Regular HVAC maintenance keeps your HVAC system performing efficiently and delivering conditioned air everywhere you need it. The nature of HVAC maintenance changes depending on the season, however. Here’s what you can expect throughout the year.
How to Do HVAC Maintenance All Year
Different parts of the system require different maintenance depending on the conditions they’re exposed to, explains Todd Tewksbury, associate and senior mechanical engineer for Bala Consulting Engineers. Here are some of the maintenance tasks you’ll likely need to schedule on the different components of your HVAC system, though note that you should follow the manufacturer’s recommendations for how and how often to do maintenance on each part.
The coils and tubes in your HVAC equipment are responsible for heat transfer during both heating and cooling seasons. Heat is transferred out of your space during the summer and into your space during the winter via the fluid flowing through your coils. Dirty equipment won’t transfer heat and energy quite as well, so cleaning is the name of the game when it comes to annual coil maintenance.
Air-handling units should have their chilled water and hot water coils cleaned annually, Tewksbury explains.
“Rooftop units and condensing units are a little different because these units are typically outdoors,” Tewksbury adds. “For rooftop units, you want to clean the evaporator coils. You’ll clean the condenser coils for both rooftop units and condensing units.”
For condensing units, this involves spraying the condenser coils (which are exposed to unfiltered outdoor air) with a microbial treatment that will prevent microorganisms from growing on the exposed coil.
You may need to clean more often than annually if your location demands it — for example, a building near a tree line that results in leaves getting trapped in the equipment.
“Tubes are very similar to coils in that they transfer heat,” Tewksbury explains. Pull out tubes annually to check for clogs and remove all of the debris — it can decrease your equipment’s capacity and efficiency.
Plate and frame heat exchangers should also have their plates cleaned and the gasket replaced. Make sure nothing is clogging the space between the plates.
Tewksbury recommends cleaning tubes in the winter because chillers won’t be operating as much. “Typically you might have one operating at partial load in the winter, so you can always service the other one while one is operating and vice versa,” Tewksbury explains.
[Related: The 4 C’s of HVAC Systems]
Checking controls annually will ensure that your HVAC system is running properly, Tewksbury says.
“Temperature sensor and thermostat calibration is one area you definitely want to focus on,” he adds. “Say the cooling setpoint of the space is 75 degrees F., but your thermostat is miscalibrated by 2 degrees. Therefore, in the summer, when your space is 77 degrees the thermostat is going to think you’re satisfied. You want to calibrate these every year.”
Control calibration tends to drift gradually, Tewksbury adds, so periodic checkups are crucial to maintaining accurate operation. In addition to the main HVAC system, Tewksbury also recommends checking the controls monitoring the temperature on heat tracing and other auxiliary equipment. The setpoints on heat tracing can drift just like the setpoints on any other controls.
“Fans, as we all know, are chief components of many pieces of HVAC equipment,” Tewksbury says. Many pieces of HVAC equipment incorporate fans, and they need to be maintained quarterly for maximum longevity. Tewksbury recommends concentrating maintenance in three key areas.
1. Wheels. “The first item you want to look into for increasing the longevity of a fan is a dirty wheel,” Tewksbury says. “That will put a lot of stress on the motor and reduce the airflow. It may also cause the fan to wobble, which puts a lot of stress on the bearings and causes noise issues.” He suggests vibration monitoring, which can reveal whether you have worn bearings that may be a symptom of something else.
2. Belts and belt tension. Belts that are too loose will slip, and belts that are too tight will stress the motor and bearings, Tewksbury says. Inspect the belts quarterly to make sure they’re not cracked or worn.
3. Bearings. Make sure your bearings are lubricated properly to reduce friction and corrosion, Tewksbury says.
Many pieces of your HVAC system also incorporate filters, Tewksbury says. Clogged filters increase the pressure drop in your HVAC system, making your fan work harder to maintain the same airflow (and ultimately reducing the airflow once your fan is working at maximum capacity). Tewksbury recommends a quarterly cleaning for most filters, unless you’re in an area with higher-than-average particulates, such as high-pollen areas.
“As we increase the total pressure as our filter gets clogged, our operating costs increase more and more,” Tewksbury says. “By adding an inch of static pressure, it’ll increase the operating costs of these units by almost $3,000. If you have multiple units, that adds up.”
Strainers filter water in HVAC systems rather than air. Like air filters, a clogged strainer will increase the pressure drop in your HVAC system. For coil strainers, Tewksbury recommends a blowdown process to flush debris out of the strainer so that you don’t have to isolate and drain that one piece of equipment.
Optimize Your HVAC System for Every Season
In addition to regular maintenance, every season brings opportunities to fine-tune your HVAC system for maximum efficiency. Go beyond simply keeping up with maintenance and actively look for places to improve in every season.
Spring and fall should trigger your team to review the sequence of operations for morning warmup and cooldown, Tewksbury says. Make sure that in the summer, your outdoor air damper is closed so you’re not trying to cool down hot outside air during morning cooldown. The same is true for winter—you don’t want to try to heat the subzero air from outside during morning warmup.
“You only have to heat to 65 degrees F.,” Tewksbury explains. “Once you bring the space back up to 70 degrees in the winter or back down to 75 in the summer, you can open up the outside air damper and allow the code-required amount of outside air to enter the system.”
Does your building have an economizer? Both the air-side and water-side models can save a lot of energy through a phenomenon called free cooling, Tewksbury says. Air-side economizers provide free cooling by bringing in outdoor air during mild or cold weather. Water-side economizers exhaust waste heat from chilled water without activating your chiller or other mechanical cooling equipment.
“The shoulder seasons are when you want to utilize your economizers,” Tewksbury says. “During these seasons, you can use 100% outdoor air to cool the building if the humidity levels are right.”
The two shoulder seasons are also the best time to reset your airflow pressure and discharge air and water temperature.
“You want to allow the temperature to drift up to reduce the mechanical cooling that’s required. This reset will increase the amount of time you can run free cooling,” Tewksbury says of the discharge air and water temperature. “When we’re in cooling mode above 80 degrees F., we want to maintain that chilled water at 44 degrees. But when we drift below 80 degrees, we want to allow that water to drift up. We’ll typically do it linearly between 80 and 60 degrees and allow the water to drift as high as 54 degrees. Once all the spaces are satisfied and the dampers or coils are 100% open, we’ll drift back in the opposite direction.”
Pressure reset is a similar strategy, but for air-side equipment, Tewksbury explains. Reduce the demand on your mechanical HVAC to reduce the pressure in the duct system, which will save some energy during the shoulder seasons.
Snow entrainment prevention is a key issue for winter. It’s an especially big issue in colder Northern climates, Tewksbury says. Snow entrainment is most prevalent in 100% outdoor air units and occurs when the unit’s supply fan pulls in snow that clogs up the filters, causing the motor to work harder, reducing air flow and increasing operating costs.
Once it happens, the only thing you can do to fix it is to get out a shovel, shut down the unit and shovel it out, Tewksbury says. However, there are a couple of solutions to stop it from happening in the first place.
“One solution is to put a heating coil upstream of your filter. It could be any heating source—hot water coil, electric coil, steam coil or a gas burner,” Tewksbury says. “Another thing you can do is bypass the filter, meaning that your air’s not going to go through the filter, it’s going to go around it. The downside of that is that you’re going to have unfiltered outdoor air during snowy seasons, but it’s a lot better than clogging up your filters and having to maintain those all the time.”
Thermostat locations should be a one-time fix unless you remodel your space. A thermostat that’s exposed to direct sunlight will consistently read your space as too warm and overcool the space, for example.
“Make sure all your thermostats are away from computers, refrigerators, cooking equipment and anything that could generate heat,” Tewksbury says. “Also, make sure your thermostats are away from any diffusers—in the summer, if your thermostat is right in front of a diffuser, it will think the space is cool but the space will tend to be hotter than it should be.”
Moisture prevention is an area to monitor year-round, Tewksbury says. Condensing boilers and dishwashers release the highest volume of moist air, he explains; both need to vent hot water vapor, which will be a problem in any season. The moist air will condense on cool building windows in the summer just like moist air condenses on a soda can; in the winter, the moist air will escape from the building and freeze as soon as it finds a surface that’s below the freezing point, potentially creating icicles down the length of the building that can fall off and hurt people.
HVAC maintenance can be time-consuming, but it’s a critical piece of the efficiency puzzle. Maintaining an energy-efficient building that’s comfortable and reliable is exactly the reason why HVAC maintenance is important.
Four Seasons of HVAC Noise Complaints
You’re not just risking money when you don’t stay on top of HVAC maintenance—you’re likely to end up with noise complaints as well. Here are some of the culprits that are likely to produce the most complaints.
HVAC operation typically consists of a few outdoor air-cooled condensers running but most of them shut off, says John Hauenstein, principal of Cerami & Associates. This can cause noise complaints from neighbors who desire to have their windows open.
Spring is a good time to perform regular maintenance on this equipment before summer comes. Make sure your condenser coils and air handler filters are both clean, Hauenstein recommends.
“If the coils and filters are dirty or clogged, the equipment will work harder and become noisier,” Hauenstein explains.
The more extreme temperatures of summer require buildings to run more air-conditioning units and run them more frequently, Hauenstein says. “You have this cumulative effect from many air conditioning units, and in some buildings the outdoor space becomes virtually unusable because nobody wants to be sitting outside with the sound of noisy fans and air conditioning equipment,” Hauenstein explains.
There are potential solutions that don’t involve shutting down your HVAC equipment, he adds. Quieter equipment selections, as well as barrier walls, enclosures, and silencing devices can reduce the noise, providing your tenants with the environment they need.
Fall is peak HVAC complaint season for a couple of reasons. Most people will have their air conditioners off, but any unit that is still running sticks out among the silence like a sore thumb, Hauenstein explains. Even though the background noise is generally quieter, it’s hard to ignore the one unit that’s still running.
Another fall HVAC complaint cause is related to the beginning of the heating season. The presence of standing water in steam heating pipes will immediately turn to steam as soon as the boiler starts pushing hot steam through the pipes, and the flashing of water into steam creates a disruptive knocking sound, Hauenstein says. This condition usually subsides as the weather gets colder and the heat stays on more regularly, but it may require re-pitching of the pipes to allow for the draining of water between heating cycles.
“In winter, when the boilers are in use, we’ll see actual boiler noise issues rear their heads,” says Hauenstein. This manifests itself in two key ways:
1. Some apartment building managers might find that the new high efficiency boilers they installed over the summer are noisier than the old ones. This especially affects the apartments closest to the boiler.
“Sometimes that problem can be mitigated by having the boiler maintenance company come in and make tweaks to the operation of the boiler or the burner that generates the steam or hot water,” Hauenstein says. “Sometimes it also requires a more detailed look at how the boiler and connected pipes attach to the structure. Oftentimes the noise that one hears is vibrational energy that comes out in an apartment or residence as noise. We can pinpoint where the vibrational energy is transmitting and can make recommendations for how to better isolate that energy to keep it out of the apartment.”
2. Boiler rooms often require an influx of outdoor air to assist with combustion. The fan that delivers that air can create noise that can travel up through a building’s courtyard and disturb occupants. If this is the case for your building, you’ll need to call in a consultant to recommend ways to silence the fan noise, Hauenstein explains.