Questions:
(Click a question to jump directly to the answer)
- What is the problem with oversizing an air conditioner? Isn't bigger, better?
- How long does it take to have load calculations and duct design work performed?
- Why would two rooms of equal size require different size ducting?
- Why can't I trust my contractor or HVAC dealer?
- Should I use Flex duct or round metal duct?
- Can I just use all one size duct to keep it simple?
Answers:
What is the problem with oversizing an air conditioner? Isn't bigger, better?
- Oversizing air conditioning equipment can lead to a host of different problems. Your air conditioner will likely short cycle, or run for only sort periods at a time. This will not allow for proper dehumidification, cause your house to feel "clammy", and potentially result in mold problems. Short cycling is also hard on the equipment and can lead to premature compressor failure, a costly repair. Every time the air conditioner turns on, it "builds up" to its rated efficiency. When it runs for many short cycles, it has to start up many times per day resulting in lower overall efficiency. Additionally, larger equipment cost more upfront.
How long does it take to have load calculations and duct design work performed?
- It typically takes about 2 business days to complete the work. You should allow for extra time if shipping your blueprints.
Why would two rooms of equal size require different size ducts?
- Duct sizes depend heavily on the heat load of a room, not the size. The load will very with external wall area, insulation levels, windows and doors, and internal loads. Additionally, rooms located farther from the air handler may require a larger duct sizes.
Why can't I trust my contractor or HVAC dealer?
- You can, provided that they actually perform heat load calculations on a room by room basis. Unfortunately, most do not take the time to do this or have the training or education specifically in design. I find that most comfort issues in homes (even expensive homes) are a result of poor or badly designed ducting systems. Additionally, some HVAC dealers have a tendency to try and sell bigger equipment for larger profits.
Should I use Flex duct or round metal duct?
- There are benefits to both. Flex duct is easier and faster to install, however, it offers more resistance to air flow, and may become kinked restricting the air flow. Round metal duct works better, last longer, and is more efficient, however it takes longer and is a bit more difficult to install. It is a trade off and depends on your preferences, installing skills and time.