What is HVAC? Get the skinny without the school.

what is hvac

Giving up heat – one example of part of an HVAC system.

You have probably seen it written just like that above, HVAC.  Maybe you’ve seen it as hva/c, or hvac/r.  I think it is evolved to that in order to indicate like refrigeration with the r or that air conditioning is two words.  For me, for you, for the building engineer industry, HVAC is fine.  And that is what we’re going to talk about today.

Ever seen HVAC equipment?

I bet you have.  If you have ever been in a plane flying over a city or in a tall building downtown, a spot where you could look down on shorter buildings.  Sometimes you’ll see metal boxes and you can maybe make out some fan blades whirring.  Or you might see some metal squares with water, fans, and steam coming out of the top.  This is all HVAC equipment.

Everybody has seen it or walked past an HVAC system (like those banks of air conditioning units at apartment complexes) they just maybe didn’t know or even really pay attention to what they were passing.  It’s cool, it’s cool.  Building engineers are behind the scenes, underappreciated people.  HVAC is one of our systems.  So don’t you worry, we got this.


What does HVAC stand for?

For me it stands for heating, ventilation, and air conditioning.  Like previously mentioned, there are some variations.  HVAC basically comprises all things that bring in, exhaust, heat, or cool, the air we breathe inside buildings and our homes.  This is my own, very basic, definition.  I’m sure as I write this, my definition of what HVAC is will evolve.

If you look at the sentence above – bring in, exhaust, heat and cool.  There are way more aspects to the systems and operation but it really is quite simple.  Also if you have been fortunate enough to read other stuff on the site, like pumps, you can see how the definition of HVAC sounds very close to that of a pump.

The difference is that pumps are using fluids while HVAC systems are moving air, or even fumes in some cases.  Of course water is involved in HVAC, but it’s primary “thing” is air.  I’ll provide some examples of HVAC equipment below.  Also, if I have already written about a piece of equipment that serves the HVAC field, I’ll link to it.

HVAC is Vital

First and foremost, HVAC is vital in building operations because it is how we get fresh air into the building and expended air out.

hvac system components

An air handling unit (ahu.)  A very small one.

Those square boxes on the roofs you see as you fly overhead, those are called air handling units, or ahu’s.  Depending on the size of the building or property, you might see 1 ahu, or 50.  The job of an ahu is to bring in an amount of fresh air continuously and deliver it either to the floor or space or to additional, smaller untis further down the line where it is heated or cooled prior to final delivery, like right above your desk.

Mechanical code requires that a certain amount of air exchanges take place every so often.  Depending on what purpose the facility has, this number of air exchanges can vary.  Hospitals for example have higher requirements because we want to get the sick stuff out of the building as quick as possible.  If we had very few air exchanges in the hospital we would be like re-circulating germy air.  Feel me?

Labs too.  They need to exhaust the fumes quicker so they may have a higher exchange code requirement.

Don’t forget about your house or car either.  They too have HVAC systems.  Your furnace at home as well as the air conditioning units in both.  Your bathroom exhaust fan…


Quick Components of an HVAC System

AHU – we already briefly discussed these just above.  AHU’s are so important that they will get their own post shortly.  But real quick, ahu’s deliver that air right?  They also run like boilers a little.  Just follow along.  AHU’s and their digital, computerized controls have gotten really advanced lately.  AHU’s have dampers that mix in some fresh air but also have other sets that will mix in some sir coming back from the building.

Why is that important and like a boiler you ask?  Because it increases the efficiency of our building or plant, or HVAC system.  We have to expend less energy to get all new air up to (or down to)  whatever temperature the tenant wants.  Awesome right?

Boilers – there is a post up on the site, a recent one, that introduces boilers. Click here for that.

Chillers – this is what cools the water which then cools the air.  For a post on how chillers use the 4 step basic refrigeration cycle, click here.

Exhaust Fans – little pieces of garbage that are supposed to draw the air out of spaces and exhaust or discharge it on the roof.  There are usually dozens or hundreds of these on properties and can be recognized from above because of the little like stainless steel domes that cover them.  These are generally not made very well, are often misaligned, and require a ton of upkeep.  I know because I am responsible for them at my current job and they suck ace.

what is hvac

Old school dx-9100 controller.

Digital Controls – these are how the components of HVAC systems communicate with one another and know what to do.  A software program is installed along with some hardware that does all of this stuff, supposedly automatically, for us.  It is important that these piece talk to each other so that they don’t end up competing with one another (reducing our efficiency.)

For example, we don’t want a boiler thinking it needs to supply full on steam demand for heat and then the chiller goes, why is it so hot?  I need to cool!  And then the boiler works harder to overcome the cooling.  Easy right?

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