Preconditions For Burner Startup; Undervoltages; Reversed Polarity Protection; Startup Sequence - Siemens LGB21.130A17 Datasheet

Functions
Preconditions for
burner startup

Undervoltages

Reversed polarity
protection

Startup sequence

Building Technologies
HVAC Products
The function diagrams show the required or permissible input signals to the control
section and to the flame supervision circuit hatched (refer to «Connection diagrams»).
If these input signals are not present, the burner control will stop the startup sequence to
trigger lockout where required by safety regulations.
Burner control must be reset
-
The contacts of gas pressure switch «GP», limit thermostat / pressure switch «W»,
-
control thermostat / pressurestat «R» and safety limit thermostat «SB» must be
closed
Fan motor «M» or AGK25 must be connected
-
Air pressure switch «LP» must be in its no load position
-
LGB... burner controls are capable of detecting undervoltages. This means that load
relay «AR» will be deenergized if mains voltage drops below AC 160 V (for nominal AC
220...240 V) or AC 75 V (for nominal AC 100...110 V).
The burner control will automatically make a restart attempt when the supply voltage
returns to a level above AC 160 V and AC 75 V respectively.
If the connections of live conductor (terminal 12) and neutral conductor (terminal 2) are
mixed up, the burner control will initiate lockout at the end of «TSA».
A – C Startup sequence
Start command (switching on)
A
This command is triggered by control thermostat / pressurestat «R».
Terminal 12 receives voltage and the programming mechanism starts running.
On completion of waiting time «tw» with the LGB21..., or after air damper
«SA» has reached the nominal load position (on completion of «t11») with the
LGB22... / LGB32..., fan motor «M» will be started.
TSA Ignition safety time
On completion of «TSA», a flame signal must be present at terminal 1.
That flame signal must be continuously available until shutdown occurs, or
else flame relay «FR» will be deenergized, resulting in lockout.
tw Waiting time
During the waiting time, air pressure switch «LP» and flame relay «FR» are
tested for correct contact positions.
t1 Prepurge time
Purging the combustion chamber and the secondary heating surfaces:
Required with low-fire air volumes when using the LGB21... and with nominal
load air volumes when using the LGB22... / LGB32...
«Type summary» and the «Function and sequence diagrams» show the so-
called prepurge time «t1» during which air pressure switch «LP» must indi-
cate that the required air pressure is available.
The effective prepurge time «t1» comprises interval end «tw» through «t3».
t3 Preignition time
During «t3» and up to the end of «TSA», flame relay «FR» is forced to close.
On completion of «t3», the release of fuel is triggered at terminal 4 or at termi-
nal 11 of the LGB41...
11/22
CC1N7435en
11.01.2007