Everything you need about an air handler

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Last updated: 
December 29, 2015

Also known by the name of air handling unit, this device was designed to circulate and control air through air conditioning, heating or ventilation systems. The metal box of an air handler unit usually comprises cooling and heating elements, a blower, dampers and filter racks. Most of the times, air handlers are linked to the ductwork ventilation system, which is in charge of distributing the air in the entire house before taking it back to the air handling unit. Air handlers are usually installed in well ventilated areas where the device is kept away from humidity and condensation. If you were planning to place your air handler in attic, you might want to reconsider your choice. In the event of the air handler leaking water, you could find your entire house flooded and a hole in the roof of your bedroom.

What is an air handler?

Air handler partsA structured framing system, an air handler can be used locally, comprising only a blower, an air filter and a coil. These types of air handlers are known as terminal units. Larger air handlers do not condition recirculated air, but only outdoors air. These are also called makeup air units. An important part of the air conditioning system, the air handler is in charge with circulating conditioned air throughout your home.

Types of air handling units

Since homeowners and building owners have different needs regarding the rooms to be cooled down in the summer or heated up in the winter, there are a few types of air handling units on the market to choose from.

  • Insulated air handlers target silent heating or cooling operations.
  • Hydronic air handlers were especially created to work with boilers.
  • Single speed air handlers have a self-explanatory name. The fan motor behind them works at a single fixed speed.
  • Five speed air handlers are preferred to single speed air handlers because they provide an increased operation precision. As a rule, if an air handling unit comprises several speeds, it will be more effective in circulating the air through the rooms of your house or building, and the process will be more silent and efficient.
  • Air handlers with variable speeds boast several essential functionalities. The built-in blower motor sports variable speeds, which guarantee precision in meeting all the requirements of the homeowner. The settings involve several adjustments for humidity levels, consistent temperatures or air quality.

Differences and similarities between a furnace and an air handler

Furnaces generate heat for a house or a building by burning fuel. They distribute the resulted heat throughout the rooms via ducts. In comparison, an air handler will blow either cool or hot air in the building via ducts. The two devices look the same, which makes many people mistake one for another. But their uses, specifications and applications are different. The biggest difference consists in the heating system they use. Generally, furnaces will work on heating oil, liquid propane or gas. On the other hand, air handlers are commonly paired with an electric heat pump.

Type of air handling unitA quick look at the structure of a furnace easily sets it apart from air handling units. Furnaces comprise four essential parts: the combustion chamber (also known as the burner) where the furnace burns the fuel; the vent, which discards carbon monoxide outdoors; the heat exchanger, which transfers the heat produced by the burner to the air supply of the building; the blower, which pushes the hot air in the house via ducts. If the furnace uses heated water within steam pipes instead of hot air through ducts, they are generally called boilers.

Working with a heat pump, air handlers use refrigerants to transfer heat energy from point A to point B. The blower of the handler will push air in the entire house, with the refrigerant lines running in the air stream. In the summer, the refrigerant will do the exact opposite: it will extract heat from the air, transferring it outdoors. This way, the air handler will cool down the building by blowing cool air inside. In the winter, the same refrigerant will pull heat energy from the outdoors air, transferring it indoors and heating the rooms with warm air. However, the air handler doesn’t cool down nor does it heat up the air, but it simply pushes it through the refrigerant lines that are in charge of switching between temperatures. This constitutes the major difference between a furnace and an air handling unit.

A thing that furnaces and air handler have in common are filters. When using either one of these devices, the quality of the air is maintained by employing filters to trap impurities and dust from the air. As long as filters are changed on a regular basis, the devices will work flawlessly. Furnaces and air handler units are both constantly incorporating outside air into the flow of air passing through the building. Another similarity between the two devices is that they are controlled by a thermostat.

In-depth look at air handler components

  • Components if an air handlerFilters – essential for keeping germs, allergens and dust at bay, filters come in a wide range of designs to choose from. Pleated or electrostatic? Factor in the environment and your budget. Filters are the first barrier used in air handler units because they are the best allies for keeping the vital components clean and dust-free. Sometimes, a single row of filters is not enough, so you’ll need to double or even triple the filter barrier. The first row usually comprises panel filters, which are inexpensive and extremely easy to maintain or replace. It’s not complicated to assess the state of a filter using a pressure gauge. Changing filters shouldn’t be neglected, since it could lead to further damage to other essential components of the air handler unit, allowing dust to reach the ductwork.
  • Humidifier – cooling down or heating up a room is bound to suck out all the moisture in the air. This can give rise to a slew of disadvantages, with complicated side effects for children and elders who have a weaker immune system or for people struggling with asthma. The uncomfortable quality of the air can cause dry eyes, sore throats, dry patches on the skin and allergies. There are several types of humidifiers that can be implemented in an air handler unit. Spray mist humidifiers diffuse water through a nozzle, allowing the air to carry the droplets. Vaporizers will take vapors or steam from a boiler and push it into the air stream. Evaporative humidifiers blow dry air on reservoirs, which results in evaporated water. Ultrasonic humidifiers employ a water tray that is transformed into fog with an ultrasonic device.
  • Fan or blower – comprising a squirrel cage blower, this is in charge with moving air with the help of the air conditioning unit. The blower or the fan will work at a single speed or it will provide various speed settings. Most of the times, flow rates will be controlled through dampers or vanes. It is not uncommon for large commercial buildings to use multiple blowers situated at the end of the air handler units. When additional power is needed, the blowers can be supplemented by installing fans within the return air duct. These are in charge of pushing the air back into the air handling unit.
  • Balancing – one of the biggest problems encountered by unbalanced fans are wobbling and vibrating. It’s easy to see why this could be a nuisance for homeowners, not only from the point of view of noise levels. Efficiency is affected, while air flow can be severely restricted at the vents. The integrity of the whole system is also endangered, with tear and wear threatening to compromise the unit. Special balancers will take care of all the above mentioned issues, keeping the fan in place and ensuring a smooth spin.
  • Heat recovery device – used to cut back on energy costs as well as increase capacity, heat recovery devices include different types. The recuperator comprises several metal or plastic plates, which are linked with air paths. Spaced six millimeters apart, the plates transfer heat via the airstreams from one to the other. The rotary heat exchanger, also known as the thermal wheel, comprises a rotating matrix that works in both airstreams. For the heating mode, the matrix absorbs the heat in the first half rotation, only to release it in the second half. For the cooling process, the same steps apply, with the only difference that heat is released.
  • Controls – the control buttons provide adjustments for every single feature of the air handling unit. The supply and mixed air temperature, the humidity levels, the quality of the air, as well as the air’s flow rate are a press of a button away.
  • Vibration or sound isolators – air handler blowers are anything but silent. The vibration and the noise could easily be transmitted in the entire building through the ductwork. To keep noise at bay, manufacturers implement vibration and noise isolators, separating the fan compartment from the rest of the components of the air handling unit. Made out of a rubberized material that resembles a canvas, the isolator doesn’t allow the sound and vibration to pass further into the ducts.

Image sources: 1, 2, 3.

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