We may take comfortable indoor climates for granted these days. But if you could reduce your energy bill by a substantial amount, would you pay a little more attention to what’s going on with your heating and air conditioning system? As the time to turn the air conditioning back on nears, we think that this is a great time to review coils and how caring for them can impact you, your comfort, and your energy bill!
Most people have probably heard about the coils used in HVAC — the evaporator coils and condenser coils. Both coils are related to the cooling process, but each handles a different part of the process.
The evaporator coil is where the refrigerant absorbs heat. Unlike furnaces, air conditioners can’t just “produce” cold air, so to speak; they must remove the heat from the air, which in turn leaves the air cooler. Evaporator coils are generally located in the air handler indoors where the fan is. These coils are usually made from copper, steel or aluminum – the most conductive metals. The evaporator coils are usually set into panels which are lined with thin pieces of metal called “fins,” which allow the passing warm room air to be cooled closer to the coils in order to maximize the effect of the refrigerant. The evaporator removes (condenses) a portion of the humidity from the air which also allows the air to reach a lower temperature. (Recall our earlier Industry Insight on Humidity)
Then there’s the condenser coil. The evaporator coil does the first part of the work, then the condenser continues it. Condenser coils are typically in the outdoor units, known as “condenser units,” which house the coils along with fins, compressor, copper tubing, fan(s), valves and switches.
After the refrigerant absorbs heat from indoor air air in the evaporator coil, it travels outside to the condenser unit. In the condenser, warm refrigerant gas enters the compressor. The refrigerant is pressurized here, becoming a hot, high-pressure gas. This gas leaves the compressor and flows into the condenser coils. The fan in the outdoor unit (condenser) blows air over the condenser coils causing the refrigerant inside to condense losing its heat in the process. The condensers many coil rows increase the amount of time the refrigerant is in the path of blowing condenser air, giving it plenty of time to release the heat it carried out from the indoor air. The refrigerant then moves back into the indoor units refrigerant metering device (thermal expansion valve (TXV) or orifice) to start the evaporation (heat absorption) process again.
Cleaning Both Evaporator and Condenser Coils
Did you know that keeping your coils clean along with maintaining a correct level of refrigerant can result in an energy savings of 10-15%? It’s not new news. You can download the full 2006 ASHRAE study here. But to summarize, the evaporator and condenser coils must be kept clean, and airflow must be maintained to both inside and outside units. If the coils are dirty, the fan and compressor will have to work harder to cool and dehumidify the air. That extra work and stress on the system will result in wasted energy and premature wear and tear on parts.
Even a fine layer of dust on the evaporator (indoor) coils reduce their efficiency. The dust acts as an insulator, keeping the heat in and the air away from the cold coils. As for condenser units, the most common threat is a buildup of outdoor debris on the fins. This can be made up of things like cottonwood, pollen, grass, leaves, twigs, etc. — all of which make it harder for the condenser to release heat.
So don’t let something as simple as dirty coils be the cause of poor air conditioning performance or system failure this year! Schedule your spring maintenance now.