HVAC Airflow and Efficiency Testing
a.k.a. Getting what your paying for...
The typical heating system in the USA deliveries less than 60% efficiency. This is regardless of the efficiency of the installed equipment. This low efficiency is caused by HVAC companies typically pushing hi-efficiency equipment, but then doing a poor job on the install. Some common errors include: ducts that are undersized, insufficient return air, transitions and bends that are too sharp, poor airsealing of the ducts, oversized equipment, and the wrong fan setting. These errors are easy to find, if you look for them. Unfortunately, most HVAC companies idea of testing is to check if the air is warm coming out of the registers. Very few HVAC companies guarantee the systems performance.
The systems performance is often made even worse by Homeowners using "hi-efficiency" air filters that are too restrictive for the system. I blame the HVAC companies for this too, because they need to teach their customers how to use and care for the system. Of course the less reputable companies like the "hi-efficiency" filters because it virtually guarantees a future motor change out or possible a new furnace.
What is Airflow and efficiency testing?
It is a series of tests to see how the equipment and system is performing. We check both because the equipment could be working badly (the problem) or perfectly (but the duct leaking like a sieve or too restrictive). In either case the air is not getting to where it needs to go. Below are the tests and their descriptions that are performed to figure out how well your system is working. These tests can also be performed on your air conditioning, but for simplicity we will only reference the furnace.
Total External Static Pressure (TESP)
This is always the starting point test. It is a lot like measuring blood pressure, it measures the resistance to airflow within the system. The higher the TESP the more resistance to airflow there is, thus the airflow will be lower and the harder the motor has to work to provide that airflow. Typically, most furnaces/airhandlers are rated at a Maximum of 0.5 IWC (inches of water column), but 0.9 IWC or higher is not uncommon. If the TESP is high for long enough, it can cause the blower motor to fail (sort of like a human having a heart attack from having high blood pressure).
Equipment Airflow and Temperature Rise
By measuring the temperature rise and airflow of the equipment, we can calculate how much heat energy the furnace is producing. This is compared to the output of your furnace derated for the elevation. If these numbers are not close, that indicates a problem within the equipment. Regardless, it also tells us how much heat energy is being sent to the house.
Gas Consumption
First, we shutdown all other gas appliances and fire the furnace for about 10 minutes to get it to a steady state. Then we go out to the gas meter and time how long it takes to consume a given amount of gas. From here, we can calculate how much gas is being consumed per hour and thus, how many btu's per hour are being produced by the furnace. We then compare this to the input from the nameplate derated for elevation. If there is a substantial difference, that would indicate that there is a problem most likely with the setting of the furnace's gas valve.
Supply and Return Registers Airflow and Temperature
We measure how much air is coming out of all the supply registers. By comparing this sum to the amount of airflow through the furnace, we can determine duct leakage on the supply side. Similarly, we can determine the return duct leakage by summing the amount of air entering the return air registers and comparing that to the furnace airflow. By measuring the temperature at the registers, we can calculate how much heat is coming into each room as well as how much heat is being lost to the ducts.
HVAC Analysis Results and Recommendations
From all these measurements, we can determine how much of the heat that your furnace is producing is actually getting to where it is suppose to be going. We then make recommendations on how your system can be improved. Once implemented, you will be getting what you pay for from your furnace.