Bosch D256A Specsheet

Fire Alarm Systems | D256A Fixed-temperature (135°F [57°C]), Rate-of-Rise Heat Detector Head

D256A Fixed-temperature (135°F [57°C]),
Rate-of-Rise Heat Detector Head

www.boschsecurity.com

u Mounts on low‑profile six‑inch diameter base

u Easy head removal for cleaning and servicing

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.

Notice

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).

Functions

u Available in 24 VDC, 135°F (57°C) or 190°F (88°C)

fixed settings

u Dual built-in power and alarm LEDs viewable from

360°

u Highly stable operation and RF/Transient protection

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 the detector is
protected from damage by the built‑in, durable plastic
guard.

Certifications and approvals

Region Certification

USA UL UQGS_S4990 - Heat-automatic Fire De-

tectors

CSFM see our website

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 heat detectors performs the same function as a
mechanical heat sensing device, but with electronic
precision. The detector sends an alarm signal when it

Installation/configuration notes

Compatible Products

The following products are compatible with the heat
detector heads:

Category Products

Control
Panels

D7022 Conventional Fire Alarm Control Panel

D7024 Conventional and Addressable Fire Alarm
Control Panels

2 | D256A Fixed-temperature (135°F [57°C]), Rate-of-Rise Heat Detector Head

Category Products

FPD-7024 Conventional and Addressable Fire Alarm
Control Panels

D9124 Addressable Fire Alarm Control Panel

D9412, D7412, D7212 Control Panels

G Series Control Panels

1

D9112 Addressable Control Panel

Detector
Bases

D250A Two‑wire Detector Base (12 VDC or 24 VDC)

D280A Two‑wire Detector Base (24 VDC)

D290 Four‑wire Detector Base (24 VDC)

D291 Series Detector Bases

1

G Series = D9412G, D7412G, D7212G, D9412GV2, D7412GV2,

2

D7212GV2, D9412GV3, D7412GV3, D7212GV3, D9412GV4,
D7412GV4, and D7212GV4

2

D291 Series = D291MMaster Addressable Detector Base (24 V) and

D291S Addressable Detector Base (24 V)

Notice

These heat detectors do not operate on standard
12 VDC two‑wire loops; they require 24 VDC.
When used with 12 VDC control panels, a UL
Listed 24 VDC auxiliary power supply is required.

Environmental

Temperature

+32°F to +120°F (0°C to +49°C)

(ambient):

Note: The normal environment where these detectors are installed
should be within the specified ambient temperature limits.

Mechanical

Color: Bone white

Dimensions

6 in. x 2 in. (15.2 cm x 5 cm)

(diameter x D):

Ordering information

D256A Fixed-temperature (135°F [57°C]), Rate-of-Rise
Heat Detector Head

Fixed‑temperature (135°F [57°C]), rate‑of‑rise
mechanical heat detector head for use in 12 VDC or
24 VDC nominal circuits; requires a base.

Order number D256A

Mounting

The detector base installs over a back box and
contains all the wiring. The detector head attaches to
the base by hand by aligning the head with the base
and turning it clockwise. No tools are required for
installation other than the hex key used to tighten the
tamper screw.

Wiring

Refer to the installation instructions for the specific
base for detailed wiring requirements.

Parts included

Quant. Component

1 Detector head

1 Literature pack

Technical specifications

Electrical

Current (alarm): 150 mA at 24 VDC

Current

0.04 mA at 24 VDC

(supervisory):

Current (surge): 0.160 mA at 24 VDC

Voltage (operating): 15.0 VDC to 33.0 VDC

3 | D256A Fixed-temperature (135°F [57°C]), Rate-of-Rise Heat Detector Head

Represented by:

Americas: Europe, Middle East, Africa: Asia-Pacific: China: America Latina:

Bosch Security Systems, Inc.
130 Perinton Parkway
Fairport, New York, 14450, USA
Phone: [phone]
Fax: [phone]
[e-mail]
www.boschsecurity.us

Bosch Security Systems B.V.
P.O. Box 80002
5617 BA Eindhoven, The Netherlands
Phone: + 31 40 2577 284
Fax: [phone]
[e-mail]
www.boschsecurity.com

Robert Bosch (SEA) Pte Ltd, Security
Systems
11 Bishan Street 21
Singapore 573943
Phone: [phone]
Fax: [phone]
[e-mail]
www.boschsecurity.asia

Bosch (Shanghai) Security Systems Ltd.
201 Building, No. 333 Fuquan Road
North IBP
Changning District, Shanghai
200335 China
Phone [phone]
Fax: [phone]
www.boschsecurity.com.cn

Robert Bosch Ltda Security Systems Division
Via Anhanguera, Km 98
CEP 13065-900
Campinas, Sao Paulo, Brazil
Phone: [phone]
Fax: [phone]
[e-mail]
www.boschsecurity.com

© Bosch Security Systems 2014 | Data subject to change without notice
12383582987 | en, V3, 31. Oct 2014