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HVAC Deferred Maintenance can be Costly and Deadly
Carl Brahe, Certified Home Inspector Copyright 2007 all rights reserved.

The results are HVAC units that wear out many years too soon, using far too much fuel and possibly endangering the occupants. Inspection Perfection Commercial Inspection SuperTeam consultant and HVAC expert Kevin Lichtenegger estimates that an HVAC unit, in a commercial usage, will cost more than twice as much in repairs and fuel consumption over 10 years if it is not properly maintained. The unmaintained unit will probably need replaced at this time while a properly maintained unit may provide good service for many more years.

All forced air units, the most common in Colorado, operate on a simple principle. They move air, usually through a hot or cold medium. The most common cause of failure is that they cannot move air properly. When air does not flow properly various parts of these units over heat and fail.

One thirty second of an inch of dust accumulated on the blades of a fan, like used with furnaces, will cut down airflow by 30%. A filter that is half clogged with dirt cuts airflow to 60%. Evaporative coils on an AC unit that are a third blocked cut efficiency by 10-15%. If totally blocked with leaves, grass clipping, dirt and/or other things the condenser will fail.

The most common way to provide heat for a forced air furnace is through heating the inside of a metal container. Air is forced to pass around this container, or heat exchanger. The air gets warm and the heat exchanger cools. If the airflow is not sufficient to cool the heat exchanger, it overheats.

When overheated, a single drop of moisture or a speck of dirt can cause the heat exchanger metal to crack or separate at the seams. The heat exchanger can get hot enough to melt. When the metal container of the heat exchanger leaks, deadly gases such as CO escape and can be drawn into the fresh air supply and delivered to living spaces.

AC units are also damaged by excess heat from lack of airflow. Gases that turn very cold when compressed produce cooling. The cold is removed from the gas as it passed through something like a car radiator. The cold gas flows inside. The air handler, or squirrel cage fan box, forces air to flow through the radiator fins then throughout the conditioned space.

When the liquefied gas is warmed by the airflow, it expands and turns back into a gas. The gas is taken outside to the compressor where it vents its heat while being compressed back into a cold liquid.

If a clogged filter, or dirt and debris restrict the airflow, the process of changing back and forth between gas and liquid is restricted. When airflow is restricted enough the gas stays liquid and damages the compressor.

Forced air systems of all kinds rely on unrestricted air movement. If air is restricted, overheating, inefficiency and damage will occur. The longer airflow is restricted the more damage results. Compressors, motors and heat exchangers are all at risk.

A simple forced air system is a whole house fan. These are the most economical cooling systems. A fan is mounted in the attic that draws cool air through the whole house, forcing warm air out. Ideally, the house is sealed very tight and the fan runs only at night.

Another simple forced air cooling system that is installed in many Colorado homes and businesses is the evaporative cooler, or swamp cooler. This is like a box of rain with a fan inside to draw warm air through the falling water and push it into the building. Power use can be as low as 1/3 that required for AC operation in a dry climate like Colorado.

Swamp coolers are handyperson friendly. They have only a few basic parts. A box with louvered sides contains shredded aspen bats, or other medium, to hold the falling water. A pump sends water to the top of the box and it falls through the bats. The fan pulls air through and directs it into living spaces. A motor turns a squirrel cage fan using a fan belt. These, along with the float valve assembly are the only moving parts.

Swamp coolers provide a moist cool that can be very welcome in our arid climate. The water filters out dust and pollen. Evaporative coolers are relatively inexpensive to install and operate cheaply when used with a thermostat. The downside is that they must be kept clean or mold and bacteria can grow. In most residential uses, servicing twice a year is sufficient and can be done by a homeowner.

Prepare the unit for use in spring. Disconnect the power and turn off water supply.

Clean the inside of the box, the squirrel cage fan and the pump filter. Cover the motor with plastic and be careful to keep it as dry as possible. A sponge with soapy water can be used along with a garden hose to rinse.

When the inside is clean inspect the fan belt and tighten as needed. Oil the motor bearings through the oil ports provided. Clean or replace the mesh cover that prevents debris from entering the pump. Reposition the pump.

Turn on the water supply and allow the reservoir in the bottom of the box to fill. A float rises with the water level and blocks the flow when the appropriate level is reached. If the water flow doesn’t stop at the right level, lift the float until flow stops. If flow doesn’t stop, clean the valve. Bend the rod attached to the float to adjust the water depth in the reservoir. Drop a time released disinfectant tablet in the water. These are available at hardware or building supply stores.

The removable side panels of the box contain the bats. Bats come in several types. Many people prefer the natural smell of wet aspen. Batting material can be purchased precut for replacing bats. The bat is held against louvers by wires to allow air to flow through them.

Lay a panel on a flat surface and remove the retaining wires from the inner side. Pull the old bat out and discard. Clean the louvers and reassemble with new batting material. Repeat until all panels have been cleaned and renewed.

Turn on the electricity. Turn the switch to “Pump Only Water should begin to cascade down the sides. Make sure there is even water flow on all sides. If not be certain water tubes are clean, attached and uncrimped. Turn off the pump.

Remove the plastic cover you put on the motor for protection. Turn the switch to “Fan Only" The fan should begin to turn. It should be quiet except for the sound of rushing air. If there is a grumbling, whining or grinding sound, the bearings are probably damaged and the motor needs replacing.

Assuming the pump and fan operate correctly, replace and secure the sides of the unit. It should be ready to provide you with healthy, moist, cool air. Evaporative coolers provide inexpensive cooling on most Colorado days. When the temperature goes over 100F cooling may need to be supplemented.

If there is no water flow, the pump may be bad, or getting no electricity. It is rare for any component in a swamp cooler to not work if the unit has been maintained properly. Call a professional if the pump or motor fail to function.

Preparing the unit for winter is simple. Turn off power. Disconnect the water line and make certain it doesn't freeze. Drain and clean the reservoir. Cover the outside with a tarp, or solid side covers, to prevent air flow into living areas.

Our commercial HVAC expert suggests that swamp coolers and all other commercial heating and cooling units should be serviced 4 times a year. A professional usually does this. If servicing is skipped, good quality, new filters should be installed and the unit cleaned with a vacuum and brush at a minimum.

A system that is regularly maintained can last far beyond normal life expectancy and save substantially on fuel costs over the life of the unit. Deferring maintenance here can have costly and deadly consequences. Regularly maintaining your HVAC systems pays back in comfort, reliability and environmental benefits while saving money.