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8.19 TYPE 18: ALARM INDICATING AN INCORRECT POSITION OF THE MODULATING
BYPASS RELATIVE TO THE ORDERED POSITION
- Conditions:
• PX units with modulating bypass
- Causes:
• This alarm indicates that the modulating bypass has not reached the ordered position within 10 seconds.
The most common reason for this is a damaged position sensor on the bypass actuator, and this must be replaced.
Other reasons may be that the control board output is damaged, implying the replacement of the board, or a
mechanical blocking verified by a visual inspection of the bypass
- Effects:
Code
B.20
Position of the modulating bypass incorrect
ALARM OUTPUT
Alarm Status
Diagnostic :
Stop the unit, do an alarm reset, check and eventually correct actuator wiring to the control board and then check that the
bypass can move physically: connect IN3 to +12V to force the bypass to open.
•
If the bypass stays in close position, check if there is some mechanical obstruction that makes the actuator stuck,
otherwise:
-Either the actuator must be replaced
-Or the control board must be replaced
•
If the bypass opens completely:
- Do several Close/open cycle using IN3 to try to reproduce the alarm and check bypass position in info
menu. If the problem cannot be reproduced, try with fans boosting.
- Either the actuator must be replaced
- Or the control board must be replaced
Operation and maintenance instructions
Displayed on HMI TACtouch
Text displayed
TAC control board
AL dPa OUTPUT
/
Manual reset mandatory.
LED ALARM
ON
Level
3
Fans
Stopped
57
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