Tooling up for Home Performance: Part 1 of 3: Manometers
This article is the first in a three part series where we will discuss the types of diagnostic equipment necessary for Home Performance work.
Even though in many cases no standard applies to the work you do, you may wish to review the publicly available standards in order to get a broader understanding from the thousands of hours of collective wisdom represented in the standards. These documents help to reinforce the concept of “the house as a system.”
In certain cases, depending on the work you do and who you do the work for, Home Performance work must take place in accordance with standards that are now publicly available. Five of such standards are:
ACCA Standard 12 (ANSI): Home Evaluation and Performance Improvement
Get a free copy here: www.acca.org/quality
ACCA Standard 9 (ANSI): HVAC Quality Installation Verification Protocols
Get a free copy here: www. acca.org/quality
BPI 1200 (ANSI): Standard Practice for Basic Analysis of Buildings
Get a free copy here: http://www.bit.ly/bpi1200
RESNET Advisory Standards: Chapter 8, Standard for Performance Testing and Work Scope
View here for free: www.bit.ly/RESNET-standards
(Will be updated by amendment with some reference to RESNET Standard 380, likely by Fall 2016.)
RESNET 380: Standard for Testing Air Tightness of Building Enclosures, Airtightness of Heating and Cooling Air Distribution Systems and Airflow of Mechanical Ventilation Systems
Get a free copy here: bit.ly/resnet380
Not yet in effect. This standard will likely supersede some parts of RESNET Chapter 8, likely by Fall 2016.)
See a “Table comparing home performance diagnostic testing standards” here: www.bit.ly/hp-standards
It is critical to recognize that standards are meant to cover the minimum activities to be compliant. In many cases contractors and technicians will go beyond the minimum diagnostic tests in order to provide more value to their customers and/or improve the quality or efficiency of their work. These standards also give great advice for customer interview questions and specific testing procedures.
Feel the Pressure
Interestingly, 7 out of the 11 types of diagnostic tests listed in table (linked above) involve pressure measurement. Almost all of these measurements require a fine-resolution pressure gauge that can read in Pascals. A Pascal (Pa) is equivalent to 0.004 Inches Water Column or 249 Pascal equals 1 Inch of Water Column – a very small amount of pressure.
Most commonly you will see a dual channel different manometer used for this work. The two channels are necessary when doing a blower door (envelope) or duct leakage test. One channel monitors for the proper test pressure you are putting on the house (eg. 50 Pa) or duct (eg. 25 Pa) and the other channel reads from the pressure-based flow sensor built into the device to give you the leakage flow rate.
Two key features of these dual channel manometers are:
the ability to give a stable reading of these minute pressures using zeroing mechanisms and display averaging
built in, real-time calculations and display of essential test data
As with many devices today, these manometers have colorful screens, along with smart device (app) and wi-fi connectivity available for fast, reliable and real-time control as well as recording and transmission of data.
Additional uses for the pressure meter are for measuring exhaust fan ventilation flow (CFM) using a flow box as well as HVAC system airflow (CFM) using a TrueFlow ® Grid placed in the air handler or at a central return.
Further, these devices can be used to measure zone pressures to check for sufficient air available for combustion appliances (CAZ test) as well as room pressure differences, which can result in poor system performance and comfort complaints.
These manometers are also handy for checking combustion draft and may be used for evaluating duct leakage to outside during a blower door test; commonly know as a pressure pan test.
Also, these manometers function well with Pitot tubes and alternatives (flow stations) for measuring air velocities in the pursuit of ventilation airflow readings (CFM).
And last, but not least, flow hoods have manometers built in to them as they typically function with a Pitot tube array to sense flow pressures and calculate ventilation airflow readings (CFM).
Lately a more advanced version of FlowHood has emerged, one with a pressure compensating fan which cancels out the “smothering effect” (also called insertion loss) when you place a flow hood over a ventilation grill.
The dual channel manometer is perfectly suited for this task, as one channel aims to neutralize the pressure under the hood by controlling the fan speed, while the other channel measures the flow under the test conditions. Of the two powered flow hoods commercially available, one is an accessory to a duct leakage tester and the other is an integrated product.
In the next installment of his series we will cover the products used in combustion safety testing.
Posted In: Building Performance, Residential Buildings
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