FCU 500, FCU 505 · Edition 02.17
85
Parameters
12 .3 .6 Temperature hysteresis
Parameter 26
Using the integrated temperature module, the FCU
decides either using the safety temperature monitor
(STM) whether the conditions for high temperature op-
eration have been met or using the safety temperature
limiter (STL) whether the furnace temperature is too
high.
To avoid frequent switching in the limit range, a hyster-
esis can be set using parameter 26 for switching the
function selected in parameter 20 (High temperature
operation with STM or Maximum temperature monitor-
ing using STL) on and off.
High temperature operation with STM
FCU 50x..H1
M
BCU 4xx..D
µC
9
BCU 4xx..D
µC
9
HT
18
6
6
HT
HT
5-8
STM
High temperature mode is reactivated as soon as the
temperature exceeds the STM limit value and the de-
fined temperature hysteresis.
If the temperature falls below the STM limit value (lower
limit for high temperature operation), High temperature
mode is ended.
Maximum temperature monitoring with STL
FCU 50x..H1
M
BCU 4xx..D
9
BCU 4xx..D
9
BCU 4xx..D
9
57
5
5
5-8
STL
If the limit value of the safety temperature limiter is ex-
ceeded (excessive temperature in furnace), the FCU will
perform a lock-out. The fault lock-out cannot be reset
until the temperature falls below the STL limit value
and the defined temperature hysteresis.
