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3 Sprinkler Challenges for Coolers & Freezers

11/29/2018

 
Walk-in commercial coolers and freezers present a unique challenge for fire sprinkler systems. Today I'm walking through some of the common issues and tips I've encountered  when protecting these units.

​Challenge #1: Ice Plugs
​
The most common and potentially dangerous issue with fire protection in walk-in coolers and freezers is the potential for ice plugs to delay or impair entirely sprinkler discharge. 

The thermal mass of water allows for high absorption of heat as compared to other materials and liquids, which is one of the reasons water works so well in suppressing fires. This same property, however, acts as a major inhibitor to activation when large ice plugs form at the sprinkler coverplate or frame.
Fire Sprinkler in Cooler Freezer
Ice blocks can prohibit effective and responsive fire protection from gaps in a continuous thermal barrier.
Why Do Ice Plugs Form?

Any gap or compromise between the sprinkler (or pipe) and the insulative cooler/freezer lid can allow moist warm air to enter the cooler/freezer near the compromise. Once this intrusion occurs, the moist air reaches the chilled freezer temperature, the moisture condenses into water and then freezes, forming an ice block. 

Those who regularly work in or survey these walk-ins no doubt notice ice plugs.

​Tips for Preventing Ice Blocks

Preventing ice blocks is all about quality and lasting seals between the dry sprinkler shaft and the adjacent insulation. 

In theory, if any clearance around the dry sprinkler is sufficiently insulated (such as with spray foam) and this foam stays in place for years without movement, then ice blocks couldn't occur.

However, such as is the case in many large retailers or groceries, the tops of the coolers and freezers are subject to some movement from personnel or storage on top of the units themselves. Even with very minor deflection, fixed sprinklers and pipe can shift away from the insulation, cause a gap in insulation, and form ice blocks.

Giving Ice The Boot

Some manufacturers (such as Tyco) offer rubber boots that adhere to the top of the cooler/freezer and tighten to the dry pendent sprinkler, which helps accommodate movement of the lid over time and ensures a better seal against the sprinkler shaft. While a little pricier than a foam insulation can, these can be quick to install and can offer a better seal against the cooler/freezer lid.
Dry Pendent Sprinkler
Rubber "boots" can simplify installation and provide a consistent seal along the top of a cooler/freezer.
Flexible Drops

Providing a boot for sealing isn't the only way to better accommodate movement. Flexible drops at the point of connection to horizontal piping, or even Victaulic's new flexibly dry sprinkler can help accommodate movement and afford flexibility to the final sprinkler location, without impairing the insulation.

Challenge #2: Dry Pendent Connections to Tees

A commonly overlooked requirement of dry pendent sprinklers is their point of connection to pipe above. Because the inlet of the runs just beyond the thread of the sprinkler's tube, we can't thread a dry pendent sprinkler directly into an elbow; instead product data requires the connection to be a tee or adapter (for CPVC connections) that have dimensions which don't contact the valve seat. It's a very often overlooked part of the dry pendent installation that's easy to miss.

Challenge #3: Refrigeration Equipment as Obstructions

Very often, the refrigeration equipment is a part of the cooler/freezer supplier's equipment package, and not indicated on mechanical HVAC plans. This poses a frequent challenge for both upfront engineering design and shop drawing, as these shop submittals showing the locations of the units aren't often compiled until very late in the construction phasing. 

Without good information on the dimensions of the equipment, it's often difficult for sprinkler layouts to incorporate the equipment without being obstructed under NFPA 13. Coordinating this with the supplier, or anticipating locations with sprinklers in front and rear of the unit help mitigate this late-forming issue.
Fire Protection in Cooler/Freezers
Size and placement of refrigeration equipment isn't often known until late in the design/shop drawing process, so their final installation often provides obstructions to sprinkler discharge
Your Experience

I know I'm not the only one to come across nuances with fire protection in these cooler and freezer units. What challenges do you come across with cooler/freezer protection, and what tips do you have? Discuss here.

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Matthew Allen
11/30/2018 11:40:33 am

Obstructions. The lights are surfaced mounted, conduits ran across the concealed pendents and rack storage up to the bottom of the evaporator. The area behind the evaporator is now unprotected.

Typically staying a minimum of 24" from lights and providing a sprinkler behind the evaporator takes care of the issues; however, this results in a large number of dry pendent sprinklers for such a small area.

Dave L.
11/30/2018 11:42:42 am

Very good synopsis (and illustration again), it’s a good topic to geek-out on. Back in the OLD days, the standard where I worked was a complex steel sleeve and nuts for the penetration. But spray foam (from a can or 2-part mix from a box) has been the go-to around here for a long time. I’ve ordered the Tyco and Reliable boots, as well as the Viking “doughnut” style. And the Victaulic flexible AB6 (not to be confused with the VS1's) is a great alternative if in the budget. (BTW fitter input on this forum would be good). As you say, after people bounce around walking on top of the freezer, now or later, the seal is often compromised. At punchlist time, I occasionally find sealing missing. Either the fitter didn't have a can of fresh foam at the time, never got back to it, or fitters changed and the new fitter didn’t know what the loose end were. Or everyone assumed the other trade was going to do it. How about dry barrel length? Our design standards often had standard length dry barrel for coolers and freezers (e.g., 12” or 18”), though manufacturer’s data, and now the barrel-length tables in Chapter 8 of NFPA can provide guidance. How about sprinkler temperature? We used to do 286°F due to the old defrost cycles, but these days they are more like frost-free freezers. What temp does everyone use for coolers and freezers? Specs often still call for 286°F.

Rusty Scott
7/3/2019 10:30:45 am

Does anyone provide heat/smoke detectors inside walk-in freezer like what you would find in a school cafeteria? I imagine you may want to put a heat detector above the freezer where a majority of the equipment is. Any thoughts?


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  • Blog
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    • SUBMIT AN IDEA
    • BACKFLOW DATABASE*
    • CLEAN AGENT ESTIMATOR*
    • CLOUD CEILING CALCULATOR
    • DOMESTIC DEMAND*
    • FIRE FLOW CALCULATOR*
    • FIRE PUMP ANALYZER*
    • FIRE PUMP DATABASE*
    • FRICTION LOSS CALCULATOR
    • HANGER SPACER*
    • IBC TRANSLATOR*
    • K-FACTOR SELECTOR*
    • NFPA 13 EDITION TRANSLATOR ('19 ONLY)
    • NFPA 13 EDITION TRANSLATOR ('99-'22)*
    • LIQUIDS ANALYZER*
    • OBSTRUCTION CALCULATOR
    • OBSTRUCTIONS AGAINST WALL*
    • PLUMBING FIXTURE COUNTS
    • QUICK RESPONSE AREA REDUCTION
    • REMOTE AREA ANALYZER*
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    • SPRINKLER FLOW*
    • SYSTEM ESTIMATOR*
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