2-28 Installation – Flame Scanner/Relay
FlexFit – Linkageless Control – Revision 1.0
PREFERRED
UTILITIES MFG CORPORATION
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Flame Relay
When a ame of sufcient intensity is detected (>25%), the scanner will activate the output relay and the ame relay LED will
illuminate. The ame relay LED is a single-color LED. If the ame signal falls below the minimum threshold for > 3 seconds or an
internal circuit or sensing element test fails, the output relay will deactivate, the 4-20mA output will go to 0mA, and the ame relay
LED will shut off.
The output relay contact is supervised by the microcomputer. If the scanner detects an absence of ame for > 3 seconds and
the contacts fail to open, a second fault relay will open the circuit, and the 4-20mA output will drop to 0mA. The ame status LED
will blink red – on for 3 seconds and off for 1 second. After one minute, the scanner will reset itself and resume its normal functions.
If the internal contact is permanently welded closed, the scanner will lockout again for one minute at the next ame off condition.
Self-Checking
In the BMU-UVSC model, the self-checking mechanism will interrupt the light coming from the ame every 10 seconds. When
this check is performed, the ame status LED will momentarily turn yellow (if a ame is present) or green (if a ame is not present).
During the self-check, the output relay does not change; however, the 4-20mA output drops to 4mA.
Should the UV sensing element continue to sense ame during the self-test, the scanner will deenergize the output relay causing
a lockout) to indicate the failure and the ame status LED will remain green for one minute. After one minute, the control will automat-
ically reset itself. The scanner's microcomputer will then continue to check the sensing element every 10 seconds. Should the UV
sensing element be in a permanent runaway condition, the scanner will immediately lockout again for another period of one minute.
Mechanical (BMU-UVSC)
Length Overall ...........................................................................................................9" (229 mm)
Diameter .................................................................................................................... 3.25" (82.5 mm)
Housing .....................................................................................................................Machined 5052 Aluminum Alloy
Finish .........................................................................................................................Clear Anodized
Sight Tube Entrance .................................................................................................. 1" Pipe Thread
Purge Air Entrance .................................................................................................... 3/8" Pipe Thread
Mechanical (BMU-UV & BMU-IR)
Length Overall ...........................................................................................................7" (177.8 mm)
Diameter .................................................................................................................... 2.25" (57 mm)
Housing .....................................................................................................................Machined 5052 Aluminum Alloy
Finish .........................................................................................................................Clear Anodized
Sight Tube Entrance .................................................................................................. 1/2" Pipe Thread
Purge Air Entrance .................................................................................................... 1/8" Pipe Thread
Electrical
Supply Voltage ..........................................................................................................120 VAC, 50/60 Hz, 2 VA
Internally-Powered Output Relay ..............................................................................120 VAC, 1 Amp max
4-20mA Output .......................................................................................................... 2-wire, Loop-powered, Isolated
External Loop Power Supply .....................................................................................12 to 30 Vdc
Environmental
Class ..........................................................................................................................NEMA 4
Temperature ..............................................................................................................-20°C to +60°C (0°F to 140°F)
Optical
Lens Material ............................................................................................................. Fused Silica
Spectral Sensitivity
Ultraviolet...................................................................................................................180-230 nanometers
Infrared ......................................................................................................................320-1000 nanometers
Product Certifications
Models BMU-UV, BMU-UVSC, BMU-IR ...................................................................UL le MH45788
Flame Scanner Installation
The actual attachment of the scanner to the burner can be varied to suit individual applications. The scanner, when applied
to multi-burner applications, should always be attached to a 5002-73/74 swivel mount to assist in burner discrimination. The swivel
mount has a 2" NPT male connection and connects to a 2" NPT coupling welded to the burner front plate. A 1" NPT nipple connects
the scanner to the swivel ball joint. The use of the swivel mount is also recommended on single burner applications.
• This product is designed to work in a variety of applications and conditions, however, some applications may not be
applicable due to the presence of high electrical noise, lack of adequate ground connections, oating neutrals or other
conditions. It is therefore important to ensure proper system environment before installing these devices.
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