Carl Brahe
Heating and cooling systems are one of the top concerns of both residential and commercial property buyers. Neglect, or deferred maintenance, is so common with these systems that concerns are well founded. Many homeowners and renters are unaware that the furnace and AC need to be cleaned and serviced periodically. It’s common that commercial building leasers are unaware that they are responsible for these units. The results are HVAC units that wear out many years too soon, using far too much fuel and possibly endangering the occupants.
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 kind 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 heating the inside of a metal container. Air is forced to pass around the outside of this container, or heat exchanger. The air warms and the heat exchanger cools. If the airflow is not sufficient to cool the heat exchanger, it overheats. This doesn’t apply to units that use liquid to transfer heat, like hot water systems. 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 returns to a gaseous state. 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 remains in a liquid state 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. HVAC systems in homes should be cleaned and serviced professionally once a year. At a minimum, the filter should be replaced monthly during heating and cooling seasons. If your furnace is not professionally serviced annually, there are some things you can do to increase efficiency and safety.
- Before you do anything else, turn off the power to the furnace at the emergency shutoff. This usually looks like a light switch and is in easy reach and plain sight from the front of the furnace. If this is not the case, call a professional to install a proper emergency shutoff.
- Remove the front covers of the furnace. The panels usually slide up or down to remove and replace.
- The top chamber contains the burners and heat exchanger. In some units this assembly may be sealed and visible only through a small viewing glass.
- The bottom chamber contains the squirrel cage fan that forces warm or cold air through the heat exchanger to deliver it to the various rooms of the house.
- If your furnace has a pilot light burning, it is an old and inefficient unit. This should be checked for safety by a licensed HVAC person and replaced if possible.
- Using a new paint brush, brush all debris and dust within reach in the top chamber into a vacuum nozzle. If you find rust, corrosion, or staining from liquids or flame, call a professional before using.
- The filter will be visible from the bottom chamber. Remove the old filter. Brush the chamber surfaces reachable with your paint brush and vacuum to collect dust and debris as it is dislodged.
- Brush the squirrel cage fan while vacuuming to collect the dust. Turn the fan to reach all the fins.
- Install a new filter making sure that when the fan is running the filter will be pulled securely against its frame to prevent air from flowing around it instead of being filtered.
- Replace the front panels and turn on emergency shutoff. Turn up the thermostat to run the furnace.
- When the fan starts, examine the duct work for holes, leaks and dried duct tape coming loose. The fan will not run if the front covers are not properly replaced. A safety shutoff switch inside the bottom chamber prevents power to the fan if the cover is not in place.
- Seal leaks using appropriate mastic. Replace dried out duct tape with metal faced tape.
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, from the lowest point to the top of the roof, forcing warm air out. Ideally, the house is sealed very tight and the fan runs only at night, sealing in the coolness of the night to cool the house during the day.
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. Hybrid systems such as the Coolerado are available for commercial use. The manufacturer claims they are the most efficient AC system made.
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.
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 or replace 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.
- Removable the side panels of the box containing 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 spring 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” position. 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” position. 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 or fan bearings 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.
FALL
- Turn off power at the breaker.
- Disconnect the water line and drain so 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.
Swamp coolers in commercial use and all other commercial heating, cooling and venting systems 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 quarterly, 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 can have costly and deadly consequences. Regularly maintaining your HVAC systems pays back in comfort, reliability and environmental benefits while saving money.