43
U-2 Diagnostics Board
The U-2 Diagnostics board is a solid-state electronic
fault indicator that has been engineered to enhance
safety, simplify troubleshooting and minimize equip-
ment down time. The U-2 safety board is the central
point for wiring, operations monitoring, and fault indi-
cation for the boiler safeties. By having each safety
report directly to the U-2 board, each safety function
can be individually monitored.
The U-2 adds complete diagnostics features that aid in
the rapid diagnosis of irregularities in boiler operation.
A single U-2 Diagnostics Board can monitor a maxi-
mum of eight safeties at one time. If, due to code
requirements, more than eight safety devices must be
monitored, two or more boards will be used to provid-
ed extended diagnostics capabilities. Advanced
Design Boilers equipped with the standard safety suite
will utilize the configuration shown in Table T.
The U-2 safety board has a series of red LED lights to
indicate a fault occurring at a monitored safety. An
additional light indicates that the diagnostics board is
energized and is currently monitoring for safety faults.
(In order to prevent spurious alarm conditions, the U-2
board monitors safeties only during the actual firing
cycle.)
Once a fault has been detected, the U-2 board will illu-
minate the corresponding LED lamp, will shut-down
the boiler, and will light the flashing red LED “Service”
lamp on the CPW board. If more than one fault is
detected, the U-2 board will display the priority fault
based on the safety hierarchy as labeled on the U-2
board. Once the first fault is cleared, the second fault
lamp will illuminate until cleared.
WARNING:
Only qualified persons shall attempt to
repair the boiler. Improper adjustment, service or
maintenance may damage the equipment, create a
hazard resulting in asphyxiation, explosion, fire,
electric shock, personal injury or property damage,
and will void the warranty.
Light
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System Enabled
Yellow
U-2 Diagnostics safety board is functional.
Manual High Limit
Red
Water temperature is over the manual high limit setting.
Auto High Limit
Red
Water temperature is over the auto high limit setting.
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F
Low Water Cut-off (option)
Red
Insufficient water volume for boiler operation.
High/Low Gas Pressure
Red
Gas supply pressure is below or above the allowed minimum gas supply
pressure to ensure safe operation.
Burner High Limit
Red
Mixer or PVC vent pipe, if installed, is over heated.
Blower/Ignition Lockout
Red
Blower failure, not enough combustion air or the equipment has an ignition
lock-out condition.
Blocked Vent
Red
The vent pressure switch has detected a blocked vent.
Table T: U-2 Diagnostic Board LEDs
Summary of Contents for 751
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Page 6: ...6 Component Locations Fig 1 Component Locations...
Page 15: ...15 Fig 6 Dual Boiler Piping Fig 7 Dual Boiler Piping with CHX...
Page 20: ...20 Fig 13 Single Boiler Pool Application Fig 14 Single Boiler Pool Application with CHX...
