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Display message
O u t d o o r
s e n s o r
f a i
l
9 9 9 , 5
h r s
Reason
No outdoor sensor detected.
Cause:
The unit is programmed to check if an outdoor sensor is present and does not detect an
outdoor sensor.
Corrective action:
Check for loose wiring/connections in the outdoor sensor circuit.
Check the state of the outdoor sensor and replace it if necessary.
Display message
R e t u r n
t e m p
h i g h
9 9 9 , 5
h r s
Reason
Return temperature has exceeded the blocking temperature, but it
has not exceeded the lock-out value.
Cause:
Systems that pre-heats the boiler return temperature too much/high.
Corrective action:
Reduce pre-heat temperature of external heat source.
Cause:
The need for heat in the system suddenly drops causing hot return water to the boiler.
Corrective action:
Dampen external heating system control to prevent sudden boiler temperature rise.
Display message
T 2 - T 1 h i g h
9 9 9 , 5 h r s
Reason
Difference between T2 and T1 has exceeded the blocking value
which has been set in the parameters.(return temp higher than
flow)
Cause:
The water flow through the unit is too low.
Corrective action:
Check functioning of the pump.
Check/open all valves that might restrict the water flow through the unit.
Check for an external system pump that influences the flow through the unit.
Check if the system resistance exceeds the spare capacity of the unit pump.
Make sure the heat exchanger is clean. Heat exchanger fouling (partly blockage) will in-
crease the resistance causing the water flow to drop.
Display message
W a t e r p r e s s u r e
f a u l
t
9 9 9 , 5
h r s
Reason
Water pressure is too low or high.
Cause:
The water pressure in the system is too high.
Corrective action:
Check if the system pressure is too high after (re)filling.
Make sure that there is a pressure relief valve and expansion vessel installed in the sys-
tem, according to the applicable standards.
Check if there is an open connection between the unit and the relief valve plus expansion
vessel.
Be aware that if the unit is installed in the basement of a tall building, only the static pres-
sure of the water column above the units can raise above the maximum allowable limits.
Make sure that this is not the case.
Cause:
The water pressure in the system is too low.
Corrective action:
Check if there is no leakage in the system that causes the pressure to drop. Fix any leak-
age and fill the system.
Check if there is an external system pump that sucks water through the boiler, causing an
under pressure. (bad installation design).
