Welcome to HVAC Tech Talk, brought to you by Vital Mechanical Service. These are short trainings on different components, equipment and systems.
Ron: With Michelle who’s new to the industry and understands how difficult learning HBAC can be.
Michelle: And Ron, who’s a mechanical engineer and understands how these systems really work.
Ron: AHU Session two, level beginner, air types.
So Michelle, today we’re going to learn about the different airflows with an air handler.
Michelle: Got it.
Ron: Let’s start with an example space. Let’s say it’s an office, let’s put some people in it and we’ll put an air handler someplace above a ceiling.
Michelle: Now wait, is it always located in the ceiling or it can be in other areas?
Ron: It could be in a lot of different areas. We put them on the roof, we put them in attic spaces, sometimes they’re hanging on the wall, sometimes they’re so large that they are the actual room.
Michelle: Wow, and are they always vertical or can they be horizontal as well?
Ron: All different configurations.
Michelle: Okay, and I think we’ve seen some of those bigger rooms and it really is ginormous.
Ron: Yeah, air handlers can be big. The tricky part is there’s so many different configurations, so many different types and you see them in so many different locations, it can be difficult to understand where the air is entering the air handler, where it’s leaving the air handler, is it supplying the space, is it return from the space, just how it’s operating. That’s why we’re doing this training. Let’s get back to the air handler in the ceiling. We’re going to have supplier coming from the air handler going to the space. We’re going to have air from the space going back to the air handler. And remember the CO2 that we talked about earlier?
Ron: We’re going to want to replace some of that air with fresh air from the outside.
Michelle: Because it makes us sleepy.
Ron: Because it makes us sleepy, but we also have to remove that air from the space or else…
Michelle: The room’s going to explode?
Ron: Kind of, not really. Have you ever opened a door to a building and air just gusts by like you’re in a wind tunnel?
Michelle: Oh yeah, I have actually.
Ron: Or it’s hard to open, like it’s being sucked in?
Michelle: Thought it was you holding the door knob.
Ron: That is what’s going on, but what’s really happening is we’re not removing or replacing the fresh air that’s necessary to keep the building in balance.
Michelle: Oh, so that’s why maybe sometimes the door slams too.
Ron: That’s correct. What’s tricky is here the relief air’s shown coming from the air handler but in actuality it could be like in a window, it could be an exhaust fan someplace else, it could be a damper that’s tied back to the air handler so it knows to relieve the air.
Michelle: Oh, okay.
Ron: Let’s review the different kind of airs.
Michelle: Yes, let’s review.
Ron: Okay. What are the different kind of airs?
Michelle: There’s return air, relief air, fresh air and supply air.
Ron: Boom perfect. Let’s get back to our cutaway air handler so we understand how air moves through it.
Michelle: Okay, visuals are good.
Ron: We have a return air getting motivated by a fan, it’s either going to get relieved out of the space or recirculated back into the space. It’s going to get mixed with fresh air, and you see that little dust cloud down there?
Michelle: Yeah, what is that?
Ron: That is stuff that we want to get out of the air. An example, I don’t know if you knew this, but the average human loses somewhere around 40,000 skin cells per hour.
Ron: A million per day.
Michelle: That’s disgusting.
Ron: That’s why we filter the air and here the air is going through the filter and another fan pushes out to the space. Now if we need to heat it, the heating section is going to turn on and if we need the cool air then the cooling techs will turn on. Yay! We’re finally done with this training.
Next time the training’s going to be on the two main type of air handlers we see in our area. Till next time!
Michelle: Thanks Ron.
Ron: And thanks Michelle.