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Fire Protection System Firestat
The Firestat (page 36) is a device installed in the riser of the hood, at the duct connection, that measures
temperature. One sensor shall be installed in each exhaust riser. Secondary downstream detectors in the duct are
not required except as outlined in the Non-Solid Fuel Appliances and Solid Fuel Appliances section. Sensors
are not required
above each appliance or in the hood grease plenum. The standard temperature setting is 360°F.
Depending on heat produced by appliance, a higher rated temperature Firestat will be required. If a temperature
higher than the setpoint is sensed, the Firestat contacts will close and energize the electrical control board. The fire
system will activate.
The supervised loop must be run through metallic conduit. Do not run wiring with high voltage wires. Verify all
supervised loop wires are free from damage/stress. All supervised loop wires must be terminated in terminal
blocks, junction boxes, and push-stations.
The Firestat has 2 black wires and 2 white wires. These wires must be connected to the supervised loop. Use high-
temperature wiring when installing Firestat components. Wago connectors (part number: 221-412) must be used.
Multiple sensors are wired in parallel in the supervised loop. The Firestat may be installed on the opposite side of
the quick seal for access in the duct.
Non-Solid Fuel Appliances (Rated 450°F)
Non-solid fuel appliances rated for 450°F will not require additional firestats, regardless of the configuration and
length of ductwork.
Non-Solid Fuel Appliances (Rated 600°F)
Non-solid fuel appliances rated for 600°F will require downstream detection if the duct run contains any horizontal
section over 25 feet in length. Downstream detection should be installed at the end of a horizontal section. Duct
layouts that include less than 25 feet of horizontal ductwork will not require additional detection.
Solid Fuel Appliances (Rated 700°F)
Solid fuel appliances produce effluents that can accumulate inside the duct, especially in long horizontal duct runs.
Sparks from solid fuel appliances can travel into the ductwork and create fires that occur beyond the point where
the hood riser Firestat can detect them. Additional downstream Firestats ensure that these duct fires are detected
and the fire system actuates. Solid fuel applications require 600°F rated Firestats, and SOLO filters. Exhaust fan(s)
used with solid fuel appliances must use a steel wheel.
In addition to the 600°F rated Firestat, located in the hood riser, a second Firestat is required at the duct discharge
for solid fuel applications when the ductwork exceeds 10 feet in length or contains horizontal runs. Even if the
entire duct run is inaccessible, this additional Firestat is still needed. Mounting a Firestat in the fan may be an
option. On duct runs longer than 50 feet, a third Firestat will be required somewhere in the duct run, ideally at the
end of a horizontal run, if present. Duct runs longer than 100 feet will require additional Firestats, contact your
local sales office for more information.
NOTE: When additional Firestats are required, install in an accessible location near an access door, hood
riser, or fan. The door will provide access to install, clean, and replace the Firestat when needed. If a PCU
is equipped with electronic detection, PCU Firestats can serve as downstream detectors, if present. The
temperature rating of the Firestat in the duct must always match the temperature rating of the Firestat in
the riser.
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