Sprinkler Heads, Nozzles and Spray Systems Installation
What the exam tests
This domain tests head selection and installation: temperature rating, K-factor, orientation, deflector position, spacing, obstruction rules and protection from damage. Expect questions that show a ceiling, an obstruction and a head location.
Core rules and concepts
- Temperature rating. Ordinary ratings are roughly 135 to 170 F, intermediate 175 to 225 F, high 250 to 300 F and extra high 325 to 375 F. Choose a rating above the expected ceiling temperature, and use high-temperature heads near skylights, unit heaters and cooking equipment.
- K-factor. The K-factor relates flow to pressure: Q = K x square root of P. A larger K-factor delivers more flow at the same pressure. Do not substitute a different K-factor without recalculating.
- Orientation. Upright, pendent and sidewall heads have different deflector and spacing rules. Sidewall heads have distance limits from the wall and coverage limits.
- Deflector position. Standard spray heads usually require the deflector 1 in to 12 in below the ceiling, depending on head type and construction. Follow the listing.
- Obstructions. The obstruction rules require heads close enough to an obstruction to wet the surface behind it; the common rule of thumb is not more than three times the obstruction width from the head.
- Protection. Do not paint, coat or damage heads. Use the listed wrench, keep the spare-head cabinet stocked, and replace any head that has been painted, dropped or corroded.
Worked example
An 8 in wide duct runs 4 ft below a 10 ft ceiling. The three-times rule gives 8 x 3 = 24 in. A standard spray pendent is located 30 in horizontally from the duct, so it is too far away. Options are to move the head within 24 in of the duct, add a head on the far side, or use a head listed for that obstruction condition. Also check that the deflector is within the listed distance below the ceiling and that the duct does not block the spray pattern.
Traps that cost marks
- Painting or coating a head, which voids the listing.
- Using an ordinary-temperature head beside a unit heater.
- Applying the three-times rule without checking the actual listing.
- Changing the K-factor without recalculating pressure and flow.