Layout Example: Ambulance Bay, Part III

MeyerFire University | FX108.72E3

​By Joe Meyer, PE

< PREVIOUS

NEXT >

RESOURCES

FX174 SERIES

RESOURCES

RESOURCES

• One-Page Summary [PDF]
• MeyerFire Sprinkler Database

LINKS

• Tyco Dry Sprinkler Boot
• Reliable Dry Sprinklers - Model F3QR56

CODE & STANDARD REFERENCES

• ​NFPA 13 – 2016: Table 8.7.2.2.1 Standard Spray Sidewall Sprinkler Spacing
• NFPA 13 – 2022: Table 10.3.3.2.1 Standard Spray Sidewall Sprinkler Spacing

FX174 SERIES

1. What are the Steps to layout sprinklers?
2. Layout Example: Conference Room
3. Layout Example: Mechanical Room, Part I
4. Layout Example: Mechanical Room, Part II
5. ​Why does sprinkler spacing matter?
6. Layout Example: Ambulance Bay, Part I
7. Layout Example: Ambulance Bay, Part II
8. Layout Example: Ambulance Bay, Part III
9. Exercise: Layout for Conference Room
10. Exercise: Layout for a Fire Pump Room
11. Exercise: Layout for a Covered Patio​ 

---

TRANSCRIPT

Sprinkler Layout for an Ambulance Bay, Part III.

INTRODUCTION

So, in part one of this multi-part example, we explored whether fire sprinklers were even required underneath an overhang that's above an ambulance parking bay. The owner has elected to provide further coverage in this situation.

In Part II, our last segment, we talked at length about determining the hazard classification. Again, we found a discrepancy that we had to resolve. We've settled on an occupancy hazard classification of Ordinary Hazard Group 2, which aligns with the latest published edition of NFPA 13.

Here in this segment, we're continuing the steps for sprinkler layout in this ambulance bay. This is the last of the three-part series.

#3 OBSTRUCTED OR UNOBSTRUCTED

So, our Step #3 after the following two segments, is our determining of whether we have obstructed or unobstructed construction.

We spent a whole series on this concept previously that this situation is about as easy as we can get. We have a continuous, smooth level concrete deck that makes up the level above.

Now, I'm not entirely sure how this concrete came to be structurally. Remember, this is an existing building that we're working with. My guess is that the concrete itself is structurally relevant, meaning that it serves some function. This slab itself serves some structural function and I say that because it's not resting on top of any large concrete beams or girders. So perhaps this was precast concrete or maybe post tension concrete so the strength of the slide itself is supporting itself and the floor above without needing additional concrete beams. But regardless, we're continuous. We have Unobstructed Construction here in this situation. 

#4 COMBUSTIBLE OR NONCOMBUSTIBLE

Step #4, combustible or non-combustible.

Here with concrete, we have non-combustible construction.

#5 PIPE SCHEDULE OR HYDRAULICALLY CALCULATED

Moving right along – next step is whether we have pipe schedule or a hydraulically calculated system.

Now since this is a new design – we’re retrofitting sprinklers into this existing bay – we will hydraulically calculate it. There's no need to hunt down a reasoning or code path to see if pipe schedule would even be allowed. We're not going to worry about that. We're not going to look for AHJ approval and go in that process. We'll just calc it. Simple enough, hydraulically calculated.

#6 SPRINKLER TYPE AND ORIENTATION

Next is Step #6, selecting the sprinkler type in orientation. So, we have a few options here.

We have a smooth concrete deck with walls that go around on three sides. We can't penetrate the concrete deck above. It's existing and maybe structural and in reality, core-drilling for each individual sprinkler would be problematic if it's even possible.

So even if we could feed sprinklers from above, it's difficult enough, we're just not going to go with that option.

If we were to go with upright sprinklers, we could put those on threaded tees or thread the sprinkler right onto a welded outlet and keep the sprinkler as close to the bridge pipe as possible. Basically, we want to keep as high of a clearance as we can for an ambulance to still park below comfortably.

But the downside to using uprights is the environment. We're outdoors. This is the Midwest United States. The pipe will certainly be prone to freezing in the winter.

There are options we could use to address this.

We could make this a dry system. If we work through all the newer limitations for antifreeze systems, they're listing their capacity and all of that. It's possible we could also use antifreeze and go that route. But there's something easier that's still on the table and that's using sidewall sprinklers.

SIDEWALL SPRINKLERS

If we can use sidewall sprinklers and come through the wall for sprinkler protection, then it might be possible that we keep the pipe in only worn areas and negate the need for a dry system or an antifreeze system altogether. That would be by far the most cost-effective approach over using a small dry area free system.

So, let's explore sidewall sprinklers.

Now, the sprinkler itself will still be exposed to freezing conditions. The deflector, the bulb, all of that will still be outside and prone to freezing even if it's only rarity, but it's only in the winter time. So, we want to make use of a dry type sprinkler or a dry sidewall sprinkler where the sprinkler itself incorporates a dry barrel, which holds back the water back at the threaded connection and not right at the plug. Basically, the plug, instead of being on the edge of the glass bulb, that plug is all the way at the back of the barrel. The barrel is filled with air and it acts kind of like a thermal break from the cold temperatures outside to the water and the warm temperatures inside.

So, to see if we can get this to work, we need to check on the spacing. What are the spacing rules? That's step #7 in our process.

#7 SIDEWALL SPACING

So, here's a plan view of the ambulance bay overhang. Again, we have walls on free sides. There's a depth of 9-ft (2.7 meters), and there’s a width of 14-ft (4.3 meters) across. 

So, what is our maximum sprinkler spacing that's allowed for the situation if we're using sidewalls?

Again, this is Ordinary Hazard Group 2, unobstructed, non-combustible, hydraulically calculated using sidewall sprinklers. Well, we go to NFPA 13 to find out.

SPACING IN 2016 EDITION

NFPA 13 in the 2016 edition, which again is what applies what's required for this project, gives us spacing rules in Chapter 8 Installation Requirements, then Section 8.7 for standards spray, sidewall sprinklers. Section 8.7.2 gives us the Protection Area per sprinkler, and then Table 8.7.2.2.1 gives us the table we’re familiar with for standard spray sidewalls sprinklers.

Now we have an Ordinary Hazard Situation, Ordinary Hazard Group 2. If non-combustible ceiling finish so our maximum distance according to this table, our maximum distance along the wall S, is 10-ft (3.0 m), and our maximum room width is also 10-ft (3.0 m). That means the throw distance, the distance that runs out straight out from the sprinkler. Our maximum protection area is 100 sqft (9.3 sqm). 

Now Joe, in our last video you pulled content from NFPA 13 in the 2022 edition. You can’t just pick and choose which edition you want to follow. 

And in a general sense that's true, we don't get to pick and choose which edition we want to follow. We don't get to pick and choose, choose which requirements we want to apply. In this case for this project, we're still following NFPA 13, 2016 edition, and my references and the drawings and details will all be in accordance with that code will still reference the 2016 edition.

But as we discuss our last video, we voluntarily step up our hazard classification from Ordinary Hazard Group 1 to Ordinary Hazard Group 2, because we know what's coming down the puck. We know what the 2022 edition says. We know what their latest industry understanding is, and so we're voluntarily stepping up that hazard classification to Ordinary Hazard Group 2, we could always provide more than what code requires. Code is only a minimum. We are stepping up the hazard classification so that we provide a proper Standard of Care. We have a defensible stance, and our design would also meet newer additions of the code in the future should any of that ever apply.

All that said, let's run down the same code path for the 2022 edition in case you're following along, and that's the layout that you're more familiar with.

SPACING IN 2022 EDITION

So, in the 2022 Edition of NFPA 13, we start in Chapter 10, which is the Installation Requirements for Standard Pendent, Upright, and Sidewall Spray Sprinklers, then Section 10.3 for Sidewall Spray Sprinklers, then 10.3.3 Protection Areas per Sprinkler, and finally Table 10.3.3.2.1, which hasn’t changed a whole lot between these editions, other than the decimal points being added for SI on the unit conversion.

So that's our table here, Table 10.3.3.2.1. And our limits for using standard spray sidewall sprinklers are still 10 feet (3.0 m) in either direction.

Now, could we knock out this whole space with one extended cover sprinkler? Well, yeah, that would be possible. But remember, this isn't just a Light Hazard overhang, it's Ordinary Hazard Group 2. So, we have a higher density that we're going to apply here. So, an Extended Coverage Sprinkler, would it have to just ramp up to the pressure that it requires force listing?

It would also have to be listed specifically for Ordinary Hazard Group 2. There's only a handful of dry sidewall sprinklers that can do this, and the pressure that we need is going to bump up dramatically anyways.

In my opinion, it's just not worth going to one sprinkler and ridicule a bunch of hoops to step out the pressure when we can just use standard spray and cover this with two sprinklers.

SPRINKLER SELECTION

Now we get into sprinkler selection. So, if we're laying this out as a consultant, perhaps we're less concerned about selecting or declaring the exact sprinkler make and model for this layout. Maybe as a consultant, we're only concerned with the K factor, the finish, and whether a model that works from the situation exists and it is listing. Maybe that's the extent of all that we care about.

If we're on the contracting side, we don't have that luxury. We need to make a selection for the make and model for the sprinkler and call that out on our drawings. So, we can do this by combing our favorite manufacturer websites. But there's another way too.

THE SPRINKLER DATABASE

If you want to search across different manufacturers, we do have a tool for that which you already have access to as part of this platform. The sprinkler databases are live database of all the different makes and models of sprinklers that we know about today. These include sprinklers that are actively on the market, sprinklers that have been replaced, and sprinklers that have been recalled. 

So here in the sprinkler database, we can search for (1) sidewall orientation, (2) standard spray (dry) type. We can search for (3) Ordinary Hazard Classification and we can search to make sure that it's available on the market today. We then get a list of the make and models and we can click links and explore the product details or the sprinkler to be sure that it works for our needs. A link to the sprinkler database is below this video.

#8 POSITION THE SPRINKLERS

So, after we've done a selection and we know that a sprinkler exists, we found a solution for this lamp. Our last step in the layout process is to position the sprinklers.

We should always be thinking in three dimensions. What's the spacing and the length, direction and the width direction, and what is an appropriate height for the sprinkler?

Now, that's a little bit easier to remind ourselves to do, or thinking of 3D if we're a Revit or a three-dimensional space like native AutoSPRINK. Because if we're not thinking about height, then we drop in sprinklers in a spot that's on the floor or 20 feet in the air or somewhere that's inappropriate. We're going to know when we try to connect, we're going to get some more key stuff in. It's pretty obvious. If we’re in CAD and we're working mostly two dimensions, then we have to remind ourselves continuously that we need to be thinking about the height of the sprinkler as well as the spacing in the two-dimensional plate.

In looking at this layout and plan view, the width of the overhang at 14 feet means we're going to need at least two sprinklers. That's because our sprinkler spacing's 10 feet. Our overhang is 14 feet, so we're going to need at least two. Even if we have sprinklers pointed on opposite sides of each other, one on the west wall and one on the east wall, we would still need two sprinklers. And since this is a retrofit, I've going to try and keep things as simple and non-intrusive as I can. So instead of spacing these sidewalls and opposite walls where I have to run pipe all the way around the three walls, I'm going to run one branch slide and try to serve both the sprinklers from the north wall just facing down.

The spacing in the east west direction or along the wall out of NFPA 13 is 10 feet (3.0 m) between the sprinklers. Half that distance or the distance from the sprinkler to the wall is going to be 5 feet (1.5 meters). So, each sprinkler just cannot be more than half that distance. It can't be more than 5 feet (1.5 meters) off its adjacent wall. 

Now, because there are automatic sliding doors here, I would like to get the side walls out and away from being above the doors as much as possible, if that's possible. I would feel the same about window curtain walls where there are tall floor-to-ceiling glass. These doors, these windows, it requires a lentil above to structurally support so that the whole wall isn’t bearing right on those doors or those windows and the framing that is routed above the doors and the windows, well, it can be problematic to cut through. So, my first intuition in general, if I've got really tall windows or I've got under sliding doors, is to try avoid routing dry sidewalls directly above those so that we avoid the structural lintel that could be right there above them.

So, in this situation, if I maxed out the spacing between the sprinklers all the way to 10 feet (3.0 meters) in between the sprinklers, I'd have about 2-feet (0.6 m) to the adjacent wall on either side. Now just personally, this layout's fine. It ends up we're still above the doors anyways. So, we're really not helping ourselves out a whole lot where we're looking at that structural lintel. But personally, I'll bunk each side in, I'm fine keeping the sprinklers at this distance just with one caveat. I'm going to bunk each sprinkler in by half a foot so that we have just a little bit of flexibility in the field if they need to move on, if the misaligned, we're not stretching the spacing to the absolute limit, to the point where somebody could measure, say that it's over-spaced and then have to do some rework. I would add in some field flexibility where I can.

So, I'm going to bump these in half a foot (6 inches) and set them there. This is more art than science when we're fine tuning and thinking about what's the absolute optimum way, and there's not necessarily a perfect answer here, but from my standpoint, I feel like this is good enough.

With any spacing, we absolutely need to make sure that we meet all the rules. So no more than 5-ft (1.5 m) meters away from a sprinkler to its adjacent wall, no more than 10-ft (3.0 m) in between the sprinklers and the minimum space in between the sprinklers here is 6-ft (1.8 m). So, if we meet all those rules, we're good. We could debate at length about what the exact perfect optimum location is, but that's really not the goal for this exercise or necessarily even this platform.

We want to be thoughtful, we want to be creative, we want to do what's best for our team, and we want to meet the rules. That's pretty much it.

So, what about sprinkler height?

SPRINKLER HEIGHT

We talked about sprinkler height in length in an earlier segment. Our preferred sweet spot for sidewall sprinklers 4-6 inches (100-150 mm) down from the ceiling or the roof deck. There's no reason here to avoid that zone. So, let's just spot the sprinkler there. Say I set it at 5 inches on setter below the deck.

Now we have just a few stops to visit before we're done here.

DRY SIDEWALL NEEDS: BARREL LENGTH

The first is that dry sidewall sprinklers need to have a long enough barrel or the light of the barrel and leads to be long enough so that we adequately separate the warm side from the cold side. The longer that barrel is, the more it acts like a thermal break or a warm blanket that separates the cold face of the sprinkler to the threaded connection on the inlet side of the sprinkler. The longer that is, the bigger the blanket is, so to speak.

If we look at the product data for the sprinkler, we can determine how long that barrel needs to be based on the anticipated temperatures for each side of that sprinkler.

DRY SIDEWALL NEEDS: CONNECTION

A second issue for dry sprinklers is that they need to be threaded into a tee, a welded outlet or a coupling or adapter that does not have an internal obstruction. So, part of the inlet on the dry sprinkler actually projects into the connection or into the fitting that connects with.

The problem comes if we were to connect a dry sprinkler, say to an elbow because the inside of the elbow immediately bends and curls and will come into contact with the inlet of a dry sprinkler. So that's not allowed. The product data on all of the dry sprinklers explicitly say to connect to a tee or something that doesn't obstruct that inlet.

So, in order to avoid that inlet from rubbing or getting stuck on an elbow, we have to thread dry sprinklers into a fitting that is open and unobstructed from the inside. Now, normally in both, in almost every case, this is simply a threaded tee with a plug.

The orientation of the tee doesn't really matter. We can use the through side of the tee or the Bullhead side of the tee, either orientation is usually okay. What's important is that we do not thread the dry sprinkler into an elbow. So, for more information on this, check your favorite dry sprinkler's product data and how they show the installation. That's going to be detailed in the product data for the dry sprinkler.

DRY SIDEWALL NEEDS: INSULATION

Another important consideration with dry sprinklers, including dry sidewalls, is to make sure we have healthy amount of insulation around the sprinkler itself. Now, there is a few ways to do this, but perhaps my favorite and the cleanest option is to use a “boot" for a dry sprinkler.

These are flexible rubber light covers that go around dry sprinklers and are actually sealed to the cold side wall or lid. So, if you have a cooler freezer, you seal the boot to the lid of the cooler freezer, or if you have a wall and you seal the boot to the wall, the sealant is applied between the boot and the wall or the lid, and then you tighten the boot to a dry sprinkler using strap ties that are just twisted and tightened.

Essentially, these work just like insulation, except they're more flexible than spray foam and they have a potentially more consistent tighter seal around the sprinkler. But perhaps most importantly, you can actually remove a dry sprinkler when it needs to be replaced or tested, which can happen in as soon as 10 years, and you don't have to cut into or rip out insulation in order to do it.

If you have spray foam insulation, you got to cut or rip it out or really ink on that sprinkler to get it out. With a boot, all you have to do is loosen that strap tide and you've got some flexibility in getting that joist sprinkler back out and replaced.

Now, because the boot's not a critical part of the system and they don't alter any function on the sprinkler system, these aren't actually required to be listed, nor do you have to match manufacturers or anything like that. If you've got a boot model that you like and you can use it with a dry sprinkler that you like, and that's kind of convenient.

DRY SIDEWALL NEEDS: INTERIOR FINISH

Last, if you route exposed pipe anywhere inside a building that's near an architect or interior designer, well it's best to mention that to them. I say architect or interior designer because they're usually the ones who care most about the finished look for interior spaces.

If we have an industrial warehouse, well no one's really paying too close attention to exposed pipe.

But for a space like this where there's an ambulance entrance at the hospital where surfaces need to be cleaned regularly and we don't want horizontal surfaces like pipes or exposed pipes that could collect dust, well, it's worth flagging and addressing with an architect or interior designer.

How do they want that to show? Do they want it painted? Are they okay with the surface? If it's painted and cleanable, is that good enough? Or do they want to build a soffit, a ramp of the pipe and hide the pipe? If the architects or interior person wants soffit on the pipe, that's fine. We just want to check and confirm that the soffit is going to be on the warm side of any insulation so that any wet pipe that would be in that soffit will be at the same temperature as the building interior to keep it from freezing.

SUMMARY

So, with our layout, where did we end up?

Well, we have standard spray, dry sidewall sprinklers that are about as high and tight as possible, and that's a somewhat reasonable approach that we end up with here.

So as a recap, for all the steps of the sprinkler layout that we executed in this example, we first determined whether or not sprinklers were even required for the space. Then we determined the occupancy hazard classification, then unobstructed construction, the non-combustible hydraulically calculated. We went with a dry, standard-spray sidewall sprinkler to avoid the need for a dry or anti-free system, and we determined the spacing limits within NFPA 13, and we applied that to position the sprinklers.

With dry sidewalls, we paid attention to a few extra details that might individually warrant some additional worker coordination if needed.

Thanks for following along in this example. Hopefully, some of this thought process here gives a little real-world touch to the steps that we've outlined in this series.

Being introduced to the concepts is one thing. It's good and it's healthy, but practicing and building skill is another. So in our next few segments, we're going to work on those skills and do some exercises to get practice in the sprinkler layout process.

I’m Joe Meyer, this is MeyerFire University.