A Few Condensate Considerations

Water from the fan coil ends up draining outside; the condensate goes into the drain downhill and then spikes upward in a trap and then exits the drain. There may be a lot of standing water in the drains, especially when the system is off. The standing water provides a breeding ground for fungi, bacteria, and other undesirable living organisms, making backups even more possible.

Some drains have traps at the unit with a cleanout before the trap and a vent after it; the vent is tall and stays uncapped. If we were to leave the cleanout open, however, air would get sucked into the drain. We can leave the vent open as long as the trap is deep enough to create a seal and allow the column of water to overcome the negative static pressure of the system. Trap size depends on the system, but we typically use P-traps that are a few inches in length. The trap tends to get the dirtiest, which is why the cleanout allows you to flush water into the trap or clean it out with a bottle brush.

Systems with multiple traps are undesirable, but as long as all the traps are sufficient, a water column may be strong enough to travel all the way through. However, air bubbles can form in systems with multiple traps. We often see double traps due to misalignment with the chase pipe, but those are easily fixed by removing the tee and pulling the drain up a bit.

Drains can get nasty buildup if they have a low pitch out of the drain pan. On a horizontal drain line, we try to aim for at least 1/4″ of fall per foot of horizontal run. Strapping is also critical to avoid sagging; systems should be strapped at least every 4 feet or so. Sagging can cause double and triple traps over time, especially if the pipework was poorly done in the beginning. The Kalos techs are supposed to find and rectify the double traps wherever possible. If that’s not possible, we may have to rely on chemicals to get the hard deposits out of the drain.

The float switch typically goes somewhere near the platform top. In many cases where the float switch is above the platform top, it will only trip if the water level in the pan is also high enough to trip the switch. So, we try to avoid overflowing shallow pans by keeping the float switch below the drain pan’s level. Sagging platforms can also cause the float switch to back up, though. At Kalos, we need to learn to quote new platforms instead of holding off on dealing with sagging platforms.

Static pressure can also cause drain issues. High negative static pressure may cause air to be sucked in all over the place, meaning that you get turbulent flow inside our drains. Make sure everything is as sealed as possible to avoid drawing air into the drain where it shouldn’t be coming in.

In horizontal applications, poor airflow, platform level, and improper pan installation can cause condensate not to go where it’s supposed to go. If the insulation gets saturated, we need to figure out why before we ultimately replace it; we have to check orientation and clean the drain BEFORE we replace the insulation. Whenever you have to tape the insulation (or anything else), clean the surface with rubbing alcohol and microfiber towels first to make sure the surface is clean and will keep the tape fastened as long as possible. Spray glue is a type of contact cement, so you have to spray both surfaces, wait for it to tack up, and then press the surfaces together to form a bond. Whenever you have a horizontal air handler, there also needs to be some overlap with the duct in every direction to keep the horizontal drain pan in place.

When cleaning drains, we have to clean horizontal portions, drain lines, and the drain pan. We should be using brushes, Panduit straps, and everything else at our disposal to get the drains as clean as possible. We should also be looking down the tees to look for signs of drain line buildup and be willing to quote drain cleanings when necessary.