Sunday, August 29, 2010

New A/C Condensate Traps

We started to get a putrid smell in our air system this summer every time the system ran. I figured condensate pan had grown some algae or something so I decided to clean it and the coil. To my surprise the drain pan had several slugs in it, some alive, some in various stages of decay - hence the smell. My system has p-traps on the condensate line, which usually prevent this sort of thing. So I did some research and read the air handler manual. Turns out my traps are too shallow, and didn't meet the minimum requirements specified for installation. *sigh*

I have a draw-through system, since my blower is located after the condenser coil in my air handler. What this means is that my coil/condensate pan operates at a negative pressure, and thus requires deep p-traps to prevent air/water from getting sucked back into the handler through the condensate lines. Shallow traps sputter water back inside the handler, as well as allowing the pan to overflow. Since the traps get sucked empty every time the system turns on, this allows slugs to crawl into the air handler and then they die in the drain pan. Fun.

According to the manual my traps must have at least 2 inches of drop, the old ones have about 1.5 inches. So, I built new ones from schedule 40 pipe. PVC pipe is easy to cut and then must be cleaned with chemical cleaner at the joints, and then put together with solvent cement.

Assembled and glued in the workshop instead of while cramped under the house. Something I learned from past plumbing in a tight crawl space.

Old traps that I cut out with a hacksaw that are too shallow to work properly with my particular air handler.

New traps installed with pipe-dope on the threads. The new traps have 3.5" of drop and more length to store more water. They also have clean-outs on top for inspecting water level, and adding mineral oil to prevent evaporation during the winter when no condensate is produced to replenish the trap.

Before I finished up I hooked up my shop vac on the outlets to suck up and garbage that had collected in the lines. Got a few slugs and a bunch of algae. Then I primed the traps with water and turned the system back on. Both lines are dripping outside just fine now.

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