Notifier 30-2021E-24 User Manual

Ultraviolet flame detectors, General, Theory of operation

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DN-1253:B • 8/25/2010 — Page 1 of 4

30-2021-24 &
30-2021E-24

Ultraviolet Flame Detectors

Conventional Initiating Devices

DN-1253:B • I-207

General

The

Pyrotector Model 30-2021-24 and Model 30-2021E-24

Ultraviolet (UV) Flame Detectors are highly sensitive to the

ultraviolet radiation given off by all types of flames, including

those produced by flammable liquids and gases. Since the

detector does not respond to normal ambient light conditions

such as sunlight, incandescent or fluorescent lighting, it is ide-

ally suited for use as a flame detector in a variety of areas.
The Pyrotector Ultraviolet Flame Detector is a compact unit-

ized package consisting of a detection tube, encapsulated

solid state electronic circuitry, and a dry-contact Form-C

(SPDT) alarm relay. In the event of an alarm, the relay latches

on and an alarm light is illuminated for easy identification of

the unit in the alarm state. The relay is reset by momentarily

interrupting power to the unit. A three-second time delay is

built in to minimize false alarms cause by the presence of

sparks, lightning, etc.
• Model

30-2021-24 is contained in a general purpose enclo-

sure

and is intended for indoor use only. It mounts on a

standard 4" (10.16 cm) octagonal electrical junction box

(not included).

• Model

30-2021E-24 is intended for indoor use and is con-

tained in an explosion-proof enclosure that meets all

requirements for NEC Class I Groups C and D; Class II

Groups E, F, and G; and Class III hazardous locations.

• Both models operate on 24 VDC.

Theory Of Operation

The Model 30-2021-24 and Model 30-2021E-24 UV Flame

Detectors operate with a Geiger-Muller-type tube that utilizes

an ultraviolet sensitive photocathode within a fused silica enve-

lope. When exposed to UV radiation, the photocathode emits

electrons that ionize the inert gas inside the tube. This initiates

the current flow that produces an alarm signal.

Application Considerations

To ensure proper operation of the detector, the viewing window

and the surface of the sensing tube must be kept clean and

free of contaminating films at all times. When cleaning the

sensing tube, the user must exercise caution to apply mini-

mum pressure, thereby minimizing the possibility of damage to

the detector tube.
Cutting and welding operations within the cone of vision of the

detector can generate high levels of UV radiation that can

result in actuation of the detection system. To avoid unwanted

alarms, it is suggested that the detection system be de-ener-

gized while these activities are occurring.
It should be noted that ultraviolet detectors will not detect glow-
ing embers

. A high-speed ember detector such as the Model

30-2054-24 or 30-2054A-24 should be used for this type of

application.

Specifications

Operating voltage: 22 to 27 VDC for 24 VDC unit.

Operating current: STANDBY: 12 mA maximum @ 24

VDC. ALARM: 100 mA@ 24 VDC.

Alarm relay contact rating: 1 A @ 26 VDC.

Spectral sensitivity range: 1700 to 2900 angstroms, with

peak response at 2100 angstroms.

Temperature range: –13°F (–25°C) to +140°F (+65°C).

Humidity range: up to 90% RH.

PHYSICAL SPECIFICATIONS, 30-2021-24:

Enclosure type: general-purpose painted steel with pro-

tective cage and totally encapsulated electronics.

Dimensions: 4.09" (10.389 cm) diameter; 3" (7.62 cm)

deep.

Weight: 0.75 lb. (0.34 kg).

PHYSICAL SPECIFICATIONS, 30-2021E-24:

Enclosure type: explosion-proof housing with 3/4" (1.905

cm) NPT female entries. NEC Class I, Groups C and D;

Class II, Groups E, F, and G; Class III.

Dimensions: 6.76" (17.17 cm) x 2.75" (6.985 cm) x 4.75"

(12.065 cm).

Weight: 3.75 lbs. (1.7 kg).

Detector Sensitivity

The response time of the detector is a function of the size of

the fire, fuel type, and the distance from the detector to the fire.

Smaller fires and greater distances normally require greater

response times. Figure 1 illustrates the relative sensitivity of

the Model 30-2021-24 Detector to gasoline fires. Figure 2

shows the relative sensitivity of the Model 30-2021E-24.
The Model 30-2021E-24 is approximately 10% less sensitive.

For example, a three-second response time is achieved at 10

feet (3.048 m) rather than 12 feet (3.658 m) when detecting a

6" (15.24 cm) gasoline fire.

Model 30-2021-24

30-2021.tif

30-2021e.tif

Model 30-2021E-24

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