Air conditioning season is in full swing and by now you are well aware of any shortcomings in your system’s operations. If one room or a part of your house is warmer than another the cause is not necessarily the mechanics of your main system.
All about your HVAC unit
Over the past decade or more, particularly with tract homes, Bryan Whitlock of Integrity Air Conditioning and Heating tells us that most residential equipment has been oversized. He believes there are several reasons for this mistake:
- One size fits all practice- In builder tract homes, and some custom-built homes, the science behind sizing an HVAC unit properly is largely overlooked in favor of the convenience of expedited construction and cost.
- System design may not be carefully thought out for ease of construction and repeatability.
- The skill set needed for proper installation is not always available. We know it’s no secret that the trades are hurting for skilled employees at all levels, not just HVAC installs.
There is a tendency to think that solving a problem such as temperature differences throughout the home can be solved by supplying a larger unit. By unit size, we are referring to BTUs for heating and tons for air conditioning. Trust us, this is one case where bigger is not always better.
Just as one-size-fits-all solutions rarely work, the range of climates in Arizona makes hiring a local professional necessary for your home.
Properly sizing a system involves many factors:
- Heat loss or gain through insulated walls and ceilings, doors & windows
- Lot orientation
- Building exposure.
All these components come together through math and experience to conclude a proper unit size.
Distribution and duct work
The distribution of treated air is as important, if not more important, to a properly functioning system as the unit itself. It is common to find homes that have oversized units and poorly designed and installed ductwork.
Bryan relates the design of a good ductwork system to an irrigation system comprised of a water source (the HVAC unit) and a system of canals (the duct work), to move that water to where it is needed efficiently and effectively to water a field (the room) where it is needed. The room, or field, size determines the amount of air needed.
That, in turn, determines the size of the duct or canal needed to move the air efficiently to that room. The reservoir, (equipment) size is determined by collectively quantifying all the rooms, or fields, that need to get air or be watered.
What’s next when it comes to your HVAC unit?
Next is determining the course the canal (or duct) will take. Here is a good place to talk about static pressure.
Duct work that has to many twists and turns, or is too small in diameter, creates increased pressure in the ducts. That pressure is static pressure which is hard on equipment and can be the cause of inconsistent temperature throughout the house. This is hard on the unit and greatly decreases its efficiency.
In some tract homes, Integrity’s experienced technicians find that a unit delivers air to a box in the attic and then the air is distributed from that box through a web of twisted, bent, or crushed ductwork. This is not the best way to heat or cool your home.
Duct type and installation contribute to the inefficiencies in a system’s performance. Leaks at poor connections are one obvious contributor. Builders frequently use a flexible duct that, while effective in some applications, is not the one-size-fits-all solution.
Fixing the problem with your HVAC unit
As we said, most units are oversized to hopefully compensate for poor design and construction. While different homes require different solutions, there are some basic steps to take for your HVAC unit.
- Assess the basic HVAC unit for operational efficiency and determine if more efficient operations are possible is step one.
- If the basic units are working and the home is not comfortable the problem is usually uneven air distribution, the first step is to look at the duct work if you can.
- In most homes, the ductwork is exposed in an attic. This makes for easy examination.
- In multi-story homes, ductwork between floors, or in flat-roofed homes without an attic, there is little that can be done without extensive removal of drywall.
Often a redesign of the ductwork, with proper sizing, duct type and proper installation will solve the problem folks are having.
What about when you need to replace your HVAC unit?
In some instances where unit replacement is needed, coupled with duct redesign, the size of the unit can be reduced by typically half a ton or more.
Having a properly functioning HVAC system means you need to look at the whole system, not just one component. Unfortunately for the homeowner, many HVAC contractors will mask the problem by selling a unit too large, which delivers lots of cold air, enough to keep the occupants satisfied.
However, this is an overly expensive solution to install, and very inefficient to run every single day. If your home is having some issues with warm spots call a Rosie Certified air conditioning company to come out and give you a fair and full assessment and solution.
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