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AIR CONDITIONING & HEAT PUMP SYSTEMS
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AIR FLOW MEASUREMENT CFM
APPLIANCE DIAGNOSIS & REPAIR
APPLIANCE EFFICIENCY RATINGS
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CAPACITORS for HARD STARTING MOTORS
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
DEFINITION of HEATING & COOLING TERMS
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM & DUCT DEFECTS
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST, HVAC CONTAMINATION STUDY
ELECTRIC MOTOR OVERLOAD RESET SWITCH
EVAPORATIVE COOLING SYSTEMS
FAN LIMIT SWITCH
FAN NOISES, HVAC
GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION INSTRUMENTS
HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEATING SMALL LOADS
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS
LEED GREEN BUILDING CERTIFICATION
LOST COOLING CAPACITY
LOW VOLTAGE TRANSFORMER TEST
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
OPERATING COST, AIR CONDITIONER
OPERATING DEFECTS, AIR CONDITIONING
REPAIR GUIDES A/C / HEAT PUMP
REPAIR & DIAGNOSTIC FAQs for A/C
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
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.
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Air Conditioning or Heat Pump Condensate Drip Tray or Condensate Overflow Pan Installation, Inspection, & Diagnosis
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.
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.
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.
But this 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.
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.
Details are at CONDENSATE PAN SWITCH LOCKOUT
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.
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.
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.
Readers who need to clean or unclog a blocked or leaky overflowing A/C or heat pump condensate drain should
Continue reading at CONDENSATE HANDLING, A/C or select a topic from the More Reading links shown below.
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Frequently Asked Questions (FAQs)
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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.
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:
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
Question: A/C condensate leaks into ceiling or into the attic
I noticed leakage in my ceiling after a technician rewired my brand new conditioner to run at a higher fan speed which forced more air into my house. Made sense and now feels cooler. a few hours later is when I noticed the water leak. I went into the attic and can see that there is water in the catch tray but the kicker is that there is a small hole a couple of millimeters round at the end of the tray allowing the water to leak out into the insulation down the roof into my plaster ceiling. What in the world is a hole doing in my catch tray? - Frank 7/22/11
My a/c unit on my roof is leaking into the attic and causing water spots inside the house (ceiling, walls). After having a friend check it out, we think the plastic drip tray, which the condenser is resting in, has a crack or hole causing the leak. The question: How do we get to the drip tray to repair or replace without removing the condenser? - J. 8/1/11
I rent my home and have for 5 years. I noticed a water spot in my bathroom ceiling and went upstairs to check the air conditioner being that it is right above the bathroom. The tray was FILLED. I laid towels down to soak up the water. Today is Saturday. Can I wait to call my landlord on Monday as long as I continue to soak up the water? Also, what could the problem be. It DOES have that switch mentioned above but it must not be working... - Kelli 6/23/12
at higher fan speed sometimes the blower pushes water droplets into the ductwork instead of allowing all of the condensate in the air handler to run into the drip tray. But when you find an obvious leak like a hole in the drip tray, that's a good diagnosis for leaks into the ceiling. If your drip tray is metal it may just have corroded; plastic - it was damaged. Usually there is a primary condensate collection drip pan connected to a drain location, and a separate condensate overflow pan and drain to handle the sort of problem you describe.
replacing the drip tray under a rooftop A/C unit is easy or difficult depending on how it was installed. If the installer left sufficient slack (a flexible loop) in the refrigerant piping and electrical wiring, the system can be raised very carefully, disturbing the piping as little as possible to avoid causing a leak in the refrigerant lines. Then the new tray is placed beneath.
I suspect that the condensate drain is clogged - usually a little brush can clear a trap in that line - but yes, if you keep water from overflowing into the attic by any means you can keep running the system. But it sounds troublesome. I'd focus on getting someone to clear the drain.
Thanks Dan. We will see if the condenser has any slack to lift it off of the tray. Any other ideas?? I also saw someone mention something about some of the moisture from the condenser being sucked into the air intake then resting in the ventilation somewhere, pooling, then leaking. Since the air intake is a big hole just under the condenser, I consider this a possibility. Any ideas on this one? - J
Sometimes in the air handler the blower pushes moisture off of the cooling coil and off into the ductwork - common in very humid spots like Florida.
Question: A/C condensate pan emergency overflow float switch
Can someone tell me what an emergency float switch typically cost? I have one attached to my drip pan on an Amana. - Molly 8/11/11
if you need 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.
Question: A/C condensate blows into the duct work
An earlier comment mentioned air pushed into the duct by the blower. I have had condensate leaking from the bottom duct of my downflow system for several years on to the garage floor. Has not been a big issue because I live in Oregon and only use AC a few days a summer and humidity is very low. I have determined that the condensate is blowing or splashing out of the tray in the center of the evaporate. The drain is OK. What can be done about this? I will be selling the house next year and I,m sure it will be an issue. - Dan 8/20/11
While some of my associates (M. Cramer, Tampa) point out that a small amount of condensate blow-off at the cooling coil and even small amounts of mold in that area (usually Cladosporium sp. in my tests) are not necessarily a functional issue, I'm still looking for a "fix" for condensate blowing out of the drip tray; I agree that it's common, especially in very humid areas. My associate Mark Cramer, a Florida home inspector and educator, says they just live with it and they don't believe mold is much of an issue in ductwork; I think .... also paraphrasing Mark... it depends. Small amounts of immobile Cladosporium sphaerospermum sticking to insulation may have no detectable effect in the living area; Aspergillus or Penicillium in the same area would be more of a worry. This is a good question to take to the manufacturers to ask what design changes in air handler airflow control may be in the works. - DF
Question: Condensate Drip Tray Replacement
can the drip pan be replaced with out replacing the condenser itself - Peter 5/6/12
Question: Condensate Drip Tray Not Level
Our condensation drip pan is not level, so the condensate water is flowing away from the drain hose and overflowing into our furnace instead of down the drain. I was told the pitch of the pan needs to be adjusted- what is the best and safest way to adjust the pitch? Our AC unit is on top of our furnace. - Tony 6/22/12
Tony, to properly adjust the slope of the condensate drip pan you need to know how it is secured and what movement is possible; I don't have enough information to figure it out from just your comment; you could try sending some sharp photos to the CONTACT US link. If the pan is "pinned" under the A/C unit itself, you may not be able to level the pan without moving the whole assembly. If the pan moves freely it may just be shimmed. But if this is a new problem, that is if it used to drain, I'd look for what changed and ask why - that'd be diagnostic.
Question: Condensate dripping out of the air handler
My indoor ac unit is dripping water from somewhere in the upper part of the system. I checked what I believe is the condensate drain and it doesn't appear blocked. Interestingly, this drain goes into the floor (concrete basement floor) into a hole. I can't see into the hole since it's under a corner of the unit. I cut the PVC drain pipe so I could get my wet vac to it. I didn't get an appreciable amount of junk from the pipe and will replace it shortly. Also, the lines from the outside unit are freezing a bit and I see condensation along the lines that lead to the inside unit. Any information would be appreciated. - Duane 7/8/12
Recently, I have noticed water dripping down the outside of my furnace. The A coil is above the furnace, drain is located on the side of the drip pan, and the coil and integrated pan are "lift able" (not attached to the furnace) so it can be shimmed which I tried. I cleared the drain, but it was not clogged. The drip pan is showing a large amount of rust and I suspect pinholes in it, so the water is dripping through it rather than going to the drain. I have researched and found a product called Pancrete which appears to be made for just this problem. Has anyone here used this product and would they recommend it? System is Ruud upflow furnace approximately 18 years old. - Jeff F. 7/21/12
A first step in diagnosing condensate dripping out of the air handler is to determine if the entry into the condensate drain or any later portion of the drain is clogged - if water can't get from the pan into and down the drain the pan is going to overflow.
Also on occasion I find misaligned A/C components, a pan that is not in the right place, a pan that has corroded and is leaky, or missing insulation on a refrigerant line that is causing condensate to drip somewhere other than into the drip tray.
I haven't looked at PanCrete but will see if I can find and review the product literature; it's worth a try if it can seal a corroded condensate pan instead of having to tear the system apart to get a new one in place.
Question: Blower unit won't come on - the condensate drip tray is filled up - is there a float switch?
my outside unit is working but my blower in the attic is not, After checking my one 10amp fuse I noticed that not only was my drip pans filled but so wa the bottom insulation of my system, I have to separate drain pipe...do I still have a float switch and what should I do next? - Anon 7/16/12
Question: How Much Condensate Flow Should I be Seeing From My Air Conditioner - what's normal?
I have noticed quite alot of water draining from my drain hose which comes from the unit located in the attic. The drain hose comes from the attic unit, then outside and down the side of my home. I placed a bucket under the drain pipe due to the amount of water pooling around the foundation of the home. I can usually fill up this 5 gallon bucket within a day or two with the water draining. Is this normal? - Patrick S 7/30/12
Normal A/C or heat pump condensate flow ranges from nothing to considerable, even quarts per hour in some residential installations and of course still more in larger commercial systems. A system that is operating in a dry environment or that has been on for some time may be encountering little moisture to remove from the conditioned air, while an air conditioner running in very humid conditions may pull an enormous amount of water from the air.
In humid conditions an A/C system can produce a lot of condensate - it's not abnormal unless there is also an abnormal source of moisture in the building. Also when a cooling system is first activated after some period of disuse, as it removes moisture from the building air, more moisture from absorbent building materials (drywall, for example) continues to enter the building air until the moisture level in both air and building contents has been reduced to a stable level.
And of course there is no simple "correct" condensate quantity because in addition to these environmental variables, the cubic feet and type of area being air conditioned varies from building to building as does the dehumidification capacity of the equipment.
you're probably ok.
Watch out: about too little condensate production from an air conditioner or heat pump: we explain in detail at DEHUMIDIFICATION PROBLEMS that if an air conditioner is over-sized it will cool the space off too rapidly and it won't dehumidify adequately.
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