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NISM/NHD/03
NHD-G SERIES
HEAT DETECTOR
INSTRUCTION MANUAL
MARCH 2001
1
5
OF
03
CONTENTS
Section 1
-
Introduction
- Page 1
Section 2
-
Operation
- Page 1
Section 3 -
Detector Models
- Page 2
Section 4
-
Base Models
- Page 2
Section 5 -
Installation
- Page 2
Section 6 -
Wiring
- Page 2
Section 7 -
Maintenance &
Cleaning
- Page 3
Section 8 -
Specification
- Page 4
SECTION 9 -
EMC
- Page 4
Section 10 -
DIMENSIONS
- Page 4
Section 11 -
Accessories
- Page 5
Section 12 -
Response
Characteristics
- Page 5
SECTION 1 - INTRODUCTION
The NHD-G range of attractively styled, fast re-
sponse, low profile heat detectors.
They have been designed, in most cases, to replace
our 2SA-70T-LS, TCA-70-LS AND TCA-60-LS
Features:
* Low profile, stylish appearance
* Four different response grades
* Non-polarised terminals
* Head removal signal facility
* Low monitoring current
* Integral LED alarm indicator
* Remote indicator output
* Easy maintenance
SECTION 2 - OPERATION
The NHD-G range of heat detectors are non mechani-
cal and use a thermistor of low thermal mass as the
sensing element giving a fast response. Although
these detectors operate on a fixed temperature
threshold only, their fast response makes them
generally suitable for use where rate-of-rise detectors
would be used.
Fig. 1. Block Diagram of NHD-G Detector Circuit
RECTIFIER
AND
FILTER
OPERATION
INDICATOR
SWITCHING
UNIT
VOLTAGE
STABILISER
P+
L
CI
CII
SENSING
THERMISTOR
INTERNAL
REFER-
ENCE
COMPARITOR
UNIT
FIG. 1
