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Siemens Building Technologies Basic Documentation LMU54... / LMU64... CC1P7494en
HVAC Products 3 Functions 07.11.2002
Actions
Description of fault Function Operating state Lockout
Faulty
Unfa-
vora-
ble
Diagnosis /
fault display
Start
prevention
Immedi-
ately
After
(min.)
After number
of faults
(in 24 h)
Short-circuit flow X X X 10
Open-circuit flow X X X 10
Measured value of flow not
plausible
TkIst < 0 °C X X X 10
Measured value of flow not
plausible
TkIst > 124 °C X X X 10
Short-circuit return X X X 10
Open-circuit return X X X 10
Measured value of return not
plausible
TkRuec < 0 °C X X X 10
Maximum return temperature
exceeded
TkRuec > TSTB X X X 10
(S)LT cutout temperature
reached
TkIst > TSTB
Burner is switched off
X
Over-
temperature
Already
activated
by TW
Parameter:
GrenzeNach
erwaermung
Maximum temperature
gradient exceeded
∆TkIst > TempGradMax
Switch burner off
X
Small heat
consumption
X
Parameter:
GrenzeGradi
ent
∆ϑ > dTkTrSTB
Reduce output by 20 %
X
Excessive ∆T
∆ϑ > dTkTrSTB + 8K
Reduce output to min.
X
∆ϑ > dTkTrSTB + 16K
Burner off
X X X
Parameter:
GrenzeDelta
T
Return temperature above
flow temperature
TkRuec > TkIst +
Sd_RL groesser _VL
(X) X X X
Parameter:
GrenzeRL_gr
oesserVL
∆ϑ TkIst - TkRuec
∆TkIst Gradient of actual boiler temperature
If a fault occurs and the limit thermostat’s (TW) cutout temperature is reached, the
accumulated heat must be carried away from the boiler by activating the fan or the
heating circuit pump (if not yet running).
Response if the cutout temperature is reached:
• Pump and fan overrun
In the event the above faults occur, following applies:
If the TW cutout temperature «TkMax» (parameter) is reached, the heating circuit pump
will be activated to accelerate the dissipation of heat and optional heating circuits will be
forced to draw off heat.
If the (S)LT’s cutout temperature is reached, the fan will also be activated.
Both are active until the relevant trigger criterion is no longer present, the maximum time
being «ZGebNach» (parameter).
Fault list and actions
Legend
Fault handling routines
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