HVAC PERFORMANCE TESTING
HVAC Performance Testing measures how efficiently your system is running, where system problems exist, and thus where to make improvements to maximize efficiency.
Close to 50% of the electricity you buy is for heating and cooling, so better HVAC performance saves lots of money and makes equipment last longer. The national average for HVAC performance is a dismal 57% of your system's rated capacity
[Source: National Comfort Institute]
Since air conditioners are the largest consumers of electricity in most hot, humid climates, energy efficiency requires that ...
1) A/C units perform close to their design capacity when cooling the air (system performance)
2) Very little of this cool air leaks into attics and other place where it is wasted (system tightness)
3) Cool air is distributed in the proper amount to every room (system balance)
These variables can be tested scientifically and the A/C system optimized with the data gathered. It is often possible to gain more performance from your existing unit by optimizing it than from buying new equipment - at a small fraction of the cost.
Most air conditioning contractors do not have the knowledge, equipment, or motivation to optimize systems, as they make more money simply replacing equipment. Perhaps this is why the national performance average for these systems is 57% of rated capacity (data from over 20 years of testing by the National Comfort Institute).
Here are the diagnostic tests for diagnosing performance:
System Temperature Change
This test measures the temperature of air entering your system at the return grill and compares it to the temperature delivered to the supply registers in your ceilings. This shows the actual
temperature change your system is delivering.
This measures the volume of air flowing into each room and total system flow.
The purpose of an air conditioning/heating system is to remove/add heat to the air passing through
it and deliver this "conditioned" air to your rooms. The Btu your system is removing/delivering is
simply a function of how much your system changes the air temperature and how much of this
conditioned air is delivered. [12,000 Btu is 1 “ton”]
We calculate your system’s Delivered Btu with the data collected (above) about delivered air volume
and system temperature change.
This is a comparison of how many Btu your system is delivering to how many it is rated to deliver.
The national average is 57%. The goal should be over 90%.
If performance is less than 90% of rated capacity, these further tests uncover where the problem lies.
Equipment Temperature Change
This measures how much heat is being taken out of the air as it passes through the air
conditioning equipment. Comparing equipment temperature change to entire system
temperature change reveals ...
- how much heat is being lost or gained in the duct system
- if the HVAC equipment is producing adequate temperature change
External Static Pressure
This is the pressure in your A/C system that your fan must push against. If it is higher
that what the fan is designed for, the volume of air distributed to your rooms can
Filter Pressure Drop
This test measures how much your air filter is restricting air flow and reveals if you need
a better approach to filtration or a larger area of air return grill.
Evaporator Coil Pressure Drop
This tests the difference in pressure on either side of the evaporator coil. It shows how much
the coil is restricting air flow and whether it needs cleaning.
A small camera is inserted into the equipment to literally see the condition of the
evaporator coil or other components of the A/C system.
Duct Leakage Tests
These tests measure the volume of air, in cubic feet per minute, leaking from the
distribution system. Tests for both total duct leakage and duct leakage to outside
the conditioned space can be performed.
Pressure Pan Test
This test is run in conjunction with a blower door test to reveal which supply duct runs and return air channels have major leaks.
Smoke Machine Test
This test, used in conjunction with duct blaster equipment, gives visual evidence of where duct
leakage is occurring. It is particularly valuable in spotting leakage points in hard-piped ducts covered up by insulation.
Air Balancing Test
Air Balancing is the process of measuring and adjusting the volume of conditioned
air flowing into each room to ensure the room is comfortable. Usually the process
begins with a calculation of how much air should be supplied (a Manual J room-to-room
heat load calculation). Then the volume of air actually entering each room is
measured in cubic feet per minute with an Air Flow Hood. Finally, airflow to
each room in your house is adjusted to "balance" the house.
This is the gold standard for testing air conditioning system efficiency. And since
A/C efficiency is a prime determinate of overall home energy efficiency in hot, humid
climates, these system performance tests provide the data needed to increase your
home’s actual (as opposed to theoretical) efficiency.