E93.1001EN.C Manual CD
+
39
8.5
Flow monitoring
Flow
In the control of the water heater an extensive flow monitoring function has been implemented. If the temperature
difference between incoming cold water and outgoing hot water gets too high, this indicates a too small water flow
through the appliance.
Safety actions
-
If the temperature difference exceeds the maximum at a certain load,
for a longer time than specified in the
software
, the display will show ‘Delta direct block’ and the appliance will
block:
it switches immediately to
reduced power. Power is then slowly increased to the required level again. The fourth time, so after three of
these blockings, the water heater will go in
lock-out
(F16) and the display shows ‘FlowReturn dt fault’.
-
At very bad flow rates (
temperature difference for 10 seconds exceeding a certain entered safety value
), the
appliance will skip the blockings and immediately go in lock-out: F16, display ‘FlowReturn dt fault’.
-
In
Service mode
the appliance will immediately go in lock-out when the maximum value corresponding to the
applied power is exceeded, skipping the blocking procedures that apply at normal operation. Again F16, dis-
play ‘FlowReturn dt fault’.
NB!
All values of this flow monitoring have been programmed by EHS in order to get the best performance com-
bined with a long life time.
8.6
Water pressure switch
Water pressure getting too low indicates a blocking of the water flow. If that is the case, heat from the flue gases
cannot be transferred and will flow away through the flue gas channels. Also overheating of the heat exchanger
and/or other parts of the system could occur, if no measures would have been taken. For this reason a water
pressure switch,
WPS
, has been integrated in all CD
+
system models.
Operating values
The water pressure switch has one Normally Open (NO) contact, meaning the contact is open in rest position
when no pressure is applied. As soon as the system has been filled and the pressure exceeds 0.85 bar, the switch
closes, enabling operation. If, by any cause, the pressure drops below 0.75 bar, the system will be blocked.
In this case the display will show:
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.
Check if there is any leakage or maybe the pressure in the service pipe has dropped down.
See also § 16.2 ‘Blocking codes’, from page 111 on.
