Air Conditioning / Heat Pump Condensate Drip Trays, Defects, Repairs
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Condensate drip trays:
This air conditioning repair article discusses the inspection and repair of air conditioning condensate systems, including Air Conditioning Condensate Drip Trays, Defects, and Leaks.
Condensate overflow or drip tray leaks, piping, and float switches can shut down an air conditioner or heat pump.
These leaks can also damage the building, even causing costly mold contamination. A/C or heat pump condensate leak
health and safety concerns are also reviewed.
This article is part of our series of diagnostic & repair articles for cooling system condensate piping, traps, drains,
condensate pumps, and the detection and hazards of air conditioning system condensate leaks in buildings.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
Air Conditioning or Heat Pump Condensate Drip Tray or Condensate Overflow Pan Installation, Inspection, & Diagnosis
Using an Auxiliary Condensate Drain Line from an Attic Cooling Coil Condensate Overflow Pan
As Carson Dunlop Associates' sketch (left) illustrates, one method of insuring against building damage due to a clogged A/C condensate disposal line is the installation of a second, auxiliary drain line to empty the condensate overflow pan that should be installed beneath the indoor cooling unit
[Click to enlarge any image]
When an air conditioning unit is located in an attic where damage may result from air conditioning system
condensate overflow from the primary condensate collection and drain equipment,
an additional water-tight corrosion-resistant pan (an air conditioner condensate drip tray or "drip pan") should
be installed below the air conditioning equipment to catch overflowing AC condensate should
the primary AC condensate drain become clogged.
The sketch illustrates that the condensate drain from the auxiliary condensate tray is not only separated from the primary condensate drain, it is best routed to a different destination and one at which the discharge will be noticed, prompting a repair.
Also, a basement
air conditioning system condensate pump can overflow and spill into the living area if the condensate pump fails
or if the condensate pump drain line becomes kinked or clogged.
Missing air conditioner condensate overflow pans
A missing air conditioning system condensate drip tray risks leaks into the attic ceiling, where air conditioner condensate can damage the building or cause
a (hidden) mold problem, especially if condensate is leaking onto the upper, hidden (by insulation) attic side
of drywall forming a ceiling of a room located below the equipment.
Both the drywall and the insulation itself
may become mold reservoirs.
Improperly connected or joined air conditioner condensate drain lines and overflow pan drains
Air conditioning drip pan drains: The air conditioner's condensate overflow pan or tray requires its own
separate drain. In the left photo above, the overflow pan has its own drain line, but it joins with the
main air conditioner condensate drain line almost immediately.
A blockage in the condensate drain is going
to lead leaks out of the air handler into the overflow pan. but since the overflow pan itself shares the same
drain the pan will overflow into the building ceiling, inviting a mold problem or other damage.
is the most common way we see these drains installed.
Most likely the installer is considering that the main
risk of a blockage in the condensate drain system is going to be inside the air handler unit itself. We're
not sure what data supports this view.
The float switch approach, discussed next, might be a safer approach.
Float switches on air conditioning condensate overflow pans
A condensate leak or overflow into the drip tray can trip this switch, shutting down your air conditioner or heat pump system.
Float switches on condensate trays: Some air conditioning system air handler installations provide
a float switch in the condensate overflow tray. This switch has a floating lever resting in the overflow pan.
The lever senses the presence of water and "floats up" until it shuts down the air conditioning system.
This may be inconvenient in hot weather, but the installer or owner have chosen to protect the building against a potentially costly mold or other leak-related problem by shutting down
the air conditioner, forcing attention to the problem.
Remember that if the condensate float tray switch senses condensate in the tray (or is otherwise defective) it will shut the air conditioning system down - if your air conditioning system seems ok but won't turn on, this switch could be one of the items to check. Thanks to Lester Richter for this tip.
Watch out: if your air conditioner has suddenly shut off and won't start, don't forget to check the condensate overflow tray for water, and if this switch was used (instead of a second condensate drain pipe), see if the switch is keeping your air conditioner turned off. If your condensate tray switch is a lever type (shown in our photo) try pushing the lever down to see if the A/C will turn back on. Other switches may have no moving parts: you'll need to remove the condensate and dry the switch.
An air conditioner condensate pan or drip tray float switch installed, the cost will principally be the fee for an HVAC service call to install the switch in the pan (trivial) and wire it to the A/C controls (less than an hour). Figure $100. to $150 for a service call to install the switch if none is already present.
If there is an drain pan overflow shutoff switch already installed but needing replacement, it should be a simpler operation since it's just a swap-in part. The wiring to the HVAC system controls will already be in place.
The condensate pan or overflow pan safety switch itself, such as the Safe-T-Switch Model SS3 made by Rectorseal and sold as a drip pan overflow shut-off switch, retails from $30.00 to $50.00 U.S. 
Don't forget to find and fix the cause of condensate leakage into the overflow tray or you'll continue to have air conditioner operating problems.
Evidence of Leaks into an A/C Condensate Overflow Pan May Indicate Trouble
In this photograph of the interior of an air conditioner overflow drip pan or tray, the air conditioning system condensate overflow tray shows evidence of leaks.
Since normally condensate produced in the indoor air handler is carried from the air handler interior to a condensate drain, we don't expect to see condensate falling into the
condensate overflow drip tray as a normal event.
If we see evidence of leaks into the condensate tray, the air conditioning system service technician should investigate the cause of this condition.
Reader Question: My condensate drain seems clean but the overflow tray still is leaking
My AC unit inside unit overflows into the crawling space. I have cleaned the drain pipe and the air handler coil but the unit still overflows out of the coil tray. What could be the cause(s) of this? - Angel J 6/16/11
Cleaned out the condensate drain pipe with shop vac, bleach, and weak mattress blower.
Only observed draining from the primary pipe during the day (85 - 100 degrees F) but noticed a little dripping from the overflow pipe at night (not continuous). Guessing up to a cup of water from overflow.
Primary condensate pipe still clogged? What kind of plastic tube would work as snake? - Mark 6/27/11
Angel: Carson Dunlop Associates' sketch (above left) illustrates what happens when a condensate tray leaks, risking costly damage to the equipment. Your question is why the condensate keeps flowing out of the tray when you are confident that the drain is not blocked.
When the air handler condensate system is leaking into the crawl space and you are sure that the condensate drain pipe is unclogged and properly pitched, I have to guess that there is a problem with the condensate collection pan inside the air handler such as:
- the drain in the pan itself is clogged with debris - you'll need to turn off and look inside the air handler
- the drain pan is corroded through and leaks - it will need patching or replacement;
- the drain pan or the whole air handler is not properly leveled - it may be sloped away from the condensate pan drain opening so that condensate collects in and runs over the edge of the pan in another direction.
Let us know what you find - it'll help other readers.
There is an almost overwhelming number of products and methods sold for cleaning out A/C condensate lines, drains, and traps, and various tricks of the trade that fit to individual installations and situations.
I've used a small flexible bottle brush to clean A/C condensate traps; if the blockage is further along the line I've successfully used a small diameter flexible plastic tube bought at the local hardware store. - DF
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 Safe-T-Switch Model SS3, Rectorseal, 2601 Spenwick Dr., Houston TX 77055, Tel: 713-263-8001 or 800-231-3345, web search 8/11/11, original source: rectorseal.com Thanks to Mike Giaquinto and Scott at SJM Inspect for technical editing remarks, 5/16/07
 Thanks to Lester Richer, a professional home inspector, for the reminder that a bad air conditioner condensate drip tray switch can shut the whole system down.
 "Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
 Fiberglass: Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation
 Fred Nickols, "Solution engineering: choosing the right problem solving approach", Veracruz University, 2000, Web search 7/30/12, original source: http://cdigital.uv.mx/handle/123456789/5997 - Quoting: "Then he asked himself, “What should be happening
here?” He was not an expert on air conditioning systems, but he knew enough to realize that
condensate from the evaporator was sup- posed to run down into the drip tray, out the ..."
 AP Sawant, N. Agrawal, "Performance assessment of an evaporative cooling-assisted window air conditioner", nt. J. Low-Carbon Tech. (2011) doi: 10.1093/ijlct/ctr029 First published online: November 23, 2011 Abstract:
Substantial growth in refrigeration and air-conditioning industry has made a significant impact on net energy consumption. Condenser pressure is one of the critical parameters in the energy-efficient operation of refrigeration and air-conditioning systems. A novel system is developed to use the condensate, available at the cooling coil, for condenser cooling of a window air-conditioner unit by employing evaporative cooling. Performance testing of the system has shown 13% savings in energy and up to 18% enhancement in coefficient of performance. The maximum benefit of the evaporative cooling cycle over the basic cycle was found to be in the region of moderate climatic conditions.
 Yunho Hwang, Reinhard Radermacher, William Kopko, "An experimental evaluation of a residential-sized evaporatively cooled condenser
Evaluation expérimentale d'un condenseur à refroidissement évaporatif en application résidentielle", International Journal of Refrigeration
Volume 24, Issue 3, May 2001, Pages 238–249, Abstract:
In this paper, the performance of an innovative evaporatively cooled condenser is compared with that of a conventional air-cooled condenser for a split heat pump system. The system was tested in an environmentally controlled test chamber that was able to simulate test conditions as specified by ASHRAE Standard 116. Tests to optimize refrigerant charge and short tube restrictor size were conducted using refrigerant HCFC-22. The wheel rotation speed of the evaporative condenser was also optimized experimentally to maximize the coefficient of performance. Using these optimum parameters, steady state and cyclic performance tests were conducted. The experimental results showed that the evaporative condenser has a higher capacity than the air-cooled condenser by 1.8 to 8.1%, a higher COP by 11.1 to 21.6%, and a higher SEER by 14.5%.
Dans cette communication, on examine la performance d'un nouveau condenseur refroidi par évaporation ; on compare sa performance à celle d'un condenseur refroidi par air classique utilisé dans un système split de pompe à chaleur. On a testé ce système dans une chambre à environnement contrôlé afin d'obtenir des conditions d'essai requises par la norme ASHRAE 116. On a réalisé des essais destinés à optimiser la charge en frigorigène et les détendeurs pour HCFC22. On a optimisé de façon expérimentale la vitesse du moteur de rotation du condenseur évaporatif afin d'augmenter le coefficient de performance le plus possible. A partir de ces paramètres optimaux, on a effectué des essais en régime permanent et sur la performance du cycle. Les résultats expérimentaux montrent que le condenseur évaporatif a une puissance supérieure à celle du condenseur refroidi par air (de 1,8 à 8,1 %), un COP de 11,1 à 21,6 % supérieur, et un SEER* de 14,5 % supérieur.* SEER (Seasonal Energy Efficiency Ratio) = Rapport d'efficacité énergétique saisonnier
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