With Arizona’s intense heat, most people have a lot of questions about their HVAC system. How does the unit work? What’s the best size? How can I reduce my power bill during the relentless heat of summer?
Whether you’re looking for a new unit, a new thermostat, or wondering about common HVAC maintenance, the following FAQ should answer any questions you have. Of course, if you still have questions, the pros at Isley’s Home Service are only a phone call away.
How do air conditioners work?
Your air conditioner (A/C) has several jobs. First, it moves or transfers heat from one place to another. When you’re in air conditioning the system absorbs heat from inside then transfers it outside. If you have ever been by an air conditioner on the ground outside in the summer it blows lots of heat when it’s running. That’s the heat from inside being transferred outside. When a heat pump is running in heating it actually picks up heat from outside, even when it cold outside and transfers it inside. Next, it uses the ductwork system to distribute the conditioned air throughout the home. Another function of the system is to clean the air in the home. We use air filters to capture dust particles and this also helps keep the systems coils and parts clean. In the summer time when an air conditioner runs it will also remove humidity or moisture out of the air which make us feel more comfortable.
What should I look for in an A/C unit?
If you’re buying a new A/C unit, you first concern is likely the unit’s sticker price. This is obviously important, but you should also consider a number of other factors. A unit installed properly with a higher up-front cost may actually cost you less over the lifetime of the unit, due to savings gained in your monthly power bill.
We offer six recommendations when choosing a new A/C unit:
- The cooling capacity measurement, called tonnage, tells you how much heat an A/C unit removes from a room each hour. A one-ton A/C unit removes 12,000 BTUs of heat in an hour.
- Square footage helps determine the size unit you need. One that’s too large wastes money. One that’s too small won’t properly cool the area and has to work harder, shortening its lifespan and costing you more in your monthly power bill.
- Look for an ENERGY STAR-certified unit, guaranteed by the EPA to be at least 15 percent more efficient than non-certified models.
- The Energy Efficiency Ratio (EER) applies to room A/C units, and the Seasonal Energy Efficiency Ratio (SEER) applies to central air systems. Higher ratings equal higher energy efficiency.
- What kind of maintenance plan does the A/C company provide? Yearly maintenance extends the life of the unit and prevents expensive repairs. Ask about the company’s efficiency checklist, which should include checking and changing filters, as well as inspecting coils, compressors, capacitors, and refrigerants.
- Look for units with programmable thermostats, which are exactly what they sound like. You program the thermostat for specific times of day, and even days of the week, saving you money on your power bill.
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Will closing the vents in rooms I don’t use save money?
Not if your system was designed correctly. Your HVAC system design should consider flow requirements for the entire home. Closing vents negatively impacts efficiency and may increase pressure within your ductwork, leading to leakage.
Which is better, letting the A/C fan run continuously, or using my ceiling fans?
It’s more economical to set your A/C to Auto and run your ceiling fan in whatever room you’re in. The exception is if you have an electronic air filter requiring a continuous stream of air.
How do I ensure energy efficient air conditioning?
To limit heating and cooling costs, Isley’s recommends 12 things:
- Seal your home, including walls, doors, windows, vent fans, outdoor faucets, crawl spaces, and dryer vents.
- Install high R-value insulation to resist heat flow and reduce heat loss.
- Reduce heat transfer with advanced framing and wall construction.
- Exterior air duct sealing improves ENERGY STAR efficiency by 20 percent or more.
- Triple-pane windows help improve sealing and reduce heat transfer.
- Air sealing doors and windows with caulk or liquid/foam-applied air barriers improves efficiency.
- Indoor air quality systems warm air without using a furnace or heat pump.
- Heat pump water heaters transfer heat from the air to water in the tank.
- Energy saving lighting, such as LED lights, give off less heat and last longer than compact fluorescents or incandescent bulbs.
- Ceiling fans allow you to set your thermostat 4 degrees higher and feel just as cool.
- Thermostat settings allow you to lower the temperature while at home and raise it when away, lowering your cooling bill.
- Regular maintenance, such as changing filters regularly, improves efficiency.
Does it save energy to turn on the A/C for five-minute bursts, or is it better to set it on Auto? Which causes less wear and tear?
When you first turn on your A/C unit, it takes seven to 10 minutes to reach peak efficiency in removing moisture and hot air from the living space. Running it for short bursts means that, every time you turn it on, the unit is working overtime and never quite reaching maximum efficiency. It’s also harder on the unit.
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I usually only go up to the second story at night, since that’s where the bedrooms are. Is it okay to set the first floor thermostat lower during the day and higher at night, and reverse those settings for the second story?
You save money when you increase the temperature on your thermostat but, again, it takes seven to 10 minutes to hit peak efficiency. It’s better for the unit to run longer after reaching peak efficiency as it works to lower the temperature, especially at night, when the rates are lower (assuming you use SRP’s Time of Use plan). You should achieve a saving by adjusting the temperature. We would recommend only setting back the temperature a few degrees on the floor you’re not in for extended periods of time.
I noticed my room feels cooler when I leave the bedroom door open. Is it better to leave interior doors open?
Yes, leaving interior doors open helps air move through the home more efficiently. Closed doors cause an increase in air pressure, as the unit pushes air into the room but struggles to remove air, as the gap under the door is insufficient to maintain proper airflow.
How do heat pumps work?
Your heat pump’s job is to move hot air. During the summer months, this means pulling hot air out of the home. In winter, your heat pump pulls warmth from the outside air and moves it into the house.
Sometimes my lights flicker when the heat pump runs. Is this normal?
Some units sometimes do cause lights to dim, as they draw more current when they start.. This causes a drop in voltage at the service panel (only for a fraction of a second), which may cause lights to flicker.
What is variable speed?
A variable speed motor starts up at a lower speed, allowing the unit to “ramp up” before moving large amounts of air. This takes advantage of the seven to 10 minutes required for the unit to reach peak efficiency, and also results in a quieter start-up.
Does my home’s square footage tell me exactly the right size A/C unit to buy?
Square footage is a good starting point when you’re looking to replace your A/C unit, but you also need a heat-load calculation (performed by a certified HVAC contractor) to select the right size system.
When we are away from home, is it better to set the thermostat just a few degrees higher than when we’re home, or is it okay to set it higher, say to 85 or 90 degrees?
There’s a myth that, if you set your thermostat too high while you’re away from home, the unit spends so long cooling the house once you return that you don’t actually save any money on your power bill. This is, as we said, a myth. However, if you have a programmable thermostat, you may wish to set it at the lower temperature starting around 30 minutes before you come home, to ensure the home is at a comfortable temperature when you arrive.
What is the best programmable thermostat?
This is more a question of which thermostat is best for your unit, not which brand is best. Ask your HVAC contractor for a recommendation on the model your system needs. From there, you can select the best thermostat based on your programming requirements. There are three main types. The 5-2 model lets you set two temperature schedules, one for weekdays and one for weekends. The 5-1-1 model lets you choose three schedules, one for weekdays, one for Saturday, and one for Sunday. Finally, the 7-day model lets you create independent settings for each day of the week.
What type of air filter should I use?
If you have tight ductwork free of leaks, you can use the high-efficiency air filters without harming your HVAC unit. It’s important to note, though, that these add resistance and may actually reduce efficiency if your filter size is too small for the capacity of your system or if your ductwork has any leaks. We recommend if you’re using a high efficiency filter to have 200 square inches of filter area per ton of air conditioning. For example if you have a 3 ton system, with a 20×30 filter, you would have 600 square inches of filter area which should be sufficient for the 3 ton system.
How often should I change the air filter?
The fine dust common in the Valley requires regularly changing your air filter, preferably every month, but definitely every two months. A good schedule is changing the filter every time you make your mortgage or rent payment.
Will shading my A/C unit lower my power bill?
If you do it properly, you may notice a slight difference in energy consumption. Doing it improperly blocks airflow, resulting in increased energy consumption. Any shelter built around your unit must leave at least 12″ on all sides, with a 30″ clearance at the access panels. You also need at least 5′ clear at the top of the unit.
If you’re looking to lower power bills, strategically planted trees and shrubbery offer a greater impact.
Is there any way to tell how much running my A/C actually costs?
You can’t get an exact figure, but you can get an estimate. March is the time of year in the Valley that requires no heating or cooling. Subtract the amount of your March power bill from the amount of your summer bills to determine how much your A/C costs.
Do the dust storms we get during monsoon season harm my A/C unit?
Ah, the haboob. Decades in the Valley, and it’s only in recent years that these seem to be a thing. Yes, they can damage your A/C unit and definitely make it work harder due to clogged coils and filters. Change your filter every 30 days during summer months. Also, use your garden hose to spray the outer unit. You can do this whenever you change the filter. At the same time, make sure there are no obstructions and look at the fan blade fins. If they’re bent or damaged, they won’t function properly, so straighten them.
Cleaning the indoor coils requires the attention of a professional HVAC tech and should happen at least once a year, during regular maintenance.
What should yearly A/C maintenance include?
In a perfect world, your A/C tech provides a detailed performance report, including weak spots and any damage found during inspection. He or she should also:
- Check refrigerant levels (too low indicates a leak)
- Check electrical components, wires, circuits, and controls
- Check voltage and amperage
- Check evaporator coils and condenser
- Lubricate motors and bearings
- Inspect and adjust belt
- Inspect duct seal and panel
- Inspect blower and outdoor motor
- Check temperature splits
- Test thermostat operation
- Run and test the entire system
