Air conditioner not correctly installed
Q. The people who are buying our house hired a home inspector. He reported two problems with our heating and air conditioning system, and neither seems to make sense. The equipment is located in the attic. According to the home inspector, there are gaps that need to be sealed at the refrigerant pipes, and the condensate drainpipe should be trapped and vented. This is all Greek to me. Can you please explain it?
A. These two defects are commonly reported by home inspectors when inspecting aid conditioning systems. Explaining them without illustrations is a little tricky, but let's give it a try, beginning with the gaps at the refrigerant pipes.
When an air conditioner is installed in an attic, it has two refrigerant pipes connecting it to the condenser unit on the outside of the building. These two pipes enter the air unit in the attic through two holes in the casing. These holes are always larger than the refrigerant pipes. Unfortunately, this allows air to escape through the gaps around the pipes. Since you don't want to heat or cool your attic, these gaps need to be sealed. Leaving them open reduces the efficiency of the system. Fortunately, sealing the gaps is a simple and inexpensive repair. All that's needed is some flexible caulk.
Your other question involves moisture condensation inside your air conditioning system. Here are the basics for that issue: Whenever moist air comes in contact with a cold surface, water vapor condenses into liquid water. This is what happens when you breathe against a cold window or when you leave a glass of ice water on your table. The cold surface becomes wet with condensation. The same thing happens inside an air conditioner. When air circulates against the cooling coils, condensation occurs, and the water that forms needs to be drained to the exterior of the building. Otherwise, it can leak into the attic, causing moisture damage and mold.
Special openings are provides as drain outlets for the moisture, and each of these should be connected to a drainpipe. One outlet is the primary drain; the other is the backup, in case the primary drain becomes blocked for any reason. That brings us to the question of the trap and vent in the primary drainpipe. As condensate builds up inside your air conditioner, the water needs to drain into the pipe. Unfortunately, the air pressure inside the A/C unit is lower than the pressure outside the unit. This causes air to flow into the condensate opening, and this can prevent water from flowing out. That's the reason for installing a trap in the line.
The trap is a U-shaped pipe that slowly fills with water from the A/C unit. Water in the trap blocks the backflow of air, and this allows the condensate to drain freely from the A/C unit.
A short vertical vent pipe is also required in the condensate drainpipe. It should be located downstream from the trap. It's purpose is to prevent the flow of water from siphoning the trap. However, it is highly unlikely that siphoning will ever occur because the water flow is very slow. Therefore, the vent is installed primarily for code compliance but is not actually necessary. The trap, on the other hand, is there to prevent actual leakage and water damage.
• To write to Barry Stone, visit him on the web at www.housedetective.com, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.
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