Slant/Fin VGH-299-CH, Installation And Service Manual

Page: 71 / 128

E93.1601EN032.C VGH installation manual 71
12.7.1 F
LAME DETECTION
When the boiler is firing, and 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.
The presence of a flame is measured through the flame rod that points into the flame. The flame current is measured
by the control as ionization in micro amps (
μ A).
When the flame current is above Flamerod_Se Flamerod_Hysterese (1.0 μ A + 0.5 μ A) a flame will be
present. When the flame current is below Flamerod_Setpoint (1.0 μ A) the flame will not be present.
12.7.2 F
LAME RECOVERY
When the ionization current is too low, the system responds by increasing the minimal fan speed, in order to keep
the flame present. This is done by increasing the minimal fan speed when the ionization current is too low.
Whenever the ionization current is high enough, the minimal fan speed will be decreased again. When
the flame still disappears the minimal fan speed will be increased for the next burn cycle.
• When the flame current is below Flamerod_Se Flamerod_Delta (1.0 μ A + 0.2 μ A) the minimal fan speed
will be increased.
• When the flame current is above Flamerod_Se Flamerod Flamerod_Delta * 2 (1.0
μ A + 0.2 μ A
+ 0.4 μ A) the minimal fan speed will be decreased.
When the flame still disappears the minimal fan speed will be increased for the next burn cycle.
When the system successfully completes a burn cycle, the minimal fan speed will be reset to the set minimal fan
speed in the system.
Control functions
Dependent on the required functions of the appliance and connected sensors and components, several operation
modes for Central Heating (CH) and Domestic Hot Water (DHW) can be selected.
12.8.1 R
OOM THERMOSTAT ONLY
; CH
MODE
0 (D
EFAULT SETTING
)
For this mode the CH mode must be set to 0 and no outdoor sensor is needed.
If the room thermostat closes, the boiler and system circulators are switched ON. When the supply temperature
drops CH_Hysterese_Down below the CH_Setpoint (settable via the menu) the boiler is switched ON. The power
for the boiler is PID regulated between T_Supply and the CH_Setpoint using the PID parameters for Central
Heating.
XXX
If the supply temperature reaches a temperature CH_Hysterese_Up above the CH_Setpoint the boiler is switched
OFF. However, if CH_Se CH_Hysterese_Up is greater than maximum setpoint the boiler switches OFF at
the maximum setpoint.
If the room thermostat opens the boiler is switched OFF (if this was not already happening) and the boiler and
system circulators run ON for CH_Post_Pump_Time.
Anti-cycling time
(This function is also applicable to all other CH modes) When the boiler is switched OFF because the supply
temperature reaches CH_Se CH_Hysterese_Up, the control will wait a period of time (Anti_Cycle_Period
→ 180 sec. settable) before it is allowed to be switched ON again.
This function is to prevent short cycling ON and OFF of the boiler. However, when during the anti-cycle wait time
the differential between setpoint and supply temperature gets greater than Anti_Cycle_T_Diff, anti-cycle will be
aborted, and the boiler is allowed to start.
Maximum CH power
(This function is also applicable to all other CH modes)
The maximum boiler power during CH operation can be limited with parameter P_CH_Max.
Minimum CH power
(This function is also applicable to all other CH and DHW modes)
The minimum boiler power during operation can be limited with parameter P_CH_Min.
Table 12. 9
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 12. 10