Don't Forget To Consider the Condensate

Safety Precautions and Options
Almost every condensate pump is available with a secondary safety switch, designed to stop the flow of condensate in the event of a pump failure, clogged drain line, or loss of power to the pump. Any pump installed in an area susceptible to water damage should include a secondary safety switch.

Normal wiring of a condensate pump safety switch is connected to the thermostat circuit. The switch is wired as normally closed. In the event of a high water condition in the condensate pump, the switch opens the thermostat circuit, stops the air conditioner and the flow of condensate, preventing pump overflow. Installations in attics, utility closets, finished basements, ceiling mounts, etc. should always install a pump with a safety switch.

The proper wiring for a safety switch is as follows:

• Disconnect power to the AC/furnace and unplug condensate pump before connecting the safety switch
• Disconnect the red wire from the AC/furnace bundle coming from the thermostat
• Connect the red wire to one of the two safety switch wire leads coming off the condensate pump, using a wire nut
• Connect the second safety switch wire lead from the condensate pump to the red terminal on the AC/Furnace block. Comply with all local wiring codes.

For installations where interruption of heating or cooling is not acceptable (such as a computer room), most safety switches can be wired normally open and connected to an alarm device.

When a Standard Pump Won't Work
Once you've determined what pumps meet your requirements, you can narrow your choices by size, materials of construction, temperature rating, and price. Here are some installations that require more than a standard condensate pump:

Low level condensate drain: Some appliances, such as gas condensing furnaces, have condensate drains that exit below the inlet port of a standard sized pump. Pumps with a low-profile reservoir or bottom inlet port will solve the problem. The low-profile style pump has a shortened reservoir (about 2-in. tall) to accommodate the lower drain. Pumps with low-level inlets allow connection to a threaded fitting or barbed tubing connection.

High temperature condensate: Steam humidifiers found in many computer room air conditioning systems generate hot water condensate. High temperature pumps are available for use up to 212F. Commercial boilers also generate a steam condensation requiring a high temperature rated pump.

Ductless split systems: The growing popularity of ductless mini-splits has led to more than a few technicians scratching their heads to solve the condensate problem, particularly when the split is mounted on an interior wall. Several "mini-pumps" are available that offer a small reservoir equipped with a float/switch that connects directly to the drain pan in the air handler. The pump (a positive displacement pump vs. the typical centrifugal style condensate pump) can be mounted from six to 13 ft. above the reservoir. Condensate is drawn from the reservoir, through the pump, and out to a drain.

Due to limitations of the positive displacement design, the length of the horizontal run (the distance you need to move the water horizontally, once the lift is achieved) must be considered. Maximum horizontal run for a two ton split is about 10 to 12 ft.; however, larger pumps are available for horizontal runs up to 27 ft.

Plenum rated pumps: There is actually no agency such as UL that certifies a pump as "plenum rated." Local codes and inspectors have much to do with what is suitable for a pump installed in the plenum or ductwork. Cast aluminum reservoir pumps with flame retardant plastic components and wiring will satisfy most local codes for these installations.

Maintenance
You've specified the right pump, properly installed it, and it has worked brilliantly over the course of the first air conditioning season. Now what?

Particularly in locations with four seasons, the pump may not run for another six months. Algae scale and scum that has accumulated in the pump over the past few months can solidify and bind the pump impeller, creating a potential pump failure at start-up.

Ideally, the pump should be disassembled and cleaned. However, a cup of household bleach diluted with one gallon of water can be poured into the pump and cycled several times to clean the internal parts. Consult your pump's maintenance manual to be sure the materials are compatible.

Safety Switches for Gravity Drained installations
Several styles of safety switches designed to shut down the air conditioning system or furnace are available for installation in the condensate drain pan or drain line. Most are wired in the same fashion as the secondary safety switches included on the condensate pumps. The least expensive and most common is the drain-pan safety switch. The product can be attached to the secondary drain pan, and opens the thermostat circuit in the event of a drain pan or drain line clog. More recent adaptations include condensate traps equipped with safety switches, and inline switches that are easily installed in the actual drain line.

Algae and Slime Prevention
There are a number of additive products designed to retard or prevent algae growth in the drain pan or drain-line. This helps keep the condensate pump and the condensate drain line clean, and free of potential blocks. The most popular products are:

Pan strips or pan tablets are inserted directly into the drain pan, and dissolve over the course of about a month, or up to three months, depending on size and formulation. Pan strips are water activated, time-released materials that can prevent algae and slime for about six months.

In-line systems allow you to treat the drain line without requiring access to the drain pan. The tablet is easily installed in a small reservoir that connects directly to the drain line.

Liquid additives can be poured directly into the drain pan, drain line, or condensate pump. The treatments remove and resists clog creating algae and slime, and lasts about 90 days.

As you can see, ensuring proper function of the condensate drain system is an important part of your routine service calls.

It's not difficult to design and maintain a proper condensate drainage system. With a little planning and attention to detail, you can avoid not only annoying call-backs, but potential health issues and property damage as well.

Mike Connors is product manager for Hartell Pumps, Ivyland, PA. He can be reached at 215/322-0730, e-mail mconnors@miltonroy.com. For more information, visit http://www.hartell.com/.