Bosch D256A Leaflet

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Fire Alarm Systems | D256A/D257A Fixed‑temperature, Rate‑of‑Rise Heat Detector Heads
Use these detectors for indoor confined areas where high
heat‑output fires are expected, or in areas where ambient
conditions do not allow the use of other detection methods.
These heat detectors are intended for
detection circuits that protect property. Use
smoke detectors to protect personnel.
Use the D256A (response-rated at 135°F [57°C]) in areas
where the ambient temperatures do not exceed 120°F
(49°C). Use the D257A (response-rated at 190°F [88°C]) in
areas where the ambient temperatures exceed 120°F
(49°C) but not 160°F (71°C).
Detector Head and Base System
These heat detectors have two components: the detector
base and the detector head. The bases are permanently
attached and wired to back boxes. The interchangeable
heads quickly detach for replacement and cleaning without
affecting the circuit wiring.
Detection Method
The D256A and D257A Heat Detectors perform the same
function as a mechanical heat sensing device, but they do
so with electronic precision. The detector sends an alarm
signal when it reaches its fixed temperature value or when
the temperature rises more than 12°F (6.6°C) in less than
a minute. When an alarm signal is sent, the red alarm LEDs
latch on.
The thermistor heat element used in both the D256A and
D257A is protected from damage by the built‑in, durable
plastic guard.
Certifications and Approvals
UQGS: Heat - Automatic Fire Detectors
7270-1615: 170   July 2008
Installation/Configuration Notes
Compatible Products
The following products are compatible with the D254 and
D255 Heat Detector Heads:
D256A/D257A Fixed‑temperature,
Rate‑of‑Rise Heat Detector Heads
▶ Mounts on low‑profile six‑inch diameter base
▶ Easy head removal for cleaning and servicing
▶ Available in 24 VDC, 135°F (57°C) or 190°F (88°C) fixed
▶ Dual built-in power and alarm LEDs viewable from 360°
▶ Highly stable operation and RF/Transient protection
▶ Electronic heat sensing operation