90 seconds.
(d) Record the number of revolutions (Nrev) and time period (trev, seconds).
(e) Using the following equation, compute the WHF watt draw (Wfan).
Equation RA3.9-1
WHF Fan Watt Draw Wfan = (Kh x Nrev x 3600) / trev
(f) Return all circuit breakers to their original positions.
The WHF watt draw measurement shall be performed using the following procedures:
(a) Turn off every circuit breaker except the one exclusively serving the WHF(s).
(b) The WHF(s) shall be operating at the WHF-OP used for the airflow rate measurement procedures specified in Section RA3.9.4.1.
(c) Read the Watt draw from the digital utility meter digital display.
(d) Return all circuit breakers to their original positions.
Demonstrating compliance with WHF efficacy requirements requires simultaneous measurement of the WHF airflow rate using Section RA3.9.4.1 procedures and fan watt draw using Section RA3.9.4.2 procedures. The results of the simultaneous airflow rate and fan Watt draw measurements are used for calculation of a value for the WHF efficacy as follows:
The measured value for fan watt draw (watt) shall be divided by the measured value for airflow rate (cfm) to determine the fan efficacy (watt/cfm).
In order for the WHF to comply, the requirements in both subsections (a) and (b) below shall be met.
(a) The measured WHF airflow (cfm) shall meet or exceed the WHF airflow compliance criterion specified on the Certificate of Compliance.
(b) The calculated value for fan efficacy (watt/cfm) shall be less than or equal to the WHF efficacy compliance criterion specified on the Certificate of Compliance.