Servicing
5
Installation and maintenance instructions for wall-mounted condensing gas boiler 600 - 28C • 01/2004
39
Subject to modifications resulting from technical improvements!
Boulter Buderus Ltd. • http://www.boulter-boilers.com
Code
Meaning
2U
Non blinking fault code
: Temp. difference between the bi-sensor and the return sensor is greater than 50 °K
Possible
cause
Action
1
Resistance in the installation is too high
Check if not all (thermostatic) radiator valves are closed or
clogged with dirt
2
Water pressure is too low in the installation
Top up the system (see subsection 2.1.1)
3
Problem with the pump or pump cabling
(no circulation)
Check if the pump cabling is faulty or if the pump is stuck.
Replace pump when necessary (see subsection 5.3.6 and
subsection 5.3.7)
4
Bi-sensor is dirty or faulty
Check the bi-sensor for dirt. Measure if resistance over the
sensor is correct. If not replace bi-sensor (see subsection
5.3.8, subsection 5.3.9, subsection 5.3.10)
5
Return sensor may be faulty
Check return sensor and when necessary replace sensor
(see subsection 5.3.8)
Code
Meaning
3A
Non blinking fault code
: No communication between fan and UBA
Possible
cause
Action
1
Faulty cable or connection
Check the cabling and connections and replace when
necessary (see subsection 5.3.3)
2
Fan is defect
Replace fan (see subsection 5.3.3)
Code
Meaning
3L
Blinking fault code
: Fan signal not detected at power up stage
Possible
cause
Action
1
Faulty cable or connection
Check the cabling and connections and replace when
necessary (see subsection 5.3.3)
2
Fan is defect
Replace fan (see subsection 5.3.3)
Code
Meaning
3P
Blinking fault code
: Fan running too slow
Possible
cause
Action
1
Fan may be dirty
Check fan for dirt (see subsection 5.3.3)
2
Power supply may be faulty
Check the power supply
3
Fan wiring or connections faulty
Check the fan wiring and connections
(see subsection 5.3.3)