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Find It Now Or Pay For It Later

March 03, 2011
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Some building maintenance departments don''t realize the importance of heating, ventilation and air conditioning (HVAC) condensate maintenance until it''s too late and the property they''re supposed to be maintaining incurs thousands of dollars worth of water damage or, worse yet, significant mold or mildew problems.

All HVAC systems condense humidity from the airstream that collects in the drain pan.

When a blockage prevents a drain pan from properly draining, it overflows into its surrounding area.

While property damage is visually apparent, the hidden dangers of mold, mildew and other indoor air quality (IAQ) problems can lurk for months.

Obviously, overflowing HVAC units in attics or internal building areas can cause substantial damage.

However, many maintenance departments overlook the potential of overflowing external units on rooftops because they think the roof pitch will drain away the condensate.

Unfortunately, many HVAC units sit on a curb and use bottom air discharge, a design where condensate can overflow the drain pan and drop into the building.

All HVAC units should include an adequately sized and pitched drain line to transport the condensate away from the unit.

Drain lines are a necessity; however, biological or inorganic particulate matter in the unit''s airstream invariably washes down into the condensate and eventually clogs the drain line.

Units in areas with high pollen counts are the most susceptible to biological growths.

Therefore, HVAC condensate drain lines should be checked by maintenance departments a minimum of every three months or simultaneously when air filters are checked and changed.

Luckily, technology has developed solutions such as traps, overflow switches and other HVAC condensate overflow prevention devices to minimize these problems.


Condensate traps are available in many varieties, but the best maintenance solutions are the transparent and cleanable models.

The see-through feature allows easy blockage detection and the cleanable aspect offers up to three accessible cleaning ports on the trap for a brush, which is not included with most trap brands.

Generally, condensate traps are mandated by the International Mechanical Code and the Uniform Mechanical Code, as well as the HVAC manufacturer.

That doesn''t necessarily mean that the installer of an HVAC unit actually complied with or was aware of these code requirements, though.

Traps are easy to install and should be fitted to every HVAC unit regardless of size or whether the unit is under positive or negative pressure.

Good practice dictates that the first fitting off the drain pan should always be a capped cross, which provides permanent access into the drain line or trap.

This also permits access into the drain pan itself without the necessity of opening the unit or removing access panels.

The mechanical codes mandate the use of rigid pipe, which may be polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), acrylonitrile butadiene styrene (ABS), copper or other metals.

Coiled pipe is specifically prohibited because it can develop sags, which create secondary traps and inhibit water flow.

The pitch of the condensate drainpipe is also mandated by mechanical codes and must not be less than one quarter of an inch per foot.

To check an HVAC unit''s draining integrity, water is poured into the condensate pan to assure proper drainage.

Another strategy is antimicrobial condensate tablets that dissolve in the drain pan over the course of several months.

This method introduces unnecessary chemicals into the environment and therefore should be used only in locations with histories of extreme biological growths.

Maintenance departments planning a trap installation should know that there are different trap sizes and specifications to consider.

Therefore, it''s important to choose the right trap as per the HVAC unit manufacturer''s specifications.

It is equally important to see that the HVAC unit is sufficiently elevated to a minimum height of six inches to ensure there is room for a trap and adequate pitch in the drain line.

Conventional P-traps depend on residual water level for a seal.

This usually dries up when the cooling season is over, creating what is known as "dry trap."

A dry trap will allow insect ingress and air infiltration, retard drainage on a negative pressure system and increase energy costs on a positive pressure system.

A good solution to these problems is a waterless trap, which relies on a float to act as a check valve and create a seal.

Waterless traps are freeze-resistant, require no priming, don''t allow air to flow in both directions and permit the free flow of water at all times.

Waterless traps are available in ¾-inch, 1-inch and 1-¼-inch diameters.

Overflow Switches

An overflow float switch is useful because it deactivates the HVAC unit during an overflow event.

During a trap blockage, water rises up into the cross and lifts the switch''s mechanical float, which cuts power to the 24-volt circuit that''s wired inline with the HVAC unit.

While there are many overflow switches on the market, it''s important to note that switches with a capacity of less than four amps may not perform properly on many HVAC units because they may not be able to handle the higher currents associated with modern systems.

Overflow switches are invaluable, but are not a cure; they should not be used as a substitute for the regular maintenance of traps and/or drain lines.

An overflow switch is a second line of defense that only treats the symptoms of a blockage by cutting power to the unit.

Once the water recedes, as in the case of a partial blockage, the unit activates and the cycle perpetuates until the drain line blockage is physically removed.

While an overflow cut-off switch prevents the unit from operating during blockages, there is one disadvantage: Iced evaporator coils will continue to thaw and feed the slow receding or blocked drain pan even though the unit is deactivated.

For up to five-ton capacity units, the ultimate in overflow protection is an overflow switch with a self-evacuating pump.

Regardless of thawing ice, which may form on evaporator coils, the pump will continue to pump out the drain pan and prevent an overflow even though the switch has deactivated the unit.

The pump remains live while the unit stays deactivated until a maintenance staffer removes the blockage and manually presses the integral pump''s reset button.

Traps, overflow switches and switches with integral pumps are inexpensive to purchase and install in-house when compared to the costs of replacing damaged property.

These devices are invaluable when applied along with a periodic maintenance schedule.

A maintenance staff that''s well-versed in controlling condensate from HVAC units will save its employer a significant amount of money in the long run while also improving building IAQ.

Gerry Spanger is a 46-year veteran of the HVAC industry. Founder of Marketair, EZ Trap and Slimduct, Spanger is now vice president of Airtec Products Corporation, a leading importer/manufacturer and distributor of components for the HVAC industry. Airtec is the exclusive U.S. distributor for Aspen condensate pumps, manufacturer of Airtec diffusers, EZ Trap condensate control products, Fortress lineset protection covers and fittings and global marketer of NOVENT locking refrigerant caps.

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