Condensate Backups Continued

Leaks & Overflows

The wet, warm environment of a condensate collector beneath a central air conditioner evaporator coil is a perfect algae breeding ground. This biological growth may migrate into the condensate drain line or the drain trap and form a blockage. Condensate overflow due to a blocked drain may be caught by an overflow pan beneath the air handler, but if the overflow pan is missing, or has cracked or developed a hole, or if the overflow pan’s drain line is plumbed to the same primary drain line that is clogged, water leakage will ensue. Property damage from unseen condensate leakage can be extensive and expensive by the time a leak is finally noted by occupants.

Drain Trap

A central air system routes condensation through a U-shaped trap located in the drain line just outside the air handler. It’s similar to the trap under your kitchen or bathroom sink; water in the trap prevents sewer gases originating where the condensate drain pipe terminates from infiltrating the air handler. In some conditions, such as during a long season of non-operation or when a gravity-fed drain line is not installed with the proper incline, the condensate drain trap may dry out and allow sewer gases to pass through the line. Unexplained noxious odors emitted from air conditioner supply vents in the home are the primary symptom of a dry condensate drain trap.

System Shutdown

Because of the potential of severe property damage from unseen leaks, many condensate drain systems incorporate an overflow sensor. When a clogged condensate drain causes a backup that reaches overflow stage, the sensor cuts off power to the system. The coil and collector are sealed inside the air handler and generally not accessible for a do-it-yourself project. Until an HVAC technician can arrive to open the air handler, unblock the drain line, and clear the pan, the air conditioner will be unusable.

Condensate Backups

Central air conditioners produce something other than cool comfort: water, lots of it. Because dry air holds less heat energy, humidity extraction is a critical part of an efficient air conditioning process. When the air conditioner blower pulls warm household air through the frigid passages of the evaporator coil, the cooling effect causes water vapor to condense out of the air rapidly. Condensation drips down into a collector pan under the coil and is conveyed through a drain line to a household sewer connection. Things that might go wrong in the condensate drain system include damaging leaks, bad air quality, toxic mold growth, and even a complete air conditioner shutdown. As seen below, a condensate line backup caused water damage through walls and into carpet and padding. Luckily, this home in Mount Laurel New Jersey didn’t sustain major damage prior to it being discovered.

HVAC Filter Change – Part 2

Your HVAC or furnace technician should service your unit once a year. Because a furnace/HVAC unit contains moving parts, it’s important that belts are not cracked and dry, ventilation ductwork is not gapped, cracked or rusted, and components, such as coils and fans, are clog-free and adequately lubricated for unimpeded operation. This sort of evaluation is best left to the professional, unless the homeowner has had the appropriate training. The filter of the unit, especially if it’s an HVAC unit that will tend to get nearly year-round use, should be changed by the homeowner at least every three months, but possibly more often.

Check your filter’s condition and change it once a month if:

  • You run your unit six months a year to year-round.
  • You have pets. Pet dander can become airborne and circulate through the home’s ventilation system just as typical household dust does.
  • You have a large family. More activity means more household dust, dirt and debris.
  • You smoke indoors.
  • You or someone in your household suffers from allergies or a respiratory condition.
  • You live in a particularly windy area or experience high winds for extended periods, especially if there are no nearby shrubs or trees to provide a natural windbreak.
  • You live in an area prone to or having recently experienced any wildfires. Airborne ash outdoors will eventually find its way indoors.
  • You have a fireplace that you occasionally use.
  • You live on a working farm or ranch. Dust and dirt that gets kicked up by outdoor work activity and/or large animals can be pulled into the home’s ventilation system, especially through open windows.
  • You have a large garden. Depending on its size and how often you work it, tilling soil, planting, pulling weeds, using herbicides and pesticides, and even watering mean that dirt, chemicals and condensation can be pulled into your home’s ventilation system.
  • There is construction taking place around or near the home. You may be installing a new roof or a pool, or perhaps a neighbor is building a home or addition. Even if the activity is only temporary, dust and debris from worksites adjacent to or near the home can be sucked into the home’s ventilation system, and this increased activity can tax your HVAC system.

HVAC Filter Change Part 1

Part of responsible home-ownership includes, of course, regular home maintenance. And there are some tasks that, if deferred, can lead to a home system that’s inefficient and overworked, which can result in problems and expenses. One such task is changing the filter of the home’s HVAC system. It’s simple and inexpensive, and taking care of it at least every three months can mean the difference between optimum comfort and avoidable repairs.

What’s At Stake?

Most homes have some sort of furnace or heat pump, and many of those homes (especially newer ones) have combined heating, ventilation and air-conditioning or HVAC systems. Each type uses some type of air filter or screen to prevent larger airborne particles (up to 40 microns) from entering the system and clogging sensitive machinery. A system that has a dirty filter can suffer from pressure drop, which can lead to reduced air flow, or “blow-out,” resulting in no air infiltration at all. Any of these conditions can cause the system to work harder to keep the home warm or cool (depending on the season and the setting). And any mechanical component that has to work harder to run efficiently puts undue stress on the whole system, which can lead to premature failure, resulting in repair or replacement. Also, a dirty filter that’s exposed to condensation can become damp, which can lead to mold growth that can be spread throughout the home by the HVAC system. This can lead to serious health consequences, not to mention a compromised unit that will likely require servicing and may require replacement, depending on the severity of the moisture problem.

Types of Filters

Most HVAC and furnace filters are disposable, made of biodegradable paper or similar media, and shaped in cells, screens or fins designed to trap as much airborne debris as possible. Filters can typically be purchased in economical multi-packs, and there are many types that will fit different models of furnace/HVAC units. It’s important to use the appropriate filter for your unit; using the wrong filter that doesn’t fit the unit properly can create the same types of problems as having a dirty filter. Your HVAC installer can show you where the filter goes and how to remove the old one and install a new one. Your unit may also have an affixed label with directions for easy filter replacement.


Condensation on Ductwork

Condensation occurs when air is cooled below its dew point temperature. The study of air containing moisture (or plain old air as we know it) is called psychrometrics (pronounced si-crow-met-ricks), and deals with the relationships between temperature, relative humidity, absolute humidity, dew point and several other properties of the air/moisture mixture. A basic psychrometric relationship is that air can only hold so much moisture at a certain temperature. When the air is full of moisture, the relative humidity is 100%. When the air contains half as much moisture as is can at a temperature, the air is at 50% relative humidity. The next relationship is that if you cool the air, the relative humidity increases. (Cool air can’t hold as much moisture as warm air) At some point, the air becomes saturated. Cooling it any further causes condensation. This is the dew point.

So how does this relate to sweating ducts? Air conditioners make air cold. The cold air is forced through ducts. As a result, the outside surface of the ducts is cooled. If the air outside the ducts is humid enough, condensation will form on the ducts. The colder the air in the ducts and the more humid the air around the ducts, the more chance of forming condensation. Note that sweating ducts has nothing to do with moisture in the air inside the ducts. Solutions to sweating ducts involve 1) warming the surface, and 2) drying the air around the ducts. Insulation is added to the exterior of ducts to help warm the duct surface. The insulation should be enclosed in a vapor barrier to keep moisture from moving through the insulation itself. Joints in the ducts, insulation and vapor barrier should be sealed. The insulation and vapor barrier should extend completely to the registers, or condensation can form on the exposed ends.

If the ducts are in a crawlspace, a complete vapor barrier on the soil is an essential first step. Increasing crawlspace ventilation may help in some parts of the country, but be careful because increasing ventilation in other areas can actually increase the condensation. In basements and crawlspaces, sometimes adding a dehumidifier is necessary. Most duct condensation issues I have seen are the result of problems with duct insulation. In some cases, fixing the insulation solves the problem. Adding insulation typically does not solve the problem. In cases where the insulation is in good shape, crawlspaces and basements have been wet, or ducts have been pressed together.

When is the air conditioner at fault? Some newer air conditioning systems and controls actually make the air inside the ducts colder. This is an attempt by the manufacturer to help make the air in the house dryer, but often causes more condensation on the outside of ducts. Dirty filters can restrict air flow through the system, resulting in colder air. This is the easiest one to deal with: keep your filters clean. Otherwise, make sure the duct insulation and vapor barrier are continuous, contiguous and complete. And keep the air around ducts dry by covering exposed soil in crawlspaces, keeping ducts apart, and reducing other moisture sources in the air as much as possible.


Changing Your Filters

Regular maintenance of your home heating, ventilation and air conditioning system (HVAC) is critical to ensure its long life and efficient operation. Proper maintenance of this system can help keep your loved ones safe from extreme temperatures —and may also help save you some money.

The HVAC system heats your home during the cold winter months and keeps your home cool in the sweltering summer. Regularly changing the HVAC air filter is critical for its long life. The air filter keeps pollution and debris out of your HVAC system, ensuring proper and efficient operation. A dirty filter will slow down the air flow, making both the furnace work harder to heat your home and your AC work harder to cool it. This wastes energy and can result in higher energy bills.

How Often?

According to, the filters on your home system likely need to be changed either once a month or once every three months, depending on the type you’re using. You should check the product information on the filters for the manufacturer’s suggested frequency of change. Depending on where you live, the time of year, and how much you’re using your AC or furnace, you may end up having to change your air filter more frequently. For instance, during a steamy summer when you’re running your system constantly, you may end up having to change the filter more often than if the weather is nice and you’re relying on open windows.

Winterizing An Outdoor Air Conditioner

An outside air conditioning unit, often referred to as an HVAC unit, is a lifesaver during hot summer months. During the winter, you may want to winterize the unit to protect it against cold weather, snow and ice. Winterizing the unit also protects it against rust damage. A few protective measures can keep the air conditioning unit in your real estate investment in top working condition.

  • Find the air conditioning circuit near your unit. Usually, it has a plastic or metal lid that covers the electrical circuit. Open the lid and flip the switch to turn the unit off. This prevents the unit from turning on during an unusually warm winter day, keeping water out of the unit that could potentially freeze.
  • Wash the air conditioning unit with a hose to remove bird droppings, dead bugs, dirt and dust. Remove leaves, small branches and grass clippings from the unit. Allow the unit to dry completely.
  • Install foam pipe covers around exterior exposed pipes. Cut the foam to fit the length and diameter of the pipe. The foam covers insulate the pipes and protect them against freezing temperatures. Wrap duct tape around the foam covers to hold them in place.
  • Cover the HVAC unit with a plastic or vinyl cover. Choose a cover that is waterproof. Some manufacturers make covers that are specifically designed for air conditioners, but you can use any plastic or vinyl covering that fits over the unit.
  • Wrap vinyl ropes or bungee cords around the air conditioning cover to keep it secure. Make sure the cover is wrapped tightly so it doesn’t blow away in strong winds.
  • Check your air conditioner once a week to make sure the cover is secure. Brush water, snow and ice off the unit. Remove twigs, pinecones and leaves from the cover.

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