To cover all the air handler parts and accessories I would have to write a book, especially considering all of the new communicating systems that are out there. This is supposed to be Hvac training for customers to learn more about their components of the split air conditioning system. To learn more about the condensing unit components check out my post here.
I am not going to get into the ins and outs of these fancy new communicating systems and variable speed motors and modules, but just go over the basic parts and accessories that will find in your central air conditioning air handler, which is almost always located indoors.
So lets first go over the basic air handler parts located in your residential central air conditioning system.
Evaporator Coil– Next to the compressor, this is usually the most expensive part to get replaced should it go bad. And by go bad I mean that the evaporator coil is leaking refrigerant, which is very common for Trane copper coils made from early 2000-2010. The evaporator coil is where the inside part of the heat transfer takes place, and any obstruction such as dirty filters or dirty coils will reduce the efficiency of the unit as a whole.
Condensate Drain Pan – The drain pan catches the condensate that falls off the evaporator coil, which then directs the condensate to piping that goes either outside or a sewer system. Drain pans can be a semi-expensive repair if they get cracked and start leaking water as usually the evaporator coil will have to be removed for replacement of the condensate drain pan.
Metering Device – TXV or Piston
Metering devices are usually mounted inside of the air handler on the suction line. There are two typical types, which are the more reliable fixed piston metering device, and the TXV or TEV, which meter the refrigerant more efficiently but fail way more than a piston metering device does. Unfortunately nearly all the new split residential air conditioning systems come with a TXV metering device.
Blower Motor and Wheel – Newer, high SEER rated systems have variable speed motors, along with a module, controlled by a computer board, and computer signals, and all sorts of other safety and efficiency features that give us technicians headaches. But basically in simple terms you have a motor and you have wheel, which is inside what us Hvac Technicians call a squirrel cage, and its job is to suck in the hot or cold air inside of the residence.
Transformer – On residential units the transformer is almost always located inside of the air handler. It’s main purpose is to take high voltage 208-240 and make it into 24 volts. 24 volts in air conditioning is used as a control voltage, such as thermostats, safety switches and such. It’s good practice to always make sure these are protected by a 3-5 amp fuse, so if you get a low voltage short it blows the fuse and doesn’t fry the transformer. In the picture this fuse is on the blower motor relay board.
Blower Motor Relay – Controlled by 24 volts and contacts are normally open, when 24 volt power is applied the contacts close making a high voltage connection. These can look like little black switches with 4 or more spade connections or they could be a small like computer looking board such as the one pictured.
Thermostat – Essential to be able to regulate the temperature to your desired comfort. These days there are thermostats that can control humidity, be programmed to turn off when you go to work and turn on when you get home, to being able to be regulated from thousands of miles away through an internet connection. In the near future I will be dedicating an entire post to Hvac thermostats trying to cover every aspect possible.
Accessories for Your Air Handler
Electric Heaters – Electric heat will consist of one or more heating elements, along with a contactor or some type of relay to control when the heating elements are to engage. Other types of relays may be involved in electric heating also such as sequencers, and also involve safety devices such as temperature limit switches which will shut the unit off by breaking the electrical connection if the elements get to hot.
Water Safety Cutout Switch – In the event that your condensate line gets clogged, or your condensate drain pan gets cracked or warped, instead of the condensate pouring over onto the floor or ceiling, the water safety switch will cut off the 24 volt supply which will turn the unit off, preventing further damage. Water safeties come in many different varieties, from the super efficient water gards to the less reliable SS1 float switches. Either way its always good (and code in most cities) to have a primary and secondary water safety cut out switch.
Ultraviolet Lighting – Studies have shown that the air outside is up to 10 times cleaner than the air inside our homes that is constantly being recirculated. One reason for this are the UV rays from our sun do a great job of neutralizing airborne bacteria and viruses. By putting a UV light in your air handler or duct work, its almost like having a mini sun in your home doing the same thing by purifying the air inside of your home. These lights are so powerful though, if you look at them while they are on, they can damage your vision or even blind you, just as if you were staring at the sun.
High Efficiency Air Filter Boxes – For those that are concerned about air quality high efficiency filters that are longer in width provide more filtering capacity without restricting air flow compared to the purple ones you get at home depot. Basically there is a slight duct work modification that must be done right before the return grill if this was a modification you or your customer may be interested in.