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Building Technologies Basic documentation LMV37.4... CC1P7546en
HVAC Products 6 Basic unit 01.12.2009
It must be ensured that the 2 test times are correctly set. It is to be checked whether the
gas required for the test may be fed into the combustion chamber (on the relevant appli-
cation). The test times are safety-related. After a reset and in the case of aborted or
prevented valve proving, the unit performs valve proving on the next startup (only when
valve proving is activated). In the case of a valve proving, prepurging is active during the
startup phase, even if it has been deactivated.
Examples of aborted valve proving:
When the safety loop or the start prevention input for gas (containing Pmin) opens dur-
ing valve proving.
Valve proving – calculation of leakage rate
(P
G
- P
w
)
• V • 3600
t
Test
= ⎯⎯⎯⎯⎯⎯⎯⎯⎯
P
atm
• Q
Leck
QLeck in l / h Leakage rate in liters per hour
PG in mbar Overpressure between the valves at the beginning of the test phase
PW in mbar Overpressure set on the pressure switch (normally 50%
of the gas inlet pressure)
Patm in mbar Absolute air pressure (1013 mbar normal pressure)
V in l Volume between the valves (test volume) including valve volume
and pilot pipe, if present (Gp1 mod)
tTest in s Test time
6.5.2.1. Valve proving with separate pressure switch (P LT) X9-
04
GP
Bild 187e/1109
P
LT
Figure 25: Valve proving with separate pres-
sure switch (P LT)
When performing valve proving, the gas valve on the
burner side is opened first to bring the test space to at-
mospheric pressure.
Then, the valve is closed whereupon the pressure in the
test space must not exceed a certain level. Then, the
gas valve on the mains side is opened to fill the gas pi-
pe.
When the valve is closed again, the gas pressure must
not drop below a certain level.
t80 Evacuation (P242)
t81 Atmospheric test (P243)
t82 Filling (P244)
t83 Pressure test (P245)
V… Fuel valve
GP Gas pressure switch
Signal ON
Signal OFF
Permissible signal
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