Don't Forget To Consider the Condensate

Water. There would be no life without it, yet it sure can cause problems, too.

For example, failure to properly drain condensate from central air conditioning systems has the potential to cause property damage and can lead to standing water that can create a "bacteria playground" and affect indoor air quality. That's why it's important to ensure proper function of the condensate drain system on every service call.

Condensate Drain Options
The first and easiest option is to allow condensate to drain using gravity, from the drain pan to one of the following: main sewer drain line, floor drain, sump pit, laundry sink, window, or through the wall to the outdoors. Of course, local codes will have a say in your options here.

Gravity drains can create their share of problems and maintenance challenges, however. Long, slow moving, condensate lines, combined with dark and humid environments, can promote clogged drains and breed algae and fugal growth. Be sure to clean these drains on every visit, either by sucking them out with a Shop-vac or blowing them out with compressed air.

But what happens when gravity drainage is impossible or not feasible? The alternative to relocating the entire system near a gravity drain rests in the use of condensate removal pumps. A wide variety of condensate removal pumps are manufactured for virtually every possible installation.

When a Pump Is Required
If you encounter a system that needs a condensate pump or a pump replacement, how can you be sure that you're choosing the right pump for the job?

First, consider the condensate output of the equipment or appliance. When the system includes air conditioning alone, the rate of condensate production is based on a rough estimate that a 5-ton unit, under hot/humid conditions, can produce approximately 2.5 gal. of condensate per hour.

Next, consider the installation site. Where will the pump be mounted? What route will the discharge tubing need to follow in order to properly reach the desired discharge point? The answer to these questions will determine the lift requirement for the pump.

How high do you need to pump the condensate up to access the drain? As the vertical lift increases, the quantity of water pumped, or flow, declines to the point of maximum lift where the effective flow of water is zero. This is called the "shut-off" lift. Most pumps are typically rated to a maximum lift rating, so it's important to remember that the higher the lift required, the lower the flow of the pump.

Obviously, the pump must be rated to achieve the necessary lift, as well as handle the required flow calculated at that lift. Residential grade pumps typically lift 15 or 20 ft., while commercial grade pumps start at 20 ft. and continue on up to 60 ft. A common mistake is made by adding the horizontal run (the distance the water needs to be moved horizontally once the lift is reached) in order to specify the pump. The two measurements are not additive; in fact, most centrifugal pumps will be minimally impacted by the length of the horizontal run. (Note: this is not the case with smaller, piston or positive displacement style pumps designed for ductless mini-split applications.) A run of greater than 50 ft. will only reduce the flow of a standard pump by about 10%. This can be minimized by forming an inverted "U" trap with the discharge tubing, creating a siphon that minimizes the loss of flow. Using gravity to aid the horizontal run will also help prevent loss of flow.

Condensate pumps for residential applications can move up to 70 gal./hr. at low lifts, and about 15 gal./hr. at lifts of 13 to 14 ft. To be safe, the output flow of the pump should be at least double the input rate from the appliance. Check your equipment service manual if you're not sure about the size of the unit or the amount of condensate produced.

The last piece of information required is the line voltage. Most pumps are available in either 115 or 230V; but specialized commercial grade pumps are available in 460V.

Now that you know the basics, you can specify a pump, right? Well, yes and no. There are still a few other factors to consider.