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Display message
Reason
Cause:
It is not proven that the non-return valve of the burner, that is not burning, is closed.
Corrective action:
When a closed non return valve is proven this message will disappear.
If not a lockout message will appear.
Cause:
It is not proven that the non-return valve of the burner, that is not burning, is closed, but the fan is running to
prevent recirculation. (If P2MT =1)
Corrective action:
Check the state of the Non Return Valve:
> Is the valve moving freely to the open and closed position.
> Is there debris/fouling or corrosion in the valve to prevent the valve to move freely.
Cause:
The fan of the non-burning burner is not able to run to prevent recirculation, but the non-return valve is closed
to prevent recirculation. (If P2MT =1)
Corrective action:
Check the 4 wired wiring and connections at the fan and at the main control board.
Check the 3 wired power supply wiring and connections at both ends.
Replace the fan.
Replace the main control board of that specific burner.
Cause:
It is not proven that the non-return valve of the unit is closed.
Corrective action:
Check and repair or replace NRV.
Display message
Reason
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 increase the resistance
causing the water flow to drop.
Display message
Reason
Cause:
Low water flow.
Corrective action:
Clean the heat exchanger on the water side. Heat exchanger fouling (partly blockage) will increase the
resistance causing the water flow to drop.
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.
N
R
V
o
r
Non return valve still open.
D
e
l
t
a
D
Temperature difference between flow and return has exceeded the blocking
value
H
e
a
t
e
x
c
Temperature difference between flow and return has exceeded the blocking
value 3 times (P2LL = 2)
F
a
n
f
a
u
9
9
9
i
r
e
c
t
b
9
9
9
h
a
n
g
a
t
9
9
9
l
t
,
5
h
r
s
l
o
c
k
,
5
h
r
s
r
i
s
k
,
5
h
r
s
110
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