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Building Technologies Basic documentation LMV37.4... CC1P7546en
HVAC Products 6 Basic unit 01.12.2009
6.3.7 Pressure switch-min-gas (Pmin) / -min-oil, start release
gas X5–01
Input for connection of a pressure switch-min for gas or oil: If the plant does not require
a pressure switch-min, a wire link between terminal 2 and terminal 3 must be fitted.
Pressure switch-min-gas
In all types of gas trains, the minimum gas pressure is expected from phase 22. If no
gas pressure is detected after the maximum time (P214) has elapsed, the gas shortage
program is started (refer to subsection Gas shortage program).
LMV...
Bild 394e/1109
X5-01
Protective earth PE
Pressu re switc h-min-ga s (Pm in)
L for pressure switch
Figure 13: Pressure s witch-min-gas (Pmin) / -min-oil X5-01
Caution!
The OEM must check to see whether the burner can be operated without using
an air pressure switch-min. This may necessitate a special approval, depending
on the application.
No. Parameter
214 Max. time to start release
During the safety times (TSA1 / TSA2), the signal received from pressure switch-min is
only assessed after a certain period of time has elapsed, in order to ignore the pressure
shocks that occur the moment the valves open. The time to elapse for signal assess-
ment can be parameterized.
No. Parameter
229
Gas: Time to respond to pressure faults within safety time 1 (TSA1) and safety
time 2 (TSA2)
If the gas pressure fails, at least safety shutdown is initiated.
Error
code
Diagnostic
code
Meaning for the LMV37.4... system
20 0 Pressure switch-min (Pmin)
No min. gas / oil pressure
For the input, a repetition counter can be parameterized. It can be used to set the num-
ber of errors permitted until lockout occurs. The counter also impacts the gas shortage
program (refer to subsection Repetition counter).
No. Parameter
223
Repetition limit pressure switch-min-gas
1 = no repetition
2...15 = number of repetitions
16 = constant repetition
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