Camus Hydronics Valiant FT VA0080, Manual

Page: 36 / 79

29
5.6.2 Flame Detection
When the Valiant FT is running but the flame is not detected
anymore, the gas valve will be closed and the control will
perform a post-purge, after which a restart will take place.
When the flame disappears 3 times within one heat demand
the control will lockout.
The presence of a flame is measured using the flame rod
which points into the flame. When a flame is present, the
free electrons in the flame flow from the flame rod to ground.
This flow of electrons is the flame current. The flame current
is measured by the control as ionization in uA.
When the flame current is above 1.5uA , the Valiant FT will
register a flame.
When the flame current is below
0.8uA
, the flame will be
registered as extinguished.
5.6.3 Flame recovery
When the ionization current is too low, the system responds
by increasing the minimal fan speed, in order to keep the
flame present.
When the ionization current is high enough, the minimal fan
speed will be decreased again.
If the flame still disappears the minimal fan speed will be
increased for the next burn cycle.
No. of flame losses Description
0 Minimal fan speed as set in the
system
1 In between minimal and ignition
fan speed
2 Ignition fan speed
Table 22: Flame Recovery Logic
When the system successfully completes a burn cycle, the
minimal fan speed will be reset to the set minimal fan speed
in the system.
5.6.4 Freeze Protection
The Frost protection function protects the systems’ primary
heat exchanger from freezing.
The
Supply
and
Return
sensors are checked for generating
a frost protection demand.
•
If one of the sensors drops below
FP_Start_Pump
the
pump is switched ON for CH.
• If any of the sensors drops below FP_Start_Burn the
burner starts.
•
When all sensors measure above
FP_Stop
Frost
protection demand is ended.
When the demand for Frost protection is ended the pumps
will post-circulate for CH_Post_Pump_Period .
Relevant variables
Specific
Parameters
Level Default
Value
Range
FP_Start_Pump 2: Installer 10°C
50°F
-10 – 117°C
14 – 243°F
FP_Start_Burn 2: Installer 5°C
41°F
-10 – 117°C
14 – 243°F
E2_FP_Stop 2: Installer 15°C
59°F
-10 – 117°C
14 – 243°F
Table 23: Frost protection variables for Valiant FT
5.6.5 Flue temperature protection
The flue temperature protection function protects against
the flue gas reaching too high temperatures.
The Valiant FT utilizes a flue gas sensor.
• When the Flue sensor measures above the
Max_Flue_Gas_Temp,
the control generates a
Flue_Gas_Error.
When the control has a
Flue_Gas_Error
the fan will run at
minimum fan speed.
Burner power limitation
The control will limit the burner power when the flue gas
temperature reaches the set
Max_Flue_Gas_Temp
. The
maximum burner power is linearly limited when the flue gas
temperature is within
Max_Flue_Gas_Temp – 5ºC (41°F)
and
Max_Flue_Gas_Temp
.
Specific Parameters Level Default
Value
Range
Max_Flue_Gas_Temp 2:
Installer
95°C
203°F
40 – 130°C
104 – 266°F
Table 24: Maximum Flue Temperature Limitation setting
5.6.6 Heat exchanger protection: Max differential
To avoid temperature differences that are too large in the
primary heat exchanger, the burner load automatically
decreases when the Return/Supply temperature differential
increases too much.
At high fire, the ΔT ( Hx_Diff_DeltaT_Min) is limited to 60°F.
At a lower rate of fire, the control allows the temperature to
be within a 14°F tolerance to avoid sporadic heat
disruptions but it is crucial to check for correct water flow to
make sure that the ΔT remains well below the 60°F limit to
prolong the life of the heat exchanger.
To achieve its max ΔT differential algorithm, the PID output
value is linear limited between minimum and maximum fire.