ARE 5.0 Project Development & Documentation Exam Prep

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DX RTU Example

7m 57s

In this ARE 5.0 NCARB-approved Project Development and Documentation Exam Prep course you will learn about the topics covered in the ARE 5.0 PDD exam division. A complete and comprehensive curriculum, this course will touch on each of the NCARB objectives for the ARE 5.0 Project Development and Documentation Exam.

Instructor Mike Newman will discuss issues related to the development of design concepts, the evaluation of materials and technologies, selection of appropriate construction techniques, and appropriate construction documentation.

When you are done with this course, you will have a thorough understanding of the content covered in the ARE 5.0 Project Development and Documentation Exam including integration of civil, structural, mechanical, electrical, plumbing, and specialty systems into overall project design and documentation.

Let's look at DX RTU. So that would be a direct expansion, so that means there's no chilled water loop. It's just directly the refrigerant to the air paneling side and rooftop unit. So this is something that's sitting up on the roof. And this might be sort of a perfect thing for, say, multiple tenants. Try setting this up here. So I'm gonna do two of them. We're a little out of scale here. Let's separate these spaces into two tenant spaces. And...

What we're saying here is that, this thing, up here, is a package unit. It's a DX RTU and it comes, you literally buy it off the shelf. They would adjust it, customize it just a little bit to fit to your exact needs but essentially, you're just buying it off the shelf and then they just drop it off with a crane and it sits up on the roof. And inside there, it's got a little refrigerant loop in it, so it's got its own little chiller system going on there.

And it has the ability to have air, sort of, being blown through it so that can create, sort of, a cooling tower effect in this small space. Sometimes with these DX RT units, you actually do have a separate cooling tower but sometimes, it's literally built right into the same box. So it all comes all in one element. I've got my fan and I've got the ability to have air blowing down into the space.

And then, that's gonna blow around each of those spaces. Now, these might be separate. If this was one tenant on two floors, it might be one unit. If it was two different tenants, it might be two different supply trunks going down, so you weren't working off of the same one.

Or it just, even if it was two tenants, you might just treat is as one, sort of, general space. But any number of different ways of doing these layouts, the biggest issue here is that I've got a great big chunk of space taken up by these vertical shafts because I have to get all of the air from that air handling unit up on the roof, down into whatever floor I'm going to.

So this is two floors, so that means I would have two tenant spaces worth of air going down through that floor. So this element on the second floor is gonna be a big chunk of space missing from that which I can't rent or I can't use, I can't move it around. I can't alter in any, 'cause it's gotta go straight on through. And then I would have a return system. That presumably would go, kind of, near it but it would reach, you know, to other locations so you didn't get that short-circuiting.

And then the air would find its way to the return system and then get brought back up to this rooftop unit, get reconditioned and then get blown out. So you have everything happening all right there, including that little coil that's going right there straight from the refrigerant and that return air is being blown right across. We also have handy, we're right there outside, so we can get some fresh air.

We just mix it right in, same that we would've otherwise but instead of having a duct bring it in from somewhere, we can just grab it right there from the outside because we're already up on the roof on the outside. So we could have two of these, we could have ten of them, we could have 100 of them, depending on how big the building was, how many tenants you had, whether you wanted to have each space done separately. This is sort of a perfect thing for, like, a strip mall. Maybe I've got more like a, somewhere, closer towards a big box.

I could, instead of having one central system, I might just put, say, five, six, different rooftop units on and just spread them out through the space and I just blow in air and pull air back from, sort of, near that area and it's very, you know, I only need a little bit of duct work in order to deal with these great big buildings. I'm mostly just kind of blowing that air in from the roof area and letting it kinda settle down into the space.

So in the right situation this could be very cost-effective. The advantages to this would be, really, that it's like straight off the shelf. Whatever my situation is, I can just put one of these things in there. We have to get the duct work down through the space but once we do that, I don't have any of these other, sort of, complicated maintenance issues. Like, this thing is, something's wrong, we're probably throwing it away and buying a new one, right. They're relatively easy to get.

The biggest issue from that standpoint is, I'd probably have to put a crane out in order to get one of these things up on the roof. But, you know, still, they're still sort of simple, small. They don't have huge profile, so I don't see them from very far, typically. So, very advantageous, in the right situation. But also, compare this to that chiller in the basement. That chiller in the basement's there for 40, 50 years and it's gonna be there, easily, in this sort of nice coddled space in the basement, easily protected.

Easy to maintain. This things sitting up on the roof and it's getting all of the UV rays, all of the sleet and snow and the wind and the rain and all that stuff is pounding away on this thing. You'd be lucky to get 12, 15 years out of one of these things and often they may only last maybe five to eight years, something along those lines, in really rough situations. So, you know, while they're advantageous in a lot of situations, if you're somebody who's gonna hold on to this thing for a longer period, it's just not very great.

That's just not a great system, doesn't really make efficiency sense to have something that you're gonna have to replace every 12 years, if you're gonna be holding on to this building for 50 years. But your tenant space, you've got a lot of retail tenants, there's a lot of high turnover, so people come in, maybe they try a thing for two, three, five years. Either it works or it doesn't.

If it works, maybe they're moving on to a better retail space and so you have a new tenant coming in. Like, that kind of space, really quick turnovers, totally make sense because, worse case scenario, you just put a whole new system in to fit the new tenant. So you're not always trying to live with the existing set up in terms of how these things might sort of logically go together. So, DX rooftop units, really common in these faster paced, higher turnover.

It wouldn't really make sense if you were trying to get a rooftop unit going down, say, five floors or eight floors or something like that. That would be just too much air trying to get through all of those different floors. It would take up too much space on those upper floors. Probably doesn't make sense in somebody who's gonna hold the building for a long time and really wants to get a lot of efficiency out of it. But for those faster turnover, those lighter touch things that may or may not last any length of time, this a perfect choice.

It's that lower cost, lower infrastructure, everything's a little but more off-the-shelf. So pretty simple and straightforward. And again, this is another one of those DX systems. There's no chilled water loop in this one, so it's just three of the four loops.

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From the course:
ARE 5.0 Project Development & Documentation Exam Prep

Duration: 36h 46m

Author: Mike Newman