Curious if others interpret the obstructed construction rule the same way I do.

I've seen and heard quite a bit of dispute on how Obstructed Construction should be applied to solid beams with corrugated metal deck above (when applied perpendicular to the beams in question). So the definition of obstructed construction is really defined by applying what unobstructed construction isn't.

In summary, obstructed construction is solid members (or members less than 70% open) that are spaced less than 7-1/2 on center. That would lead you to believe that openings of 29.99% are permitted as long as members are less than 7-1/2' on center.

If you go to the appendix, it offers a LOT more information on types of obstructed construction, one of those being panel construction. There it mentions that (pockets) 300 sqft or less can also be obstructed construction, even with members more than 7-1/2' on center, as long as NO openings are allowed, including at the beam to ceiling interface.

I take this opening rule as only applying to when the 300 sqft exception is being used and where beams are more than 7-1/2' on center. Is this how you interpret this section? 

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I'm designing the fire suppression system for a 6-story wood frame residential building. There will be 6-ft wide balconies made of non- and limited-combustible materials. Normally that would mean sprinklers under the balconies could be omitted, but it occurred to me that people will likely have BBQs and the accompanying propane tank on their balconies.

Would this count as "combustible storage" and thus require sprinklers (dry sidewall heads), or can they still be omitted?

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I always seem to miss listing a pressure gauge on a project. Are any required above what I have in my checklist below?

Sprinkler:

• At each "system riser"
• Before & after backflow preventer
• Before & after any dry or pre-action valve, accelerator, air supply
• At each main drain
• Each side of a pressure reducing or regulating device

Standpipe

• Top of standpipes

Pumps

• Suction
• Discharge

Moderator note: thanks in advance for feedback, we're developing a cheatsheet on this topic in the near future

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I have a multi-story building under a single owner. It consists of a first floor 25,000 sqft area and a second floor, also of 25,000 sqft in area which has a high barrel roof, about 40 ft above the floor.

This second level is unique in that a portion of its area has two levels of rooms, one stacked on the other. Each level is 10,000 sqft in area. To visualize these, consider the first level being individual meeting/office/bathrooms having ceilings and a structure overtop. The second level is of similar area/occupancy/ceiling and is built on top of this lower structure. The architect actually refers to this second level as a mezzanine. The area above the these rooms is open to the high roof. The building is sprinklered throughout per NFPA 13 (2016). A standpipe is not required per IBC 905.3.1.

My position is that the building can be protected as a single zone without floor control valves as it is two stories in height plus a mezzanine under the control of a single owner. Further, the two levels of rooms at Floor 2 are referred in A.8.2.4.1 which gives guidance that 8.2.4.1 is not intending to require floor control valves on small buildings under the supervision of a single owner. Reference NFPA 13 (2016) 8.2.4.1, A.8.2.4.1, 8.2.1, 8.2.2.

Strictly per the standard, are floor control valves required for each level of this building?

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When you have a common office building that is classified as a Light Hazard but you have some rooms that may be Ordinary Hazard such as storage rooms and others.

When you have your layout and one or more of these rooms ends up in your design area, how do you proceed in the calculation?

1.- Do you calculate 0.10 gpm/sqft over 1,500 sqft?

2.- Do you calculate according to Chapter 23 Sections 23.4.4.2.4 and 23.4.4.2.5 specifically for that room even if it is one or two sprinklers?

3.- Do you calculate everything with the density and area for the hazard of that room even though everything else is Light Hazard?

4.- Do you calculate 0.10 gpm/sqft over 1,500 sqft and ensure that the sprinklers inside the room discharge at the minimum density for the hazard they have?

This may be very general and definitely every project is different but every time I run into this I have this same question. I was told to just calculate everything as a Light Hazard but my curiosity always keeps me thinking about it.

Moderator Note: This question is different, but similar to: www.meyerfire.com/daily/ordinary-hazard-within-light-hazard-building

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We are designing a project which has Ordinary Hazard with unique beam pockets.

We have ceiling pockets which are 988 cubic feet (28 m^3) and so sprinklers are provided within them. The beam depth is large at about 4-feet (1.2 m). Each beam width is about 1-foot wide (300 mm). The beam center-to-center distance is 6'-6" (2 m).

Are sprinklers needing to be provided below the bottom of the beam, or not?

If sprinklers need to be provided below the bottom of the beam, what is the coverage area if sprinklers are already provided in the ceiling pockets?

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​I'm designing a fire suppression system for a new boiler room at an existing hospital. It will connect to the existing fire suppression piping. The hospital is served by a fire pump, but the existing pressure at the street is satisfactory to supply this particular space with enough water for Ordinary Hazard Group 2 occupancy without the pump.

Do I still need to include the fire pump in the hydraulic calculation, or can I ignore it?

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In one of my jobs I have a fire sprinkler contractor who claims something that seemed strange to me. I have searched online but didn’t find the code section to show him.

He has laid out his Victaulic piping for two open space office under the beams and when I asked him why he didn't run them up high through the joists and instead only route the pipes underneath the beam where they have to, he responded that for each time that a pipe goes up and down, it requires a drain.

My question is in a wet sprinkler system in an office, do we need to provide drains for every time that a pipe is going few inches down and then back up? Since the entire system is wet and under pressure, are these drains necessary per any code? Whether we do require that or not, can anyone refer me to the pertaining code section?

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We have a high-rise building, with rated stair shafts. This project is under NFPA 101.

Under NFPA 101, Is is permissible to penetrate the wall of the stair enclosure (an exit enclosure) with duct that is not serving the staircase?

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One of our projects has standard-spray upright sprinklers used in a place where cable tray is above the sprinkler deflector. The roof is non-combustible, and the deflectors are about 8.7-inches below the roof.  The cable tray and cables are about 4-inches above the deflector.

Is there any code issue here?

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What is a building owner's responsibility to provide sprinkler system plans and calculations to new tenants and/or inspectors?

Is there any responsibility to provide these?

Code sections would be appreciated, thanks.

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In regards to the Darcy-Weisbach equation and Moody Diagram - why does laminar flow (Reynolds number less than 2,000) correlate to a higher friction factor than turbulent flow?

Should turbulent flow correlate to a higher friction factor and therefore a higher pressure loss per foot of pipe?

I'm designing a system using a newly listed antifreeze with a viscosity of over 300 cP at -25 deg F. This causes a very low Reynolds number (around 250) since viscosity is in the denominator of the Reynolds equation. With a low Reynolds number, the Friction Factor is high (64 / Re) which makes sense because I'm calculating for antifreeze, but I don't understand how laminar flow correlates to a higher Friction Factor.

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Do fire pumps typically come balanced from the factory for the desired flow and pressure?

I know they are supposed to, but (just like any other pump) is their balancing done similar to a regular pump to get the desired pressure so that the pump operates at its rated duty point? I am aware that many factors affect final pressure discharges (such as friction loss, etc.).

Have you ever seen pump manufacturers calibrate pumps to the desired flow/pressure in the field?

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How close can hanging baffles be spaced together before sprinklers are required below (and possibly above) them to provide full sprinkler coverage?

I have a situation where about 20 acoustical baffles will be hanging 6-12 inches below the ceiling. The baffles are 18-inches by 10-feet long, spaced 8-inches apart.

I've looked at providing sprinklers above them at the ceiling level, and it isn't clear cut; each individual obstruction is less than 4-feet wide, so I can see NFPA 13 (2019) Section 10.2.7.1.2(2) applying as long as you can sprinkler between them. But I think the baffles are located too close together to be considered non-continuous obstructions and their proximity would obstruct the sprinkler spray pattern development.

I've looked at Section 9.5.5.2, where continuous or non-continuous obstructions less than 18-inches below the sprinkler deflector prevent the sprinkler pattern from fully developing, but that section states that as long as no additional floor area is created then no additional sprinklers are required. Having a tough time believing that only sprinklering above the baffles will fully protect beneath them. Any help is appreciated!

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We have a client that is looking at building a fireworks retail store on the edge of town. The county is requiring the store to be sprinklered, but no one can give any direction on how to protect it and NFPA does not call out coverage for this type of business. 

It is an H-3 occupancy, covering roughly 10,000 sqft. 

Is there a standard that offers guidance on how to go about protecting a facility like this?

Thanks in advance.

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We have a project where we are trying to distinguish between frame and girder construction versus panel construction.

If we have steel frame and girder construction, beams are less than or equal to 7'-6" apart, but there is a corrugated deck that allows for heat flow above the girder (and wouldn't trap all heat), does this qualify as frame and girder?

Will the maximum deflector distance be 22-inches if there is a corrugated deck?

My assumption is "no" since heat is not capable of being trapped and a sprinkler needs to be placed in each bay within 12-inches of the deck.

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I'm working on a a high-end hotel which will have a vertical turbine fire pump above a water storage tank.

Can we waive a minimum pump submerge depth by installing an anti-vortex plate between the pump's bell and the strainer?

The fire pump is a 1,500 gpm vertical-turbine type, located directly above the water tank. The tank depth is 6'-3" from the overflow bottom down to the tank floor. The water tank area is 2,408 sqft. The selected pump recommends 51.63-inches as a minimum submerge depth. This is in addition to a 12-inch clearance between the bottom of the strainer and the tank floor. The water level to be maintained inside the tank then must be 63.63-inches (95,511 gallons).

The remaining active volume in the tank after extracting the required volume will be 112,582 - 95,511 = 17,071 gallons. This is not enough to run the pump set for the required time under NFPA 13 2019 (Table 19.3.2.1 and 19.3.3.1.2).

Can adding an anti-vortex plate between the pump's bell and the strainer waive this minimum submerge depth? If not, what might be a recommended solution for this?

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My question is more based on principle rather than design.

I have been in the industry for over years and keep coming to the same question lately; who is responsible for the end product on design and install?

I've had several projects in the last year where a "mechanical engineer (plumbing/HVAC)" are doing the layout for the schematic and bid drawings and don't have the complete knowledge of fire protection. I've had to deal with issues ranging from head spacing to pump specifications... and none of them have been close to code.

Specifically, I have a 3-story building with the 3rd floor at 30'-0" above apparatus / grade so there should be no need for standpipes. The plan/specs require an automatic-wet standpipe with a 125 psi @ 500 pump. I sent an RFI on why the need for the automatic-wet standpipes, where we can do away with standpipes or go to manual/wet and I was rejected. Ultimately, we were told to follow the prints....but we are "delegated" design. Eliminating the pump and standpipes, we could have saved the county $110,000+ (electric included).

I now have a church with 36-ft throw sidewalls and the engineer would like to stay with sidewalls and not have any pipe crossing the room; it's not possible with the supply.

In the end, who is responsible for the design and performance of the system?

If the contractor follows the plan/spec, is he liable because he is the "delegated" designer? But if the delegated design needs to change and is rejected, who is liable?

How do you bid plan and spec project if there are multiple issues with the bid plans? Do you redesign and bid it correct? No, you won't get the job. Or, do you bid per prints and then not be allowed change orders because you are the delegated designer?

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I have two large ducts 20-inches below sprinklers. One duct is 32-inches wide, the other is 42-inches wide. There is maybe 4- to 7-inches between them, only a couple inch gap on each side, running the length of a hallway.

The only rule for a continuous obstruction I can find says no coverage is needed below if the obstruction is under 4-feet. 

Individually these ducts aren't over 4-feet, but how does NFPA 13 address multiple obstructions like this?

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If a building has an NFPA 13R system and the building is now being converted to a commercial building and does not require a sprinkler system for new construction, can you remove the system?

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Can Permatex Form-A-Gasket No. 1 Sealant be used in a fire sprinkler system to seal the pipes and threaded fittings instead of PTFE tape?

Also, if the installer added jute (fiber), is this acceptable?

I do not believe that NFPA 13 or UFC Criteria prohibits this practice, but wanted to ask.

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I am a Fire Protection Engineer in Victoria working in a sugar refinery where we are proposing to protect existing raw sugar and white packaging storage. The raw sugar storage has piles of unrefined sugar in the warehouse which often clogs the sprinklers (like all other equipment in the area).

My advice to the client was more strict inspections and maintenance in this area, as well as to place metal guards to try and minimize buildup around the sprinklers.

The white packaging storage, although not as dirty as the raw sugar storage, has fine dust particles throughout. I'm not as concerned about this area.

We are not trying to re-invent the wheel here, and I'm sure there has been many acceptable solutions to minimize building on sprinklers.

What would you recommend to the client here to minimize the buildup?

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NFPA 13 states that for hydraulically calculated sprinkler systems the fire department connection (FDC) pipe can be less than 4-inch diameter, but not less than the system riser.

What size should the fire department connection feed pipe be for a 6-inch riser, or an 8-inch riser?

Can the FDC pipe still be 4-inch for these larger risers?

I have some clients believe that 4-inch is the maximum no matter what, and some say if the riser is 6-inch or 8-inch that the FDC pipe needs to match the larger riser size.

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When 20 or fewer sprinklers are involved in a modification, codes and standards suggest new hydraulic calculations are not required.

What is the scientific or engineering basis for the "20-sprinkler" number?

Is there some study or analysis that found this to be a reasonable breakpoint?

I'm researching whether we should require full plans for less than 20 sprinklers. Thanks!

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We are currently working on a project with a building height of 36-feet that currently has K16.8 ESFR sprinklers installed to protect open rack storage of Class I-IV commodities at 12-feet in height.

The hydraulic calculations are based on Ordinary Hazard Group 2, with a 0.20 gpm/sqft density over 1,500 sqft with a starting pressure of 7 psi. The design area is based on 18 ESFR sprinklers flowing at 100 sqft per sprinkler. The total sprinkler demand is 834 gpm. 

They are calling this an "ESFR-Ready" sprinkler system.

It seems to me that the building height would drive the starting pressure for this scenario and the calculation should actually be 12 sprinklers with a minimum starting pressure of 52 psi when using K16.8 ESFR sprinklers. This comes after examining Chapters 12-20.

What would the lowest starting pressure be for K16.8 ESFR sprinklers protecting open rack storage of Class I-IV commodities to 12-feet in height with a building height of 36-feet?

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