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Home > Energy Audit > HVAC Equipment Installation
HVAC Equipment Installation:
Heating & Cooling Performance IssuesImproving heating & cooling efficiency and effectiveness is a home performance goal. Depending on homeowner flexibility and budget, it can be achieved in variety of ways. Total system replacement and redesign combined with insulation and window improvement leads to maximum results, but it comes at high price. However, better results are possible for everyone. Discussions in this article include:
This article focuses on central heating & cooling
systems. Similar principles and processes apply to other types of
heating & cooling systems. Other types are not discussed here, but
most are evaluated as part a home energy audit.
Note: Window air conditioners and evaporative coolers are not evaluated
as part of home energy audit. Current State of Heating & Cooling System Installation Equipment tends to be twice as large or more than it
needs to be. Also, Many systems are at least partially installed in
hostile environment because of temperature extremes or high moisture
content
Contributing Issues to Under-Performing Systems This state of affairs
exists because rules of thumb, rather than engineering design, used to
install system components. To make matters worse, customer complaints
are “resolved” installing bigger equipment, rather than by replanning. The broad category most HVAC
contractors start with is equipment size. It’s the wrong place to
start, but it’s the easiest one to understand. The first system is installed
using rules of thumb, not building performance characteristics. When
the original system doesn’t make to occupants happy, the response is
bigger is better. Fixing the real problems are too time consuming and
the cut into profit margins.
The architect doesn’t help matters. They
assume the HVAC contractor will make due with whatever building
structure is given to them.
There is no real up-front planning. When
equipment is replaced, typically the assumption is made that what was
installed before was okay—only an equipment change is needed. And we
let them get away with it because we trust them. What other choice do
we have? Home Energy Audit: Diagnosing Heating & Cooling EquipmentTip: Diagnosing central heating & cooling system depend on central heating & cooling performance factors. The process for improving heating & cooling
performance follows this path:
Interview Homeowners. Improving home performance is about providing a healthier, longer lasting, more comfortable, and energy efficient house. As they relate to heating & cooling, the following questions are asked during the homeowner interview
How often do you need to dust?
Who in your family has allergies?
Who in your family has asthma?
When was the equipment installed?
Why was the equipment replaced?
What is the maintenance history?
Are there any hot or cold rooms?
Does moisture condense on the windows?
When system is running, what kind of noises does it make?
From your perspective: energy bills high, low, or average?
Is there anything else you feel is relevant? Answers to these questions help us evaluate the system in terms of moisture control, indoor air quality, and energy transfer: the golden home performance triangle. Visual Assessment. Before modifying or adding heating & cooling systems, the heat-load characteristics need to be known. This includes where and how much insulation is installed, types of windows in place, and the direction the front of the house faces. Installation & Operational Checks. The equipment and ductwork need to be looked at for proper installation, as well as find out whether the system passes basic heating and cooling checks. Define Existing System. For analysis, the conditioned floor area for each system and the volume of the house has to be known. To begin working with the HVAC contractors, we need to provide them with a map of the house, showing room size, supply register locations and sizes, and return air pathways. Diagnostic Testing. The amount of heating and cooling required is a function of heat loss, including what is lost through holes in the building and ductwork. To get a sense of what is happening now, air infiltration, duct leakage, and pressure balance measurements are made. For safety reasons, anytime there are fireplaces or fossil fuel water heaters or furnaces present, depressurization checks are needed under various fan conditions and door states (open or closed) to determine whether backdrafting smoke back into the house is a possibility. System Analysis. After the day is done evaluating the house, the results are analyzed to establish system improvement priorities. The priorities are used to develop recommendations and the scope of work. Recommendations
After the homeowner interview, a visual
assessment of the
heating & cooling system is made, followed by diagnostic testing.
The results are analyzed to prioritize recommendations. Pick Improvement Options. During the homeowner interview, the process was started to begin establishing the expectations and goals of the improved heating & cooling system. It’s not always possible, but an initial attempt is made to make recommendations based on equipment/ductwork option chosen during the interview. Scoping the Work. As recommendations, options, and price ranges are presented, other equipment/ductwork options may emerge. This process may iterate several times before the final home performance solution is chosen. Setting Expectations. Every
homeowner has expectations and unstated goals for their heating &
cooling system. At the beginning of the process, homeowners may not
have thought about their improved systems in these terms. Every homeowner needs
understand the range of possibilities to begin to make informed choices.
The process we follow is iterative, so everyone has a clear
understanding what to achieve by the end of the project. Requirements. During this interview, we all start to get a
sense for what the homeowner wants by exploring the replacement options
for equipment and ductwork. Part of the process is understanding what
else homeowners want because it directly impacts recommendations for the
heating & cooling system. Impact of Other Decisions.
Air sealing walls, windows, and floors; adding insulation, and
replacing windows has a direct impact on reducing the size of the system
to be installed. Any possible changes to the size of conditioned
spaces needs to be known before beginning to plan flexibility into the
system. Selecting Heating
& Cooling System Options. There are four options for
improving central heating & cooling systems. New Equipment, New Ductwork. When there is a willingness
to do whatever it takes to maximize heating and cooling system
efficiency and effectiveness while minimizing operating costs, home
performance savvy HVAC contractors have the greatest range of options
for delivering it. Design
System First. To accomplish this, the house’s heat load
characteristics needs to be modeled and the entire heating & cooling
system designed to engineer standards. This approach costs the most
and may not be easily feasible. Whatever option is chosen, the ductwork needs to be sealed.
There is a variety of duct sealing methods available. New Equipment, Same Ducts. When using new equipment with
the same ducts, the desire is try to use the existing ductwork, if
possible. Ductwork may be hard to get to without extensive remodeling.
Also, the may be a desire not to plug abandoned holes in the walls,
ceilings, or floors when the duct registers are relocated. Match Equipment to Ductwork. In
this approach, equipment needs to be chosen that can be made to fit the
ductwork while operating the way the manufacturer intended. To
accomplish this, the house’s heat load characteristics needs to be
modeled. Same Equipment, New Ducts. When the
same equipment / new ducts option is selected, the equipment may be new,
but the job wasn’t finished when it was installed. There are a lot of
efficiencies that can be gained designing the air distribution system.
Redesign Ductwork.
To ensure proper equipment performance, the ductwork must match the
equipment. To accomplish this, the house’s heat load characteristics
needs to be modeled. Before performance tuning the system, the filters
and coils need to be cleaned. Same Equipment, Same Ducts.
The least preferred option is using the same equipment and ductwork, in
most cases. Assuming the equipment and ductwork are reasonably matched
and is appropriate for the house, this can be the least-cost option,
but also has the least amount of flexibility. Smaller performance
efficiencies are also more likely than any other option. However, it’s a
great place to start while implementing other home performance
improvements over time. Pre-Cleaning
Required. To accomplish this, the house’s heat load
characteristics should be modeled to allow for better decision making.
Before performance tuning the system, the filters and coils need to be
cleaned. Next: Heating & Cooling System Performance Factors | Combustion Safety
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