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Heating and Cooling Terms Every Homeowner Should Know
November 24, 2017, by George Li

Are you stumped by the seemingly endless terms and acronyms in the HVAC world? Check out this list of the top HVAC terms you should know. Soon, you’ll be discussing heat pumps and your home’s ACH with the best of them.

Like most building and construction industries, the world of HVAC [Heating, Ventilation, and Air Conditioning] is filled with technical terms, complex processes and seemingly incomprehensible acronyms that only the few in-the-know feel they understand. If you want to be a part of the in-crowd, we have the perfect list for you: Read below for a quick summary on some HVAC terms that every homeowner should know. Soon you’ll be impressing your family, friends, and HVAC supplier on your HVAC expertise during the holiday season!



ACH, or “Air Changes per Hour” is a way of measuring your building’s efficiency in terms of air flow. This figure measures the number of times the indoor air in a room is replaced by the HVAC system every hour. A leaky and drafty house has a high air change rate, since the air needs to be constantly replaced as it escapes out of windows and leaky walls.

The average house built today will have an ACH of about 2 – two air changes per hour. But, many efficient homes have an ACH of 1 or lower, as more efficient homes tend to be much less leaky. The lower the ACH, the less work your system has to do to keep your indoor air conditioned and comfortable.


Air Handler

An Air Handler (Sometimes called an “Air Handling Unit”, or an “AHU”) is an integral part of your HVAC system. Put simply, the air handler regulates and circulates conditioned air.

This large metal box contains a blower fan to move conditioned air around, heating or cooling elements, an air filter, sound attenuators which limit the noise your HVAC system makes, and dampers. The air handler usually connects to a ductwork system which distributes the conditioned air throughout the building, and collects old air to be reconditioned or expelled.



A boiler is, put simply, a vessel in which water is heated. In terms of home heating, boilers heat water and send that hot water throughout your home, which radiates heat outward, into your indoor air. This hot water is usually sent to your home’s radiators, which circulate the hot water and exude hot air.


Condenser Unit, Evaporator Coils, and Condenser Coils

Does your air conditioning system have a large exterior unit, sitting outside your house and shrouded in mystery? Have you ever wondered what exactly that unit does and why it’s there?

That’s your air conditioning system’s condenser unit!

The condenser unit contains numerous components: condenser tubes and fins, a compressor, a fan and copper tubing, and valves and switches. But, in short, it’s where unwanted indoor heat is expelled.

Your air conditioning system works the same way a refrigerator works: tubes of refrigerant absorb the heat from your indoor air, and send this heat – along with the refrigerant – to your unit’s outdoor condenser unit, which expels that heat outside, and sends that same refrigerant, now cooled, back inside to repeat the process.

So, instead of an air conditioner bringing your house cold air, it’s more accurate to think of your AC as removing heat from your inside air.

Your system’s condenser coils and evaporator coils help this process along. The evaporator coils evaporate the interior refrigerant, which collects heat from the air. The refrigerant then gets sent to your exterior condenser unit, where the condenser coils remove the refrigerant’s collected heat.

Many houses have separate AC and heating systems, but in a dual or hybrid heat pump system, one set of coils does double duty as an evaporator coil in the winter, and a condenser coil in the summer.



A damper is a valve or plate that stops or regulates air flow within your system’s ducts. Dampers may be automatic, or manual, and dampers can be closed to limit air flow in a specific room or area.



Ducts are to air as pipes are to water. Typically metal, they deliver heated (or cooled) air throughout a building. Think of any character of an action movie: they’re bound to have crawled through metal ducts to sneak around a locked facility.

Air conditioning units that are ductless typically need a “head” in every room or floor, which is the unit where the air is collected and dispersed. As there are no ducts to deliver the air, the location of a ductless head is extremely important, as that’s where the air is coming from!



Hopefully your furnace is a little less ominous than this!

Furnaces are a bit like boilers, in that they act as the heart of heating in a home. However, instead of water, furnaces tend to heat air and send that heated air throughout your house, in a foced-air system. Here, the heated air moves to your system’s Air Handler and is blown through your home’s Ducts and vents to heat your home!


Heat Pump

A little bit like condenser and evaporator coils, a heat pump is another way in which heat is collected and moved. Heat pumps work in the opposite direction from condenser coils: they disperse heat into the conditioned air, as opposed to pulling it away from the air and expelling it. Heat pumps are known for their efficiency, which makes them popular among green building experts.



HRV can stand for either “Heat Recovery Ventilation”, or “Heat Recovery Ventilator”. “Heat Recovery Ventilation is a process of retaining and reusing energy (in the form of heat) and reusing it. This is done by the HRV, or the Heat Recovery Ventilator, which uses a system of crossing incoming and outgoing air channels close enough to transfer heat from outgoing to incoming air.

An “Energy Recovery Ventilator” uses a similar process, but doesn’t just stop at heat. ERVS also retain moisture and humidity from the air.

There you have it – a mini crash course on all things HVAC. Welcome to the HVAC in-group!

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