HVAC Systems Design

Managing Bacteria and Viruses in Buildings With HVAC Systems Design

Heating, ventilation, and air conditioning (HVAC) systems play an essential function in buildings since they not only provide comfort but also assist to maintain a healthy interior environment. A building with damaged HVAC systems is not only uncomfortable but also dangerous to one’s health. Indoor environmental quality is also cost-effective for businesses, as comfort and health enhance productivity.

One advantage of a well-designed HVAC system is that dangerous organisms such as viruses, bacteria, mold, and dust mites are better controlled. Building owners must ensure that these creatures are kept under control since they have a negative impact on air quality and human health. The US Environmental Protection Agency advises a relative humidity of less than 60%, ideally between 30% and 50%, to optimize IAQ.

The percentage of water in the air in relation to the maximum quantity the air can retain is known as relative humidity. Because warm air can store more humidity than cool air, 50 percent relative humidity at 90°F is higher than 50 percent relative humidity at 65°F.

How Air Humidity Helps to Reduce Virus Infections

When the air is dry, viruses like the common cold and influenza spread more quickly, and the Wuhan coronavirus is no exception. Viral infections are more prevalent in cold and dry conditions for various reasons:

  • When there is low humidity, airborne particles, including viruses, stay in the air longer.
  • The mucous membranes that protect the human respiratory system dry up under low humidity, making viral infections more common.
  • The spread of viruses is unaffected by cold temperatures. Cold air, on the other hand, contains less moisture, resulting in the two consequences outlined above.
  • During cold weather, people will stay indoors, and diseases transmit more quickly when people are in close quarters.

The Centers for Disease Control and Prevention (CDC) investigated the impact of atmospheric humidity on influenza virus infections. 70-77 percent of flu virus particles remained active an hour after being coughed into at 23 percent relative humidity. Only 14 percent of flu virus particles remained alive after one hour at 43 percent RH.

During the winter, space heating systems can dry up interior air, allowing viruses to spread more easily. Building owners should ensure that their HVAC systems manage both temperature and humidity. Insensitive applications such as healthcare and retirement homes, further humidification procedures may be required.

Increased atmospheric humidity aids in the prevention of viral transmission. Too much humidity, on the other hand, is not a good thing since it has additional detrimental impacts on IAQ.

Indoor Air Quality and Health: The Negative Effects of High Humidity

Dry air allows particles to remain in the air for longer, increasing the risk of viral infections. Humid air, on the other hand, promotes the growth of germs, mold, and dust mites. These organisms have a detrimental influence on occupant health and indoor air quality:

  • Many bacteria species, like viruses, are pathogens that cause health problems.
  • Mold spores cause allergic responses and destroy furniture and other building materials. When asthma sufferers inhale mold spores, their symptoms may worsen.
  • Dust mites can also trigger allergic responses in general, as well as asthma flare-ups.

30-50 percent relative humidity is recommended by the US Environmental Protection Agency, whereas 30-60 percent RH is recommended by ASHRAE. Because both dry and humid air have negative consequences, these intermediate limits have been established.

When relative humidity is lowered to the ASHRAE recommended range, mold and dust mites die. Filtering the air is still necessary, though, because dead mold spores and dust mites can trigger allergic responses. A vacuum cleaner with a HEPA filter, which catches 99.97 percent of particles with a diameter of 0.3 microns, is suggested.

How to Effectively Control Indoor Air Humidity

An enthalpy wheel in an energy recovery ventilation system (ERV) may interchange humidity between the outside air source and the exhaust air. This sort of ERV system can adjust humidity levels as needed:

  • When the building’s outside air is humid, the exhaust air can help to remove some of the moisture via the ERV system.
  • When the outside air is dry, the ERV system recovers humidity from the exhaust air, which has the opposite effect.

Thermal comfort is linked with space heating and air conditioning systems, although they can also give some control over air moisture. Greater humidifiers and dehumidifiers give you more control, but they use a lot of energy. They’re only useful when HVAC systems can’t get to a comfortable humidity level on their own.

Reasons to Contact an Air Conditioning Repair Company

Reasons to Contact an Air Conditioning Repair Company

After years of heavy use, air conditioning repair has to be necessary. You may have noticed that they have stopped working and have survived their useful lives. Their useful life has come to an end, and you may need to repair them with newer, more energy-efficient ones.

In certain situations, an Air Conditioning repair service would suggest you fix the appliance rather than replace it in order to save money. The reason why the air conditioner isn’t cooling the space is typically known to trained experts. Read on if you’re not sure why you should call an HVAC contractor in the first place.

1. The air conditioner isn’t properly cooling the room.

The air conditioner is one of humanity’s most brilliant technologies. On a hot summer day, it may rapidly lower the temperature. You can feel comfortable even if the day is oppressively hot, and you can get a better night’s sleep. However, after a few years, there’s a good possibility your appliance may start blowing hot air. If your unit is blowing hot air, it’s an indication that the compressor is broken and has to be repaired. Because the compressor may not be the only issue, it’s best to get your appliance inspected by a specialist. It might be caused by a blown fuse or a broken compressor. In any case, a fast reaction through appliance repairs will prevent more problems from arising. Allowing the problems to grow will only make them worse, potentially necessitating more costly air conditioning repairs in the future.

2. Automatically shutting off

When your air conditioner goes off without the power button being touched, you could assume a ghost is messing with it, but this is a symptom of malfunction. It might be an indication that your filters have gathered a lot of dirt and debris and need to be thoroughly cleaned or replaced. Be aware that the filters might restrict airflow in your unit, affecting the evaporator coils. This is why the air conditioner may turn on and off several times throughout the day. It’s essential to have the best expert on hand to see what’s going on and make sure that this minor problem doesn’t turn into something more serious down the line.

3. Increased Humidity Levels in the House

The air is naturally warm and humid in the summer. When you turn on your air conditioner, the excessive humidity levels drop a notch. There’s the temperature control, which effectively removes humidity and makes you less uncomfortable. Call the professionals for a maintenance check-up if the room is still humid despite turning on your appliance.

4. Make Loud Noises

When the compressor starts to chill the air inside the room, the window kind of makes a modest noise. Split-type air conditioners are usually efficient and quiet when in use. It might be the result of broken components or damaged internal systems if it suddenly gets noisy outside. If left unchecked, this can lead to additional deterioration and the need for significant part replacement. To ensure that your equipment is not destroyed, contact a service provider.

5. Low Airflow

If your air conditioner is straining to chill the room, this might be an indication that the filters are becoming clogged. Filters and ducts should be maintained on a regular basis, and HVAC contractors in your region should be able to do so. When the ducts and vents are clean of twigs, dirt, debris, mildew, and dried leaves, airflow should never be an issue. Clean them up today and take in some fresh air.

Other Reasons to Contact an HVAC Service provider

When you first notice that the air conditioner isn’t cooling the room properly, you should call a repairman. This problem will only get worse over time, and it will not be remedied on its own. It’s also important to schedule regular maintenance for your units since technicians have the necessary skills, equipment, and expertise to remove any debris, filth, mold, or algae that may have gotten inside the appliance. Turn off your air conditioner and call a technician right away if you hear gurgling, hissing, or screeching noises. A hissing sound might indicate that a refrigerant is seeping out of control. The screeching indicates an issue with the fan motor belt, which may need to be replaced if it is too worn out. Gurgling indicate low refrigerant levels, which need a refill. Even if they follow air conditioning repair advice from videos and publications on the internet, many homeowners are unable to remedy these issues.

If you find that your split-type unit is leaking water, you should contact an HVAC provider immediately. While condensation is normal in certain systems, know that it will drop into a particular tray and ultimately drain away. When you ignore the drips, you run the risk of harming neighboring equipment and being electrocuted by live wires. If the water is overflowing, it’s probable that the drain lines or pans are clogged, and they need to be serviced as soon as possible. Also, keep in mind that an unclean unit might harbor germs and allergies, so you should take care of your appliance for the sake of your entire family’s health.

Commercial Building Heating and Cooling HVAC System Configurations

Commercial Building Heating and Cooling HVAC System Configurations

HVAC systems loads usually constitute the biggest energy expenditure in commercial buildings. Buildings in the extreme north or south of the planet often have substantial heating costs, whilst those in the tropics may require air cooling all year.

Commercial buildings, like residential structures, have a wide choice of heating and cooling choices, each with its own set of benefits and drawbacks. The following are three of the most often utilize commercial building HVAC systems:

  • Variable-air-volume (VAV) systems with a rooftop unit.
  • Systems for chillers, cooling towers, and boilers
  • Water-source heat pumps with a cooling tower and boiler.

1) Packaged Rooftop Unit with VAV System

A condenser for air conditioning and a gas or electric boiler for space heating is basically included in package rooftop units (RTUs). In areas where the unit must offer air conditioning with low outside humidity, an economizer can be added to lower the condenser’s cooling demand. Fans are used to blast air into a duct system that distributes it throughout the various interior zones in all modes of operation.

  • Each zone includes a variable-air-volume (VAV) box with a damper that opens and shuts based on cooling or heating requirements.
  • The location of the damper is determined by the temperature setpoint of each zone. For example, if a certain zone demands maximum cooling or heating output, the damper will fully open.

When all building zones are under partial load with their dampers half-closed, duct pressure rises and the system may become loud, reducing the efficiency of traditional VAV systems. Furthermore, the excess pressure equates to wasted fan power. However, using automation and variable frequency drives, it is possible to get outstanding results:

  • The condition of all VAV boxes is continually monitored by a control system. At least one of them should be fully open; otherwise, there is a waste of fan power.
  • If none of the dampers are entirely open, the fan speed is lowered and all dampers are gradually opened until one is entirely open.
  • The fan is now producing precisely the proper amount of airflow for the current HVAC systems load.

When fan speed is regulated using a variable frequency motor, significant energy savings can be realized. In general, fan power is related to speed cubed — a fan running at 90% speed uses only around 73% of the energy it would need at full speed. The reduction of noise is another advantage of speed control.

Given that air is the primary channel for transporting heat, VAV systems with packaged rooftop units are practicable in facilities with a significant rooftop area in relation to their inside floor size. Due to the restricted rooftop surface and great vertical distances involved, these systems are not practicable in multi-story structures; systems based on water-cooled chillers or water-source heat pumps are preferable in these situations.

2) Boiler and chiller with cooling tower

Water circuits travel via air-handling units (AHUs) that supply the appropriate airflow for each building zone in these systems, which employ water as a medium to transport or remove heat.

  • The chiller collects heat from the building’s cold water circuit and rejects it into a secondary water loop linked to the cooling tower when it is in cooling mode. The heat is subsequently rejected outside by the cooling tower.
  • The flowing water runs through a boiler in heating mode. The majority of boilers run on electricity, gas, or oil.

Heat is transferred between the flowing water and the interior air at the AHUs in both circumstances. When the chiller and boiler share a water circuit (two-pipe system), the entire building must run in either heating or cooling mode; however, when each mode of operation has its own water circuit (four-pipe system), various zones can receive simultaneous heating and cooling. A four-pipe system is, of course, more expensive due to the fact that the pipes and accessories are effectively doubled.

Control and automation, like VAV systems, can result in significant cost savings:

  • Variable-speed compressors are used in modern chillers, allowing them to run effectively even when the chiller is only partially loaded. To increase efficiency, some versions integrate speed control with the staged operation.
  • Cooling tower fans, water pumps, and air-handling units are all examples of system components that might benefit from variable speed drives.
  • Economizers for water-cooled systems are also available, but they are only applicable in certain temperature zones. Where the system would offer air conditioning with low outside humidity.

Chiller-based systems are typically more efficient than VAV systems, and they are also more practical for multi-story buildings: instead of having multiple packaged rooftop units, the system can be consolidated into a single chiller and cooling tower, with only the cooling tower required to be located outdoors or on the rooftop.

3) Cooling Tower and Boiler with a Water-Source Heat Pump System

In terms of adaptability and energy efficiency, commercial HVAC systems based on water-source heat pumps are the better option. Heat pumps, like air conditioners, operate on the refrigeration cycle, but they are reversible; when numerous heat pumps are employed to service different regions of a business building, they may convert between cooling and heating modes as needed.

  • All heat pumps in a building share a common water circuit, and depending on the demands of each zone, they will either reject or absorb heat.
  • Equal heating and cooling loads balance each other out since the water circuit is share.
  • A cooling tower is used to reject the additional heat if the cooling demand is larger; on the other hand, a boiler is used to compensate for the difference if the heating demand is larger.

It is possible to make the system even more efficient by adding speed control to all pumps and fans utilized. Just as it was in the two prior cases. Heat pumps are among the most energy-efficient heating and cooling systems on the market: in cooling mode. They may match or exceed the efficiency of a chiller, and in most situations. They can offer space heating with less than 40% of the energy used by a resistance heater.

The requirement to construct a specialized heat pump for each building zone raises the expense of these systems. But the higher energy efficiency compensates for this in the long run. When cooling and heating loads are equal, for example. This system can function with both the boiler and cooling tower off.


HVAC systems configuration is one of the most important design options in a commercial building. These HVAC systems account for a considerable amount of long-term ownership expenses. Low-rise buildings with plenty of rooftop space tend to use packaged rooftop units with VAV systems. Whereas multi-story structures prefer chillers or water-source heat pumps.

Of course, there are energy efficiency improvements that may be implemented in each situation. It is more energy efficient to modulate the speed of compressors, pumps, and fans than cycling them on and off. It also adds to longer service life and lower maintenance costs.

Choosing the Best Air Conditioner Setting: AUTO and ON

Choosing the Best Air Conditioner Setting: AUTO and ON

It’s possible that what you don’t know about your air conditioner is costing you more. Especially when it comes to deciding between the AUTO and ON settings on your thermostat. Your comfort and utility cost will be affected if you make an informed selection about these settings.

Defined AUTO and ON

Let’s start with the fundamentals. There are two major thermostat operation modes on all single-stage air conditioning systems: AUTO and ON. (The term “single-stage” refers to the air conditioner’s ability to only run at one speed.) Either it’s on or it’s off when it comes to cooling your home.)

A compressor, often known as a fan, motorize component of an air conditioner that pumps warm or cooled air around your area. When the temperature reaches the thermostat’s set point, both the compressor (the portion that cools/warms the air) and the fan (the portion that propels the conditioned air) cycle on and off simultaneously when the air conditioner is set to AUTO. After your air conditioner turns on, even when the cooling or heating cycle is turned off, the fan continues continually.

Let’s move on to the advantages and disadvantages of AUTO and ON now that we’ve covered the nuts and bolts. Let’s start with energy efficiency.


  • AUTO consumes less energy than ON.

Because the fan is continually operating, the ON setting consumes more energy than the AUTO option. Using the ON option, according to one Torrent power expert, would force the fan to operate 200 hours longer each month in a home where the air conditioner would ordinarily cycle off 30% of the time. The homeowner would have to pay an extra Rs.600 per month as a result of this.

  • AUTO Controls Humidity Better Than ON

In Sarasota and Charlotte counties, humidity control is an important feature of air conditioners. The effectiveness of your air conditioner’s dehumidification is influence by the AUTO and ON settings.

Consider how beads of condensation develop on a glass of cold water on a hot day to understand how your air conditioner removes humidity from the air. Similarly, air flows across the cold surface of the evaporator (interior) coil during the cooling cycle of your air conditioner, causing moisture to gather and create droplets.

These moisture droplets trickle into the drain pan and run out of your home when the system cycles off and the coil begins to warm up in AUTO mode. When the cooling cycle turns off in ON mode, however, the fan continues to run. As the coil warms up, the air passing over it evaporates part of the moisture, allowing it to return to your house.

As a result, AUTO mode outperforms ON mode in terms of dehumidification. However, it’s crucial to remember that the thermostat setting isn’t the only thing that influences. How efficiently your air conditioner eliminates humidity. Other considerations come into play as well. Such as the size of your air conditioner in relation to the size of your home.

  • Compared to AUTO, ON improves air filtration and circulation.

ON has the upper hand when it comes to air filtering. When the blower turns on, it continuously circulates air through your AC filter. This permits the filter to capture more allergens such as dust, pollen, dander, and other particles. Some whole-house air filtration systems are more effective when there is constant air movement.

Of course, higher filtering necessitates more frequent filter replacement or cleaning. However, if you are worried about indoor air quality for health reasons, this is simply a minor disadvantage.

  • ON Can Assist You in Maintaining a Consistent Temperature in Your Home

Furthermore, in ON mode, the enhanced airflow might help to reduce hot and cold areas in your rooms. The air circulation may also help you stay more comfortable in between your air conditioner’s heating and cooling cycles. Ceiling fans or portable fans can, of course, provide a similar effect.

  • Variable-speed systems combine the advantages of both AUTO and ON modes.

Consider updating your single-stage air conditioner to a variable speed system to get the benefits of both the AUTO and ON settings. Variable speed systems modify airflow and cooling on the fly to maintain a constant temperature, removing temperature fluctuations between cooling cycles. This implies the system is virtually always on, but it is also very energy efficient. It can run at a lesser capacity and does not cycle on and off as frequently. As a result, speed control air conditioners may provide continuous filtration, adequate humidity management, and consistent temperatures while also being extremely energy efficient.