49
BASIC SEQUENCE OF OPERATION
CALL FOR HEAT:
The control determines that a call for heat is necessary when the
water temperature drops below setpoint minus the differential
temperature. The call for heat is ended when the water temperature
rises above setpoint. When there is no call for heat, the heater
remains in standby mode.
A call for heat is determined by the following conditions:
•
If tank temperature < Operating Setpoint – Differential, a call for
heat is initiated.
•
If tank temperature > Operating Setpoint, a call for heat is
ended.
The tank temperature is the water temperature measured by the
dual thermistor temperature probe.
The Setpoint is the intended temperature of the outlet water set by
end user and displayed on LCD display.
MONITOR FLAME CURRENT
When the heater is in pre-purge, warm-up or post-purge and the
control senses a flame current, the heater will go in error mode E01
(Flame detected when it is not expected); the blower will operate
at high speed until the flame current is not sensed anymore. 15
minutes after the disappearance of the flame, the control will operate
normally. When the heater is in operation (burner is “on”) and the
flame is lost, after the post-purge sequence the heater will initiate
a new heating cycle. If the flame is lost for 3 times in less than five
minutes the heater will go in error mode (E03 lose flame 3 times in
5 minutes). See
Error Codes
(page 50).
BURNER IGNITION SEQUENCE
At power up, the control board, performs an inter-purge to clean-up
the combustion chamber. After this, when call for heat is not present,
the heater is in STAND-BY status. After receiving a call for heat, prior
pre-purge stage, the control will check for inlet air pressure switch,
outlet air pressure switch, Flue ECO switch to be closed, no flame
signal presence, and no flammable vapour presence. The blower
will start to operate in pre-purge stage. At the end of the pre-purge
period the HSI will be energized. After 12 seconds (warm up time),
the HSI reaches the ignition temperature; the gas valve will be
energized (open) for the duration for 5 seconds (safety time), then
the presence of the flame signal will be verified by the control. The
heating mode will be maintained until the call for heat is satisfied (tank
temperature reaches the Setpoint). The gas valve will be turned off
(closed) and the blower will operate for the duration of post-purge
then it will be turned off. The heater will remain in standby until a
new call for heat occurs.
WATER LEAK DETECTION AND WATER SHUT OFF KIT
(OPTIONAL)
Initially the control will have the leak detection function disabled by
default. In this case the Leak Detection Module (LDM) associated
errors E10, E11, and buzzer, are disabled as well.
As soon as an LDM (Leak Detection Module) from the optional Water
Leak Detection and Water Shut OFF Kit is connected to the control,
the Leak Detection Function will be automatically enabled. Errors
E10, E11, and buzzer will be enabled as well. With the LDM
connected, if the voltage at the LDM input falls below 1.45 V a “Water
leak detected” alarm will be in place (E10 and Buzzer beeping
continuously). This alarm will cease if the LDM input voltage rises
above 1.55 V (leak condition ceased). Also when the owner
acknowledges the event, he/she can silence the buzzer for 5 minutes
by pushing the button for 3 seconds. After 5 minutes, if the leak
condition is still in place (LDM voltage <1.45 V) the buzzer will start
beeping continuously. A new push on the button will silence the
buzzer again for 5 minutes and so on. Once connected, if the LDM
gets disconnected, the error E11 warning shall be in place (to let the
owner know that the LDM function it is not operational). If for any
reason the LDM should be unplugged on purpose, the LDM function
and associated errors can be disabled by pressing the button for
5 seconds. It will remain disabled until an LDM module is connected
again.
The optional Water Leak Detection and Water Shut OFF Kit includes
a Water Shut OFF Solenoid Valve that can be installed in the
inlet water line piping and connected to the control of the heater.
Whenever a leak event is in place, the Water Shut OFF Solenoid
Valve will be activated and will turn OFF the inlet water to the heater
to avoid damages due to flooding. When the leak event is no longer
in place the Water Shut OFF Solenoid Valve will be deactivated
automatically and the inlet water flow to the heater will be restored.
Status
Voltage
Leak detected
< 1.45
Leak recover
> 1.55
LDM present
< 1.8
LDM unplugged
> 2
Vdc
3.3
Table 23.