Program Sequence; Parameters; Time Parameters; Gas Valve Proving - Siemens LMV51 Series Basic Documentation

Time parameters

Example
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HVAC Products

3.2 Program sequence

The sequence diagrams show the program sequence in detail (refer to «Sequence
diagrams»).

3.2.1 Parameters

The most important time parameters for the program sequence are the following (for
values, refer to the list of parameters):
Prepurge time (tv)
-
Preignition time / circulation time heavy oil
-
Safety time 1 (ts1)
-
Safety time 2 (ts2)
-
Interval 1 «ts1 - ts2»
-
Interval 2 «ts2 - traveling to low-fire = LC release»
-
Postpurge time 1 (tn1) with FGR damper shut (this part of the postpurge time is
-
always executed)
Postpurge time 3 (tn3) with FGR damper open (this part of the postpurge time will be
-
interrupted when there is demand for heat)
Postpurging in the lockout phase (if G = ON before lockout occurred)
-
All of the times mentioned above - with the exception of «Postpurging in the lockout
phase» - depend on the type of fuel, which means that different times can be set for oil
and gas.
The prepurge time and the safety times are safety-related. This means that, using the
AZL51..., the heating engineer can only readjust them in the «safe» direction (against
internal maximum or minimum values).
In other words, «ts» times can only be shortened and «tv» times can only be extended.

3.2.2 Gas valve proving

Gas valve proving is only active when firing on gas.
When a leak is detected, the gas valve proving function ensures that the gas valves will
not be opened and that ignition will not be switched on. Safety shutdown will take place.
V1 V2
PS
VP
Mains
V1 V2 PS-VP
t80 Evacuate
t81 Atm. test
t82 Fill
t83 Pressure test
Basic Documentation LMV51...
3 Burner control
With gas valve proving, first the gas valve on the
burner side is opened to bring the test space to
atmospheric pressure.
After the valve has closed, the pressure in the test
space may not exceed a certain level.
Then, the gas train is filled by opening the gas valve
on the gas network side.
After shutting the gas valve, the gas pressure may not
drop below a certain level.
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CC1P7550en
29.05.2002