Bosch SSB1000 TL - Safety and System Functions; Flame Detection and Measurement; Overheat Detection Safety Limit

6720892984 (2019/02) US SSB
34 | Main control
5.3 Safety and system function
5.3.1 Flame detection (Rev 3.0.0.0)
When during burning the ame 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 ame disappears three times within one
heat demand the control will lockout.
The presence of a ame is measured by an ionization rod. Between this
ionization rod and earth an electromagnetic eld is present. When a ame
is present, the free electrons in the ame ow from the ionization rod to
the earth. This ow of electrons is the ame current. The ame current is
measured by the control as ionization in uA.
When the ame current is above
Flamerod_Setpoint + Flamerod_
Hysterese
(1,0uA + 0,5uA) a ame will be present.
When the ame current is below
Flamerod_Setpoint (1,0uA) the
ame will not be present.
5.3.2 Ionization jumper (Rev 3.0.0.0)
The 900 series burner controls are equipped with an ionization-jumper.
Depending on the situation where the control is placed it is possible that
the jumper should be removed.
Mains voltage 230V
Phase-Phase network
Standard the ion-jumper should not be
placed.
Phase-Neutral network
Standard the ion-jumper should be
placed
1) 2)
Mains voltage 120V
Phase-Phase network Not possible.
Phase-Neutral network
Standard the ion-jumper should not be
placed
2)
1)
It is possible that the ion-jumper should be removed in combination with
a HIS, because the HSI can inuence the ionization measurement. This is
appliance-dependent.
2)
When the ion-jumper is removed the burner control becomes sensitive
to which way phase and neutral are connected.
Therefore check with a multi-meter if on the board mains supply
connector the phase (120/230Vac) is connected to line and the neutral
is zero. When polarized mains is used it is important to wire phase
and neutral correctly during production. In case phase and neutral are
reversed, the lack of ionization current will cause a locking error when the
burner tries to ignite.
5.3.3 Flame recovery (Rev 3.0.0.0)
When the ionization current is too low, the system responds by increasing
the minimal fan speed, in order to keep the ame 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 ame still disappears the minimal fan speed will be increased
for the next burn cycle.
• When the ame current is below Flamerod_Setpoint + Flamerod_
Delta (1,0uA+0.2uA) the minimal fan speed will be increased.
• When the ame current is above Flamerod_Setpoint +
Flamerod_
Delta
+ Flamerod_Delta * 2 (1,0uA + 0.2uA + 0.4uA) the minimal
fan speed will be decreased.
When the ame still disappears the minimal fan speed will be increased
for the next burn cycle.
No. of ame
losses
Description
0 Minimal fan speed as set in the system
1 In between minimal and ignition fan speed
2 Ignition fan speed
When the system successfully completes a burn cycle the minimal fan
speed will be reset to the set minimal fan speed in the system.
5.3.4 Overheat detection (safety limit) (Rev 3.0.0.0)
Overheat is detected using an external overheat thermostat that is placed
in series with the gas valve.
When the temperature gets too high the overheat stat opens and the gas
valve is closed automatically.
An error message is shown at the display. Details on how to connect the
overheat thermostat can be found in the connector description.
The burner always stops when T_Supply is over
STAY_BURNING_
TEMP
and starts again when T_Supply is under START_BURNING_
TEMP
.
Relevant variables
Specic
Parameters
Level
(Default) Value Settable
°C °F °C °F
START_BURNING_
TEMP
[°C/°F]
3: Factory 90 194 -10...117 14...243
STAY_BURNING_
TEMP
[°C/°F]
3: Factory 95 203 -10...117 14...243
5.3.5 Sensor availability (Rev 3.0.0.0)
The following sensors can be connected to the control:
Senor Description
T_Supply CH supply sensor
T_Supply_2 2
nd
CH supply sensor
T_Return CH return sensor
T_DHW DHW out sensor
T_Flue Flue gas sensor
T_Flue_2 2
nd
Flue gas sensor
T_System Cascade system sensor
T_DCW Cold water sensor
T_Outdoor Outdoor sensor
P_Water Water pressure sensor
P_Water_Switch Water pressure switch
0-10 Volt 0-10 Volt input
Water Flow DHW DHW ow sensor
P_Flue Flue pressure switch
Water Flow CH CH ow sensor
P_Gas Gas pressure switch
Air Damper Air Damper switch
Flue switch Flue switch input
Blocked ue Blocked ue switch
LWCO1 Low water cut off 1
LWCO2 Low water cut off 2
RT switch Room thermostat input